Abstract. The data on the synthesis, chemical transformations and practical use of aliphatic nitro alcohols published over the last 25 years are described systematically and analysed. The bibliography includes 316 references. I. Introduction Aliphatic nitro-derivatives attract considerable attention from researchers, because they are readily accessible and convenient starting compounds for the synthesis of organic derivatives of various classes.The diversity of chemical transformations of aliphatic nitro-compounds provided the basis for the paper `Aliphatic nitro-compounds as perfect intermediates' published in 1979.1 Nitro alcohols of the aliphatic series fully conform to this definition. Furthermore, since nitro alcohols contain the hydroxy group, their reactions can involve simultaneously several reaction sites; hence, the range of chemical transformations of these derivatives is even broader.The results of numerous studies devoted to the chemistry of aliphatic nitro alcohols and published before 1972 have been surveyed quite comprehensively in reviews and monographs.2 ±4 However, no reviews describing systematically the data on the synthesis, transformations and practical use of aliphatic nitro alcohols obtained during the last 25 years have been published so far.The purpose of this review is to fill this gap. We only briefly outline the preparation of nitro alcohols by nitroaldol condensa- tion (Henry reaction), because its conditions have been described quite comprehensively in previous publications.3, 4 The studies containing some novelty either in the procedure of condensation of nitro-compounds with carbonyl derivatives or in the use of the target compounds are discussed in greater detail.New data about other known methods for the synthesis of nitro alcohols and new information on their chemical transformations are presented. We also consider most of the studies that mention potential practical applications of these compounds, because this aspect has received little attention in earlier reviews.II. Methods for the synthesis of aliphatic nitro alcohols 1. Nitroaldol condensation (the Henry reaction) The Henry reaction consisting of condensation of aliphatic nitro- compounds with aldehydes or ketones is the most general method used widely for the synthesis of aliphatic nitro alcohols.The mechanism of this reaction has not yet been completely eluci- dated. It is generally accepted that nitroalkanes are condensed with carbonyl compounds according to the following scheme: a. Reactions of nitromethane and its derivatives with aldehydes The reaction of nitromethane 1 with formaldehyde 2 catalysed by Ca(OH)2 makes it possible to prepare both 2-nitropropane-1,3- diol 3 5 and 2-hydroxymethyl-2-nitropropane-1,3-diol 4.6 The diol 3 has also been prepared from the compounds 1 and 2 at 0 ± 10 8C in the presence of sodium carbonate.7 The synthesis of 3 from 1 and an aqueous solution of form- aldehyde or paraformaldehyde is carried out most often in the presence of alkali, NaOH8 ±12 or KOH,13 as catalysts.Sodium and potassium hydroxides are also used as catalysts to synthesise the triol 4 from MeNO2 and the aldehyde 2.14 The condensation of nitromethane 1 with paraformaldehyde catalysed by sodium methoxide in methanol gives the sodium salt 5.15, 16 The condensation of MeNO2 with paraform in the presence of Bu4N+Br7 and KF under an inert atmosphere at 18 ± 22 8C for C R1 R2 NO2 H +B7 7HB CNO2 R1 R2 R3R4C O 7 HB C R1 NO2 R2 C R3 R4 OH+B7.C R1 NO2 R2 C R3 R4 O7 R=H(3); CH2OH (4). MeNO2+CH2O 1 2 Ca(OH)2, H2O HOCH2CCH2OH R NO2 3, 4 MeNO2+(CH2O)x MeONa, MeOH (HOCH2)2C NOO7Na+. 076 8C 1 5 M-G A Shvekhgeimer A N Kosygin Moscow State Textile Academy, ul. Malaya Kaluzhskaya 1, 117918 Moscow, Russian Federation. Fax (7-095) 952 14 40. Tel. (7-095) 955 35 96 Received 8 September 1996 Uspekhi Khimii 67 (1) 39 ± 74 (1998); translated by Z P Bobkova UDC 547.43 Aliphatic nitro alcohols.Synthesis, chemical transformations and applications M-G A Shvekhgeimer Contents I. Introduction 35 II. Methods for the synthesis of aliphatic nitro alcohols 35 III. Chemical transformations of nitro alcohols 49 IV. Practical use of aliphatic nitro alcohols 64 Russian Chemical Reviews 67 (1) 35 ± 68 (1998) #1998 Russian Academy of Sciences and Turpion Ltd72 h affords a mixture of the diol 3 (yield5%± 10%) and the triol 4 (yield 80%± 85%).16 Treatment of the nitronate 5 with trifluoroacetic acid at low temperatures gives rise to the aci-form 6, which is rapidly converted into the diol 3 and 2-nitroprop-2-en-1-ol.16 The diol 3 obtained from MeNO2 and paraformaldehyde in the presence of KF and Bu4N+Br7 exists as a nitronate 7 stabilised by intramolecular interactions.17 The condensation of bromonitromethane with formaldehyde 2 in the presence of NaOH in methanol gives the diol 8.18 Treatment of nitromethane 1 with bromine in an alkaline medium followed by the reaction with formaldehyde in the presence of NaOH19 or the condensation of MeNO2 with form- aldehyde followed by treatment with bromine 20 afford the same compound 9, the yield of which is up to 60%.Nitro alcohols 10 containing a furyl substituent have been obtained by the condensation of MeNO2 with aldehydes 11 in the presence of sodium hydroxide.21, 22 R R0 n Yield (%) Ref. H Me 2 49 21 Me H 2 78 22 H H 1 66 ± 73 21, 22 H Me 1 59 ± 75 21, 22 The reaction of chiral complex 12 with nitromethane has been carried out in the presence of NaOH or KF and gave a mixture of diastereoisomeric nitro alcohols 13a (1S,2S) and 13b (1S,2R) in a high yield.It was found that the ratio of the resulting isomers varies over a wide range depending on the procedure used and the temperature (see Table 1).23 When nitromethane was treated with butyllithium (THF, HMPT, 790 to 760 8C), and the product was made to react with aldehyde 12 (THF, 770 to 760 8C, 1.5 h; 745 to 740 8C, 3 h), the isomer 13a was obtained as the only product.23 Sodium methoxide has been used as the catalyst in the reactions of nitromethane 1 with both aliphatic 24 and aro- matic 25, 26 aldehydes. Potassium fluoride is an efficient catalyst of the reaction of MeNO2 with aldehydes.27 Study of the condensation of nitromethane with aldehydes carried out using IR and NMR spectroscopy has shown that the process occurs efficiently in DMF at 20 8C in the presence of a complex of nickel acetate with 2,20-dipyridyl (Dipy) and gives nitro alcohols 15 in 81%± 87% yields.28 The reaction of MeNO2 with acetaldehyde catalysed by Rh(PMe3)3Cl and carried out at 23 8C for 0.5 h affords 1-nitro- propan-2-ol in 90% yield.29 Nitromethane readily reacts with aromatic aldehydes in liquid ammonia giving rise to nitro alcohols 16 in good yields.30 (HOCH2)2C N O OH 3+HOCH2C CH2 .NO2 6 (HOCH2)2C N O O 5 7 Na+ CF3COOH, MeCN 730 to725 8C MeNO2+(CH2O)x 1 KF, Bu4N+Br7, PriOH, argon 20 8C, 3 days 7 H O CH2 C N O O H O CH2 7 BrCH2NO2+CH2O NaOH, H2O, MeOH pH 9710, 45 8C (HOCH2)2CNO2 .Br 8 (76.2%) MeNO2+Br2 1 HOCH2C(NO2)Br2 , 9 1+CH2O 2 9 . 1. NaOH, H2O 2. Br2 1. NaOH, H2O, 0720 8C 2. CH2O, NaOH, 0720 8C O R CH(CH2)nCHO+MeNO2 R0 NaOH, EtOH 20 8C, 3 h 11 O R CH(CH2)nCHCH2NO2 R0 OH 10 2 Me C O H Cr(CO)3 12 Me C H CH2NO2 OH Cr(CO)3 13a,b 1 MeNO2 B R=C13H27, 3-MeOC6H4, 4-PhCH2OC6H4 (43%), Ph (59%), 4-MeC6H4 (50%), 4-ClC6H4 (63%).RCHO +1 MeOH, MeONa RCHCH2NO2 OH R=C6H13, C7H15, CH2, , Me2C CH(CH2)2C(Me) CH(CH2)2. MeNO2+RCHO KF, PriOH 23 8C, 6 h RCHCH2NO2 14 OH RCHO +MeNO2 Ni(OAc)2, Dipy, DMF 208C RCHCH2NO2 OH 1 15 R= ,PhCH2CH2, 4-NO2C6H4, 4-NCC6H4. N Table 1. Reaction conditions and the ratio of the products 13a and 13b. Base Temperature Yield Ratio /8C (%) 13a : 13b NaOH 20 100 64 : 36 NaOH 720 95 92 : 8 NaOH 740 90 97 : 3 KF/PriOH 20 80 40 : 60 KF/PriOH 0 90 88 : 12 36 M-G A ShvekhgeimerTriethylamine has been used as the catalyst in the reaction of MeNO2 with 4-chloropentanal 17; this resulted in the formation of nitro alcohol 18 in 42.5% yield.31 Difluoronitromethane condenses with trifluoroacetaldehyde on heating in the presence of sodium carbonate.The reaction gives 1,1,1,3,3-pentafluoro-3-nitropropan-2-ol in 38.5% yield.32 The condensation of difluoronitromethane with aromatic aldehydes has been carried out using KOH as the catalyst.33 It has been reported 34 that chlorofluoronitromethane reacts with aliphatic aldehydes without a catalyst. b.Reactions of nitromethane homologues and their derivatives with aldehydes It should be noted that even when primary nitro-compounds are used, the synthesis usually affords products resulting from con- densation with one formaldehyde molecule. 2-Nitrobutan-1-ol has been obtained in an almost quantitative yield by the reaction of 1-nitropropane with formaldehyde 2 in the presence of Ca(OH)2 at 30 8C.35 In a number of publications,36 ± 39 synthesis of nitro alcohols 19 from nitroalkane 20 and formaldehyde catalysed by an alkali (NaOH or KOH) or by Amberlites IRA-410 has been described (Table 2).Condensation of nitrated butadiene or isoprene oligomers with formaldehyde in the presence of alkaline catalysts gave the corresponding nitro alcohols.40 The process of condensation of nitroalkanes with formalde- hyde has been optimised by experiment design.41, 42 It was found that the reaction of paraformaldehyde with nitroethane in the presence of KOH occurs over a period of 2 ± 3 min.41 The highest yields of nitro alcohols in the reaction between an aqueous solution of the aldehyde 2 and a mixture of C1 ±C4 nitroalkanes are attained when the process is carried out at an RNO2 :CH2O ratio of 2.5 : 1 and at a temperature of 50 ± 60 8C for 35 ± 40 min.42 The condensation of 2-nitropropane with paraformaldehyde in the presence ofKFaffords 2-methyl-2-nitropropan-1-ol in 86% yield.43 2-Nitropropan-1-ol has been obtained in a yield of 62% ± 74% by the reaction of nitroethane with the aldehyde 2 in the presence of triethylamine.44 Tributylphosphine has been used as the catalyst in the syn- thesis of 2-methyl-2-nitropropan-1-ol from 2-nitropropane and paraformaldehyde.45 As a rule, high yields of nitro alcohols are achieved when formaldehyde is condensed with functionally substituted nitro- alkanes 21 in the presence of NaOH (Table 3).46 ± 48 It can be seen from Table 3 that in the case of fluorine- containing nitroalkanes, approximately the same yields of nitro alcohols are obtained when the reaction is carried out with heating.On the other hand, homologues of ethyl nitroacetate readily react with formaldehyde at room temperature. Treatment of diethyl fluoronitromalonate with potassium hydroxide gives rise to salt 22, which reacts with the aldehyde 2 to yield compound 23; the latter reacts with one more molecule of formaldehyde being thus converted into 2-fluoro-2-nitropropane- 1,3-diol in a yield of more than 70%.49 Ar=2-H2NC6H4 (53%), 3,4-(MeO)2C6H3 (98%), 4-Br-3,4-(MeO)2C6H2 (80%), 4-MeC6H4 (92%), 3,4-(CH2O2)C6H3 (83%), 4-BrC6H4 (93%), 3-BrC6H4 (91%), 3-ClC6H4 (75%), 4-MeOC6H4 (82%), 1-naphthyl (53%). 1 ArCHO MeNO2+ NH3(liq.) 16 ArCHCH2NO2 OH MeCH(CH2)2CHCH2NO2 . Cl OH 1+MeCH(CH2)2CHO Cl 18 17 Et3N, EtOH 5 ± 7 8C, 48 h; 20 8C, 24 h F2C(NO2)H+ArCHO ArCHC(NO2)F2 OH KOH, DMF 150 8C, 5 ± 15 h Ar=2-HOC6H4 (47%), 2-ClC6H4 (61%), 2-O2NC6H4 (31.5%), 3-O2NC6H4 (56%), 4-MeC6H4 (60%), 2,4-(MeO)2C6H3 (53.5%).R=H (83%), Me (55%), Et (73%), Pr (86%). F(Cl)C(NO2)H+RCHO RCHC(NO2)(Cl)F refluxing, 1 h OH RR0CHNO2+CH2O 20 2 H2O 20730 8C RR0C(NO2)CH2OH . 19 Me2CHNO2+(CH2O)x Bu3P, PriOH 35740 8C, 45 min Me2CCH2OH . NO2 NaOH, H2O RR0C(NO2)CH2OH .CH2O+RR0CHNO2 2 21 HOCH2CNO2 F COOEt 23 KOH H2O HOCH2CNO2 F COO7 7CO2 C F COOEt COOEt O2N KOH EtOH K+C NO¡2 F COOEt 22 CH2O, H2O 20 8C, 3 h Table 2. Reaction conditions and yields of products in the condensation of the nitro-derivatives 20 with formaldehyde. R R0 Catalyst Time Yield Ref. /h (%) But Me KOH 7 56.5 36 MeC(NO2)2CH2 H NaOH 48 7 37 Et H NaOH 5 see a 38 C12H257C18H37 H Amberlites 7 30 39 IRA-410 a The reaction also yields EtC(NO2)(CH2OH)2.Table 3. Reaction conditions and yields of products for the condensation of the nitro-derivative 21 with formaldehyde. R R0 Tempera- Time Yield Ref. ture /8C, /h (%) Et F 76 ± 80 2 ± 3 80 46 Pr F 76 ± 80 2 ± 3 87 46 Bu F 76 ± 80 2 ± 3 86 46 C5H11 F 76 ± 80 2 ± 3 79 46 C6H13 F 76 ± 80 2 ± 3 83 46 C7H15 F 76 ± 80 2 ± 3 85 46 C8H17 F 76 ± 80 2 ± 3 81 46 F2CCl H 710 7 7 47 COOEt Me 20 2 60 a 48 COOEt Et 20 2 67 a 48 COOEt Pr 20 2 67 a 48 COOEt Pri 20 2 79 a 48 COOEt Bu 20 2 82 a 48 a Found for the acetylated product.Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 37Reactions of aldehydes with nitro ketones carried out in the presence of strong bases are substantially complicated by side reactions of the initial compounds and reaction products.To avoid these problems and to obtain the products of nitroaldol condensation in higher yields, a convenient procedure was devel- oped48 according to which the condensation of nitro ketones with formaldehyde was carried out in the presence of triphenylphos- phine. The intermediate alcohols were isolated as the correspond- ing acetates after treatment with acetic anhydride.Thus the reaction of nitro ketones 24 with formaldehyde in the presence of triphenylphosphine gave nitro alcohols 25, which were treated in situ with acetic anhydride in the presence of pyridine to give the corresponding acetates 26 (yields 73%± 91%).48 1,4-Difluoro-1,4-dinitrobutane reacts with two molecules of the aldehyde 2 in the presence of potassium carbonate giving 2,5- difluoro-2,5-dinitrohexane-1,6-diol in 75% yield.50 Some researchers have synthesised nitro alcohols by reactions of formaldehyde with the salts of nitro-compounds prepared previously.The sodium salt 27 prepared from ethyl nitroacetate and the aldehyde 2 under the action of sodium ethoxide has been made to react with a second molecule of 2; this resulted in the synthesis of compound 28.51 The reaction of bis-salts 29 with the aldehyde 2 at 1 ± 3 8Cgave bis-salts 30, which were converted into the corresponding diols 31.Thus treatment of the salt 30b withHONH2 . HCl in water at pH 4 gives the diol 31b in 54.5% yield; treatment of the salt 30a with 18% hydrochloric acid or with 75% acetic acid affords 31a in a yield of 9.2% or 6.6%, respectively.52 Under the same conditions, the bis-salt (7O2N=CHCH2..CH2CH=NO2 7) 2Na+ reacts with two molecules of CH2O and is thus converted into the salt of bis-hydroxymethyl derivative [7O2N=C(CH2OH)CH2CH2C(CH2OH)=NO2 7] 2Na+ in 93.6% yield.52 Whereas the anions of non-conjugated mononitro-derivatives react with formaldehyde only at pH>7, the dianions of con- jugated dinitroalkanes 32 are able to react with the aldehyde 2 giving rise to diols 33 both at pH > 7 (yields 70%± 90%) and at pH=4 (yields 40%± 70%).53 The reaction of conjugated nitroalkenes 34 with the aldehyde 2 in the presence of Et3N in acetonitrile starts with the formation of allylic anions 35, which are attacked by the aldehyde at the carbon atom carrying the nitro group to give nitro alcohols 36 (yields 60%± 94%).54 Nitroalkenes 37 react successively with lithium phenylthiolate and the aldehyde 2 to afford salts of aci-forms 38, which are converted, on treatment with acetic acid, into mixtures of erythro- and threo-isomers (in a ratio ranging from 86 : 14 to 93 : 7) of nitro alcohols 39 (yields 57%± 91%).55 The reaction of the nitroalkenes 37 with PhSH and CH2O in the presence of bases yields mixtures of the erythro- and threo- isomers of 39 (1 : 1) together with nitro diols RCH(SPh) ± C(CH2OH)NO2.55 Sodium methoxide has been used as the catalyst in the reaction of 1-(nitromethyl)cyclopentene with paraformaldehyde.56 HOCH2CNO2 F 7 HOCH2CCH2OH.F NO2 CH2O, KOH H2O R, R0=Alk.Ph3P, PriOH 20 8C, 24 h RCCHR0 +CH2O O NO2 RC O CCH2OH NO2 R0 24 25 Ac2O, C5H5N RC O CCH2OAc NO2 R0 26 O2NCH(CH2)2CHNO2+2CH2O F F K2CO3, H2O 60 8C, 2 h HOCH2C(CH2)2CCH2OH . F F NO2 NO2 2 O2NCH2COOEt +CH2O NaOEt, EtOH 27 EtO C N O 2, H2O Na C CH2OH + 7 (HOCH2)2CCOOEt. NO2 28 O O 30a,b NO¡2 C C CH2OH R R 2Na+ H+ 7O2N C C CH2OH 29a,b NO¡2 ) 2Na++2CH2O (7O2N CHC CCH H2O 1 ± 3 8C, 24 h R R R=H (a), Me (b).CCHCH2OH NO2 NO2 31a,b R R HOCH2CHC n=0, R=H; n=1: R=H, R0 =H, Me. CR0)n HOCH2C (R0C NO2 R 33 CCH2OH NO2 R CR0)n C NO¡2 +2CH2O R 1 ± 5 8C, 18 h 7O2N C (CR0 32 R CNO2 R3 Et3N 7Et3NH+ 35 R1R2C 2 7 CH CNO2 R3 R1=H, Bu, PhCH2; R2=H; R3=Me, Et, C7H15, (CH2)2COOMe. 34 R1R2CHCH 7 CHCCH2O NO2 R3 Et3NH+ 7Et3N 36 R1R2C CHCCH2OH R3 NO2 R1R2C R=Me, Et, Pr, Pri, Bu, C5H11, Ph, PhCH2CH2.R OH NO2 SPh 39 HOCH2 SPh H R N O O 38 Li+ AcOH 778 8C, 1 h 7 1. PhSLi, THF, 20 8C, 1 h 2. 2, H2O, 20 8C, 3 h CHNO2 37 RCH 38 M-G A Shvekhgeimer1-Halo-1-nitroalkanes 40 smoothly react with aldehydes 41 in the presence of potassium carbonate at 20 8C, and this leads to halo-substituted nitro alcohols 42 (yields 37%± 75%).57 Several nitro-compounds 43 have been condensed with ali- phatic or arylalkyl aldehydes 44 in the presence of sodium hydroxide in methanol or ethanol; this resulted in the formation of threo-isomers of nitro alcohols 45, as a rule, in good yields.59, 60 However, the reactions of butyraldehyde with nitrobutane (43, R1=Pr) and nitrooctane (R1=C7H15) gave the corresponding nitro alcohols in yields of 26% and 30% (Table 4).60 When the same nitro-compounds 43 were made to react with aldehydes in the presence of KF, the erythro-isomers of 45 were obtained.59, 60 In some cases, water was added to the reaction mixture.60 Potassium hydroxide has been used as the catalyst in the reactions of myristaldehyde 46 with nitroethane 61 and of unsatu- rated nitro-compounds 47 with aldehydes 48;62 these reactions gave nitro alcohols 49 and 50 in 64% and 30%± 65% yields, respectively.A method for the synthesis of nitro alcohols 51 by condensa- tion of aromatic aldehydes with nitroalkanes has been patented.63 According to this method, aldehydes are treated first with sodium hydrogensulfite and then with nitroalkanes in the presence of aqueous sodium hydroxide at 20 8C.63 In the synthesis of 1,1,1-trichloro-3-nitrobutan-2-ol (yield 30%), the initial chloral was also converted first into the hydro- gensulfite derivative, and the latter was made to react with nitro- ethane in the presence of aqueous sodium hydroxide at 20 8C for 12 h.64 In the same study,64 condensation of primary or secondary nitroalkanes with aliphatic or aromatic aldehydes at 20 8C in the presence of NaHCO3,K2CO3 or NaOH was studied.The yields of the target nitro alcohols 52 were found to depend crucially on the nature of the initial aldehyde (Table 5). Synthesis of 2-nitro-1-phenylpropan-1-ol from benzaldehyde and nitroethane under mild conditions in the presence of bases in DMSO or DMF has been reported.65 Condensation of the complex 12 with nitroethane in the presence of NaOH yields a mixture of diastereoisomers 53a,b; on treatment with hydrogen peroxide, this mixture is converted into a mixture of diastereoisomeric nitro alcohols 54a (1R*,2R*) and 54b (1R*,2S*) in a ratio of 36 : 64.23 CH2NO2+(CH2O)x MeONa CHCH2OH.NO2 RC O H 41 +R0CHNO2 X 40 K2CO3, H2O 20 8C, 12 h R=Alk, CCl3; R0=H, Cl, Br, Me, Et; X=Cl, Br. RCH CR0 X NO2 42 OH NaOH, MeOH or EtOH 44 R1CH2NO2 +R2R3CHC O H 43 45 R2R3CHCHCH(R1)NO2 .OH 46 C13H27C +EtNO2 O H C13H27CHCH(Me)NO2 , 49 KOH, MeOH Et2O, 20 8C OH R1, R2=H, Me; R3=Me, Et, Pr, Pri. 47 R1CH CCH2NO2+R3C 48 O H R2 C(R2)CHCH(R3)OH 50 R1CH NO2 KOH EtOH, H2O 4-RC6H4C O H +NaHSO3 H2O R=But, Bus; R0=Me, Et. 4-RC6H4CH(OH)CH(R0)NO2 51 4-RC6H4C OH SO3Na H NaOH, R0CH2NO2 20 8C, 12 ± 16 h R1CHO+R2R3CHNO2 H2O 20 8C R1CH(OH)C(NO2)R2R3. 52 (a) NaOH, EtOH, H2O, 740 8C, 0.5 h; (b) NH4Cl, H2O.a, b CHCH(Me)NO2 Me OH Cr(CO)3 53a,b H2O2 C O H Me Cr(CO)3 12 +EtNO2 CHCH(Me)NO2 Me OH 54a,b Table 4. Reaction conditions and yields of the compounds 45. R2 R3 R1 Tempera- Time Yield Ref. ture /8C /h (%) Me H Cl(CH2)3 5 ± 10 7 65 a 58 Ph H H 30 ± 35 45 67 a 59 Ph H Me 30 ± 35 45 69 a 59 Ph H Et 30 ± 35 45 65 a 59 H H Ph 30 ± 35 45 63 a 59 Me H Ph 30 ± 35 45 58 a 59 Ph H Ph 30 ± 35 45 60 a 59 Me Me Ph 30 ± 35 45 58 a 59 H Ph Ph 20 144 85 a 59 Me H Et 38 65 80 b 60 Et H Et 38 65 63 b 60 Bu H Me 38 65 52 b 60 Bu H Et 38 65 58 b 60 Et H C7H15 38 65 30 b 60 C9H19 H Me 38 65 61 b 60 Bu H C7H15 38 65 70 b 60 Me Me Et 38 65 54 b 60 Et H Pri 38 65 26 b 60 a (R*,R*) threo-Isomers are formed; if the reaction is carried out in the presence of KF, the nitro alcohols 45 are mostly formed as (R*,S*) erythro-isomers; b water was added to the reaction mixture.Table 5. Reaction conditions and yields of the nitro alcohols 52. R1 R2 R3 Catalyst Time Yield /h (%) Me Me H K2CO3 5 54 Pri Me H K2CO3 5 40 CF3 Me H NaOH 5 8.2 4-O2NC6H4 Et H NaHCO3 5 16.3 4-O2NC6H4 Me Me K2CO3 5 7 Br3C Me H K2CO3 0.5 10 Aliphatic nitro alcohols.Synthesis, chemical transformations and applications 39The reaction of 12 with the nitronate prepared previously from nitroethane resulted in the formation of a mixture of diastereoisomers 54a,b in a ratio of 77 : 23.23 Nitro-compounds 55 containing a CF3 group condense with aldehydes 56 in the presence of potassium fluoride in isopropyl alcohol or without a solvent to give nitro alcohols 57.66 R R0 Solvent Yield (%) H Pr PriOH 71 H Pr 7 73 H C6H13 PriOH 65 H C6H13 7 71 H Ph(CH2)2 7 83 H Me(Ph)CH 7 46 H Ph PriOH 26 H Ph 7 9.5 Me Pr PriOH 54 Me Pr 7 35 Me C6H13 PriOH 54 Me PhCH2CH2 7 40 During the last 10 ± 15 years, neutral alumina (Brockmann activity I) has been used as a catalyst in the Henry reaction.In the presence of this catalyst, nitro-compounds 58 condense with various aliphatic aldehydes 59 at ambient temperature.67 The reaction of nitro-compound 60 with propanal carried out in the presence of Al2O3 at 20 8C affords condensation product 61 as a mixture of erythro- and threo-isomers in a 54 : 46 ratio and in 22% overall yield.68 Nitro alcohols 62 have been prepared by the reactions of primary or secondary nitro-compounds 63 with aldehydes in the presence of neutral Al2O3 without solvents.66, 69 R1 R2 R3 Yield Ref.(%) Me Et H 80 69 Et Me H 71 69 Et (CH2)2COOMe H 84 69 Pri MeCH(OH) H 69 69 Me H 75 69 R1 R2 R3 Yield Ref. (%) C6H13 H 86 69 C6H13 H 86 69 Ph(CH2)2 Me H 71 69 Ph(CH2)2 Me Me 69 69 Ph(CH2)2 see a H 82 69 See b Me H 78 69 Pr CF3 H 73 66 Ph CF3 H 9.5 66 CF3 H 3 66 Pr CF3 Me 33 66 a R2=Me(CH2)3OCH(Me)OCH2; b R1=Me2C=CH(CH2)2CH(- Me)CH2.The product 64 resulting from interaction of acrolein with two molecules of nitroethane has been synthesised by two procedures: by the reaction of the aldehyde with a fivefold excess of EtNO2 (yield 39%) or by the addition of one molecule of EtNO2 to the double bond of the aldehyde followed by condensation of the resulting adduct 65 with a second molecule of the nitro-derivative (yield 89%).70 It has been reported 71 that the following nitro alcohols are formed as mixtures of erythro- and threo-isomers upon reaction of the corresponding aldehydes with nitro-compounds in the pres- ence of Al2O3 (Brockmann activity I) at 20 8C for 23 h: It can be seen from published results 66, 69 that the condensa- tion of nitro-compounds with aromatic aldehydes in the presence of KF or Al2O3 gives the corresponding nitro alcohols in low yields.When the reactions of nitroalkanes 66 with aromatic aldehydes 67 are conducted 30 in liquid ammonia, the correspond- ing nitro alcohols 68 are formed in 53% ±98% yields. CF3CHNO2+R0C F3CCCH(R0)OH NO2 55 56 57 R R O H KF, argon R1, R2, R3 : Me, Et, H; Me, , H; Pri, Et, H; C6H13, Et, H; R1CHC(NO2)R2R3 OH R1CHO+R2R3CHNO2 Al2O3, CH2Cl2 20 8C, 23 h 58 59 O O H2C Me C6H13, , H; CH2 CH(CH2)2, Me, Me; Ph(CH2)2, C6H13, MeOCO(CH2)2, H; Ph(CH2)2, , H.O O H2C Me Me, H; CH2 CH(CH2)2, Me, H; C6H13, , H; H2C O O O O H2C Me 60 EtCHO+MeCHCH2 O O 61 CCH2 NO2 EtCH OH Me Al2O3 20 8C, 3 days O O C NO2 R1C 63 +R2R3CHNO2 R1CHC(NO2)R2R3 OH 62 O H 20 8C, 24 h Al2O3 CH2O O O O Me H2C O O MeCH(CH2)2CHCHNO2 NO2 OH Me 64 MeCH(CH2)2CHO NO2 65 5 equiv.EtNO2, Al2O3 CH2Cl2, 20 8C, 17 h EtNO2, Al2O3 CH2Cl2, 20 8C, 24 h 1 equiv. EtNO2, Al2O3 CH2Cl2, 20 8C, 3 h CHC H2C O H OH Me OH MeCHCHNO2 , where R=Me, Et, (CH2)4COOMe, OH R Me OH CH(CH2)2CHCHNO2, Ph(CH2)2CHCHNO2, OH Me EtCH EtCHCH2NO2, C6H13CHCH2NO2, EtCHCHNO2, OH OH NO2 OH NO2 EtCHCH(CH2)6OH, EtCHCHCH2OH, C6H11CHCHCH2OH.OH NO2 40 M-G A ShvekhgeimerNitro alcohols have been obtained in good yields by the condensation of nitromethane, nitroethane or 1-nitropropane with the corresponding aliphatic, aromatic or heterocyclic alde- hydes in the presence of KF supported on Al2O3 (Scheme 1).72 Scheme 1 R R0 Time /h Yield (%) Et H 5 71 Pri Me 5 75 Et Me 5 75 Pri Et 5 78 Me Et 5 77 Bu Me 5 62 See a Me 5 79 See a H 5 50 Ph Et 6 55 Me 15(N2) 77 a R=Me2C=CH(CH2)2CH(Me)CH2.Sodium methoxide 73 and sodium ethoxide 74 have been used as catalysts in the nitroaldol condensation of primary nitroalkanes with functionally substituted aldehydes 69 and 70. The reaction of sulfide 71 with acetaldehyde carried out in the presence of potassium tert-butoxide (0 8C, 20 min) gives nitro alcohol 72 (yield 95%), whereas the reaction with isobutyralde- hyde carried out under the same conditions affords nitroalkene 73 (yield 83%).75 Esters of chloronitroacetic acid 74 react with aliphatic alde- hydes in the presence of sodium acetate.76 The reaction of nitro-compounds 76 with aldehydes in the presence of butyllithium led to g-nitro alcohols 75 in 75% ±80% yields instead of the normal products of nitroaldol condensa- tion.77 This unusual reaction pathway was explained 77 by the fact that at low temperatures nitro-compounds 76 are doubly depro- tonated at the a- and b-positions with respect to the nitro group to give dilithio-derivatives 77.The formation of g-nitro alcohols in the condensation of nitro-compounds with aldehydes in the presence of BuLi is not a specific feature peculiar only to 2-arylnitroethanes.It was found that g-nitro alcohols are also formed in the reactions of some secondary nitro-compounds with aldehydes in the presence of BuLi or ButLi. For example, 3-nitro-1-phenylbutan-1-ol was synthesised in 50% yield by the reaction of 2-nitropropane with benzaldehyde in the presence of BuLi and ButLi.77 The condensation of 1,1,1-trifluoro-2-nitropropane with ali- phatic and aromatic aldehydes in the presence of BuLi and ButLi occurs via unusual doubly deprotonated products 78 and yields g-nitro alcohols 79.67 Primary nitro-compounds 80, doubly deprotonated upon treatment with BuLi, react with aldehydes to give products of nitroaldol condensation, namely, b-nitro alcohols 81.66 The reactions of primary nitro-compounds 82 with aldehydes in the presence of butyllithium and TiCl3(OPri) at nitroalkane : al- dehyde ratios of 1 : 1 or 2 : 1 have been studied in detail.This process was found to afford b-nitro alcohols 83 as mixtures of erythro- and threo-isomers.78 R=H, Me; R0=H, Me; Ar=3-ClC6H4, 4-ClC6H4, 3-BrC6H4, 4-BrC6H4, 4-MeOC6H4, 4-MeC6H4, 2-O2NC6H4, 2-H2NC6H4, 3,4-(MeO)2C6H3, 6-Br-3,4-(MeO)2C6H2, ArCHO+RR0CH2NO2 NH3(liq.) ArCHCRR0 OH 67 66 68 NO2 , .H2C O O RCHO +R0CH2NO2 OH KF/Al2O3 RCHCH(NO2)R0 O 69 1. MeONa, 20 8C, 18 h 2. H3O+ R(R0O)PCH2CHO+EtNO2 O R(R0O)PCH2CHCHNO2 O OH Me R, R0 (yield, %): MeO, Me (66); EtO, Et (60); PriO, Pri (50); Bu, Pri (46); MeCH CHCH2, Pri (20); MeCH CHCH2, Pr (20).R=Me (52%), Et (51.5%), Pr (54%), Pri (28%), Ph (65%). EtOCCHO+RCH2NO2 O 70 RCHCHCOOEt NO2 OH 1. EtONa, EtOH, PhH, 20 8C, 12 h 2. H3O+ PhSCHCHMe NO2 OH 72 0 8C, 20 min MeCHO 0 8C, 14 h PhSCH2NO2 71 ButOK, ButOH, THF Me2CHCHO PhS O2N C H Pri 73 C R, R0 (yield, %): Me, Me (65); Me, Et (92); Et, Me (98); Et, Et (45); PhCH2, H (71). O2NCHCOOR +R0CHO 74 Cl 20 8C, 172 h R0CHC(NO2)COOR OH Cl AcONa .3H2O, EtOH, H2O 76 Ar, R: 4-ClC6H4, Et; Ph, Ph; Ph, 4-ClC6H4. 778 8C, 0.5 h BuLi, C6H14, THF ArCH2CH2NO2+RCHO RCHCH(Ar)CH2NO2 75 OH ArCH2CH2NO2 BuLi 790 to778 8C 77 Ar H N H O7 O7 2Li+. 7 7 Ar H H + N O O7 7 Ar H + N O7 O7 H F3CCHMe 1. BuLi, THF, argon,770 8C 2. ButLi, THF, HMPT,770 8C NO2 R=C6H13 (12%), PhCH2CH2 (9%), Ph (21%) . 78 LiO N OLi C F3C CH2 1.RCHO,780 8C 2. H2O F3CCHCH2CHR NO2 OH 79 X, R (yield, %): F, But (90); H, But (40); F, Ph (67); H, Ph (32); H, 4-O2NC6H4 (52); F, 3,4-(CH2O2)C6H3 (40). F2CCH2NO2 X 80 BuLi, DMF,THF, argon 790 8C F2(X)C Li C 7 O N OLi 2. H2O,775 8C, 1 h 1. RCHO, THF, argon F2CCHCH(R)OH NO2 X 81 Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 41The ratio of the erythro- and threo-isomers formed varies over a wide range.For a nitroalkane : aldehyde ratio of 1 : 1, it varies from 3.9 : 1 (in the case of R0 = 4-O2NC6H4, R = Bu) to 11.2 : 1 (in the case of R0 = MeOOCC6H4, R = Et); for a nitroalka- ne : aldehyde ratio of 2 : 1, it ranges from 2 : 1 (R0=COOMe, R=Et) to 8 : 1 (R0 =PhCH=CH, R=Et).78 The reaction of nitroethane with benzaldehyde in the presence of butyllithium has been studied systematically using two approaches.79 According to one of them, EtNO2 was treated with BuLi in THF and HMPT at various temperatures and various HMPT/BuLi ratios, and after that, the aldehyde was added at a temperature between 778 and 735 8C, and the reaction mixture was quenched with acetic acid (procedure A).The second approach included treatment of the aldehyde with butyllithium in THF and HMPT at 790 8C and subsequent addition of the nitro-compound at various temperatures and various HMPT/BuLi ratios followed by acidification of the reaction mixture (procedure B).It was found that in both cases, the reaction resulted in the formation of a mixture of b-nitro alcohol 84 and g-nitro alcohol 85.When the reaction was carried out by procedure A at an HMPT/BuLi ratio of 2.6 and at a temperature of790 to725 8C, the yields of the compound 84 varied in the range 68.8% ± 11.3%. In the absence of HMPT, the yield of 84 was 47.3%, and that of the compound 85 was 3% (at 790 8C). At higher temperatures, the yield of 85 increased, whereas the overall yield decreased. The reaction carried out by procedure B withoutHMPAafforded only the nitro alcohol 84 (yield 56.8%).At HMPT/BuLi ratios greater than 2, the nitro alcohol 85 was formed as the major product (yields 50.8% ± 72.6%, the yields of 84 formed simultaneously being 3.8% ± 10.6%. Triethylamine has been used as the catalyst in the condensa- tion of nitro-compounds with both aliphatic 30 and heteroaro- matic 80 aldehydes.Mixtures of erythro- and threo-isomers of nitro alcohols 86 are formed when the nitro compound 60 or its derivative 87 is made to react with acetaldehyde or propionaldehyde in the presence of tetrabutylammonium fluoride trihydrate (Table 6).69 In a study on the development of the synthesis of b-amino alcohols according to the scheme it was found 81 ± 83 that the nitroaldol condensation of nitroalkanes with molecular weights much greater than that of nitromethane in the presence of conventional catalysts gives b-nitro alcohols in low yields.In order to increase the yields of the target compounds, the researchers studied the nitroaldol condensation of aldehydes with silyl ethers 88, which were obtained from nitroalkanes and chlorotrimethylsilane or tert-butyl(chloro)dimethylsilane under the action of Pri 2NLi (LDA), in the presence of tetrabutylammo- nium fluoride. This resulted in the formation of nitro alcohol derivatives 89 in good or high yields.Silyl ethers of nitro alcohols 90 have been prepared in 30%± 40% yields by treatment of 2-nitropropane derivative 91 with aldehydes.81 The reaction of the silyl ether 87 with aldehyde 92 gives rise to four isomeric nitro alcohols (overall yield 59%, isomer ratio R=Et: R0=4-O2NC6H4, Ph, 4-MeOC6H4, 2-CF3C6H4, 4-MeOCOC6H4, R=Bu: R0=4-O2NC6H4 .(a) BuLi, THF,778 8C, 15 min; (b) R0CHO, TiCl3(OPri), CH2Cl2,778 8C, 1 h; 20 8C, 3.5 h. RCH2NO2 82 R0CHCH(R)NO2 OH 83 a, b CH, Bu, C5H11, But, COOMe; , PhCH MeCH2NO2+PhC PhCHCH(Me)NO2+PhCHCH2CH2NO2 . 84 85 OH OH O H Me2CHNO2+MeCH(CH2)2CHO Cl Et3N, EtOH 577 8C, 2 days; 20 8C, 24 h MeCH(CH2)2CHC(NO2)Me2 , Cl (42.5%) OH O C O H O +O2NCH2CHO Me Et3N 20 8C, 12 h O NO2 OH CHCHCHO O Me Me 86 O O NO2 CCH2 RCH OH R0=ButMe2Si. Bu4N+F7. 3H2O RCHO O MeCCH2 N O O R0O 87 MeCHCH2 NO2 O O 60 RCHO +R0CH2NO2 RCHCH(R0)NO2 OH RCHCH(R0)NH2, OH R2CH2NO2 1. LDA, THF,778 8C 2. Me3SiCl or ButMe2SiCl R1=SiMe3, SiMe2But: R2=C5H11, R3=C6H13 (71 ± 80%); R2=C5H11, R3=But (57%); R2=C5H11, R3=Ph (75783%); R2=C5H11, R3=4-MeOC6H4 (70%); R2=C5H11, R3=4-O2NC6H11 (91%); R2=Et, R3=Pr (82%, erythro : threo=20 : 1); R2=Et, R3=Pri; R2=Pri, R3=Pr; R2=Me, R3=C5H11 (erythro : threo=20 : 1); R2=Et, R3=C5H11 (erythro : threo=20 : 1); R2=C7H15, R3=Pr (erythro : threo=20 : 1); R2=Me, R3=C10H21; R2=Me, R3=C9H19; R2=Et, R3=Ph (erythro : threo=3.5 : 1).+ R2CH O7 OR1 N R3CH(R2)NO2 OH 88 89 R3CHO Bu4N+F7 R=C6H13, But, Ph, 4-MeOC6H4, 4-O2NC6H4. Me2CHNO2 1. LDA, THF,778 8C 2. ButMe2SiCl 91 + Me2C O7 OSiMe2But N 90 Me2CCHOSiMe2But NO2 R RCHO, Bu4N+F7 Table 6. Reaction conditions, yields and isomeric ratios of the nitro alcohols 86. R Nitro- Tempera- Time Yield Ratio compound ture /8C /h (%) erythro : threo Me 87 778 ± 20 15.5 20 56 : 44 Me 87 0 2.3 89 55 : 45 Et 87 0 0.75 74 54 : 46 Me 60 0 ± 6 23 52 62 : 38 42 M-G A Shvekhgeimer58 : 28 :12 : 2).The isomer 93 was isolated from this mixture in a pure state in a yield of 34%.69 The condensation of 1-nitrohex-3-ene 94 with aldehydes catalysed by Amberlyst A-21 occurs successfully at 20 8C; this gives nitro alcohols 95a,b, their yields being 74% and 71%, respectively.84 The reactions of nitroalkanes RCH2CH(R0)NO2 with 4-ethoxybenzaldehyde carried out in the presence of 1,5-diazabi- cyclo[4.3.0]non-5-ene (DBN) give rise to the corresponding nitro alcohols 4-EtOC6H4CH(OH)C(R0)(NO2)CH2R (R, R0 : H, H; H, Me; Me, H).85 Nitro alcohols 96 resulting from the condensation of alde- hydes 97 with methyl 4-nitrobutyrate in the presence of 1,8- diazabicyclo[5.4.0]undec-7-ene (DBU) have been treated in situ with acetic anhydride in the presence of sulfuric acid; the corre- sponding acetates 98 were prepared in this way in 75% yield.86 The reaction of nitroalkenes MeCH(R)CH=CHNO2 (R = H, Me) with propionaldehyde in the presence of DBN is accom- panied by isomerisation of the double bond in the nitroalkene and gives unsaturated b-nitro alcohols EtCH(OH)CH(NO2) ± CH=C(Me)R (R=H, Me).54 To synthesise nitro alcohols 99, a mixture of nitroethane and aldehydes was treated with a mixed acetal of dimethylketene in the presence of [Rh(C5Me5)Cl]2(m-Cl)2 and then with tetrabutylam- monium fluoride.The reaction conditions and the product yields are listed in Table 7.87 c.Reactions of nitroalkanes with ketones Reactions of nitro-compounds with ketones have been much less studied than the nitroaldol condensation involving aldehydes. This is due to some features peculiar to the reactions with ketones. These reactions are often accompanied by spontaneous dehydra- tion of the adducts yielding nitroalkenes, which enter into the Michael reaction with the initial nitro-derivatives. Only few studies dealing with the reactions of nitro-com- pounds with ketones have been published over the last 25 years.The reaction of phenylnitromethane with acetone in the presence of sodium methoxide at 20 8C for 50 h gave the corresponding nitro alcohol, 2-methyl-1-nitro-1-phenylpropan- 2-ol, in a yield of only 10%.59 When nitromethane 1 was made to react with ethyl methyl ketone in the presence of sodium methoxide, the product of nitroaldol condensation, 2-methyl-1-nitrobutan-2-ol 100, was obtained.When this reaction was carried out in the presence of piperidine, 2-methyl-1-nitrobut-2-ene 101 was isolated from the reaction mixture. In the presence of sodium methoxide, 101 reacted with 1,3,5-trioxane being thus converted into nitro alcohol 102.56 The method for the synthesis of b-nitro alcohols from alde- hydes and nitroalkanes developed by Colvin et al.81, 82 and described above proved to be inapplicable to nitroaldol conden- sation between nitroalkanes and ketones.Therefore, a modified procedure for the synthesis of silyl ethers of b-nitro alcohols 103 from 1-nitrohexane and ketones RCOR0 was proposed.81 When trifluoroacetophenone was treated with nitroethane in the presence of an aqueous solution of potassium carbonate for 5 h, nitro alcohol 104 was formed.6 g-Nitro alcohol 105 was synthesised in 77% yield by con- densation of 1-nitropropane with benzophenone in the presence of butyllithium in THF and HMPT at low temperatures.79 O O Me Me C O H 92 +87 Bu4N+F7. 3H2O 0 8C, 3.5 h 93 Me NO2 OH CH Me Me O O CH2 C O O CH(CH2)2 (b). EtCH CHCH2CHCHR NO2 OH 95a,b 94 EtCH CH(CH2)2NO2+RCHO R=Me (a), CH2 R=Me, (CH2)2COOMe. 98 RCH CH(CH2)2COOMe NO2 OAc RCHO +O2N(CH2)3COOMe 97 MeCN DBU Ac2O H2SO4 96 RCHCH(CH2)2COOMe OH NO2 Me EtNO2+RCHO Me2C 2. Bu4N+F7 1. [Rh(C5Me5)Cl]2(m-Cl)2, C(OEt)OSiMe3 RCHCHNO2 . 99 OH (CH2O)3, MeONa MeNO2 NH MeONa EtCCH2NO2 100 MeCH CCH2NO2 Me 101 OH Me MeCEt O CCH(NO2)CH2OH.Me 102 MeCH 7 C5H11C C O7 R R0 NO2 a or b CCHC5H11 OSiMe3 R R0 NO2 103 C5H11CH2NO2 2 equiv. BuLi, HMPT, THF RCR0 O [C5H11C NO2]27 R=R0 =Ph, R,R0 =(CH2)5; (a) Me3SiCl; (b) 1. AcOH; 2. Me3SiCl7(Me3Si)2NH. PhCCF3+MeCH2NO2 K2CO3, H2O 20 8C, 5 h C CF3 OH Ph CHNO2 . Me 104 O EtCH2NO2+Ph2CO Ph2CCH(Me)CH2NO2 . OH 105 BuLi, THF, HMPT 790 to770 8C, 0.5 h Table 7.Reaction conditions and yields of the nitro alcohols 99. R Solvent Number of Yield (%) equivalents of EtNO2 Ph CH2Cl2 5 7 Ph THF 10 16 Ph THF 43 82 a PhCH=CH THF 43 48 PhCH2CH2 THF 43 54 a The ratio syn : anti=39 : 61. Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 43The reactions of 2-arylnitroethanes 76 with ketones in the presence of butyllithium also afford g-nitro alcohols 106 rather than the b-derivatives.77 d.Reactions of 1,1-dinitro- and 1,1,1-trinitro-derivatives with aldehydes In a study dealing with the kinetics and mechanism of the condensation of acetaldehyde with 1,1-dinitroethane or with methyl 2-nitropropionate in DMSO,88 it has been found that the addition of the anions derived from nitro-compounds to the carbonyl group of the aldehyde is the rate-determining step of this reaction.The researchers determined the equilibrium and rate constants of the process, which characterise the basicity and nucleophilicity of the nitronate anions. It was found that there exists a normal correlation between the basicity and nucleophi- licity of the two anions in DMSO: the more basic anion reacts faster than the less basic one.In the presence of alkali, 1,1- dinitroethane reacts with an aqueous solution of formaldehyde to give 2,2-dinitropropan-1-ol in 80% yield.89 Condensation of the potassium salt of 1,1-dinitroethane, formed upon treatment of 1-chloro-1-nitroethane with an aque- ous solution of potassium carbonate for 1 h at 25 ± 30 8C, with excess formaldehyde resulted in the formation of 2,2-dinitropro- pan-1-ol in 20%± 25% yield.90 2-Fluoro-2,2-dinitroethanol 107 was prepared by the reaction of chlorofluorodinitromethane with potassium iodide and form- aldehyde at 70 8C.91 2,2-Dinitro-3-vinyloxypropan-1-ol is formed in 19.2% yield when 2,2,2-trinitroethyl vinyl ether is treated successively with alkaline hydrogen peroxide and with formaldehyde in the pres- ence of sodium hydroxide, and the reaction mixture is then acidified by HCl to pH 2.92 The ether 109 containing an HC(NO2)2 group reacts readily and rapidly with formaldehyde in the presence of sodium hydrox- ide and is thus converted into hydroxymethyl derivative 110.93 Compound 111 containing two HC(NO2)2 groups reacts with two molecules of formaldehyde in the presence of sodium hydro- gencarbonate to give tetrol 112; under the action of a base, it eliminates a glyoxal molecule giving rise to salt 113.The latter reacts with the aldehyde 2 to give 2,2-dinitropropane-1,3-diol 114 in an overall yield of 74%.94 The compound 111 can also react with formaldehyde without a catalyst yielding the tetrol 112, which eliminates a dinitro- methane molecule and CH2O even at 20 ± 30 8C being thus converted into aldehyde 115, which cyclises in situ into tetrahy- drofuran derivative 116.94 When the dipotassium salt of 1,1,2,2-tetranitroethane 117 is made to react with formaldehyde, this gives tetranitrodiol 118, which is cleaved on treatment withKOHto give 2,2-dinitroethane salt. This salt reacts with the aldehyde 2 yielding diol 114.95 The sodium 95 or potassium 96 salts of dinitromethane react with glyoxal to give salts of 1,1,4,4-tetranitrobutane-2,3-diol 119.The salt 119 (Y = Na) is converted into the tetrol 112 by the reaction with formaldehyde.95 Treatment of the salts 119 (Y=Na or K) with 10% sulfuric acid 95 or hydrogen chloride 96 results in the formation of the diol 111 in a yield of 71.8% or 57.2%, respectively.Potassium salts of fluoro-containing dinitroalkanes 120 or tetranitroalkanes 121 react readily with formaldehyde to give the corresponding nitro alcohols 122 or tetranitro-diols 123.97 R, Ar (yield, %): Me, Ph (70); Ph, 4-ClC6H4 (67); (CH2)5 , Ph (69). OH ArCH2CH2NO2+R2CO 106 76 R2CCH(Ar)CH2NO2 BuLi 790 to778 8C, 0.5 h NO¡2 MeC NO2 MeC(NO2)2CH2OH.NO¡2 7Cl7 NO¡2 MeC Cl CH2O H+ NO¡2 MeC OH NO¡2 +MeCHO, MeCHNO2 Cl K2CO3, H2O 25730 8C, 1 h H2O 7HCl NO¡2 MeC Cl F(Cl)C(NO2)2 FC(NO2)2CH2OH. 107 KI, CH2O, EtOH, H2O 70 8C (a) H2O2, NaOH, H2O, MeOH,74 8C; (b) CH2O, H2O; (c) HCl, MeOH, 40 8C. a, b, c (O2N)3CCH2OCH CH2 CHOCH2C(NO2)2CH2OH 108 CH2 F(NO2)2CH2OCH2CH(NO2)2+CH2O NaOH, H2O 18725 8C, 20 min 109 2 FC(NO2)2CH2OCH2C(NO2)2CH2OH. 110 OH OH HOCH2C(NO2)2CHCHCH(NO2)2CH2OH 112 7OHCCHO OH HC(NO2)2CHCHCH(NO2)2+2CH2O 111 2 NaHCO3, H2O 075 8C, 4 h OH 2 7 HOCH2C(NO2)2 HOCH2C(NO2)2CH2OH. H2CO 114 113 30 8C, 15 min; 20 8C, 14 h 111+2CH2O 112 7CH2C(NO2)2,7CH2O HOCH2C(NO2)2CHC 115 116 OH O H HO HO NO2 NO2 O (O2N)2C 2K+ +2CH2O H2O, Et2O 117 C(NO2)2 27 118 HOCH2C(NO2)2C(NO2)2CH2OH KOH +7 KC(NO2)2CH2OH H2CO H2O 7OH7 HOCH2C(NO2)2CH2O7 114 . 7 2(O2N)2CH Y++ C C O H O H YOH, H2O H2SO4, H2O, Et2O, 2 8C or HCl (gas), 075 8C Y=Na, K 112 111 2CH2O, H2O, Et2O Y=Na 119 C(NO2)2 C(NO2)2 CHOH CHOH 27 2Y+ 44 M-G A ShvekhgeimerSynthesis of 2,2,2-trinitroethanol by the condensation of trinitromethane with formaldehyde in the presence 98 or in the absence 99 of CuSO4 has been reported. 2. Synthesis of nitro alcohols by introduction of a nitro group into hydroxyl-containing compounds This route for the preparation of nitro alcohols has not found wide application, because the two existing methods for the introduction of a nitro group into compounds containing a hydroxy group suffer from serious drawbacks restricting their use.One of these methods, namely, treatment of halo-substituted alcohols with some metal nitrites, normally permits preparation only of nitro alcohols containing a primary nitro group.In addition, there are some limitations as regards the use of the initial halohydrins and solvents. The second method, namely, nitration of alcohols, has also found limited use, because only in some cases does it permit the target compounds to be obtained in reasonable yields.The main reaction pathway in this case is the oxidation of alcohols yielding carboxylic acids and the corresponding nitroalkanes. During the last 25 years, the former method has hardly been used to synthesise aliphatic nitro alcohols. It was not until 1987 that the synthesis of 12-nitrododecan-1-ol (yield 79.5%) by the Meyer reaction of 12-iodododecan-1-ol was reported.100 Over the period of time considered, only in rare cases has nitration of alcohols been used to prepare nitro alcohols; for example, nitro alcohols 124 have been obtained in this way by treating alcohols 125 with dinitrogen tetroxide.101 The reaction of Ph2C(OH)Et withN2O3 orN2O4 at 20 ± 25 8C in chloroform affords nitro alcohol Ph2C(OH)CH(Me)NO2 in a yield of 47% or 62%.When the same alcohol is treated withN2O5 in chloroform or with HNO3 (20 8C, 1 h; 80 8C, 4 h), nitration involves not only the side chain but also the aromatic ring and the hydroxy group and results in the formation of O2NC6H4C(Ph)(O- NO2)CH(Me)NO2 (yields 35% and 70%, respectively).102 An original method for the synthesis of nitro alcohol 126 reported in a patent 103 consists of the transformation of butyne- 1,4-diol into 1,4-dihydroxybutan-2-one by the Kucherov reaction followed by replacement of the b-hydroxyl with respect to the carbonyl group by a fluorodinitromethyl group by treatment with fluorodinitromethane. 3. Synthesis of nitro alcohols by introduction of a hydroxy group into compounds containing a nitro group Syntheses of nitro alcohols by this route can be clearly divided into two groups: (a) formation of a hydroxy group in nitro-compounds from other oxygen-containing groups incorporated in the initial molecule and (b) the formation of nitro alcohols from nitro- compounds containing no oxygen-containing groups. a.The formation of a hydroxy group from other oxygen-containing groups present in nitro-compounds The reaction of unsaturated nitro ketones 127 (A = C=CH) or saturated nitro ketones (A = CHCH2) with lithium aluminium hydride at 20 8C and at a LiAlH4 : 127 ratio of 1 : 4 involves only transformation of the carbonyl group into a hydroxy group and affords nitro alcohols 128 (yields 64%± 95%).104 When nitro ketones 129 containing an epoxy group are reduced with lithium aluminium hydride, the structure of the reaction product depends on the LiAlH4 : 129 ratio.When this ratio is 1 : 4, only the carbonyl group is reduced, and nitro alcohols 130 are formed (yields 67% and 74%); at a ratio of 1 : 2, cleavage of the epoxide ring occurs, in addition to the reduction of the carbonyl group, and the process gives nitro-diols 131.104 Unsaturated nitro alcohols 132 have been synthesised in 62%± 68% yields by the reduction of nitro ketones 133 with lithium aluminium hydride at 715 8C and at an LiAlH4 : 132 ratio of 1 : 4.105 Ketone 134 is converted into nitro alcohol 135 in 71% yield on treatment with sodium tetrahydridoborate.32 R=C6F13 (36%); C10F21 (62%); n=4 (55%), 6 (75%).RCH2C(NO2)¡2 K++CH2O 120 RCH2(NO2)2CH2OH 122 2 H2O 20 8C, 2 h HOCH2CCH2(CF2)nCH2CCH2OH NO2 NO2 123 NO2 NO2 + 7 7+ 2 121 H2O 20 8C, 2 h NO2 NO2 K CCH2(CF2)nCH2C K+2CH2O NO2 NO2 I(CH2)12OH+AgNO2 O2N(CH2)12OH.Et2O, in the dark 20 8C, 18 h R=H: R0=Me, Et, Bu; R =R0 =Me. 125 124 (53% ± 62%) N2O4, ClCH2CH2Cl 710 8C, 1 h; 22 8C, 12 h Ph2CH OH CRR0 NO2 Ph2CHCHRR0 OH HOCH2CH2CCH2OH O F(NO2)2CH, N2 HOCH2C CCH2OH+H2O HgSO4, H2SO4 50 8C, 1 h FC(NO2)2CH2CH2CCH2OH. 126 O Me2AC(CH2)2CRR0 127 Me2ACH(CH2)2CRR0 OH 128 O NO2 LiAlH4, Et2O 20 8C, 1 h NO2 R=H, Me; R0=H, Me, Et, Pr; A =C CH, CHCH2.O CHC(CH2)2C(R)Me Me2C O 129 NO2 R=H, Me. LiAlH4, Et2O 20 8C, 1 h 131 (62%) Me2CHCH2CH(CH2)2C(R)Me OH OH NO2 O CHCH(CH2)2C(R)Me Me2C OH 130 (61%) NO2 R=H, Me, Cl, Br. 4-RC6H4CHCH 132 OH O2N HC 715 8C, 1.5 h LiAlH4, Et2O 133 4-RC6H4CCH O O2N HC Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 45The outcome of the reduction of esters 136 with sodium tetrahydridoborate depends on the nature of the radical R; if R=PhCH2, the reaction gives rise to the nitro alcohol 107 (yield 70%), whereas with R=Me2CH, hemiacetal 137 is formed.106 When cyclic a-nitro ketones 138 are treated with sodium tetrahydridoborate, the reduction is accompanied by ring opening and yields nitro alcohols 139.107 3-Nitropropanal was converted into 3-nitropropan-1-ol in 89% yield by treatment with the complex BH3 .SMe2 in Et2O at 20 8C for 4 h under a nitrogen atmosphere.108 Nitro alcohol 140 was synthesised in 77.5% yield by the reduction of 5-nitropentan-2-one with diborane in THF.31 The reaction of tetrahydrofuran derivatives 141 with borane in THF results in ring opening and formation of diols 142.109, 110 Nitro ketone 143 was converted into nitro alcohol 144 in 72% yield on treatment with SnCl4 and Et3SiH at 0 8C.66 The reduction of the compounds RCOCH(R0)(CH2)2NO2 (R, R0 = Me, H;111 Ph, H; MeO, 2-MeOC6H4 112) in the presence of baker's yeast occurs stereoselectively to give (S)-nitro alcohols as the major products; the highest stereoselectivity (99%) is observed in the case of R=MeO, R0 =2-MeOC6H4.111, 112 When epoxide 145 (R = Me) is heated in water at 50 8C, the corresponding diol MeCH(OH)CH(OH)CH2NO2 is formed in 56% yield.113 Heating of 145 in aliphatic alcohols leads to ethers 146 (yields 55%± 68%).113 In the presence of triethylamine at 18 ± 20 8C, the epoxide 145 (R=Me) isomerises into the unsaturated nitro alcohol MeCH(OH)CH=CHNO2 (yield 62%).113 2,3-Epoxy-1-nitropropane reacts with hydrazines RC6H4NHNH2 (R=2-NO2, 4-NO2) at 20 8C in aqueous ethanol affording 2- or 4-O2NC6H4NHNHCH(CH2OH) ±CH2NO2 in 86% yield.114 Epoxides 147 with a more complicated structure have been converted into mixtures of unsaturated nitro alcohols 148 and 149 in four ways: by treatment with triethylamine in aqueous acetoni- trile (procedure A); in the presence of alumina in diethyl ether and in dichloromethane (procedure B); at 25 8C over silica gel (proce- dure C); over aluminium isopropoxide (procedure D) (Scheme 2).115 The reaction conditions and the yields of the alcohols 148 and 149 are listed in Table 8.Scheme 2 On treatment with hydrohalic acids, 3-fluoro-3-nitrooxetane 150 is converted into nitro alcohols 151 in high yields (96.5% and 93.1%), whereas on treatment with phosphorus trifluoride, it is converted into polymer 152 (yield 82.6%).49 O2NCF2CCF3 134 O O2NCF2CHCF3 .Et2O. 135 OH 5720 8C, 15 min NaBH4, Et2O FC(NO2)2CH2OH 107 FC(NO2)2CHOH OCHMe2 137 a R=PhCH2 b R=Me2CH F2C(NO2)COOR 136 (a) NaBH4, THF, H2O, 10712 8C, 0.5 h; (b) NaBH4, (MeOCH2)2, 20725 8C, 0.5 h.O NO2 R 138 (CH2)n R=H, n=0710 (50%785%); R=But, n=1 (75%). HO(CH2)3CH(CH2)nCH2NO2 139 R NaBH4, MeCN H2O, 0 8C, 4 h O2N(CH2)3CMe O2N(CH2)3CHMe. O 140 BH3 .THF 20 8C, 172 h OH R1=NO2, R2=H, R3=OH (35 8C, 72 h, 98%);109 R1=F, R2=H, R3=OH (25 8C, 24 h, 100%);109 R1=NO2, R2, R3=O (35 8C, 72 h, 98%).110 O R2 R3 R1(NO2)2C HOCCH2CHCH2OH R2 R3 142 141 BH3 .THF, N2 C(NO2)2R1 C(CH2)2CMe NO2 F3C Me 143 O C(CH2)2CHMe. NO2 F3C Me 144 OH SnCl4, Et3SiH CH2Cl2, 0 8C, 2 h R=H; R0 =Me, Et, Pri; R=Me, R0 =Me, Pri. 145 O CHCH2NO2+R0OH RCH refluxing RCHCH(OR0)CH2NO2 OH 146 CCHR0 OH RCH 149 CH2NO2 148 RCH2CCHR0 + OH CHNO2 O CHR0 RCH2C CH2NO2 147 HX, H2O 20 8C, 0.571 h X=Cl, Br. PF3, CH2Cl2 O F NO2 150 XCH2CCH2OH F NO2 151 HO CH2CCH2O H n 152 F NO2 Table 8.Reaction conditions and yields of the nitro alcohols 148 and 149. R R0 Time/ h Yield of (148+149) (%) Yield of 148 (%) E/Z Ratio in 148 A B C D A B C D A B C D A B C D H Me 2 2 2 7 97 92 92 7 16 15 0 7 7 7 78/22 7 H Et 2 4 4 7 82 96 96 7 15 11 0 7 7 7 78/22 7 H C5H11 2 4 5 7 89 82 84 7 33 18 0 7 7 7 80/20 7 H Pri 2 3 3 7 90 87 83 7 17 15 0 7 7 7 84/26 7 Me Me 7 3 2 7 7 85 85 7 7 9 0 7 7 7 65/35 7 Et Et 7 4 48 1 7 86 0 80 7 7 7 traces 7 7 7 70/30 Bu Bu 7 5 48 1 7 80 0 83 7 2 7 traces 7 83/17 7 71/29 46 M-G A ShvekhgeimerKetone 153 has been treated with ketene diethyl acetal at 730 8C; this gave compound 154 (yield 88%). Acid 155 was synthesised by reaction of the ketone 153 with malonic acid in the presence of pyridine.This acid was converted in situ into ester 156 (yield 48%) by reaction with ethanol in the presence of sulfuric acid.116 When the trinitromethane derivative Hg[C(NO2)3]2 is refluxed with an aqueous solution of formaldehyde, the HgC(NO2)3 group is substituted resulting in the formation of 2,2,2-trinitroethanol in 95% yield.117 On heating with formalin at 60 ± 70 8C for 20 h, compounds of the formula (O2N)3CCH(R)CH2HgC(NO2)3 (R=H, Me) eliminate an alkene and are thus converted into 2,2-dinitropro- pane-1,3-diol 114 in 91% yield.117 b.Formation of a hydroxy group in nitro compounds containing no oxygen-containing groups The rates of hydration of CH2=CHNO2, MeC(NO2)=CH2, MeCH=CHNO2 and MeC(NO2)=CHMe have been studied by spectrophotometry at 40 8C and pH 6 in an AcOH±Me2CO buffer solution.The effective pseudo-first-order rate constants for these reactions were found to be (78.82.2)1073, (6.50.1)1073, (57.81.0)1073 and (5.70.15)1073 min71, respectively. The rate of formation of the corresponding nitro alcohol depends on the charge on the b-carbon atom in the p-system and also on the steric effect of the b-substituent.118 Having studied the kinetics of hydration of nitroethylene in buffer solutions by spectrophotometry, Fakhrutdinov et al.119 proposed the following scheme for this process: It was found that the rate of hydration increases with an increase in the pH, and at a constant pH it increases with an increase in the concentration of the base in the solution.At low pH, the reaction rate is limited by deprotonation of CH2(áOH2) ¡CHNO2, whereas at high pH, it is limited by the interaction of the nitroalkene with water.It was found that at pH = 0.96, 2.01, 2.98, 6.00 and 7.15, the activation energies of hydration are 10.9, 14.1, 15.2, 13.5 and 11.1 kcal mol71, respectively, and the corresponding activation entropies are 743.0, 730.1, 729.2, 726.4 and735.4 e.u., respectively.119 The kinetics and mechanism of hydration of 1-nitroprop-1- ene have been studied.120 The researchers proposed the following scheme for this process: At low pH and a low buffer capacity, the reaction rate is limited by proton abstraction, and when these parameters are increased, the interaction of the nitroalkene with water becomes the rate-determining step of the process.120 g-Nitro alcohols 157 have been synthesised by radical addition of aliphatic alcohols to nitroalkenes 158 in the presence of tert- butyl peroxide at 150 8C.121 Treatment of 3-fluoro-3,3-dinitropropylammonium sulfate with sodium nitrite in an acid medium yields 3-fluoro-3,3-dini- tropropan-1-ol in 56% yield.122 When tetranitroalkane 159 reacts with potassium iodide in methanol, in parallel with the replacement of one of the nitro groups by potassium, replacement of one more nitro group by a hydroxy group occurs, and the reaction affords the nitro alcohol salt 160.123 Unexpectedly, the reaction of an excess of nitroalkanes 161 with methyl bromoacetate in the presence of sodium methoxide in dimethylacetamide resulted in the formation of compounds 162.124 Evidently, the compounds 162 result from the condensation of nitroalkanes RR0CHNO2 with methyl glyoxylate generated according to the following scheme:124 4.Synthesis of nitro alcohols by simultaneous introduction of nitro and hydroxy groups Reactions of alkenes with nitrogen oxides are used most often for the synthesis of nitro alcohols with simultaneous introduction of NO2 and OH groups to vicinal positions.O2NCF2CCH2COEt 156 CF3 OH O O2NCF2CCF3 O 153 O2NCF2CCH C(OEt)2 154 CF3 OH refluxing for 25 h O2NCF2CCH2COH 155 CF3 OH O EtOH, H2SO4 CH2(COOH)2 C5H5N 730 8C, 2 h 20 8C, 0.5 h CH2 C(OEt)2 + 7 CH2(OH2)CHNO2+B 7 CH2(OH)CHNO2+BH+, HOCH2CH2NO2+B. 7 CH2(OH)CHNO2+BH+ CH2 CHNO2+H2O 7 + CH2(OH2)CHNO2 , MeCH CHNO2+H2O k1 k71 + 7 MeCHCHNO2 , OH2 + 7 MeCHCHNO2+B OH2 k2 k72 7 MeCHCHNO2+BH+, OH k3 k73 7 MeCHCHNO2+BH+ OH MeCHCH2NO2+B.OH R0 =Me: R=C5H11 (28%), Pr (11%), Bu (20%); R0 =Et: R=Pr (6%). RCHCH(R0)CH2NO2 OH 157 RCH2OH+O2NCH CHR0 158 (ButO)2 150 8C, 12715 h FC(NO2)2CH2CH2NH2 .H2SO4 NaNO2, H2O (pH 1.271.5) 60 8C, 1.5 h FC(NO2)2CH2CH2OH. 7 + KC(NO2)2CH2CCH2COH. 160 Me Me Me Me (O2N)3CCH2CCH2CNO2 159 Me Me Me Me KI, MeOH 20725 8C, 2 days R=Me: R0 =Me (48%), Et (52%); R=H: R0=Et (11%), Ph (68%). 161 RR0CHNO2+BrCH2COOMe RR0CCHCOOMe NO2 OH 162 MeONa 20 8C, 12 h + + 7 7 7 RR0C N O ONa BrCH2COOMe + RR0C N O OCH2COOMe RR0C NOH+HCCOOMe.O Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 47The nitro alcohol C12H25CH(OH)CH2NO2 (yield 10%) and its nitrate C12H25CH(ONO2)CH2NO2 (yield 86%) have been prepared by the reaction of C12H25CH=CH2 with N2O4 in CCl4 in the presence of sulfuric acid at 0 ± 5 8C for 0.5 h.125 The nitro alcohol Ph2C(OH)CH(Me)NO2 has been synthes- ised by the reactions of the alkene Ph2C=CHMe with N2O4 (CHCl3, 20 ± 25 8C, 6 h), N2O3 (CHCl3, 20 8C, 17 h) or HNO3 (d 1.51, CHCl3, 100 8C, 4 h), the yields of the product being 56%, 46% or 50.8%, respectively.103 When the same alkene was treated with N2O5 (CHCl3, 18 8C, 12 h), the product O2NC6H4 ± (Ph)C(ONO2)CH(Me)NO2 containing a nitro group instead of a hydrogen atom in one of the benzene rings was obtained in 32.2% yield.102 The reactions of various alkenes with NO2 in hexane at 20 8C have been studied in detail.Nitro alcohols and their derivatives 163 ± 170 were synthesised in this way.126 The formation of the compounds 165, 166 and 168 was explained 126 in terms of the following scheme: Diethyl vinylphosphonate 171 readily reacts with N2O4 in dichloromethane to give nitro alcohol 172 (yield 34%).127 2-Hydroxy-3-nitropropionic acid was synthesised in 60% yield by the reaction of acrylic acid with N2O4 in dichloroethane at 18 ± 20 8C over a period of 10 h.128 Nitro alcohol 173 is formed in 23% ± 25% yield in the reaction of nitrogen oxide with 4-phenylbut-1-ene in various solvents (dichloroethane, tetrachloromethane or benzene) at 20 8C.129 Simultaneous introduction of NO2 and OH groups into alkenes 174 was accomplished by treating them with alkyl nitrites with heating in acetic acid under an inert atmosphere; the yields of nitro alcohols 175 were 20%± 33%.130 The synthesis of compound 176 (yield 55%) from alkene 177 was carried out using acetyl nitrate formed in situ from Ac2O and HNO3.131 The reaction of isoprene with acetyl nitrate at 20 8C affords a mixture of nitroalkenyl acetates 178 and 179 in a ratio of 7 : 3.132 Treatment of unsaturated ketones 180 with nitronium tetra- fluoroborate at 730 8C in a solution in SO2 followed by treat- ment with water gives compounds 181 in low yields.133 An original method has been proposed 134 for the synthesis of dichloro-substituted nitro alcohols 182.It is based on the reaction of trichloronitromethane with aldehydes in the presence of SnCl2. Me2CC(ONO)Me2+ NO2 163 (17%) 20 8C, 5 min NO2 . +Me2CC(ONO2)Me2+O2NCH2C(Me)C(NO2)Me2 , 164 (3%) 165 (3%) NO2 OH 20 8C, 5 min NO2 .CHEt Me2C CMe2 Me2C 167 (36%) O2NCH2C(Me)CHEt+Me2CCH(OH)Et , 166 (8%) OH NO2 NO2 CHBu CH2 170 (48%) O2NCH2CHBu . 20 8C, 5 min NO2 . CEt2 CH2 20 8C, 5 min NO2 . 169 (47%) OH 168 (4%) O2NCH2C(Et)CHMe +O2NCH2CEt2 , OH NO2 OH C C CH2R NO2 C C CH2 NO2 R NO2 . . C C CH NO2 R NO2 C C CH NO2 R NO2 NO2 . . C C CH NO2 R NO2 ONO C C CH NO2 R. NO2 OH (EtO)2PCHCH2NO2 . 172 N2O4, CH2Cl2 0720 8C, 3 h (EtO)2PCH CH2 171 O O OH Ph(CH2)2CH CH2 Ph(CH2)2CHCH2NO2 . OH 173 NO 20 8C R1R2C CHR3 174 R1, R2, R3: Ph, Ph, H; Me, Ph, H; Me, COOMe, H; Et, Et, Me. AlkONO, AcOH, N2 115 8C, 30750 min R1R2C 175 CHR3 OH NO2 1. Ac2O, HNO3, 10 8C, 1 h 2. H2O, 20 8C, 12 h 177 O2N NO2 N N N CH2C CHMe Me 176 O2N NO2 N N N CH2CCH(Me)NO2 . OH Me CH2 C CH CH2 Me AcONO2 20 8C, 1 h O2NCH2C CHCH2OAc+O2NCH2CCH CH2 . 178 179 Me Me OAc R=Me (4%), Pr (17%), Pri (34%). 180 + 1. NO2BF¡4 , SO2, CH2Cl2730 8C, N2 2. H2O RC(CH2)2C CH2 Me O RC(CH2)2CCH2NO2 181 OH Me Cl3CNO2 SnCl2, Et2O 0 8C ClCNO2 SnCl3 Cl RCHO 4 h 48 M-G A ShvekhgeimerThe reaction of ethyl 4-methylpent-2-enoate 183 with nitryl chloride or nitrosyl chloride yields nitrite 184, which is converted into compound 185 on refluxing with water, the overall yield of the latter being 34%.74 III.Chemical transformations of nitro alcohols 1. Reactions involving the nitro group The reduction of 2-nitrobutan-1-ol in the presence of Raney nickel at 35 ± 40 8C under a hydrogen pressure of 10 atm results in the formation of 2-aminobutan-1-ol in 62%± 74% yield.44, 135 The same catalyst is effective in the reduction of nitro alcohols 186 to amino alcohols 187 (Table 9).66 Raney nickel has also been used to reduce the compounds PhCH(OH)(CH2)2NO2 and Ph2CHCH(OH)CH2NO2 to amino alcohols PhCH(OH)(CH2)2NH2 (yield 49%) and Ph2CH± CH(OH)CH2NH2 (yield 18%).79 The reduction of the erythro-isomers of silyl ethers of nitro alcohols in the presence of Raney nickel occurs stereoselectively; treatment of the reaction mixture with Bu4N+F7 gives the erythro-isomers of amino alcohols 188.82 2-Hydroxymethyl-2-nitropropane-1,3-diol 4 is converted into the amine H2NC(CH2OH)3 (yield 89%) by hydrogenation in the presence of the Pd/C catalyst at 59 ± 63 8C for 4.5 h.136 When 4-MeOC6H4CH2C(OH)(Et)NO2 is reduced with ammonium formate in the presence of Pd/C in THF and MeOH, the amino alcohol 4-MeOC6H4CH2C(OH)(Et)NH2 is formed in 73% yield.137 The amino-diols HOCH2C(R)(NH2)CH(OH)C13H27 (R = H, Me) have been synthesised in high yields (83% and 86%) by the reduction of the corresponding nitro-diols with ammonium for- mate in the presence of Pd/C in MeOH at 20 8C for 16 h under an atmosphere of nitrogen.61 An active catalyst of reduction, Ni2B, which is formed in situ from NiCl2 . 6H2O and NaBH4, has been used to convert the nitro alcohol O2NCMe2(CH2)2CH(OH)Me into the corresponding amino alcohol (yield 76%). The reaction occurs in MeOH at 20 8C over a period of 5 min.138 Reduction of nitro alcohols to amino alcohols with hydrogen has also been carried out in the presence of a number of rhodium- containing catalysts. For example, 2-nitrobutan-1-ol has been converted into 2-aminobutan-1-ol by hydrogenation in the pres- ence of di(rhodiumnorbornadienechloride) and Ph2PCH2CH(PPh2)Me at 60 8C under a hydrogen pressure of 67 atm for 20 h.139 The reduction of 2-nitrobutan-1-ol to 2-aminobutan-1-ol catalysed by rhodium-, iridium- and palladium-containing sys- tems has been studied in detail (Table 10).140 Nitro glycols 189 have been hydrogenated at 80 ± 100 atm in the presence of Ru/C catalyst or Raney Ni ± Ru for 2 ± 5 h; this gave amino glycols 190 in 78%± 96% yields.141 Hydrogenation of the nitro alcohols 4-RC6H4CH(OH). .CH2NO2 (R = H, Me, Cl) in the presence of PdO2 in 80% AcOH at 1 atm gives rise to the corresponding amino alcohols RC6H4CH(OH)CH2NH2 in 59%, 50% and 63% yields, respec- tively.26 The nitro groups in nitro alcohols and their derivatives 191 and 192 have been reduced to amino groups using LiAlH4.23, 25, 81, 83, 142 R=H (67%), Me (76%), Et (82%), Pr (83%), Bu (92%), C5H11 (85%), Ph (52%), CCl3 (77%), 4-MeC6H4 (57%), 4-ClC6H4 (59%), 2-furyl (53%), 2-thienyl (61%). O2NC CHR OSnCl3 Cl Cl H3O+ O2NC CHR OH 182 Cl Cl Me2CHCHCHCOOEt NO2 ONO Me2CHCHCHCOOEt .NO2 OH 185 184 D, 5.5 h H2O CHCOOEt 183 Me2CHCH NO2Cl, PhH, 0 8C, 5 h; 20 8C, 3 days or NOCl, PhH, 0 8C, 3 h; 20 8C, 5 days H2, Raney Ni, EtOH 24 h F3CC(R)CHR0. 187 OH NH2 F3CC(R)CHR0 186 OH NO2 R, R0: Pr, Et; Pri, Et; C5H11, Me; C5H11, Et; Pr, C7H15; C10H21, Me; C9H19, Me; Ph, Et. RCHCHR0 OSiMe2But NO2 188 RCHCHR0 OH NH2 1. H2, Raney Ni 2. Bu4N+F7 EtCHCH2OH EtCHCH2OH. NH2 H2, Cat., EtOH 65 atm NO2 R=H, Me, Et, CH2OH.HOCH2CCH2OH 189 R NO2 H2, Ru/C or (Raney Ni) ±Ru 275 h HOCH2CCH2OH 190 R NH2 Table 9. Reaction conditions and yields of the amino alcohols 187. R R0 Pressure /atm Temperature /8C Yield (%) H Pr 1 20 52 H C6H13 25 50 76 H Ph(CH2)2 1 20 79 H PhCHMe 25 50 82 H Pr 30 50 59 Me Pr 30 50 5 Me C6H13 25 50 22 Me Ph(CH2)2 25 50 53 Table 10. Hydrogenation of 2-nitrobutan-1-ol.140 Catalyst Phosphine Catalyst: Time/h Tempera- Yield phosphine ture/ 8 (%) Rh2Cl2(NBD)2 a see b 1 : 1 20 60 78 Rh2Cl2(NBD)2 PPh3 1 : 1 16 50 36 Rh2Cl2(NBD)2 DIOPc 1 : 1 65 80 57 Ir2Cl2(COD)2 d PPFA e 1 : 2 16 50 67 Ir2Cl2(COD)2 BPPFA f 1 : 2 16 50 56 Ir2Cl2(COD)2 DIOP 1 : 2 16 50 54 Ir2Cl2(COD)2 DIPHOS g 1 : 2 16 50 47 PdCl2(COD)2 DIPHOS 1 : 2 18 75 24 PdCl2(PhCN)2 BPPFOH h 1 : 1 18 75 41 a NBD�norbornadiene; b Ph2PCH2CH(Me)PPh2; c DIOP�(S,S)-2,3- O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane; d COD � cyclooctadiene; e PPFA � (R)-a-[(S)-2-(diphenylphosphino)- ferrocenyl]ethyldimethylamine; f BPPFA � (R)-a-[(S)-2,10-bis(diphenyl- phosphino)ferrocenyl]ethyldimethylamine; g DIPHOS � bis(1,2-di- phenylphosphino)ethane; g BPPFOH � (R)-a-[(S)-2,10-bis(diphenyl- phosphino)ferrocenyl]ethane.Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 49When unsaturated nitro ketones 193 are reduced with a twofold excess of lithium aluminium hydride, the nitro groups are converted into amino groups, whereas the carbonyl groups are reduced to hydroxy groups; thus, the reaction yields amino alcohols 194.104 Nitro-diols 195 have been converted into amino-diols 196 by treatment with zinc and hydrochloric acid in ethanol.143 Electroreduction of 2-methyl-2-nitropropane-1,3-diol giving 2-amino-2-methypropane-1,3-diol in 99% yield has been patented.144 Nitro alcohols or nitro-diols 197 have been converted into the corresponding amino-derivatives 198 by electroreduction at bimetallic electrodes consisting of copper deposited on zinc or cadmium.145 Electroreduction of the triol 4 in the presence of sulfuric acid at 75 ± 80 8C and at a current density of 0.1 A cm72 for 12 ± 13 h affords amino-derivative H2NC(CH2OH)3 in 40%± 50% yield.6 The hydrochloride (HOCH2)3CNH2 .HCl has been synthes- ised by electroreduction of the triol 4 at a perforated palladium cathode at 75 ± 80 8C in the presence of 6.5% HCl.146 Electroreduct3-hydroxy-2-nitrobutyrate giving rise to the DL-threonine ester 199 (substance yield 72%± 77%; current yield 7%± 10%) can be described by the following scheme:147, 148 Treatment of nitro alcohol acetates 200 with tributylstannane in the presence of azobis(isobutyronitrile) in boiling benzene results in the replacement of the nitro group by a hydrogen atom.48 R R0 Yield (%) PrCO Et 74 PriCO Et 75 C5H11CO Me 83 C6H13CO Me 84 EtCO C5H11 83 C6H13CO (CH2)2COMe 85 C6H13CO (CH2)2COOMe 80 COOMe (CH2)2CH(OAc)Me 88 COOMe (CH2)2COOEt 83 The reduction of the nitro group in an acetate of a more complicated structure occurs under the same conditions.48 The researchers cited 48 proposed yet another method for the introduction of a hydrogen atom instead of the nitro group in nitro alcohol acetates 201.The method involves treatment of 201 with 1,8-diazabicyclo[5.4.0]undec-7-ene in boiling benzene. 2. Reactions involving hydrogen atoms attached to a carbon atom carrying nitro groups Nitro alcohols containing one or two hydrogen atoms at the carbon atom carrying the nitro group are able to enter into nitroaldol condensation.The reaction of the salt [7O2N=CHCH(OH)CH(OH)CH=NO72 ] 2Na+ with formalde- hyde at 0 ± 5 8C and pH=10 in Et2O gives the tetrol HOCH2C(- NO2)2CH(OH)CH(OH)C(NO2)2CH2OH.95 The reactions of salts derived from 2-nitropropane-1,3-diol 3 or from 2-nitropropan-1-ol with an aqueous solution of form- aldehyde have been studied.149 Reversible reactions give 2- hydroxymethyl-2-nitropropane-1,3-diol 4 or 2-methyl-2-nitro- propane-1,3-diol, respectively.R1CHCH(R3)NO2 191 OR2 LiAlH4, Et2O, N2 R1CHCH(R3)NH2 OR2 R1=Ph, R2=H, R3=H (55%);23 R1=Ph, R2=H, R3=Me;23 R1=PhCH2 , R2=H, R3=H (28%);25 MeO R1= , O R2= , R3=H (80%);142 O R1CHC(NO2)R3R4 192 OR2 1. LiAlH4, Et2O, 36 8C, 5 h 2. Na2SO4, H2O R1CHC(NH2)R3R4 (50%785%) OH R2=SiMe3 or SiMe2But; R3=H, Me; R4=C5H11, Me.81, 83 R1=C6H13, But, Ph, 4-MeOC6H4, 4-O2NC6H4; R=H (35%), Me (37%), Et (38%).CHCH(CH2)2CHR OH 194 Me2C CHC(CH2)2CHR O 193 NO2 LiAlH4, Et2O 20 8C, 1 h Me2C NH2 R=C7H15 (25%), C9H19 (33%), C11H23 (38%), C13H27 (40%). 196 RCHCHCH2OH NH2 OH 195 RCH(OH)CHCH2OH NO2 Zn, HCl, H2O, EtOH R1, R2: H, Me; Me, CH2OH; H, Et; Et, CH2OH. R1R2C(NO2)CH2OH 197 R1R2C(NH2)CH2OH 198 CHCOOMe NO2 MeCH OH 2H+, 2e7 CHCOOMe NO MeCH OH 2H+, 2e7 CHCOOMe N HOH MeCH OH 2H+, 2e7 CHCOOMe NH2 199 MeCH OH 4H+, 4e7 NOH CCOOMe MeCH OH RR0C(NO2)CH2OAc 200 Bu3SnH, AIBN, PhH 80 8C, 2 h RR0CHCH2OAc EtOOC(CH2)2C(NO2)(COOMe)CH2OAc Bu3SnH, AIBN, PhH 80 8C, 2 h EtOOC(CH2)2CH(COOMe)CH2OAc.(83%) R=Me (66%), Et (71%), Pr (88%), Pri (83%), Bu (78%). RCCOOEt CH2OAc NO2 201 DBU, PhH 80 8C, 5 h RCHCOOEt CH2OAc HC(CH2OH)2NO¡2 +CH2(OH)2 K1 O2NC(CH2OH)3+OH¡ 4 MeC(CH2OH)2NO¡2 +CH2(OH)2 K2 HOCH2C(NO2)CH2OH+OH7. Me 50 M-G A ShvekhgeimerThe equilibrium constants K1 and K2 are (4.30.4)61073 and (3.60.2)61072, respectively.The characteristics of these reac- tions are retained over a broad range of concentrations: [CH2(OH)2]=0.058 ± 3.06 M and [OH7]=1.81072 ± 0.36 M.In the presence of Dowex-1 anion-exchange resin, the con- densation of nitro alcohols with formaldehyde or acetaldehyde at 20 8C is completed over a period of 1 ± 2 h.150 2-Nitroethanol 202 reacts with aliphatic aldehydes in the presence of sodium methoxide to give salts 203 (yields 67%± 99%), which are converted into nitro-diols 204 (yields 91%± 98%) on treatment with hydrochloric acid.143 Alumina (Brockmann activity I) has been used as the catalyst in the condensation of nitro alcohols 205 with aldehydes.69 The reaction of the nitro alcohol 202 with benzaldehyde in the presence of triethylamine at 0 8C is completed over a period of 23 h resulting in the formation of DL-threo-2-nitro-3-phenylpro- pane-1,3-diol (yield 98.7%).151 The reaction of furfural with 1-nitropropan-2-ol in the pres- ence of triethylamine gave the corresponding nitro-diol 206 in a yield of only 35%.152 The condensation of the nitro alcohol 202 with hexadec-2-enal in the presence of K2CO3 or Et3N at 20 8C affords nitro-diol 207 and a minor quantity of the product of its cyclisation 208.153 When this reaction is carried out in methanol in the presence of K2CO3 at 20 8C, the tetrahydropyran derivative 208 (yield 50%) is formed together with compound 209 (yield 12%) (see Scheme 3).153 On treatment with butyllithium, compounds 210 were con- verted into the corresponding lithio-derivatives. Condensation of the latter with carbonyl compounds R1R2C=O followed by hydrolysis of the condensation products gave nitro-diols 211 in 52%± 88% yields.154 A single diastereoisomer of nitro-tetrol 212 was obtained in a similar way from compound 213 and benzaldehyde (yield 73%).154 Aldehydes have been made to condense with 4-nitrobutan-2- ol in the presence of the Amberlyst A-21 ion-exchange resin at 0 8C for 15 h.This resulted in the formation of nitro-diols 214 (yields 45%± 70%).155 Dinitro-diols 215 have been prepared in two stages, namely, by the reaction of salts 216 with nitroalkenes 217 and subsequent treatment of the resulting reaction mixtures with formaldehyde in the presence of phosphorous acid at pH 6 ± 5.5.156 The reaction of 1-nitropropane with formaldehyde in the presence of Ca(OH)2 in water at 30 8C for 1 h followed by treatment of the reaction mixture with bromine in CCl4 at 20 8C gives rise to 2-bromo-2-nitrobutan-1-ol in 90% yield.35 R1=R2=Me, R3=H (63%); R1=Bu, R2=H, R3=Me (79%); R1=Me, R2=H, R3=H (91%).R1 CH(OH)CH2NO2 R2 R3CHO R1 C(OH)CHCHOH R2 NO2 R3 O2NCH2CH2OH+RCHO 202 MeONa, MeOH 6724 h R=C7H15, C9H19, C11H23, C13H27. RCHCH(NO2)CH2OH. OH 204 HCl, H2O 7 C CH2OH 203 RCH OH + NO2Na R, R0: Me, MeCH(OH)CH2; Et, (CH2)6OH; Et, CH2OH.RCHO +R0CH2NO2 205 Al2O3 20 8C, 24 h RCH(OH)CH(NO2)R0 CHCH(NO2)CHMe . OH OH 206 +MeCHCH2NO2 OH Et3N O O C H O O OCH2CHR3 NO2 210 C6H14 BuLi 2. H3O+ 1. R1R2C O R1R2C CCH2OH R3 NO2 211 OH O OCH2CLi NO2 R3 R1, R2, R3: H, Pri, H; H, Br, H; H, , H; trans-PhCH CH, H, H; H, C13H27C C, H; H, Ph, H; H, 4-MeOC6H4, H; Me, Ph, H; H, (S)-MeCH2CH(Me), H; H, Pri, Me; H, 4-CNC6H4, H; H, , Me; H, Ph, Me; R1,R2=(CH2)5, R3=H, Me.(a) BuLi, THF, HMPTA790 to740 8C, 3 h; (b) PhCHO,790 to760 8C, 1.5 h; (c) AcONa, H2O. HOCH2CHCHCH(NO2)CHPh OH OH OH 212 O O CH Me Me O O 213 CH2NO2 a, b, c RCHCH(NO2)CH2CHMe OH OH 214 RCHO +O2NCH2CH2CHMe OH R=Me, Pri, C5H11, C10H21, , Ph(CH2)2, (Z)-Me(CH2)7CH CH(CH2)7, Me(CH2)4CH(NO2)(CH2)2. NO2 R R=Me: R0 =Me (45%), Et (42%); R=R0 =Et (31%). 216 217 HOCH2C NO¡2 Na++R0C 2.CH2O, H2O, H3PO3 CH2 1. MeOH, H2O, 072 8C, 1 h; HOCH2CCH2CCH2OH NO2 R 215 NO2 R0 Scheme 3 O2N(CH2)2OH+ K2CO3(Et3N) Ar, 20 8C K2CO3, MeOH 20 8C, 19 h Me(CH2)12CH CHCHO Me(CH2)12CHCH2CHCHCH2OH+208 209 (12%) (50%) Me(CH2)12CH CHCHCHCH2OH+C13H27 OH NO2 207 OH O NO2 208 202 OMe OH NO2 Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 51When nitro-diol 218 or 219 is treated with an aqueous solution of sodium hydroxide and then with a mixture of fluorine and nitrogen, fluoro-derivative 220 or 221 is formed in a yield of 71% or 68%, respectively.50 The potassium salt of 2,2-dinitroethanol is converted into 2-chloro-2,2-dinitroethanol on treatment with chlorine in water at 0 ¡À 5 8C.157 When salts of nitro alcohols react with chlorine or bromine, halogenation products are formed: When the products resulting from reactions of MeNO2 with aldehydes (CH2O or Cl3CCHO) were treated with bromine, 2,2- dibromo-2-nitroethanol 158 or 3-bromo-1,1,1-trichloro-3-nitro- propan-1-ol 35 were synthesised.In a number of patents,5, 7, 9 ¡À 12, 20 it has been proposed to synthesise 2-bromo-2-nitropropane-1,3-diol 8, which is a known bactericide agent `Biocide', according to the following scheme (the reaction conditions and product yields are listed in Table 11): Similarly, Cl3CCH(OH)C(NO2)Br was prepared from MeNO2 and Cl3CCHO;5, 7 MeCH(OH)C(NO2)BrCH(OH)Me was synthesised from MeNO2 and MeCHO;10 and MeCH(OH)C- Me(NO2)BrCH(OH)Me was obtained from EtNO2 and MeCHO.11 The reactions of salts of nitro alcohols 222 with aryldiazonium cations 223 in water at low temperatures yield arylhydrazones 224.159 R R0 Yield (%) H 4-Me 51 Me H 60 Me 4-Me 45 Me 4-Cl 23 Ph 4-Cl 22 H 4-Br 31 Me 4-Br 20 H 4-NO2 20 H 4-NH=C(NH2)NHSO2 25 H 3-NO2 17 Me 4-NO2 35 H 4-H2NSO 22 H 4-MeCONHSO2 20 H 4-H2NCONHSO2 21 H 56 2-Nitropropane-1,3-diol 3 is nitrated with tetranitromethane in an alkaline medium giving 2,2-dinitropropane-1,3-diol 114.8 However, an attempt to carry out alkaline nitration of the salt 30b was unsuccessful; the reaction resulted in the formation of diene 225 (yield 21.4%).52 Dinitro alcohol acetates 226 [the compound 226 with n = 3 has been obtained by catalytic oxidative nitration of the nitro alcohol O2NCH(CH2)3OH] have been introduced into the Michael reaction with acrolein.This afforded compounds 227, which were then converted into dinitro-diols 228.160 CHCH2NO2 OH 218 O2NCH2CH OH 1. NaOH, H2O 2. F2/N2, 5 8C, 1 h MeCHCH(NO2)CHMe OH OH MeCHC(NO2)CHMe . HO 219 221 1. NaOH, H2O 2. F2/N2, 1 h F OH O2NCHCH CHCHNO2 , OH OH 220 F F OH 7 K+[C(NO2)2CH2COH] Br(NO2)2CCH2COH (Ref. 123), (91%) Me Me Br2 CCl4 Me Me 7 C(Me)CNO2] 2Na+ CH2OH 7 [O2NCC(Me) CH2OH Br2, Et2O 0 8C, O2NC C(Me) HOCH2 Br C(Me) (44%) CBr (Ref. 52), NO2 CH2OH X=Cl (73.8%), Br (75%). (O2N)2CCHCHC(X)(NO2)2 (Ref. 96) OH X OH 7 7 [(O2N)2CCHCHC(NO2)2] 2Na+ OH 5710 8C X2, Et2O HOCH2CCH2OH . Br NO2 8 MeNO2+CH2O (HOCH2)2C NO¡¦2 K+ Br2 B R0C6H4NHN CCHR NO2 OH 224 H2O 8 8C, 16 h RCHCHNO2 OH 222 7 Na+ +R0C6H4N�¢2 223 S N 4-Et NHSO2 N HOCH2CH(NO2)CH2OH 3 114.NaOH, C(NO2)4, H2O 15 8C, 1 h HOCH2C C NO2 Me 225 C Me CCH2OH. NO2 NaNO2, AgNO3 H2O, pH 778, 0 8C, 1 h 2Na+ C NO2 CH2OH 7 O2N C Me 30b C Me C HOCH2 Table 11. Reaction conditions and yields of the compound 8. Conditions of nitroaldol Conditions Yield Ref. condensation of bromination (%) Base Sol- ¡ä /8C t/ ¡ä /8C t /h vent min Ca(OH)2 H2O 0 30 0 1 74 5 Na2CO3 0 ¡À 10 10 1 80 7 NaOH H2O 5 ¡À 10 5 ¡À 10 86 9 NaOH MeOH 20 0.5 83 10 NaOH H2O, 20 60 5 ¡À 20 98 11 DEGa MeONa MeOH 5 5 86 b 20 NaOH H2O see c 12 aDEG D diethyleneglycol; bCHCl3, c paraform, CCl4, BrCl. 52 M-G A ShvekhgeimerThe nitro alcohols O2NCH2CH(R0)OH add to a,b-unsatu- rated ketones in liquid ammonia to give adducts 229 (yields 45%± 96%).161 Adduct 230 was synthesised by the reaction of the nitro alcohol 202 with 2-(4-methylphenyl)-1-nitroethene under similar conditions (yield 23%).161 The reaction of salts of nitro alcohols 231 with nitroalkenes 232 in aqueous methanol gives adducts 233 in quantitative yields.On treatment with an aqueous solution of hydroxylamine hydro- chloride, the adducts 233 are converted into dinitro alcohols 234 in 37%± 55% yields.162 Chloro-substituted dinitro alcohols 235 have been synthesised by the reaction of the salts 231 with 2-nitroprop-1-ene in aqueous methanol followed by treatment of the resulting adducts 236 with chlorine.163 3.Reactions involving the hydroxy group When dinitro alcohols 237 react with compound 238 in the presence of toluene-p-sulfonic acid, intermolecular elimination of water occurs to give acetals 239 (yields 73%± 100%) as mixtures of cis- and trans-isomers (in a ratio of 15 ± 35 : 85 ± 65).109 Ethers derived from nitro alcohols are often synthesised by reactions of nitro alcohols with halo-derivatives in the presence of bases.The reaction of 3-nitropropan-1-ol with ButMe2SiCl carried out in DMF in the presence of imidazoline at 20 8C for 15 h gave the ether O2N(CH2)3OSiMe2But in 91% yield.108 Ethers 240, 241 and 242 have been prepared in high yields by the reactions of triol 243 with various halo-derivatives at 20 ± 25 8C in the presence of KOH, NaH or Et3N.164 R X Time /h Yield (%) Me I 2 89 Bu Br 0.5 78 The reaction of 2,2-difluoro-2-nitroethanol 244 with com- pounds RX in the presence of 5% aqueous sodium hydroxide at 25 ± 30 8C affords ethers 245.165 Condensation of the nitro alcohol 107 with allyl bromide or propargyl bromide catalysed by sodium hydroxide has been carried out in the presence of formaldehyde; this led to ethers 246 in 66% or 55% yield, respectively.93 The role of formaldehyde was to prevent the nitro alcohol 107 from decomposing in the alkaline medium.93 1,3-Dichloropropan-2-ol reacts with two molecules of the nitro alcohol 244 in the presence of 20% aqueous sodium hydroxide to give the diether (NO2CF2CH2OCH2)2CHOH in a yield of 78.6%.166 n=1, 3.(O2N)2C(CH2)nCH2OH 228 CH2CH2CH2OH (O2N)2C(CH2)nCH2OAc 227 CH2CH2CHO (O2N)2CH(CH2)nCH2OAc+CH2 226 CHCHO O2NCH2CHOH R1 NH3 (liq.), 10748 h R2CH CHCOR3 R3=Me, Ph, 4-MeC6H4, 4-MeOC6H4; R1=Me, R2=R3=Ph. R1=H, R2=Ph, 4-BrC6H4, 4-O2NC6H4, O ; R2CHCH2COR3 CH(NO2)CH(R1)OH 229 202 4-MeC6H4CH CHNO2 4-MeC6H4CHCH(NO2)CH2OH CH2NO2 230 (23%) NH3 (liq.), 48 h .[RC(NO2)CH2OH]7Na+ +R0C 231 232 CH2 NO2 MeOH, H2O 072 8C, 1 h R, R0 =Me, Et. 233 [HOCH2C(NO2)(R)CH2C(R0)NO2]7Na+ H2O, pH 4 HONH2 . HCl, HOCH2C(NO2)CH2CH(NO2) R 234 R0 Me R=Me, Et. Cl2 (pH*171.5) 0710 8C HOCH2C(NO2)CH2C 236 R 7 + NO2Na HOCH2CCH2CCl NO2 R 235 NO2 Me 231+CH2 CNO2 Me MeOH, H2O 072 8C, 1 h R=F, Me, NO2; R0=F, NO2. O C(NO2)2R0 RC(NO2)2CH2OH+HO 237 238 TsOH, ClCH2CH2Cl 1057110 8C, 2 h RC(NO2)2CH2O O C(NO2)2R0 239 O2NC[(CH2)3OH]3+3RX KOH, DMSO 20725 8C 243 O2NC[(CH2)3OR]3 240 243+R0Cl NaH, DMSO 25 8C O2NC[(CH2)3OR0]3 241 R0=Bu (78%); 4-ClC6H4 (63%); 243+ButMe2SiCl Et3N, DMF, DMAP 25 8C, 24 h O2NC[(CH2)3OSiMe2But]3 242 DMAP= .N NMe2 R, X (yield, %): Me, MeOSO2 (78); CH2CHCH2, Cl (75.5); F2C(NO2)CH2OH+RX NaOH, H2O 25730 8C 244 F2C(NO2)2CH2OR 245 CCH2, Br (27). HC R (time /h): CH2CH CCH2 (30). CH2 (45); HC FC(NO2)2CH2OR 246 FC(NO2)2CH2OH+RBr 107 CH2O NaOH, H2O, 20725 8C FC(NO2)2CH2OH OH7 FC(NO2)2CH2O7 FC¡(NO2)2 +CH2O. Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 53Ethers 247 containing ester groups have been prepared by the reaction of the nitro alcohol 244 with alkyl haloacetates 248 in boiling acetone in the presence of potassium carbonate.167 The reaction of the nitro alcohols 237 with bis(chloromethyl) ether involves the replacement of only one chlorine atom and gives products RC(NO2)2CH2OCH2Cl (R=Me, F, Cl, NO2).168 2-Fluoro-2-nitropropane-1,3-diol resulting from the reaction of diethyl 2-fluoro-2-nitromalonate 249 and the aldehyde 2 in the presence of potassium hydroxide has been introduced in situ in the reaction with chlorotrimethylsilane in boiling acetonitrile; this gave bis-silyl ether 250.49 The reactions of dichlorosilanes 251 with nitro alcohols 252 giving rise to compounds 253 (yields 10%± 69%) have been studied in detail.169 Polysiloxanes 255 have been synthesised by the condensation of dichlorosilanes 251 with nitro-diols.169 Compounds 256 containing one, two or three residues of nitro alcohols 257 are formed in the condensation of 257 with chloro- silanes 258 in the presence of pyridine.170 n R1 R2 R3 X Yield (%) 3 Me H Me Cl 44 2 Me H Me Cl 66 2 Me Me H Cl 40 3 Me CCl3 H H 14 2 Me CCl3 H H 15 1 H H Me Cl 7 1 H CCl3 H H 30 3 Me Et Et Br 12 The reaction of the nitro alcohol 107 with epibromohydrin has been carried out at 0 ± 2 8C in the presence of sodium hydroxide for 48 h; the ether resulting from the replacement of bromine in epibromohydrin was obtained in 32% yield.171 The reaction of the nitro alcohol 107 with epichlorohydrin has been described in two publications.In a patent,172 ether FC(NO2)2CH2O was reported as the reaction prod- uct (yield 31%). However, in another study 171 the same process gave a different compound containing two nitro-alcohol residues, namely, FC(NO2)2CH2OCH2CH(OH)CH2OCH2 ± C(NO2)2F. The nitro alcohol 244 reacts with ethylene oxide or propylene oxide in the presence of aqueous sodium hydroxide at 0 8C for 16 h to give ethers RCH(OH)CH2OCH2C(NO2)F2 (R = H, Me) (yields 32% and 67%); in the case of ethylene oxide, the com- pound F2C(NO2)CH2O(CH2)2OCH2CH2OH is also formed (yield 4%).173 The reaction of the nitro alcohol 202 with epoxides 259 at 50 8C in the presence of boron trifluoride etherate or sulfuric acid results in the formation of ethers 260 (yields 51% and 46.4%).174 The compounds CH:C(R)C(OH) CH(R0) ±OCH2CH2NO2 have been obtained by the reaction of the nro alcohol 202 with epoxides HC:C(R)7 ) (R and R0 are H or lower alkyls) in the presence of 4-MeC6H4SO3H or the KU-2 ion- exchange resin.175 Nitro alcohols 261 react with trifluoromethanesulfonic acid to give cations 262, which add in situ to nitro alcohols 263 yielding compounds 264 (Table 12).176 The ether Me3SiCH2OCH2C(NO2)2F has been prepared in 45% yield by the reaction of the nitro alcohol 107 with Me3Si- CH2OSO2CF3 in dichloromethane in the presence of K2CO3 at 20 8C for 16 h.177 Refluxing of the nitro alcohols 237 with divinyl ether in the presence of HgO and trifluoroacetic acid leads to transetherifica- tion yielding vinyl ethers 265.92 X=Cl, Br; R=Me (74%), Et (67%), Bu (65%). 244 +XCH2COOR 248 O2NCF2CH2OCH2COR 247 K2CO3, Me2CO D, 475 h O Me3SiOCH2CCH2OSiMe3 . NO2 F 250 C F COOEt COOEt O2N 249 KOH, CH2O, EtOH, H2O 20 8C, 3 h HOCH2CCOOEt NO2 F HOCH2CCH2OH NO2 F Me3SiCl, MeCN D, 5.5 h; 20 8C, 12 h KOH, H2O CH2O, R1=Me, Et, MeO, EtO; R2=Me, Et, Ph, MeO, EtO; R3=H, Me. R1R2SiCl2+HOCHCH2NO2 R3 251 252 R1R2Si(OCHCH2NO2)2 R3 253 n=3, 4; R1=Et, Ph, MeO; R2=Me, Et, MeO; R3=Me, Et. 251+HOCH2CCH2OH NO2 R3 254 40755 8C 6 ± 16 h HO SiOCH2CCH2O R1 R2 255 NO2 R3 H n R1n SiCl4-n+(4-n)HOCHCNO2 258 257 R2 R3 X C5H5N Et2O R1n Si(OCHCNO2)4-n 256 R2 R3 X FC(NO2)2CH2OCH2CHOCH2 CH2CHOCH2 R=Et, CCl3. RCH(OH)CH2OCH2CH2NO2 260 +O2NCH2CH2OH 259 202 R O BF3 . Et2O or H2SO4 50 8C, 3 h COCH(R0 RC(NO2)2(CH2)2O(CH2)nC(NO2)2R0. 264 RC(NO2)2(CH2)á2 ] 262 R0C(NO2)2(CH2)nOH (263) 7H2O + RC(NO2)2(CH2)2OH 261 [RC(NO2)2(CH2)2OH2 CF3SO3H, N2 ClCH2CH2Cl R=Me (64.2%), F (64%), NO2 (25.9%).RC(NO2)2CH2OH+CH2 CH2 237 CHOCH RC(NO2)2CH2OCH CH2 265 CH2Cl2, D, 22.5 h HgO, F3CCOOH Table 12. Reaction condition and yields of the compounds 264. R R0 n Temperature /8C Time /h Yield (%) Me F 2 60 20 9 Me Me 2 60 20 80 F F 2 60 96 15 NO2 NO2 2 65 ± 70 72 16 F F 1 30 ± 35 168 20 NO2 Me 1 70 ± 75 72 46 NO2 F 1 60 ± 70 72 48 54 M-G A ShvekhgeimerThe addition of nitro alcohols to alkenes or to buta-1,3-diene and the addition of alcohols to nitroalkenes have been used to synthesise ethers of nitro alcohols.For example, the reaction of 3-nitropropan-1-ol with 2-methylpropene in CH2Cl2 in the pres- ence of sulfuric acid (20 8C, 12 h) gave the ether ButO(CH2)3NO2 (yield 95%).108 Adduct 266 was obtained by reaction of 107 with 2-methyl- pent-1-ene at 20 8C in the presence of HgSO4 or Hg2SO4 (yields 74% and 58%, respectively).178 The reaction of the nitro alcohol 107 with buta-1,3-diene affords a mixture of 1,2-addition product 267 and 1,4-addition product 268 in a ratio of 77 : 23, their total yield being 53%.178 Two products 269 and 270 resulting from radical C- and O-addition (yields 28% and 70%, respectively) have been syn- thesised by the reaction of hexan-1-ol with 1-nitroprop-1-ene in the presence of tert-butyl peroxide.179 1,1,1-Trinitroethanol adds to the C=N bond in perfluoro- guanidine at ambient temperature to give compound 271.180 Acyclic and cyclic acetals containing one or two nitro-alcohol residues are promising compounds for practical purposes.Acetals 272 have been synthesised by the reactions of the nitro alcohols 237 with 1,3,5-trioxane or with paraldehyde in the presence of sulfuric acid 181, 182 or sodium hydroxide. The reaction conditions and the yields of products are presented in Table 13.89 Mixed acetals 273 182, 183 and 274 184 have been prepared by condensation of three components.The acetal 273 (R=F) was synthesised by the reaction of the nitro alcohol FC(NO2)2CH2OH with the ether MeC(NO2)2- CH2OCH2Cl in the presence of TiCl4.183 Polycondensation of formaldehyde with the diol HOCH2C(- NO2)2CH2CH2C(NO2)2CH2OH in the presence of sulfuric acid affords poly(nitroformal).185 Nitro alcohols add to acyclic 178, 186 or cyclic 108, 142, 178 vinyl ethers 275 in the presence of catalysts to give acetals 276 (see Table 14).The addition of nitro alcohols 277 to 2,3-dihydropyran in THF and HMPT in the presence of butyllithium at a temperature between790 8C and740 8C leads to the compounds 209.154 The nitro alcohol 107 adds to ethoxyacetylene in CH2Cl2 at 20 8C in the presence of HgSO4 187 or Hg(OAc)2 178 or in the presence of HgO in CF3COOH92 giving rise to 2 : 1 adduct 278 (yields 100%, 95%, or 70%, respectively).When this reaction is carried out in the presence of Hg(OAc)2 in CH2Cl2 and hexane at 20 8C, the 1 : 1 adduct 279 is produced in 73% yield in addition to the adduct 278 (yield 27%).178 CPr Me FC(NO2)2CH2OH +CH2 107 FC(NO2)2CH2OCH2CHPr. 266 Me FC(NO2)2CH2OH+CH2 107 CH CH CH2 HgSO4, CCl4, sealed tube 55 8C, 16 h CHCH2OCH2C(NO2)2F. 268 267 Me CHCHOCH2C(NO2)2F+MeCH CH2 Me(CH2)4CH2OH+MeCH (ButO)2 CHNO2 C5H11CHCH2NO2+C6H13OCHCH2NO2 . 269 270 OH Me (O2N)3CCH2OH+(F2N)2C NF H2NCONH2, MeCN 23 8C, 72 h 271 (O2N)3CCH2OC(NF2)2NHF. RC(NO2)2CH2OH+(R0CHO)3 [RC(NO2)2CH2O]2CHR0. 237 272 (NO2)3CCH2CH2OH+FC(NO2)2CH2CH2OH+F5SN CCl2 C[OCH2CH2C(NO2)3]OCH2C(NO2)2F. 274 F5SN R=NO2 ,182 F;183 237+(CH2O)x+MeC(NO2)2CH2OH 80% H2SO4 RC(NO2)2CH2OCH2OCH2C(NO2)2Me 273 R1OH+R2OCH R2OCH(OR1)CH2R3. CHR3 20 8C 275 276 R=H, Me.RCH(NO2)CH2OH+ O 277 BuLi, THF, HMPT 790 to740 8C, 3 h O OCH2CH(NO2)R 209 Table 13. Reaction condition and yields of the compounds 272. R R0 Catalyst Yield (%) Ref. F H H2SO4 7 181 Me H NaOH 78 89 Me H H2SO4 78 182 Me Me NaOH 35 89 NO2 H H2SO4 7 182 Table 14.Conditions for the formation of the acetals 276. R1 R2 R3 Catalyst Solvent T /8C Time /h Yield (%) Ref. O2N(CH2)3 7(CH2)37 TsOH Et2O 20 5 95 108 7(CH2)37 TsOH Et2O 20 12 90.5 142 FC(NO2)2CH2 Et H Hg(OAc)2 CH2Cl2 20 16 73 178 FC(NO2)2CH2 7(CH2)37 Hg(OAc)2 CH2Cl2 42 17 100 178 FC(NO2)2CH2 FC(NO2)2CH2 H Hg(OAc)2 CH2Cl2 20 24 61 178 (O2N)3CH2CH2 FC(NO2)2CH2 H BF3 .Et2O 7 0 12 7 186 MeC(NO2)2CH2 FC(NO2)2CH2 H Mol. sieve 5A 7 0 12 7 186 FC(NO2)2CH2 FC(NO2)2CH2 H Mol. sieve 5A 7 0 12 7 186 O CHCH2NO2 Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 55Two compounds, 1 : 1 adduct 280 and 2 : 1 adduct 281, were obtained by refluxing the nitro alcohol 107 and divinyl ether in CH2Cl2 in the presence of HgSO4 or Hg2SO4.It was found that the ratio of 280 to 281 depends appreciably on the 107 : ether ratio. For example, when this ratio is 1 : 1, reaction in the presence of HgSO4 gives 280 in 12% yield and 281 in 58% yield; at 2 : 1 ratio, the yield of 280 is 70%, while that of 281 is 20%. When this reaction is carried out in the presence of Hg2SO4 and 107 : ether= 1 : 2 (refluxing for 26 h), the yields of 280 and 281 are 40% and 34%, respectively.178 The orthoformate HC[OCH2C(NO2)3]3 or orthocarbonate C[OCH2C(NO2)3]4 have been synthesised from 2,2,2-trinitroetha- nol and CHCl3 or CCl4 in the presence of FeCl3.188 Cyclocondensation of nitro-diols of various structures with aldehydes or ketones in the presence of acid catalysts has found wide application as a method for the preparation of nitro- derivatives of 1,3-dioxane. 2-Nitropropane-1,3-diol 3 reacts with acetone or with aro- matic aldehydes in boiling benzene in the presence of toluene-p- sulfonic acid to yield 5-nitro-1,3-dioxane derivatives 282.189 2-Bromo-2-nitropropane-1,3-diol 8 has been involved in the condensation with acetone or aliphatic aldehydes in the presence of various catalysts; this resulted in the formation of 5-bromo-5- nitro-1,3-dioxane derivatives 283.The reaction conditions and the yields of reaction products are listed in Table 15.190 ± 192 Acetals 284, which are promising as monomers, have been synthesised from diol 285 and carbonyl compounds 286 in the presence of toluene-p-sulfonic acid.193 The stereochemistry of the reactions of halo-2-nitropropane- 1,3-diols with acetaldehyde in the presence of toluene-p-sulfonic acid has been studied.194 It was found that these reactions yield mixtures of diastereoisomers 287 and 288.the ratio 287 : 288 =16 : 83 (X=Cl), 5.5 : 94 (X=Br). 2-Alkyl-5-hydroxymethyl-5-nitro-1,3-dioxanes 289 were pre- pared in*90% yields by cyclocondensation of 2-hydroxymethyl- 2-nitropropane-1,3-diol 4 with aliphatic aldehydes in the presence of toluene-p-sulfonic acid and CuSO4 at 20 8C.194 A series of 5-nitro-1,3-dioxane derivatives 290 have been synthesised by cyclocondensation of nitro-diols 291 with esters of aldehydo acids 292 in the presence of zinc chloride and orthophosphoric acid in boiling benzene.195 R1 R2 R3 Yield (%) H Me 2-OCH2COOEt 90 H Et 2-OCH2COOEt 96 H Br 2-OCH2COOEt 95 H Me 3-OCH2COOEt 92 H Br 3-OCH2COOEt 84 H Me 4-OCH2COOEt 92 H Et 4-OCH2COOEt 90 H 3-O2NC6H4 4-OCH2COOEt 50 H Br 4-OCH2COOEt 75 2-MeO Me 4-OCH2COOEt 74 2-MeO Cl 4-OCH2COOEt 88 2-MeO Br 4-OCH2COOEt 87 2-EtO Me 4-OCH2COOEt 92 2-EtO Et 4-OCH2COOEt 91 2-EtO Br 4-OCH2COOEt 78 C EtO OCH2C(NO2)2F OCH2C(NO2)2F Me 278 279 +H2C C(OEt)OCH2C(NO2)2F . 107+EtOC CH FC(NO2)2CH2OH+CH2 107 CHOCH CH2 CH2Cl2 36 8C, 16 h 280 CHOCHMe OCH2C(NO2)2F CH2 +MeCHOCHMe 281 OCH2C(NO2)2F OCH2C(NO2)2F R, R0: Me, Me; H, 4-Cl6H4; H, Ph; H, 4-BrC6H4.HOCH2CHCH2OH +RR0C O NO2 3 O O H O2N R R0 282 TsOH, PhH 80 8C, 3 h HOCH2CCH2OH +RR0C O 8 Br NO2 O O Br O2N R R0 283 R, R0 (yield, %): H, (47); H, Ph (65); H, 4-O2NC6H4 (70); O 285 286 TsOH, PhH 80 8C, 476 h HOCH2CCH2OH +RR0C O CH NO2 CH2 O O CH O2N R R0 CH2 284 Me, Me (71); (CH2)5 (62).H, 3,4-(CH2O2)C6H3 (56); H, PhCH=CH (67); +MeCHO TsOH, PhH 80 8C C X CH2OH CH2OH O2N X O O Me + O2N O O Me 287 288 NO2 X 289 O O HOCH2 O2N Alk 4 HOCH2CCH2OH +AlkCHO CH2OH NO2 20 8C, 7 days TsOH, CuSO4 R1 290 O O R2 O2N R3 +HOCH2CCH2OH NO2 R2 291 H O C 292 80 8C, 3 h ZnCl2, H3PO4, PhH R3 R1 Table 15. Reaction conditions and yields of the compounds 283.R R0 Catalyst Solvent � t Yield Ref. /8C /h (%) H Me p-TsOH PhH 80 0.5 7 190 H Et p-TsOH PhH 80 0.5 7 190 H Pr p-TsOH PhH 80 0.5 7 190 H Pri p-TsOH PhH 80 0.5 7 190 H H H2SO4 DCEa 83 7 7 191 Me Me BF3 . Et2O 7 447 7 40 192 H Me BF3 . Et2O 7 447 7 85 192 H Et BF3 . Et2O 7 447 7 7 192 H Pr BF3 . Et2O 7 447 7 7 192 H Pri BF3 . Et2O 7 447 7 7 192 a DCE �dichloroethane. 56 M-G A ShvekhgeimerThe rate of the reaction of 5-substituted furfural derivatives 293 with 2-ethyl-2-nitropropane-1,3-diol in the presence of the KU-2 ion-exchange resin (H-form) has been shown to decrease in the series NO2>I>Br>H>Me. It was assumed that attack by the diol on the protonated formyl group is the rate-determining step of the reaction.196 Cyclocondensation of mono- and disubstituted 2-nitropro- pane-1,3-diol derivatives 295 with aldehydes or ketones in the presence of TsOH gave di-, tri- or tetra-substituted derivatives of 5-nitro-1,3-dioxane 296.197 The compounds 296 were obtained in low yields for R1 = H, R2 = R3 = R4 = R5 = Me (27%); R1 = H, R2 = R3 = Me, R4= R5 = H (30%) and R1 = R4 = R5 = H, R2 = R3 = Pri (32%).197 1,3-Dioxane derivatives 297 were synthesised from the nitro- diol 206 using acetone dimethyl ketal or benzaldehyde dimethyl acetal as the second reactant.152, 198 The reaction of 206 with benzaldehyde dimethyl acetal affords three diastereoisomers 297a,b,c in 55.5% overall yield and in a ratio of 4 : 1 : 1.152 Refluxing of the nitro-diol HOCH2CH(NO2)CH(OH)C13H27 with acetone dimethyl ketal in acetone in the presence of toluene- p-sulfonic acid results in the formation of 2,2-dimethyl-5-nitro-4- tridecyl-1,3-dioxane in 61.5% yield.61 Yet another method for the synthesis of acyclic and cyclic acetals of aromatic aldehydes and nitro alcohols consists of the reaction of dichloromethyl arenes with alcohols or 1,3-diols.This procedure was used, for example, to prepare acetals 298 or 299 from dichloromethylarenes 300 and polynitro alcohols 301 or 2,2- dinitropropane-1,3-diol 114.199 The reactivity of nitro alcohols decreases in the order NO2> Cl>HCCH2>Me, i.e.in parallel with their acidity.199 By refluxing nitro-diol 302 with arylboronic acids 303 in acetone, 2-bora-1,3-dioxane derivatives 304 have been synthes- ised.200 Cyclic compound 305 containing two oxygen atoms and a phosphorus atom in the six-membered ring has been obtained by cyclocondensation of the triol 4 with phosphorous acid.201 2-Bromo-2-nitropropane-1,3-diol 8 reacts with dichloro- derivatives 306 at 50 8C to give 5-bromo-5-nitro-2-R-2-oxo- 1,3,2-dioxaphosphorinanes 307.202 Cyclocondensation of the diol 8 with 2,2,2-trichloro-1,3- dimethyl-1,3,2l5-diazaphosphetidin-4-one 308 gives rise to com- pound 309.203 5-Chloromethyl-5-nitro-1,3,2-dioxathian-2-one 310 was syn- thesised by the reaction of the triol 4 with thionyl chloride in the presence of pyridine.204 Esters derived from nitro alcohols are usually synthesised either by reactions of nitro alcohols with acid chlorides or anhydrides or by reactions of nitro alcohols with carboxylic acids in the presence of anhydrides of other acids.The preparation O R C O H +HOCH2CCH2OH Et NO2 293 KU-2, PhH R=H (66%), Me (70%), Br (84%), I (79%), NO2 (82%). O R O O Et NO2 294 296 O O R4 R5 R1 O2N R2 R3 HOCHC(NO2)CHOH+R4CR5 295 TsOH PhH R3 O R1 R1=H, Me, CH2OH; R2=H, Me, Pr, Pri; R3=H, Me, Pr, Pri; R4=H, Me; R5=H, Me, Et, Pri, Bu, Ph, 2-HOC6H4, 4-O2NC6H4, PhCH CH; R4, R5=(CH2)5.R2 R=H, R0 =Ph; R=R0 =Me. 297 O O O Me R0 R NO2 O CHCHCHMe +RR0C(OMe)2 OH OH NO2 206 TsOH, DMF 60 8C, 1 h O O H Ph 297a 297b 297c O2N Ph H O O H Ph O O Me Me Me Y Y Y O2N O2N Y= . O R=Cl, Me, NO2; Ar Ph, 3-O2NC6H4, 4-O2NC6H4 ; ArCHCl2+RC(NO2)2CH2OH 300 301 507100 8C AlCl3 or FeCl3 ArCH[OCH2C(NO2)2R]2 298 300+HOCH2CCH2OH 114 NO2 NO2 Ar=Ph, 3-O2NC6H4 (AlCl3,), 4-O2NC6H4 (FeCl3).AlCl3 or FeCl3 507100 8C Ar O O NO2 NO2 299 Ar=Ph (90.5%), 4-ClC6H4 (67%). HOCH2CCH2OH +ArB(OH)2 Me2CO 50 8C, 2 h 302 303 304 ArB COOEt NO2 O O NO2 COOEt HOCH2CCH2OH +H3PO3 4 NO2 CH2OH 305 O POH O O2N HOCH2 R=Me (60%), Cl (28%), PhO (56%), 4-MeC6H4O (49%), 3-MeC6H4O (42%), 4-O2NC6H4O (60%), OH (39%). 307 O O Br ON2 O R P 50 8C HOCH2CCH2OH +RPCl2 8 306 NO2 Br O , N2 O O 8+O N PCl3 N Me Me CH2Cl2 O N P N Me Me Cl O O Br NO2 308 309 HOCH2CCH2OH +3SOCl2 4 NO2 CH2OH 30 8C, 1 h C5H5N 310 O S O O2N ClCH2 O Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 57of nitro alcohol acetates has been described in numerous publica- tions.There is no need to consider these studies in detail, because the acetates have been synthesised by conventional procedures, which have been described fairly comprehensively in mono- graphs.3, 4 Syntheses of halocarbonates 311 and 312 (yield 91%) by the reactions of nitro alcohols 313 with carbonyl dichloride or difluoride or by the reaction of 2,2-dinitropropane-1,3-diol 114 with carbonyl difluoride have been reported in patents 205, 206 and papers.207, 208 Carbonates 314 205 or 315 (yield 64%) 208 were prepared by the reaction of nitro alcohol 316 with the chloroformate 311 (R=F, X=Cl) or of 2,2,2-trinitroethanol with carbonyl difluoride. 2,2-Dinitropropane-1,3-diol 114 reacts with two molecules of chloroformate 317 giving rise to diester 318 (yield 83%).209 The exothermic reaction of the nitro alcohols 237 or 202 with chloride 319 in the presence of iron(III) chloride has led to the synthesis of O-alkyl S-ethyl thiocarbonates 320 210 or 321.The three-component reaction involving the nitro alcohol 107, thiophosgene and Cl3CSH, taken in a ratio of 3 : 1 : 1, carried out in the presence of a base under conditions of phase transfer catalysis affords compound 322, which is converted into com- pound 323 (yield 81%) upon treatment with 1,1,1-trinitroethanol and chlorine.211 When 2,2-dinitropropanol is made to react with bis(1,2,4- triazol-1-yl) thioketone in acetone in the presence of pyridine at 20 8C, the ester [MeC(NO2)2CH2O]2C=S is formed in 83% yield over a period of 2 days.212 Similarly, the reaction of (O2N)3CCH2OH or the alcohol 107 with bis(1,2,4-triazol-1-yl) sulfoxide yields the corresponding esters.212 The reaction of 2-nitropropane-1,3-diol with trimethylacetyl chloride in dichloromethane carried out for 3 h at 40 8C and then for 12 h at 25 8C affords the corresponding bis-ester in 95% yield.15 Esters 324, which are of interest as monomers, have been synthesised in 60%± 70% yields by the reactions of dinitro alcohols 325 with chlorides of a,b-unsaturated acids.213 ± 215 It should be noted that the yield of 324 (R1= F, R2= R3 = Me) was as low as 5%.214 The reaction of the nitro alcohol 325 (R1=Me, R2=H) with acryloyl chloride carried out for 3 h at 20 8C in the presence of TiCl4 affords the corresponding ester 324 (R1=Me, R2=R3=H) in 93% yield.213 The reaction erfluoroacryloyl chloride with the nitro alcohol 244 in the presence of triethylamine at 740 to 735 8C follows two competing pathways: esterification of the nitro alcohol giving the ester F2C=CFCOOCH2C(NO2)F2 (yield 7.9%) and the addition of the nitro alcohol to the double bond of the chloride leading to the ether F2C(NO2)CH2OCF2 ± CH(F)COCl (yield 7%).216 Esters derived from nitro alcohols and unsaturated dicarbox- ylic acids have been described in the literature.217, 218 Tris-esters 326 have been prepared by the reactions of the nitro-triol 4 with benzoyl, 4-chlorobenzoyl and toluene-p-sulfonyl chlorides in the presence of pyridine.164 Ar Y � /8C Time /h Yield (%) Ph CO 70 15 51 4-ClC6H4 CO 20 30 93 4-MeC6H4 SO2 0 12 47 R, X: F, Cl; F, F; Me, F; NO2, F; FCOOCH2, F; RC(NO2)2CH2OH+XCX 313 RC(NO2)2CH2OCX 311 O C5H5N or NaF O HOCH2CCH2OH +FCF 114 312 NaF FCOCH2CCH2OCF .NO2 NO2 O O NO2 NO2 O 316 311 FC(NO2)2CH2OCCl +O2NCF2CH2OH O C5H5N 314 FC(NO2)2CH2OCOCH2C(NO2)F2 , O C5H5N (O2N)3CCH2OCOCH2C(NO2)3 . 315 O 2(O2N)3CCH2OH +FCF O 2(NO2)3CCH2OCCl+HOCH2C(NO2)2CH2OH O 317 114 (NO2)2C[CH2OCOCH2C(NO2)3]2 . 318 O CH2Cl2, MeCN RC(NO2)2CH2OCSEt 320 O RC(NO2)2CH2OH 237 ClCSEt (319), FeCl3 O R=F, Me, NO2 ; NO2CH2CH2OH 202 NO2CH2CH2OCSEt . 321 O 319, FeCl3 CH2Cl2, MeCN FC(NO2)2CH2OH+ClCCl +Cl3CSH 107 S B 75 to 5 8C [FC(NO2)2CH2O]3COCH2C(NO2)3 . 323 [FC(NO2)2CH2O]3CSSCCl3 322 (NO2)3CCH2OH, Cl2 60770 8C, 75 h R=F, Me, NO2. +2RC(NO2)2CH2OH C5H5N, Me2CO 20 8C, 48 h [RC(NO2)2CH2O]2C S C S N N N N N N 2ButCCl+CHNO2 O CH2Cl2 40 8C, 3 h; 25 8C, 12 h CH2OH CH2OH CHNO2 O O CH2OCBut CH2OCBut R1=H, F, Me; R2=H, Me; R3=H, Me.R1C(NO2)2CHOH +CH2 325 R2 CCOCl R3 65780 8C, 578 h CH2 CCOOCHC(NO2)2R1 R3 324 R2 O2NC(CH2OH)3+ArYCl C5H5N O2NC(CH2OYAr)3 4 326 58 M-G A ShvekhgeimerCompound 327 has been obtained in 40% yield by treatment of the bis-ester, resulting from the reaction of 2-butyl-2-nitro- propane-1,3-diol with methanesulfonyl chloride, with chlorophe- nol in the presence of sodium hydride.219 Synthesis of hydroxy ketone 328 has been accomplished using trifluoroacetic anhydride.103 The reaction of the dinitro-diol 114 or the nitro-diol 4 with trifluromethanesulfonic anhydride 329 at 20 8C in the presence of pyridine results in the formation of mixtures of mono-triflates 330 (yields 46.8% or 44.4%) and bis-triflates 331 (yields 14% or 16.2%).49 The researchers cited 49 also proposed conditions under which the reaction of 2-fluoro-2-nitropropane-1,3-diol with 329 gives either mono-triflate 332 (yield 78.9%) or bis-triflate 333 (yield 75.5%).The nitro-diol HOCH2C(NO2)(Br)(CH2OH) has been esteri- fied with formic acid in the presence of acetic anhydride and pyridine at 40 8C to give the corresponding bis-ester (HCOOCH2)2C(NO2)Br.220 Esters 334 (yields 47% ± 100%) have been synthesised from polynitro alcohols 335 and dicarboxylic acids in the presence of the anhydride 329 and aluminium chloride.221 Under the same conditions, the following esters were obtained: (NO2)2(R)CCH2O2CCH(Et)CO2CH(R)(NO2)2 (R = NO2, 63%; R = F, 100%) and RCOOCH2C(NO2)2F (R = Ph, 92%; R=PhCH=CH, 100%).221 The urethane FC(NO2)2CH2CH2OCONHCH2CH2C(NO2)2F is formed in 72% yield when the isocyanate FC(NO2)2CH2CH2NCO and the alcohol FC(NO2)2CH2CH2OH are refluxed for 6 h in chloroform in the presence of iron acetylacetonate.122 Study of the kinetics of the reactions of 2-R-2-nitropropane- 1,3-diols with the bis-isocyanateCH2(C6H4NCO)2 has shown that the nitro group adjacent to the hydroxy group decreases the reaction rate owing to its inductive effect and also owing to the formation of intra- and intermolecular OH.. .O2N hydrogen bonds.222 It has been found that the reaction between 2-methyl-2-nitro- propane-1,3-diol and o-phenylene diisocyanate yielding polyur- ethane follows second-order kinetics, its rate constant being 0.685 mol71 h71 at 20 8C or 1.127 mol71 h71 at 30 8C.223 Compounds 336 have been synthesised from isothiocyanates and nitro alcohols.224 Substitution of the hydroxy group in nitro alcohols has been studied fairly comprehensively.The replacement of all three hydroxy groups in the triol 243 by fluorine, chlorine, bromine or iodine atoms has been described.164 The hydroxy group in nitro alcohols 337 is substituted by an amine residue on treatment with primary or secondary amines in water; this gives compounds 338 in 60%± 89% yields.225 ± 227 If the reaction of formaldehyde with trinitromethane is carried out in water in the presence of urea at 70 8C for 2 h, the resulting (O2N)3CCH2OH reacts in situ with urea, and [(O2N)3CCH2NH]2CO is formed as the reaction product.98 Three-component condensation of the nitro-triol 4, form- aldehyde and primary amines in the presence of sodium hydro- gencarbonate gives rise to tetrahydro-1,3-oxazine derivatives 339.228 HOCH2CCH2OH +MeSO2Cl NO2 Bu MeSO2OCH2CCH2OSO2Me Bu NO2 4-ClC6H4OH, NaH, DMF 90 8C, 17 h 4-ClC6H4OCH2CCH2OSO2Me. 327 NO2 Bu FC(NO2)2(CH)2COCH2OCOCF3 . 328 (82%) FC(NO2)2(CH)2COCH2OH (F3CCO)2O R=NO2 (114) ; R=CH2OH (4). CF3SO2OCH2CCH2OH+CF3SO2OCH2CCH2OSO2CF3 331 330 R NO2 R NO2 HOCH2CCH2OH +(CF3SO2)2O NO2 R C5H5N, Et2O 20 8C, 172 h 329 4, 114 (b) 2 equiv.(CF3SO2)2O, C5H5N, CHCl3, 5 8C, 3 h. (a) 1 equiv. (CF3SO2)2O, C5H5N, Et2O, 20 8C, 16 h; HOCH2CCH2OH NO2 F 332 HOCH2CCH2OSO2CF3 NO2 F [CF3SO2OCH2]2C(NO2)F 333 a b n=1, 3, 4, 5, 6, 8, 10; R=F, NO2. RC(NO2)2CH2OH+HOC(CH2)nCOH 329, AlCl3 20 8C, 1.5 h 335 O O RC(NO2)2CH2OC(CH2)nCOCH2C(NO2)2R 334 O O R1ZCNS+HOCH(R2)CR3R4NO2 70 8C, 6 h R1ZNHC(S)OCH(R2)CR3R4NO2 336 Z=SO2, R1=Ph, R2=H, R3=H, Br, R4=H, Me (23% ± 31%); Z=CO, R1=Ph, 4-ClC6H4, 4-O2NC6H4, 2-furyl, R2=H, Me, R3=H, Br, R4=H, Me, Et (18% ± 75%). +7 +7 (a) Bu4NF, THF, MeCN, 90 8C, 12 h (75%); (b) Bu4NF, 4-MeC6H4SO2F, THF, 4A mol.sieve (86%); (c) PBr3, C5H5N, PhH, 50770 8C, 2 h (69%); (d) SOBr2, C5H5N, CH2Cl2, refluxing for 2 h (64%); (e) NaBr, (HOCH2CH2)2O, 1507170 8C, 3 h (55%). a or b c, d or e NaI, Me2CO 25 8C, 12 h SOCl2, C5H5N, CHCl3 50 8C, 2 h O2NC[(CH2)3F]3 O2NC[(CH2)3Br]3 O2NC[(CH2)3Cl]3 (80%) O2NC[(CH2)3I]3 (89%) O2NC[(CH2)3OH]3 243 R1R2C(NO2)CH2OH+R3R4NH H2O 20 8C, 20 h 337 R1R2C(NO2)CH2NR3R4 338 R1=F, Me; R2=H, Me, NO2; R3=Me, Et, Pri, Bu, Me2CH(CH2)2; R4=H, Me.Aliphatic nitro alcohols.Synthesis, chemical transformations and applications 59The compounds 339 (R = Me, Et, Pr, Pri, Bu and But) have also been obtained by another method, namely, the reaction of the nitro-triol 4 with the corresponding 1,3,5-trialkylhexahydro- 1,3,5-triazines.229 The pyrazolidine derivative 340 has been synthesised by the reaction of hydrochloride 341 with 2,2-dinitropropane-1,3-diol 114 (yield 86%) or with the potassium salt of 2,2-dinitroethanol (yield 23.5%).230 Cyclocondensation of the nitro-diols 302 or 114 with form- aldehyde and primary amines leads to hexahydropyrimidine derivatives 342. The reaction conditions and the yields of reaction products are listed in Table 16.200, 231, 232 When the nitro alcohol 202 is treated successively with phosphorus tribromide and sodium thiophenoxide, the corre- sponding thioether is formed in an overall yield of 73%.233 The hydroxy group in nitro alcohols 343 is replaced by aryl groups when 343 are treated with arenes 344 in the presence of sulfuric acid; this yields diphenylmethane derivatives 345.63, 234 ± 236 R1 R2 R3 R4 Ref.But Me H EtO 63 EtCHMe Et H EtO 63 Bui Me OCH2O 234 EtCHMe Et OCH2O 234 EtO H H EtS 234 Cl H H EtS 235 HC:CCH2O Me H H, F, Me, Pri 236 Et H MeO, PrO, HC:CCH2O On treatment of acetates 346 with sodium tetrahydridoborate in DMSO or ethanol at 20 ± 25 8C for 1.5 h, the acetoxy group is substituted by a hydrogen atom giving nitro-compounds 347 (yields 41%± 90%).27, 237 The formation of 347 from the acetates 346 involves the intermediate formation of nitroalkenes 348.237 4.Reactions involving several sites Oxidation of nitro alcohols to nitro-carbonyl derivatives can involve simultaneously two reaction sites, namely, the hydroxy group and the hydrogen atom attached to the carbon atom carrying the hydroxy group. Nitro alcohols 349 have been converted into nitro ketones 350 by treatment with chromium(VI) oxide supported on montmor- lonite at715 8C accompanied by ultrasonic treatment.72 Pyridinium chlorochromate has proved to be a good reagent for the transformation of nitro alcohols into nitro ketones.Treat- ment of nitro alcohols 349 with this reagent in the presence of molecular sieves at 20 8C gave nitro ketones 350 (yields 61%± 87%).83, 238 R=Me (32%); Pri (22%); But (77%). O2NC(CH2OH)3+CH2O+RNH2 NaHCO3, H2O 60 8C, 3 h 4 HOH2C O2N R O N 339 341 EtOCCH2NHNH2 .HCl O pH 4, 55760 8C, 15 min H2O, AcONa HOCH2C(NO2)2CH2OH HN NCH2COOEt , NO2 O2N 340 +7 341+KC(NO2)2CH2OH 340 . 60 8C, 15 min EtOH, H2O N N R R O2N R0 342 (HOCH2)2C(NO2)COOEt 302 (HOCH2)2C(NO2)2 114 CH2O, RNH2 O2NCH2CH2OH+PBr3 0 8C O2NCH2CH2Br PhSNa, THF 20 8C 202 O2NCH2CH2SPh . 4-R1C6H4CHCHR2 NO2 R3 R4 CHR2 + NO2 4-R1C6H4CH OH H2SO4 R3 R4 345 343 344 R1=Me, Et, Bu, Ph, MeCH(Et)(CH2)3; R2=H, Me; R3=H, Me, Et, Pr; R2, R3=(CH2)5.237 R1R2CCHR3 346 R1R2CHCHR3 347 NaBH4, DMSO 20725 8C OAc NO2 NO2 R1=C6H13, C7H15, CH2, , Me2C CH(CH2)2C(Me) CH(CH2)2; R2=R3=H;27 346 348 NaBH4 R1R2CHCHR3 347 R1R2CCHR3 NO2 OAc CR3 NO2 R1R2C NO2 B 7AcOH R, R0 (yield, %): Me, Me (90); Et, H (76); Pri, Me (93); Pri, Et (90). 715 8C, 373.5 h RCCH(NO2)R0 O 350 RCHCH(NO2)R0 349 OH Table 16. Reaction conditions and yields of the compounds 342. R R0 Solvent � Time Yield Ref. /8C /h (%) But COOEt EtOH 78 2 25 200 Me NO2 EtOH 5 ± 20 19 231 But NO2 MeOH 20 1 29 231 Mea NO2 see b 20 24 35 232 CH2COOMea NO2 see b 20 18 22 232 CH2COOEt a NO2 see b 20 18 15 232 a Hydrochlorides of the amines were used; b in the presence of AcONa, pH 4. 60 M-G A ShvekhgeimerIt has been found 239 that both the rate of the oxidation of EtCH(OH)CH(NO2)Et with pyridinium chlorochromate on silica gel in CH2Cl2 and the yield of the nitro ketone EtCOCH(NO2)Et formed in this reaction markedly increase upon ultrasonic treat- ment: without ultrasound the yield of the product is 60% over a period of 1.5 ± 2.5 h at 25 8C, whereas the reaction carried out with sonication is completed over a period of 20 min at 718 8C (yield 71%). On treatment with K2Cr2O7 or K2CrO4 in the presence of Bu4N+HSO74 , H2SO4 and FeSO4 at 710 8C, nitro alcohols 351 are readily oxidised to give nitro ketones 352 in high yields (70% ± 93%),67 and nitro-diols 353 are easily oxidised to nitro diketones 354.155 3-Chloro-6-nitrohexan-2-one has been synthesised in 75% yield by the oxidation of 3-chloro-6-nitrohexan-2-ol with a solution of Na2Cr2O7 in H2SO4 at 10 ± 20 8C for 10 h.58 Heating of 1-nitropropan-2-ol with hydrochloric acid (18% ± 36%) at 95 ± 107 8C for 5 ± 30 h affords lactic acid in 14% ±16% yield.240 Attempts to dehydrate compounds 356 with phthalic anhy- dride, P2O5 or MeCOCl were unsuccessful: the reactions were accompanied by rupture of the C± P bond.Dehydration of these compounds was accomplished by heating them with thionyl chloride in the presence of pyridine. This gave the corresponding unsaturated compounds 357.127 Primary and secondary nitro alcohols 358 are readily dehy- drated on treatment with cyclohexylcarbodiimide, being con- verted into mixtures of diastereoisomeric nitroalkenes 359.241 R R0 Time Yield Isomeric /h (%) ratio Z/E H Me 3.5 35 Me Me 17 82 70 : 30 H C6H13 2.5 60 Bu H 10 90 83 : 17 see a H 14 75 But H 17 94 MeCH=CH H 60 70 Bu Me 17 99 55 : 45 2-Furyl H 24 66 aMe2C=CH(CH2)2CH(Me)CH2 .The methanesulfonyl chloride ± triethylamine system has also been used for the transformation of nitro alcohols 358 into nitro- alkenes 359 (yields 30%±80%).70, 242 The nitroalkene Z-MeCH(NO2)CH2CH2CH=C(NO2)Me is formed in 80% yield when the nitro alcohol MeCH(NO2)CH2 ± CH2CH(OH)CH(NO2)Me is refluxed with MeSO2Cl and Et3N in dichloromethane under nitrogen.75 The E-isomers of nitroalkenes 359 were synthesised by dehy- dration of the nitro alcohols 358 over alumina (Brockmann activity I) at 40 8C.71 R R0 Time /h Yield (%) Me Me 8 75 Me Et 7 77 Me (CH2)4COOMe 7 76 Me CH2CH(OH)Me 7 73 EtCH=CH(CH2)2 Me 7 85 Ph(CH2)2 Me 9 68 Et H 48 60 C6H13 H 50 61 Et (CH2)6OH 7 68 cyclo-C6H11 C5H11 24 72 The dehydration occurs selectively: when the molecule con- tains both primary and secondary hydroxy groups, the secondary group is eliminated preferentially.71 It is of interest that the dinitro-diol resulting from acidification of the solution of the salt 30 with hydrochloric acid to pH 1 is dehydrated under the reaction conditions to give triene 360 in 26.7% yield.52 CHCH2;83 R=Me, Pri, R=Me,CH2 CH(CH2)2; R0=EtCH RCCH(NO2)R0 O 350 3A mol.sieves; 20 8C, 36 h PCC, CH2Cl2 RCHCH(NO2)R0 OH 349 PCC is pyridinium chlorochromate. Ph(CH2)2, O O Me H2C ; R0=Me, Et, (CH2)2COOMe, ;238 O O Me H2C CH2Cl2,710 8C, 2 h R1CC(NO2)R2R3 O 352 R1CHC(NO2)R2R3 OH 351 R2=Me, Et, H2C O O O O Me H2C , , (CH2)2COOMe; R3=H, Me.R1=Me, Pri, C6H13, Ph(CH2)2, CH2 CH(CH2)2 ; R=Me (53%), Pri (45%), C5H11 (47%), C10H21 (58%), (58%), RCHCH(NO2)CH2CHMe OH OH 353 CH2Cl2,710 8C, 2 h RCCH(NO2)CH2CMe O 354 O Me(CH2)4CH(NO2)(CH2)2 (65%). PhCH2CH2 (70%), Z-Me(CH2)7CH CH(CH2)7 (58%), R, R0 (yield, %): Me, Me (58); Me, Et (69); Et, Pri (59); Pri, Et (53).(RO)2P CCH2NO2 OH R0 356 C R0 CHNO2 357 SOCl2, C5H5N, CHCl3 60765 8C, 15 min O (RO)2P O 358 RCH CHR0 OH NO2 25735 8C Cu2Cl2, argon C6H11N C NC6H11 C C R NO2 R0 H 359 R=Me, Et, R0=Me, Et;242 R=Me, R0=PhS.75 358 RCH CHR0 OH NO2 0 8C, 15 min MeSO2Cl, Et3N, CH2Cl2, N2 359 C C R R0 NO2 H 40 8C 358 RCH CHR0 OH NO2 Al2O3, CH2Cl2 359 C C H R0 NO2 R HOCH2 CH2OH Me Me NO¡2 C C C C 7O2N 30 2Na+ HCl, H2O C H2C 360 C NO2 Me Me C C NO2 CH2 .Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 61When a mixture of 2-nitrobutan-1-ol and isoprene is kept at 150 8C, the nitro alcohol is dehydrated, and the resulting 2-nitro- but-2-ene reacts in situ with isoprene to give a mixture of [4+2]- adducts 361 and 362.243 On treatment with potassium hydroxide in Et2O for 2 h at 715 to 720 8C, the nitro alcohol O2NCH2CH(OH)CH2Cl is converted into the aldehyde O2NCH2CHCH2CHO (yield 21%).244 The reactions of 1,1,1-trinitroethanol or trinitromethane with formaldehyde in the presence of CuSO4 followed by treatment of the reaction products with ammonia at 100 ±105 8Cfor 8 ± 9 h lead to the same product, 2,2-dinitroethylamine.98, 245 Under conditions of the Mitsunobu reaction (treatment with triphenylphosphine and diethyl azodicarboxylate under an inert atmosphere),246 g-nitro alcohols 363 are converted into nitro- derivatives of cyclopropane 364.247 R R0 Yield (%) Ratio trans : cis C5H11 H 82 10 : 1 C5H11 Me 87 10 : 1 4-PhC6H4 H 75 trans 4-MeOC6H4 H 92 7 : 1 PhCH2OCH2CH=CH H 64 trans Under the same conditions, PhCH2OCH2CH(OH) ± CH(CH2OCH2Ph)CH2NO2 is converted into 1,3-bis(benzyl- oxy)-2-nitrocyclopropane in 98% yield (the ratio of the isomers was not determined).247 When hydrochlorides 365 are introduced into the Mitsunobu reaction, they are converted into hydrochlorides of 1-alkyl-3- hydroxymethyl-3-nitroazetidines 366.229 When acetates of nitro alcohols 367 and isonitrile 368 are heated in the presence of DBU, 367 are converted into nitro- alkenes 369, while the isonitrile is deprotonated to give carbanion 370.The nitroalkenes and the carbanion react to give pyrrole derivatives 371.248 Pyrrole derivatives 372 have been obtained in high yields (70% ± 86%) by cyclocondensation of the acetates 367 with alkyl cyanoacetates 373 in the presence of DBU at 20 ± 25 8C.107 Pyrazole derivatives 374 are formed in the reaction of 2,2- dinitroethanol with diazo compounds 375 in benzene or ether.249 2-(1-Hydroxy-2-nitroethyl)furan 376 reacts with bromine and sodium methoxide to give 2,5-dihydrofuran derivative 377 in 77.5% yield.142 2,4,4-Trimethyl-2-nitromethyltetrahydrofuran (yield 30%) is formed when the nitro alcohol BrCH2CMe2CH2C(OH)(Me). .CH2NO2 is kept over Al2O3 in benzene at 25 8C.250 Treatment of (S)-1-nitropentan-1-ol with 30% H2O2 and K2CO3 in methanol (0 8C, 24 h) followed by the addition of hydrochloric acid results in the formation of (S)-4,5-dihydro-5- methylfuran-2(3H)-one (yield 7%).111 Under the conditions of the Mitsunobu reaction, nitro alco- hols 378 cyclise to give eitr isoxazoline N-oxides or dihydro-1,2- oxazine N-oxides 379 depending on the mutual arrangement of the nitro and hydroxy groups.When R=PhSO2, the yield of the corresponding isoxazoline is relatively low; in this case, 1-nitro-1- phenylsulfonylcyclopropane is formed as the main reaction prod- uct. For the cyclisation products to be formed in high yields, it is necessary that an electron-withdrawing group or a double bond, which stabilise the aci-form 380 of the initial compounds, be present in the a-position with respect to the nitro group.251 R R0 A Yield (%) Ph H CH2 98 Ph H CH2CH2 93 EtOCO Me CH2CH2 94 Me H COCMe2 81 NO2 H CH2 98 PhSO2 H CH2 15 2-Hydroxy-6-methyl-5-nitrotetrahydropyran has been syn- thesised in 68% yield by cyclocondensation of acrolein with 1-nitropropan-2-ol in the presence of diethylamine and formic acid at 60 ± 62 8C for 20 h.252 EtCHCH2OH+CH2 NO2 C CH CH2 Me MeOH 150 8C, 14 h 361 362 Me + Et NO2 Me Et NO2 RCHCH2CHR0 OH NO2 363 20 8C, 14 h Ph3P, EtOOCN NCOOEt, PhH R R0 NO2 364 R=Me, Et, Pr, Pri, Bu, But.CH2OH CH2OH + RNH2CH2C(NO2) Cl7 365 EtOOCN Ph3P, NCOOEt CH2OH NO2 Cl7 366 + RHN DBU, THF refluxing for 16 h 368 367 R1CHCHR2+CNCH2COOCH2Ph NO2 OAc R, R0 (yield, %): Me, Me (72); Et, Me (74); Me, Et (76); Et, Et (74); N R1 R2 H 371 COOCH2Ph 369 R2 C R1CH NO2 7 CNCHCOOCH2Ph 370 (CH2)2COOMe, Me (60); Me, (CH2)2COOMe (53).R1=Et, (CH2)2COOMe; R2=Me, Et, (CH2)2COOMe; R3=Et, But. N R1 R2 H COOR3 372 367+CNCH2COOR3 373 DBU, THF 20725 8C, 10718 h R=OEt (PhH, 50 8C, 6 h, 46%); Me (PhH, 50 8C, 4 h, 64%); Ph (Et2O, 36 8C, 14 h, 63%).N N NO2 H 374 RCO HOCH2C(NO2)2H+N2CHCOR 375 PhH or Et2O 2. MeONa, 730 8C 1. Br2, MeOH,735 8C O CHCH2NO2 OH 376 O CHCH2NO2 MeO OH OMe 377 RCH A NO2 378 C N OH O 380 CHR0 OH R A CHR0 OH O N A R0 R O 379 62 M-G A ShvekhgeimerThe reaction of 4-nitrobutan-2-ol with sodium glyoxylate in the presence of Na2CO3 resulted in the isolation of compound 381 as two isomers (a and b), their yields being 32% and 10%, respectively.253 Tetrahydro-1,3-oxazine derivatives 382 have been prepared by refluxing compounds 383 with aldehydes 384 in benzene in the presence of sodium hydrogencarbonate.254 Hydrazones 385 react with carbon disulfide in the presence of potassium hydroxide to give 1,3,4-oxadiazine-2-thiones 386.159 On heating with sodium hydride, cyclic ketones 387 or 388 containing nitro and 3-hydroxyalkyl groups in the a-position with respect to the oxo group isomerise with ring expansion giving rise to compounds 389 or 390.255 n Time /min Yield (%) 4 45 91 10 30 87 5.Cleavage of nitro alcohols Under certain conditions, b-nitro alcohols (or b-nitro-diols) are cleaved to give the initial carbonyl derivatives and nitro-com- pounds (or their salts).In the presence of alumina at ambient temperature, nitro alcohols 391 are cleaved to nitromethane and ketones 392.250, 256 AcONa, BaO or KNaHPO4 can be used instead of Al2O3.256 Benzyltrimethylammonium hydroxide cleaves the nitro alco- hol Me2C(OH)CH(NO2)(CH2)2NO2 on refluxing in methanol for 6 h to give acetone and 1,3-dinitropropane (yield 50%).257 This process can be carried out in ethanol, dioxane, THF or DMF in the presence of Na2CO3, Na3BO3, MgO or BaCO3.257 Treatment of the alcohol 107 with sodium dichromate and sulfuric acid results in its cleavage giving formaldehyde and fluorodinitromethane (yield 65%).258 When the dinitro-diol 114 157 or 2,2-dinitropentane-1,3- diol 259 is treated with potassium hydroxide in methanol, the salt K+C7(NO2)2CH2OH and CH2O or MeCHO are formed.The reaction of compound 114 with potassium hydroxide and sodium carbonate yields salt 393, which reacts with chlorine to give 2-chloro-2,2-dinitroethanol (overall yield 48%).157 Treat- ment of the dinitro-diol 114 with chlorine fluorosulfonate affords dichlorodinitromethane (yield 15%).260 The decomposition of nitro alcohols 394 in an aqueous buffer solution with m 1.0 D and pH 6.5 ± 8.4 has been studied at 25.3 8C by spectrophotometry.The rate constants for the reaction were determined. It was postulated that deprotonation occurs rapidly, while the rupture of the C±C bond is the rate-determining step of the process.261 6. Intramolecular hydrogen bonds in nitro alcohols and nitro-diols Studies discussing the problems concerning intramolecular hydro- gen bonding in nitro alcohols and published before 1977 have been surveyed in a review.262 The configurations of the erythro- and threo-isomers of the nitro alcohols RCH(OH)CH(NO2)R0 (R, R0 =Me, Me; Pri, Me; CF3, Me; CCl3, Me; CBr3, Me; 4-O2NC6H4, Et; 4-O2NC6H4, Pri) have been established by IR and 1H, 13C and 15N NMR spectro- scopy.It was found that the erythro-isomers occur mostly in the gauche conformation A, and the threo-isomers exist predomi- nantly in the gauche conformation B. These conformers predom- inate because they are stabilised by intramolecular hydrogen bonds between OH and NO2 groups.64 O2NCH2CH2CHMe + O Me R1 R3 R2 R4 381a,b NaHCO3 25 8C OH 7+ CCONa O O H 381a: R1=R3=H, R2=NO2, R4=OH; 381b: R1=NO2, R3=OH, R2=R4=H. R, R0 (yield, %): PhCH2, Me (80); cyclo-C6H11, Me (60); PhCH2, Ph (60). NO2 RNHCH2C(Me)CH2OH+R0CHO 383 384 NaHCO3, PhH 80 8C, 5 h N O R0 R O2N Me 382 CCH(OH)R0 +CS2 NO2 60770 8C, 0.5 h; 20 8C, 6 h KOH, DMF 4-RC6H4NHN 385 R=H, R0 =Me (71%); R=Me, R0 =H (88%), Me (78%).N O N NO2 R0 S 4-RC6H4 386 NaH, MeOCH2CH2OMe 85 8C 389 (81%) NO2 387 (CH2)2CHMe OH O O Me O NO2 NaH, MeOCH2CH2OMe 85 8C, 1 h (CH2)n O NO2 (CH2)3OH 388 O NO2 O (CH2)n 390 R=Br (20%),250 NO2 (72%).256 RCH2CCH2CCH2NO2 391 OH Me Me Me Al2O3, PhH 7MeNO2 RCH2CCH2CMe 392 Me Me O Cl2C(NO2)2 .ClSO2F 725 to720 8C, 1.5 h; 0 8C, 2.5 h 114 HOCH2CCH2OH NO2 NO2 114 KOH, MeOH 0 8C ClC(NO2)2CH2OH, 393 +7 KC(NO2)2CH2OH Cl2, H2O Ar, 104 k (litre mol71 s71) : Ph, 3.02 (pH 4.6 ± 8.4); 4-MeC6H4, 3.37; 4-MeOC6H4, 5.09; 4-ClC6H4, 4.22; 4-O2NC6H4, 4.54; 3-ClC6H4, 3.79; 3-MeC6H4, 3.07.O2NCMe2CHO7 k2 k72 Ar O2NCMe2CHOH Ar 394 k1[B] k71[BH+] 7 O2NCMe2+ArCHO Aliphatic nitro alcohols. Synthesis, chemical transformations and applications 63The conformation equilibria for the alcohols RCH(OH)CH2NO2 [R = H (202), Me, Ph, CCl3] and for 2- nitropropane-1,3-diol 3 have been studied.In the case of the alcohols, equilibrium conformations A1, B1 and C1 were consid- ered.263 For the diol 3, equilibrium conformations A2, B2 and C2 were discussed. It was found that the nitro alcohol 202 (R = H) exists predominantly in conformations A1 and C1. In other cases (R = Me, Ph, CCl3), conformation C1 predominates.The dihedral angle of 100 ± 125 8 is in agreement with the synclinal arrangement of the OH and NO2 groups and with the formation of a hydrogen bond between them. In the case of the nitro-diol 3, conformer A2 with the synclinal arrangement of the CH2OH and OH groups predominates in the equilibrium. Thus, the interaction between the two hydroxy groups is stronger than that between the OH and NO2 groups.263 IV.Practical use of aliphatic nitro alcohols Possible applications of aliphatic nitro alcohols have been dis- cussed in a large number of publications. Aliphatic monoatomic and polyatomic nitro alcohols and their derivatives both in a pure state and in various compositions are used most widely as bio- logically active compounds and as components of rocket fuels or explosives.Other applications of these compounds have also been proposed. 2-Bromo-2-nitropropane-1,3-diol 8 is used most often as a biologically active compound known as `Biocide'. This nitro-diol as well as nitro alcohols of the general formula R1R2C(OH)CR3(Br)NO2 (R1 = H, alkyl, phenylalkyl; R2 = H; R1R2 = cycloalkyl; R3 = H, Me, Et, Br) are active against Staphylococcus aureus and Pseudomonas aeruginosa.264 ± 266 The nitro-diol 8 has been used as an antimicrobial additive 267 and as a component of agents controlling the amount of slime in wood pulp during the manufacture of paper,265, 268 antimicrobial com- positions controlling Chlorella,269 antiulcer compositions 270 and compositions controlling the development of Cosmarium.271 It has been proposed to use the bis-formate of nitro-diol 8 and 5-bromo-5-nitro-1,3-dioxane and its 2-substituted derivatives, resulting from condensation of 8 with aldehydes, as bactericides and fungicides;190, 191, 220 the mixed ester 4-ClC6H4OCH2 ± C(NO2)(Br)CH2OSO2Me has been used as a component of an agent that fully controls the growth of Erysiphe gramin.219 The nitro-diol 8 has been patented as a deodorant for the toilets of buses and campers,272 as a deodorant for refuse bins 273 and as a component of compositions removing NH3, H2S and MeSH from aircraft toilet waste waters.274 The use of the nitro-diol 8 and 2-chloro-2-nitropropane-1,3- diol as inhibitors of light- and heat-induced paint changes has been patented.275 The polyester obtained by polycondensation of 8 with tereph- thaloyl dichloride has been claimed as an agent for cotton processing in order to make cotton fabrics resistant against Escherichia coli JFO 3134 and Staphylococcus aureus JFO 12732 and more comfortable for wearing.276 The nitro alcohols R1C(NO2)(X)CH(OH)R2 (R1, R2 = H, halogen, substituted alkyl; X = halogen) have been patented as components of microbicide agents, in particular, of those active against Alternaria tenuis,47 Pseudomonas aeruginosa,277 Plasmo- diophora brassicale 278 and Baccillus subtilis.279 The nitro alcohols Cl3CCH(OH)CH(Br)NO2,7 2-nitro-1-(2- and 4-pyridyl)propan-1-ols,280 EtC(NO2)(Br)CH2OH,35 2-nitro- 1-(2- and 4-quinolyl)propan-1-ols and 2-nitro-1-(2 and 4-quino- lyl)propane-1,3-diols 281 have been used as bactericides and fungi- cides. 2-Hydroxymethyl-2-nitropropane-1,3-diol 4 has been recom- mended as an agent for treating water infected with Streptococ- cus.282 FC(NO2)2CH2OH 107 suppresses the growth of Escherichia coli or Staphylococcus aureus, while 2-chloro-2,2-dinitroethanol exhibits antispasmodic activity.283 2-Methyl-4-nitropent-3-en-2-ol has been reported to improve blood circulation.284 A broad spectrum of biological activities is exhibited by the nitro alcohols R,R0CH(OH)C(NO2)(X) (R,R0,X=CCl3, Me, Cl; H, Pr, Cl; Me, Cl, Cl; Pri, H, Br; Bu, H, Br; C5H11, H, Br; C6H13, H, Br; Me, Me, Br; Et, Me, Br; CCl3, Me, Br; H, Et, Br; Me, Et, Br; Me, Br, Br; Et, Br, Br; Pri, Br, Br.57 It has been proposed to use formate, methyl carbonate and some other esters of nitro alcohols RC(NO2)2CH2OH (R = Cl, Br, Me) as bactericides and fungicides.157, 285 The compounds R1ZNHC(S)OCH(R2)CR3R4NO2 (R1, Z, R2, R3, R4 = Ph, SO2, H, H, H; Ph, SO2, H, Br, Me; Ph, CO, H, H, H; 4-O2NC6H4, CO, H, Br, Me; 4-O2NC6H4, CO, Me, H, Et; 4- ClC6H4, CO, H, H, H; Ph, CO, H, H, Et; 4-O2NC6H4, CO, Me, H, Me; 2-furyl, CO, H, H, H) have been patented as fungicides and bactericides for deodorants, creams and cleaning compositions,224 while the esters (2-thienyl)COOCHRCHR0NO2 (R=H, Me, Pr, Pri;R0=H, Me, Et) have been used as fungicides and bactericides for deodorants, soaps and creams.286 The nitro alcohols RR0C(NO2)(CH2)nOH (R, R0 =H, Cl, Br, Br; n = 1 ± 3) and their acetates have been recommended as components of compositions improving the properties of paper, dyes, cosmetics and adhesives.287 The addition of the nitro-diol 8 to a mixture used for the development of photographic materials inhibits contamination of waste waters.288 The nitro alcohols RC(NO2)BrCH(R0)OH (R = CH2OH, lower alkyls; R0 =H, lower alkyls) increase the stability of dyes in photographic materials with improved photosensitive layers.289 These nitro alcohols combined with isothiazol-3-one derivatives permit high-quality development of photographic materials even at low pH without decreasing the sensitivity.290 The nitro alcohols RC(NO2)(Br)CH(OH)R0 (R, R0 =H, Me, Et) are added to paper pulp in order to improve the properties of photographic paper.291 A film coated by a composition of polyamide with 2-hydr- oxymethyl-2-nitropropane-1,3-diol 4 becomes more resistant to abrasive wear.292 H OH R NO2 H R0 H OH R R0 H NO2 A B NO2 H H OH R H NO2 H H R H OH NO2 H H H HO R A1 B1 C1 NO2 H HOCH2 H HO H NO2 H HOCH2 OH H H NO2 H HOCH2 H H OH A2 B2 C2 S COOCHRCHR0NO2 R=H, Me, Pr, Pri; R0=H, Me, Et. 64 M-G A ShvekhgeimerThe use of the nitro alcohols R1R2C(NO2)CH(OH)R3 [R1, R2= H, C1 ± 5 alkyl, CH2OH; R3 = H, alkyl (C1 ± 5)] as compo- nents of toning agents protecting colloidal photographic materials from X-rays has been patented.293 The nitro-diol 4 has been used as a stabiliser of developers for colour photography.294 The compound 4 and 2-methyl-2-nitro- propane-1,3-diol have been recommended as agents increasing light resistance of dyes.295 2-Methyl-2-nitropropan-1-ol can be used for the preparation of polymerisation inhibitors for esters of unsaturated carboxylic acids.296 The nitro alcohols XX0C(NO2)CH(R)OH (X, X0=Hal; R= H, alkyl) are used to prevent fur formation.297 2-Methyl-3-nitropropan-2-ol has been used as a plasticiser for cellulose triacetate.298 The same nitro alcohol blended with the product of condensation of urea and formaldehyde imparts permanent-press and wrinkle-resistant characteristics to cotton textiles.299 The nitro-diols O2NC(R)(CH2OH)2 (R = Me, Et, CH2OH) react with melamine at 70 8C and pH 9.5 ± 10 to give adhesive resins that join surfaces under elevated pressures at 250 ± 300 8C.300 2-Methyl-2-nitropropan-1-ol has been used to improve adhe- sion of rubber to a steel cord.301 The product of reaction between 2-ethyl-2-nitropropane-1,3- diol and tetraethylenepentamine, which solidifies over a period of 15 min at room temperature, has been recommended as a coating for steel sheets.302 The nitro alcohols RC(NO2)(X)CH(OH)R0(R=H, CH2OH, lower alkyls; R0= H, lower alkyls; X = Hal) have been patented as agents protecting metal working fluids from bacteria and fungi.303, 304 2-Nitropropan-1-ol increases the covering power, the time of hardening and the strength of cements.305 3-Nitrobutan-2-ol has been used as a selective solvent for dearomatisation of directly distilled petrols.306 The nitrate MeCH(ONO2)CH(NO2)Me increases the cetane number of diesel fuels.307 Halo-substituted nitro alcohols of the general formula R1[CH(OH)]nC(NO2)(X)CR2R3OH [R1, R2, R3=H, alkyl (C1 ± 7); X = Cl, Br, I; n = 0, 1], in particular, the nitro-diol 8 have been claimed as antimicrobial agents for hydrocarbon fuels.308 Polynitro alcohols and their derivatives are important com- ponents of rocket fuels and explosives.The compound (O2N)2C(F)CH2OCOOCH2CF3 has been used as a plasticiser for plastic explosives.205 The formate, methyl carbonate and some other esters of MeC(NO2)2CH2OH have been used as plasticisers for rocket fuels;157 the compound [FC(NO2)2CH2]2NCOOCH2C(NO2)2F has been patented as a plasticiser for explosive compositions.309 Among the derivatives of polynitro alcohols proposed as plasticisers for high-energy compositions, the following com- pounds should be noted: [EtOCOCH2C(NO2)2F]2Me,187 (RO)2CHMe, MeCH(OR)OCH2C(NO2)2R0 [R= CH2C(NO2)2F, R0=F, Me, NO2]186 [RC(NO2)2CH2O]2CH2 (R=Me,182, 310 F,311 NO2 182), [RC(NO2)2CH2O] ± CH2[OCH2C(NO2)2R0] (R, R0=NO2, Me;182 Me, Et 310), RC(NO2)2CH2OC[=CHCOOCH2C(NO2)2R]COOCH2(NO2)2- R0 (R=R0=H, F, Me, NO2).218 The use of the orthoester [FC(NO2)2CH2O]2CH±[OCH(- Me)C(NO2)2F] as a co-plasticiser in high-energy compositions has been patented;312 the orthocarbonate [FC(NO2)2CH2O]3- COCH2C(NO2)3 has been used as a plasticiser and as an energetic explosive.211 2-Fluoro-2,2-dinitroethanol 107 can be used as a plasticiser and a binding agent for rocket fuels and explosive compositions;91 the ether (O2N)3CCH2OC(NF2)3 can be used as a plasticiser and an oxidant for rocket fuels.180 The following compounds have been patented as energetic binding agents for high-energy compositions: the vinyl ethers RC(NO2)2CH2OCH=CH2 (R=F, NO2) 313 and FC(NO2)2 ± CH2C(NF2)2CH2OCH=CH2,213 nitroformals synthesised by polycondensation of the tetranitro-diol [HOCH2C(NO2)2CH2]2 with formaldehyde 185 or by polymerisation of the epoxide 314 and esters formed by 2,2-di- nitropropane-1,3-diol 114 with oxalic, malonic or fumaric acids.315 The polyester resulting from the reaction of the dichloride [ClCOCH2CH2]2C(NO2)2 with the diol [HOCH2C(NO2)2CH2]2O has been patented as a component of energy-producing composi- tions.316 The nitro-derivatives [RC(NO2)2CH2O]2C=S (R = F, Me, NO2) have been used as intermediate compounds in the synthesis of energetic explosives.212 References 1.D Seebach, E W Colvin, F Lehr, T Weller Chimia 33 1 (1979) 2. 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