摘要:

OH OH S S CO2H CO2H H3L HSCH2CO2H i, CH2O, NaOH ii, 2M HCl O S S O S S M OH O O O O M O M OO O O I II J. CHEM. RESEARCH (S), 1997 347 J. Chem. Research (S), 1997, 347 J. Chem. Research (M), 1997, 2201–2214 Preparation of the New Binucleating Ligand 2,6-Bis(carboxymethylsulfanylmethyl)-4-methylphenol and its Mono- and Bi-nuclear Complexes Abdou S. Sall,*a Mohamed Gaye,a Oumar Sarr,a A. Caneschi,b Vito Di Notoc and Maurizio Vidalic aFacult�e des Sciences et Techniques, D�epartement de Chimie Universit�e Cheikh Anta Diop de Dakar, S�en�egal bDipartimento di Chimica Universit`a di Firenze, Via Maragliano, 75-50144 Firenze, Italy cDipartimento di Chimica Inorganica, Metallorganica ed Analitica Universit`a di Padova, Via Loredan, 4-35131, Padova, Italy Mono- and bi-nuclear complexes of transition metals have been prepared by the reaction of 2,6-bis(carboxymethylsulfanylmethyl)- 4-methylphenol (H3L) with the appropriate metal salt.Different approaches have been developed for the design and synthesis of polymetallic centres in order to exploit their mentioned potentials.One strategy has been to design and prepare multidentate ligands capable, through the siting of their donor atoms, of coordinating metal ions into juxtaposition (e.g. compartmental,1 face to face,2 cylindrical macrotricycles, 3 polypodal ligands,4 etc.). The development of these so-called binucleating ligands has led to the successful synthesis of homobinuclear and heterobinuclear metal chelates which have found application in the area of biomimetic chemistry.5,6 T h e l i g a n d 2 , 6 - b i s ( c a r b o x y m e t h y l s u l f a n y l m e t h y l ) - 4 - methylphenol (H3L) was prepared by direct carboxyalkylsulfanylmethylation, under a nitrogen atmosphere, of p-cresol with formaldehyde according to the following scheme.It is a one-step process based on refluxing the phenol with formalin and the sodium salt of 2-sulfanylacetic acid to give the product substituted in all the vacant ortho positions.The ligand has been isolated as the free acid. Spectroscopic studies suggest that in the mononuclear chelates the ligand is coordinated to the central metal ions through the sulfur atom, one oxygen of the carboxylic groups and the oxygen of the phenoxo moiety. Moreover, according to magnetic moment data, we suggest there to be some molecular association through the C�O of the carboxylic group. In the binuclear chelates the coordination geometry, in each arm, is realized through the carboxylic C·O, the sulfur atom, the phenolic endogenous bridging C·O and the exogenous bridging acetate.We thank Mrs Sandra Boesso, Mr Letterio Turiaco and Mr Sergio Mazzuccato for technical assistance. This work was supported by the Italian M. P. I. and by Trento University. The research was also supported by the Third World Academy of Science through Grant No. 95-351 RG/CHE/ AF/Ac. Techniques used: 1H NMR, MS, IR, UV, magnetic measurements References: 19 Table 1: Elemental analyses of the prepared compounds and their magnetic moments at room temperature Table 2: UV bands of the prepared compounds Fig. 1: xT vs. T dependence in the range 100–300 K for Cu2L(OAc).H2O Fig. 2: xT vs. T dependence in the range 20–300 K for Ni2L(OAc).4H2O Fig. 3: xT vs. T dependence in the range 80–300 K for Mn2L(OAc).2H2O Received, 25th February 1997; Accepted, 20th June 1997 Paper E/7/01315I References cited in this synopsis 1 U. Casellato, P. A. Vigato, D. E. Fenton and M. Vidali, Chem. Soc. Rev., 1979, 8, 199. 2 J. P. Collman, C. M. Elliott, T. R. Halberg and B. S. Tovrog, Proc. Natl. Acad. Sci. USA, 1997, 74, 8. 3 A. H. Alberts, R. Annunziata and J. M. Lehn, J. Am. Chem. Soc., 1977, 99, 8502. 4 Y. Nishida, K. Takahashi, H. Kuramoto and S. Kida, Inorg. Chim. Acta, 1981, 54, L103. 5 K. D. Karlin and Y. Gultneh, J. Chem. Educ., 1985, 62, 983. 6 J. A. Ibers and R. H. Holm, Science, 1980, 209, 223. *To receive any correspondence (e-mail: assall@ucad.refer.sn). Fig. 1 Proposed coordination of the ligand around the metal ions in the mono (I) and binuclear (II) complexes (the solvent molecules a

ISSN:0308-2342    

DOI:10.1039/a701315i

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

H2N OH Et ( R)-(–)-1 O HO N Ph Et R1 2 3 4 5 R = Me R = Bu R = PhCH2 R = o-FC6H4CH2 1 1 1 1 ( R)-(–)-1 (a) F HN HO Et (b) ( R)-(+)-5 ( R)-(–)-6 n 348 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 348–349 J. Chem. Research (M), 1997, 2227–2243 Asymmetric Synthesis. Part 2.† Enantioselective Conjugate Addition of Grignard Reagents to the Cinnamamide and Crotonamide deriving from (R)-(µ)-N-(2-Fluorobenzyl)- 2-aminobutanol. Determination of Diastereoisomeric Excess by 19F NMR Spectroscopy Eric Brown,* Christelle Deroye, François Huet, Christelle Le Grumelec and Jo�el Touet Laboratoire de Synth`ese Organique (ESA 6011), Universit�e du Maine, Avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France Conjugate addition of various Grignard reagents to the N-(2-fluorobenzyl)cinnamamide (R)-(+)-5 and crotonamide (R)-(+)-7 afforded the corresponding adducts 8a–e and 9a–f in good yields and in high diastereoisomeric excesses, as evidenced by 19F NMR; acidic hydrolysis of these adducts gave the corresponding b-substituted alkanoic acids (R)-10a–e and 11a–f, respectively.As part of a programme of asymmetric synthesis using N-alkyl derivatives of both enantiomers of 2-aminobutan-1-ol 1 as new chiral vectors, we recently described1a our preliminary results concerning the enantioselective conjugate addition of Grignard reagents to the chiral N,N-dialkyl cinnamamides (R)-(µ)-2–4 deriving from the amino alcohol (R)-(µ)-1 (Scheme 1).Other studies along similar lines have been described by Shimano and Meyers,1b Melnyk and coworkers, 1c and Nicolas and co-workers.1d We report herein the use of the readily available N-(2-fluorobenzyl) derivative (R)-(µ)-6 as a useful and efficient chiral auxiliary for such conjugate additions. Standard N-alkylation of (R)-(µ)-1 with 2-fluorobenzyl chloride gave the compound (R)-(µ)-6 on a 15 g scale. N-Acylation of the latter with cinnamoyl or crotonoyl chloride in a biphasic system afforded the corresponding amides (R)-(+)-5 and (R)-(+)-7, respectively (Scheme 2).The five adducts 8a–e were obtained by conjugate addition, at 0 °C for 3 h, of the appropriate alkyl Grignard reagent (3–6 mol equiv.) with the cinnamamide (R)-(+)-5, and in 60–79% yields after chromatography. The diastereoisomeric excesses (de, %) of these adducts were determined by means of 19F NMR spectroscopy. As a matter of example, the protondecoupled 19F NMR spectrum of 8b (using CFCl3 as a standard) exhibited two signals of high intensity at d µ118.6 and µ120.0 corresponding to both amide conformers of the major (R,R) diastereoisomer of 8b, and two signals of lower intensity at d µ118.7 and µ121.0 similarly corresponding to the minor diastereoisomer (S,R)-8b.The results displayed in Table 1 show that the de’s of the adducts 8a–e are within the range 92–97%. Hydrolysis of these adducts in a boiling mixture of acetic acid and 3 M H2SO4 gave the acids (R)-10a–e.The formation of the known acids 10a,b of R configuration confirms the general mechanism which was ascribed to this conjugate addition reaction.1 Analogously, it is assumed that the three new acids 10c–e also have the R configuration. Since epimerization at the b carbon of the acids 10a–e was not expected to occur during hydrolysis of the corresponding adduct 8a–e, it is likely that the enantiomeric excesses (ee, %) of these acids are very close to the de’s of the adducts 8a–e, respectively.*To receive any correspondence (e-mail: lso@lola.univ-lemans.fr). †Part 1 is ref. 1a. Table 1 Enantioselective syntheses of the b-phenylalkanoic acids (R)-10a–e (Scheme 2) Adducts 8a–e Acids (R)-10a–e Yield Yield R (%)a [a]D b de (%)c (%)d [a]e Et Bun n-C5H11 n-C6H13 n-C8H17 8a 8b 8c 8d 8e 60 70 68 77 79 µ3.81 µ2 µ1 +1.3 +1 92 94 95 97 96 10a 10b 10c 10d 10e 74 61 76 60 60 µ45 µ38 µ30.5 µ26.45 µ21.5 aYield after chromatography. bTaken in PhH. cDe’s were determined by means of 19F NMR.dYield after distillation. eSpecific rotations were measured at 22 °C in PhH at 589 nm for 10a,c–e and at 578 nm for 10b. Scheme 1 Reagents and conditions: (a) o-FC6H4CH2Cl; (b) PhCH�CHCOCl–Na2CO3–H2O–CH2Cl2F N HO Ph O Et ( R)-(+)-5 F N HO Me O Et ( R)-(+)-7 (a) (a) F N HO Ph O Et R H ( R) ( R) 8a–e F N HO Me O Et R H ( R) 9a–f a b c d e Et Bu n-C5H11 n-C6H13 n-C8H17 n R a b c d e f Ph p-MeOC6H4 p-MeC6H4 Et Bu n-Hex R n ( S) ( R) (b) (b) CO2H Ph R H CO2H Me R H ( R)-10a–e 11a–f OH CF3 H Me R H O O F3C H (c) 13a–f ( R)-(+)-12 J.CHEM. RESEARCH (S), 1997 349 In a similar fashion, the crotonamide (R)-(+)-7 was treated with various alkyl and arylmagnesium halides (3 mol equiv.), thus affording the corresponding adducts 9a–f in 62–87% yields after chromatography (Table 2). The de’s of the adducts 9a–f were determined by means of 19F NMR spectroscopy as described above and were found to be within the range 92–97%.Acidic hydrolysis of these adducts gave high yields of the corresponding acids 22a–f, respectively. Here again it was assumed that the ee’s of the acids 11a–f were equal to the de’s of the starting adducts 9a–f, respectively. In order to confirm this hypothesis, each acid 11a–f was esterified with an equimolecular amount of enantiomerically pure (R)-(+)-2-(trifluoromethyl)benhydrol5 (R)- (+)-12 by means of 1,3-dicyclohexylcarbodiimide (DCC) and 4-diethylaminopyridine (DMAP) in methylene dichloride.This gave the corresponding esters 13a–f in 63–78% yields after chromatography. the de’s of these esters were determined by means of 19F NMR spectroscopy and are displayed in Table 2. These values are in good agreement with those of the starting adducts 9a–f, respectively. The differences D(de) between the de’s of the starting adducts 9a–f and those of the corresponding esters 13a–f are in the range 2–5% in all cases but one. These discrepancies might spring from several causes.First it is difficult to purify highly the oily acids 11a–f and esters 13a–f. Secondly, both enantiomers of the acids 11a–f may not be esterified at the same rate with the benzhydrol (R)-(+)-12. Conclusion The present work represents a confirmation and an improvement of those we recently described.1a They show that the N-(2-fluorobenzyl) base (R)-(µ)-6 is a valuable chiral inducer for the enantioselective conjugate addition of Grignard reagents onto deriving alkenamides, thus leading to nearly enantiopure b-substituted alkanoic acids.The secondary base 6 is readily available in both enantiomeric forms and can be recycled without appreciable loss; moreover it is easy to assess the diastereoselectivity of the conjugate addition reaction by means of 19F NMR spectroscopy. Full text in French Techniques used: 1H and 19F NMR, IR, micropolarimetry References: 9 Schemes: 2 Received, 12th May 1997; Accepted, 16th June 1997 Paper F/7/04353H References cited in this synopsis 1 (a) J.Touet, S. Baudouin and E. Brown, J. Chem. Res. (S), 1996, 224; (b) M. Shimano and A. I. Meyers, J. Org. Chem., 1995, 60, 7445; (c) O. Melnyk, E. Stephan, G. Pourcelot and P. Cresson, Tetrahedron, 1992, 48, 841; (d) E. Nicolas, K. C. Russel and V. J. Hruby, J. Org. Chem., 1993, 58, 766. 5 E. Brown, C. Chevalier, F. Huet, C. Le Grumelec, A. L�ez�e and J. Touet, Tetrahedron: Asymmetry, 1994, 5, 1191. Scheme 2 Reagents and conditions: (a) i, RMg X; ii, H2O+; (b) 3 M H2SO4–AcOH, heat (5 h); (c) (R)-(+)-12–DCC-DMAP Table 2 Enantioselective syntheses of the b-methylalkanoic acids 11a-f Adducts 9a–f Acids 11a–f Esters 13a–f Yield de Yield Abs. Yield de R (%)a (%) (%)b Conf. (%)a (%)c D(de)d a bc def Ph p-MeOC6H4 p-MeC6H4 Et Bun n-Hex 67 72 62 87 79 68 96 97 96 92 95 95 91 93 94 76 88 90 SSSRRR 76 75 72 78 63 63 91 91 94 88 97 92 562423 aYield after chromatography. bYield before molecularion. cThe de’s were determined by means of 19F NMR. dD(de) is the absolute difference between the de of the adduct 9 and that of the corresponding ester 13.

ISSN:0308-2342    

DOI:10.1039/a704353h

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

RNHNH2 + EtOCH C CN Y N N Y NH2 R R = CSNH2 R = Ph 1a b Y = CO2Et Y = CN 2a b R = CSNH2, Y = CO2Et R = CSNH2, Y = CN R = Ph, Y = CO2Et 3a b c N N N N Z NHNH2 7 Z = CONHNH2 8 Z = CN HN N N N Y S 5a Y = CO2Et b Y = CN N N N N Y SCH2R a Y = R = CO2Et b Y = CO2Et, R = COC6H4Cl- p c Y = CO2Et, R = CONHC6H4OMe- p d Y = CN, R = COC6H4Cl- p 6 NH2NH2–H2O ClCH2R 3a,b CH(OEt)3 N N CONHNH2 NH2 Ph NH2NH2–H2O 3c 9 N N CONHN NH2 Ph CHAr N N Ph 12 N N N O N CHAr HONO a–d Ar = Ph Ar = C6H4OMe- p Ar = C6H4Cl- p Ar = C6H4NO2- p Ar = C6H4OH- p a bc d e 10 N N Ph 11 N N O N CHAr CH(OEt)3 a–e ArCHO N N N N Ph H O N CHAr S N N N S Ph H O S N N N N Ph H O S H 10a–e CS2–pyridine N N Ph CONH2 NH2 CS2–pyridine 14 15 16 13 352 J.CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 352–353 J. Chem. Research (M), 1997, 2255–2269 Synthesis of Some New Pyrazolotriazines, Pyrazolothiazines and Pyrazolopyrimidines Adel M. Kamal El-Dean* and Ahmed A. Geies Chemistry Department, Faculty of Science, Assiut University, Assiut 71516, Egypt The syntheses of novel derivatives of pyrazolo[1,5-a]-s-triazine, pyrazolo[3,4-d][1,3]thiazine and pyrazolo[3,4- d]pyrimidine, starting from 4-substituted 5-aminopyrazole-1-carbothioamides, are reported.In view of the biological activities of 5-aminopyrazoles, e.g. tranquilizing and analgesic properties,1–5 and also in continuation of our work on the synthesis of polyheterocycles containing the pyrazole moiety,7,8 we now describe the synthesis of new fused pyrazolopyrimidines, pyrazolotriazines, and pyrazolothiazines. 4-Substituted 5-aminopyrazole-1- carbothioamides 3a,b were prepared through the reaction of ethyl ethoxymethylenecyanoacetate 2a or ethoxymethylenemalononitrile 2b with thiosemicarbazide 1a in refluxing methanol (Scheme 1). Condensation of 3a,b with triethyl orthoformate in methanol led to the formation of the 8 - e t h o x y c a r b o n y l p y r a z o l o [ 1 , 5 - a] - s- t r i a z i n e - 4 ( 3 H) - t h i o n e s and the 8-cyano derivatives 5a,b respectively.The pyrazolotriazinethiones 5a,b were easily S-alkylated with halo compounds in refluxing ethanol in the presence of sodium acetate or potassium carbonate to give the S-alkylated products 6a–d. Hydrazinolysis of 5a,b in ethanol afforded 4 - h y d r a z i n o p y r a z o l o [ 1 , 5 - a] - s- t r i a z i n e - 8 - c a r b o h y d r a z i d e 7 o r 4 - h y d r a z i n o p y r a z o l o [ 1 , 5 - a] - s- t r i a z i n e - 8 - c a r b o n i t r i l e 8 respectively.The reaction of arylmethylidenehydrazones 10a–e with triethyl orthoformate in methanol catalysed with acetic acid and the reaction with nitrous acid gave the pyrazolopyrimidines 11a–e and the pyrazolotriazines 12a–d respectively (Scheme 2). When we attempted to synthesize the pyrazolopyrimidinethione 13 via the reaction of the carbohydrazone 10a with carbon disulfide in pyridine, the desired compound 13 was not obtained (Scheme 3).After careful analysis of 1H NMR and mass spectra, structure 16 was assigned to this product. In order to confirm this unexpected structure, the reaction was extended to the other carbohydrazones 10b–e and in all cases pyrazolothiazinethione 16 was obtained. Compound 16 was easily S-alkylated with a-haloesters or a-haloketones in refluxing ethanol in the presence of sodium acetate to give the substituted thiopyrazolothiazines 17a–c. When compound 16 was treated with ammonium acetate in acetic acid, the pyrazolopyrimidinethione 15 was obtained which was identical with that obtained from the reaction of 14 with *To receive any correspondence.Scheme 1 Scheme 2 Scheme 3N N N N O H SCH2CO2Et Ph 18 N N N N O R S Ph 19 15 ClCH2CO2Et 16 MeCO2NH4–AcOH N S N N O SR Ph RNH2 RX R = CH(Me)CO2Me R = CH2CO2 Et R = CH2COC6H4Cl- p a b c 17 R = Ph R = C6H4OMe- p R = NH2 a b c H N N N N O NH2 SR Ph N N N N O S Ph 19c RX ArCHO a R = CH2CO2Et b R = CH(Me)CO2Me c R = CH2CONHC6H4OMe- p 20 a Ar = Ph b Ar = C6H4OMe- p 13 N N N N O SCHCO2Me Ph 21 BrCH(Me)CO2Me Me N CHPh H N CHAr N N NH2 Ph O N N SH N N NH2 Ph O N N SH RX CS2–pyridine 9 a R = CH2CO2Et b R = CH2COPh c R = CH2COC6H4Cl- p d R = CH2CONHC6H4OMe e R = CH(Me)CO2Me 23 22 J.CHEM. RESEARCH (S), 1997 353 carbon disulfide in all aspects (Scheme 4). The S-ester derivative 18 was obtained from the reaction of compound 15 with ethyl chloroacetate. Also compound 16 reacted with aromatic amines and hydrazine hydrate to afford the pyrazolopyrimidine derivatives 19a, c which cannot be obtained by ordinary methods but only by more complex alternative methods and in low yields.13 The 5-amino-1-phenylpyrazolo[3,4-d]pyrimidinethione 19c was easily S-alkylated with a-halo compounds to afford the derivatives 20a–c (Scheme 5).The N-arylmethylideneaminopyrazolopyrimidinethiones 13a,b, which cannot be obtained from the reaction of compound 10 with CS2, were synthesized from the reaction of compound 19c with aromatic aldehydes in refluxing ethanol. Treatment of 13a with methyl a-bromopropionate gave the S-ester derivative 21.Finally compound 9 was treated with carbon disulfide in pyridine to give the sulfanylpyrazolyloxadiazole 22,14 which in turn was S-alkylated through the reaction with a-halo compounds to give the S-alkyl derivatives 23a–e (Scheme 6). Techniques used: IR, 1H NMR, MS, elemental analysis References: 14 Tables 1–3: Physical and spectral data for 5–8, 10–12 and 13–23 respectively Received, 25th March 1997; Accepted, 24th July 1997 Paper E/7/02058I References cited in this synopsis 1 Yositomi Pharmaceutical Industries Ltd., Fr.Demande, 1972, 2, 100 973 (Chem. Abstr., 1972, 77, 164691). 2 R. L. Swett and Y. G. Paris, Ger. Offen., 1972, 2 219 763 (Chem. Abstr., 1973, 78, 72131). 3 W. J. Marsico, Jr., P. J. Joseph and L. Goldman, US Pat., 1973, 3 760 028 (Chem. Abstr., 1973, 79, 146518). 4 W. J. Marsico, Jr., P. J. Joseph and L. Goldman, US Pat., 1972, 3 864 359 (Chem. Abstr., 1975, 82, 170936). 5 K. Eicken, P. Plath and B. R. Werzo, Ger. Offen., 1983, 3, 129 429 (Chem. Abstr., 1983, 98, 198212). 7 P. Scmidt and J. Druey, J. Helv. Chim. Acta, 1956, 39, 986. 8 C. C. Cheng and R. K. Robins, J. Org. Chem., 1956, 21, 1240. 13 J. Carin, M. P. Loscertales, E. Melendez, F. L. Merchan, R. Rodrigues and T. Tejro, Heterocycles, 1987, 26, 1304. 14 A. M. Kamal El-Dean, J. Chem. Res., 1996, (S) 260; (M) 1401. Scheme 4 Scheme 5 Scheme 6

ISSN:0308-2342    

DOI:10.1039/a702058i

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

MeO NCOMe OMe H + Br Br Cu2O K2CO3 180 °C MeO N OMe Br 11c KOH–H2O–EtOH MeO N OMe H Br 11b Pd(OAc)2–AcOH MeO N OMe H OAC 11f MeO N OMe H R 10b MeO N OMe CH2 Br 12 R = Br R = OAc c + + COMe N Br MeO H 13b N Br MeO H 14 OAc Pd(OAc)2–AcOH 354 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 354–355 J. Chem. Research (M), 1997, 2270–2291 Alternative Products to Carbazoles in the Oxidation of Diphenylamines with Palladium(II) Acetate M. Manuela M. Raposo,a* Ana M. F. Oliveira-Camposa and Patrick V.R. Shannonb aDepartamento di Qu�ýmica, Universidade do Minho, 4700 Braga, Portugal bSchool of Chemistry and Applied Chemistry, University of Wales College of Cardiff, P.O. Box 912, Cardiff CF1 3TB, Wales, UK Although simple diphenylamines are conveniently oxidised with palladium(II) acetate to give carbazoles, for more complex examples carbazoles are minor products amongst many. Åkermark et al.1 investigated the palladium(II) acetate cyclisation of several simple diphenylamines to carbazoles, and found that the rate of cyclisation and number of required equivalents of palladium(II) acetate depended upon the electron supply in the aromatic rings.In our studies on ellipticine synthesis, we found that the diphenylamine to carbazole reaction could give alternative products to the required carbazoles: 11 in the present paper we report the results of palladium( II) acetate oxidation on further examples of diphenylamines. Goldberg coupling of 2,3-dimethoxyacetanilide and 1,4-dibromo-2,5-dimethylbenzene (Scheme 1) gave the diphenylacetamide 11c (37%), hydrolysis of which (KOH– ethanol–H2O), gave the amine 11b (73%).Cyclisation of 11b with palladium(II) acetate in acetic acid gave the bromocarbazole 10b (4%), the diphenylamine 11f (7%), the carbazole 10c (4%) and the oxidation product 12 (3%), M+ 333.0194 (C16H14BrNO2). The 1H NMR spectrum of 12 showed only one singlet (3 H) at d 2.64 and three 1 H singlets at d 8.17, 8.20 and 8.59, assignable to the methylene and 2-H protons whilst the aromatic protons of ring A gave the expected doublets at d 7.40 and 7.74.The diphenylamine 13b was prepared by Goldberg coupling of 1-iodo-4-methoxybenzene and 4-bromo-2,5-dimethylacetanilide followed by alkaline hydrolysis of the diphenylamide. Treatment of 13b with palladium(II) acetate gave the acetoxylated product 14 in 27% yield; the carbonyl absorption at 1638 cmµ1 indicated that the acetoxy group was in the 2p-position shown (Scheme 2).The cyanodiphenylamines 15b,d and f were obtained by Goldberg coupling of 4-cyano-2,5-dimethylacetanilide12 with the corresponding halogenated compounds and alkaline hydrolysis of the intermediate amides 15a,c and e in overall yields of 43, 32 and 28% respectively (Scheme 3). Attempted palladium(II) acetate cyclisation of diphenylamines 15b,d and f in acetic acid gave the corresponding carbazoles 16a,b,c in only very low yields (3–5%) and the products 17a,b,c of acetoxylation at the 2-methyl groups (2–6%).The structures followed from the 1H NMR signals of the CH2OAc methylene groups at d 5.10–5.16 and the NOE enhancements shown for compound 17a. When the cyclisation was repeated in trifluoroacetic acid (for 15b and 15f) in each case a mixture of phenol 1814 and quinone 19 was formed. Mass spectrometric and infrared evidence showed the presence of both components, but the 1H NMR spectrum in CDCl3 indicated the presence only of the quinone imine as a consequence of air oxidation.Finally, palladium(II) acetate cyclisation of the ester N-(4-ethoxycarbonylphenyl)aniline 2015 gave only a 37% yield of 3-ethoxycarbonylcarbazole 21, previously obtained by a different route.16 These results illustrate the limitations of the palladium(II) acetate route from diphenylamines to carbazoles, except in the structurally relatively simple cases. We thank CRUP (Portugal) and the British Council for support under the Treaty of Windsor Programme, the University of Minho, and JNICT (Portugal) for financial support (IBQF-UM).*To receive any correspondence. Scheme 1 Scheme 2N H CO2Et 20 N H CO2Et 21 R1 R2 Br BnO I or HN CN COMe + R1 = R2 = H R1 = H, R2 = F R3 N CN R2 R1 a R1 = Ac, R2 = R3 = H c R1 = Ac, R2 = F, R3 = H e R1 = Ac, R2 = H, R3 = BnO 15 Cu2O K2CO3 KOH–H2O–EtOH R3 N CN R2 R1 b R1 = R2 = R3 = H d R1 = R3 = H, R2 = F f R1 = R2 = H, R3 = BnO 15 R2 N CN R1 H HO N CN H 16 18 a R1 = R2 = H b R1 = F, R2 = H c R1 = H, R2 = BnO R2 N CH2OAc CN R1 H O N CN 17 19 H H 2% 14% 4% + + Pd(OAc)2–AcOH Pd(OAc)2–TFA J.CHEM. RESEARCH (S), 1997 355 Techniques used: 1H NMR, IR, UV, MS, elemental analysis References: 17 Received, 17th February 1997; Accepted, 24th July 1997 Paper E/7/01095H References cited in this synopsis 1 B. Åkermark, L. Eberson, E. Jonsson and E. Pettersson, J. Org. Chem., 1975, 40, 1365. 11 L. Chunchatprasert, P. Dharmasena, A. M. F. Oliveira-Campos, M. J. R. P. Queiroz, M. M. M. Raposo and P. V. R. Shannon, J. Chem. Res., 1996, (S) 84; (M) 630. 12 A. M. F. Oliveira-Campos, M. J. R. P. Queiroz, M. M. M. Raposo and P. V. R. Shannon, Tetrahedron Lett., 1995, 36, 133. 14 J. L. Bernier, J.-P. H�enichart, C. Vaccher and R. Houssin, J. Org. Chim., 1980, 45, 1493. 15 H. Ishu, H. Takeda, T. Hagiwara, M. Sakamoto and K. Kogosuri, J. Chem. Soc., Perkin Trans. 1, 1989, 12, 2407. 16 S. G. Plant and S. B. C. Williams, J. Chem. Soc., 1934, 1142. Sche

ISSN:0308-2342    

DOI:10.1039/a701095h

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

N X Ph N X HN X C Ph O Ph 1 X = O 2 X = S 3 X = O 4 X = S 5 X = O 6 X = S Me C O Ph 7 CH2Br C O Ph 8 Br2 hn CH2Br C O Ph 8 X–Na+ NH2 X = O or S + CO X NH2 Ph 9 X = O 10 X = S X N Ph heat catalyst 356 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 356–357† Synthesis of 11-Phenyl-6H-dibenzo[b,f ][1,4]oxazocine and 11-Phenyl-6H-dibenzo[b,f ][1,4]thiazocine† Michael R. Jorgensen, Cedric W. McCleland* and Benjamin Taljaard Department of Chemistry, University of Port Elizabeth, PO Box 1600, Port Elizabeth 6000, Republic of South Africa A convenient synthesis of 11-phenyl-6H-dibenzo[b,f][1,4]oxazocine 1 and the corresponding thiazocine 2 is described.We are currently interested in the chemistry of the novel 11-phenyl-6H-dibenzo[b,f ][1,4]oxazocine 1 and the isomeric [1,5]oxazocine 3, and also their sulfur analogues, the thiazocines 2 and 4. Compounds of this kind have the potential for pharmacological activity.1 Although isolated reports pertaining to the preparation of the related 11,12-dihydro systems have appeared,2 syntheses for the oxazocines 1 and 3 and the corresponding thiazocines 2 and 4 have, to the best of our knowledge, not been published. Construction of such ring systems is complicated by two factors.First, benzyl ether and benzyl sulfide linkages are frequently labile and, secondly, strain associated with the central cyclooctatrienyl-like ring is likely to render any ringclosure reactions difficult to accomplish.A Bischler–Napieralski cyclisation of the benzamides 5 and 6 was attempted in the presence of polyphosphoric acid and POCl3 under a range of conditions, but proved unsuccessful, giving complex reaction mixtures with evidence that cleavage of the benzyl ether linkage had occurred. As a result, the alternative route outlined in Scheme 1 was devised. We envisaged coupling 1-benzoyl-2-bromomethylbenzene 8 with 2-aminophenoxide or 2-aminobenzenethiolate, and then effecting ring-closure through intramolecular condensation of the resulting amino ketone. 1-Benzoyl-2-bromomethylbenzene 8, prepared by photolytically brominating 2-methylbenzophenone 7 proved to be labile, readily forming 1-phenylisobenzofuran. However, this side-reaction could be minimised by dispensing with any attempts to purify the bromoketone. Instead, the freshlyprepared crude bromoketone was without delay treated with 2-aminophenoxide or 2-aminobenzenethiolate, giving the amino ketone 9 or 10.Ring-closure of the aminoketone 9 also proved to be problematic, as heating in the presence of catalysts such as TiCl4 or BF3–ether led to cleavage of the benzyl ether linkage, giving 2-methylbenzophenone 7. Ring-closure was achieved by heating the aminoketone 9 alone in the absence of solvent in an oil bath maintained at 180 °C for 2.5 d. Yields of the resulting oxazocine 1 varied from 43 to 80%. The sulfide 10 proved to be more robust and was converted smoothly to the thiazocine 2 in 87% yield upon heating in the presence of BF3–ether. Experimental Mps were determined on an Electrothermal IA9100 series digital melting point apparatus and are uncorrected.IR spectra were recorded on a Perkin Elmer 1600 Series Fourier Transform Spectrometer. 1H and 13C NMR spectra were determined with a Varian Gemini-200 spectrometer in deuteriochloroform solution, with J-values given in Hz. Mass spectra were determined in the analytical laboratories of the Cape Town Technikon, Cape Town, South Africa.Microanalyses were performed at the CSIR, Pretoria, South Africa. PLC was carried out with Merck silica gel 60 F254 (1.5 mm). Light petroleum refers to the fraction with boiling range 40–60 °C. 1-Benzoyl-2-bromomethylbenzene 8.·A solution of 2-methylbenzophenone 7 (0.30 g, 1.5 mmol) in carbon tetrachloride (5 cm3) was heated under reflux and irradiated with a 1000 W tungsten lamp while bromine (0.80 g, 5.0 mmol) in carbon tetrachloride (5 cm3) was added.The reaction was stopped after 20 min and the solvent removed. The resultant oil (3.9 g) displayed 1H NMR signals at 4.62 ppm, which were assigned to the methylene protons of 1-benzoyl-2-bromomethylbenzene 8, in addition to the methyl proton group of the starting ketone 7 resonating at 2.29 ppm. This 9:1 mixture (from 1H NMR) of the bromoketone 8 and starting ketone 7 was used in the next step without further purification. 2-Aminophenyl 2-(Benzoyl)benzyl Ether 9.·2-Aminophenol (0.20 g, 1.80 mmol) in THF (20 cm3) was treated with a slight excess of sodium methoxide in THF (20 cm3).After stirring the mixture at room temperature for 0.5 h, an approximately equimolar amount of 1-benzoyl-2-bromomethylbenzene 8 was added dropwise and stirring was continued at 40 °C for 0.8 h. The solution was then poured into water (100 cm3) and extracted with chloroform (3Å100 cm3). The combined extracts were dried (anhydrous Na2SO4) and concentrated.The crude product was purified by PLC (chloroform) to give the title compound 9 (0.16 g, 0.52 mmol, 33%) as a gum, vmax/cmµ1 3454 and 3372 (NH2) and 1663 (CO); dH (200 MHz; CDCl3) 3.63 (2 H, br s, NH2), 5.22 (2 H, s, CH2), 6.60–6.82 (4 H, m, aromatic H), 7.40–7.75 (7 H, m, aromatic H) and 7.85 (2 H, d, J 8.3, aromatic H); dC (50 MHz; CDCl3) 70.07 (CH2), 114.08, 117.23, 120.28, 123.55, 129.35, 130.52, 130.52, 130.66, 131.17, 132.18, 132.18, 132.77, 135.28 (all tertiary Ar), 138.56, 138.90, 139.49, 139.65, 148.02 (all quaternary Ar) and 199.78 (CO); m/z 303 (M+, 5%), 285 (12), 195 (48), 177 (100), 165 (35), 160.6 (195h177), 152 (36) and 108 (17); (Found: M+, 303.1247.Calc. for C20H17NO2: Mr 303.1259). *To receive any correspondence (e-mail: chacwm@upe.ac.za). †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem.Research (M). Scheme 1J. CHEM. RESEARCH (S), 1997 357 2-Aminophenyl 2-(Benzoyl)benzyl Sulfide 10.·2-Aminobenzenethiol (0.23 g, 1.84 mmol) in THF (20 cm3) was treated successively with sodium methoxide in THF and then 1-benzoyl- 2-bromomethyl benzene 8 as described above. After work-up the crude product was purified by PLC (chloroform) to give the title compound 10 (0.33 g, 1.04 mmol, 69%) as a gum, vmax/cmµ1 3484 and 3375 (NH2) and 1662 (CO); dH (200 MHz; CDCl3) 4.14 (2 H, s, CH2), 4.30 (2 H, br s, NH2), 6.55–6.67 (2 H, m, aromatic H), 7.03–7.67 (9 H, m, aromatic H) and 7.84 (2 H, d, J 7.0, aromatic H); dC (50 MHz; CDCl3) 38.41 (CH2), 116.86 (tertiary Ar), 118.93 (quaternary Ar), 120.16, 128.46, 130.41, 130.41, 131.58, 132.19, 132.41, 132.41, 132.41, 133.18, 135.17, 138.47 (all tertiary Ar), 139.79, 139.97, 140.1, 150.74 (all quaternary Ar) and 200.00 (CO); m/z 319 (M+, 23%), 195 (100), 177 (16), 165 (25), 152 (11) and m* 119.2 (319h195); (Found: M+, 319.1020.Calc. for C20H17NOS: Mr 319.1027). 11-Phenyl-6H-dibenzo[b,f][1,4]oxazocine 1.·Amine 9 (0.15 g, 0.49 mmol) was heated in an oil bath at 180 °C for 60 h. The resultant gum was purified by PLC (chloroform) to give the title compound 1 (0.06 g, 0.21 mmol, 43%), mp 112–114 °C (from light petroleum), (Found: C, 84.7; H, 5.3; N, 4.9. Calc. for C20H15NO: C, 84.2; H, 5.3; N, 4.9%); vmax/cmµ1 1618.5 (C�N); dH (200 MHz; CDCl3) 5.03 (1H, d, J 12.5, CH2), 5.51 (1H, d, J 12.5, CH2), 6.85–7.55 (11 H, m, aromatic H) and 7.86 (2 H, d, J 7.96, aromatic H); dC (50 MHz; CDCl3) 77.43 (CH2), 123.96, 123.96, 125.58, 126.64, 129.85, 130.03, 130.31, 130.31, 130.87, 131.19, 131.29, 131.29, 133.02 (all tertiary Ar), 136.76, 139.20, 140.48, 146.94, 148.03 (all quaternary Ar) and 171.9 (CN); m/z 285 (M+, 100%), 256 (43), 195 (28), 178 (35) and 165 (36); (Found: M+, 285.1148.Calc. for C20H15NO: Mr 285.1153). 11-Phenyl-6H-dibenzo[b,f][1,4]thiazocine 2.·Amine 10 (0.10 g, 0.31 mmol) in toluene (50 cm3) was treated with boron trifluoride– diethyl ether complex (0.13 g, 0.91 mmol).The mixture was refluxed for 24 h and then poured into a saturated aqueous NaHCO3 solution (100 cm3). This mixture was filtered through kieselguhr and extracted with chloroform (3Å100 cm3) whereupon e combined extracts were dried (anhydrous Na2SO4) and concentrated. Purification of the resultant gum by PLC (chloroform) gave the title compound 2 (0.08 g, 0.27 mmol, 87%); mp 106–107.5 °C (from light petroleum), (Found: C, 79.55; H, 5.0; N, 4.6.Calc. for C20H15NS: C, 79.7; H, 5.0; N, 4.65%); vmax/cmµ1 1620 (C�N); dH (200 MHz; CDCl3) 3.75 (1H, d, J 11.40, CH2), 4.26 (1H, d, J 11.44, CH2), 6.70–6.80 (2 H, m, aromatic H), 6.98–7.26 (6 H, m, aromatic H), 7.40–7.58 (3 H, m, aromatic H) and 7.90 (2 H, d, J 6.6, aromatic H); dC (50 MHz, CDCl3) 39.21 (CH2), 122.49, 123.88, 125.46, 127.69, 129.38, 130.22, 130.58, 130.58, 130.81, 130.81, 131.17, 131.23, 133.64 (all tertiary Ar), 136.32 (quaternary Ar). 136.44 (tertiary Ar), 139.07, 140.88, 156.71 (all quaternary Ar) and 174.36 (CN); m/z 301 (M+, 100%), 268 (18), 256 (4), 224 (25), 223 (15) and 197 (8); (Found: M+, 301.0923. Calc. for C20H15NS: Mr 301.0929). Financial support from the Foundation for Research Development is acknowledged. Received, 12th April 1997; Accepted, 19th June 1997 Paper E/7/02709E References 1 S. Arakawa, S. Ogawa, E. Arakawa, K. Miyazaki and A. Murofushi (Arakawa-Chotaro and Co.), Jpn. Pat., 61 83,172 [86 83,172], 1986 (Chem. Abstr., 1986, 105, 208950d); S. Arakawa, S. Ogawa, E. Arakawa, K. Miyazaki and A. Murofishi (Arakawa-Chotaro and Co.), Jpn. Pat., 61 83,171 [86 83,171], 1986 (Chem. Abstr., 1986, 105, 208951e). 2 H. L. Yale, F. Sowinski and E. R. Spitzmiller, J. Heterocycl. Chem., 1972, 9, 889; H. L. Yale and E. R. Spitzmiller, J. Heterocycl. Chem., 1972, 9, 91

ISSN:0308-2342    

DOI:10.1039/a702709e

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

OH OH HO HO H O Castasterone 1 OH OH HO HO H O Brassinolide 2 O 360 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 360–361† Improved Synthesis of Castasterone and Brassinolide† Tsuyoshi Watanabe,a Suguru Takatsuto,*b Shozo Fujiokac and Akira Sakuraic aTama Biochemical Co. Ltd., 2-7-1 Nishishinjuku Shinjuku-ku, Toyko 163, Japan bDepartment of Chemistry, Joetsu University of Education, Joetsu-shi, Niigata 943, Japan cThe Institute of Physical and Chemical Research (RIKEN), Wako-shi, Saitama 351-01, Japan Castasterone 1 is synthesized in 32% overall yield in eight steps from the known (20S)-6,6-ethylenedioxy-20-formyl- 3a,5-cyclo-5a-pregnane 4.Brassinosteroids (BRs) constitute a new class of plant hormones with plant growth-promoting activity. It has been clarified that they occur widely in the plant kingdom and that more than 40 BRs have been chemically characterized from plant sources.1 Among the natural BRs, castasterone 1 occurs most frequently, followed by brassinolide 2, and they are assumed to play an important role in plant growth and development.1 The synthesis of castasterone 1 and brassinolide 2 has been reviewed.2 We have recently reported a method for constructing the side chain of C28 BRs, using the reaction of (20S)-20-formyl-6b-methoxy-3a,5-cyclo-5a-pregnane with (Z)-prop-1-enylmagnesium bromide, the orthoester Claisen rearrangement of the resulting (22S,23Z)-allylic alcohol, and the asymmetric dihydroxylation (AD) of the side chain of crinosterol, and we have synthesized the new 6-deoxo C28 BRs, 6-deoxoteasterone, 3-dehydro-6-deoxoteasterone and 6-deoxytyphasterol.3 In order to increase the overall yield of castasterone 1 and brassinolide 2, we investigated a convenient synthesis of 1 and 2 by employing our method to construct the side chain of C28 BRs.The starting material is a known 22-aldehyde 4, which was obtained in 70% yield in five steps from an abundant stigmasterol 3, according to the reported method.4 The reaction of the 22-aldehyde 4 with (Z)-prop-1-enylmagnesium bromide provided the (22S,23Z)-23-en-22-ol 5 in 57% yield.The orthoester Claisen rearrangement of 5 gave the ester 6 in 98% yield. The ethoxycarbonyl group of 6 was transformed in 89% yield into the methyl group by reduction with LiAlH4, methanesulfonation and then reduction with LiAlH4, constructing the side chain of crinosterol. Deprotection of 7 with acid gave the known cycloketone 8,5 which was subjected to acid catalysed isomerization6 to provide the known 2,22-dien- 6-one 95 in 82% yield from 7.With respect to the AD of the side chain of the crinosterol, Sun et al. have reported a high (8:1) stereoselectivity of (22R,23R)- and (22S,23S)-22,23-diols using dihydroquinidine p-chlorobenzoate as a chiral ligand.7 Recently, Marino et al. have reported the complete stereoselectivity for the (22R,23R)-22,23-diol by the AD using 1,4-bis(9-O-dihydroquinidinyl) phthalazine as a chiral ligand.8 We have previously reported a 57:43 ratio of (22R,23R)- and (22S,23S)-22,23-diols by the AD of (22E,24S)-3a,5-cyclo- 6b-methoxy-5a-ergost-22-ene by employing dihydroquinidine p-chlorobenzoate as a chiral ligand.3 The result of Marino et al.has prompted us to investigate the stereoselectivity of the AD of the same 22E-olefinic steroid using 1,4-bis(9- O-dihydroquinidinyl)phthalazine9 as a chiral ligand. Although we have not attained complete stereoselectivity, we have found a good ratio of 90:10 for the desired (22R,23R)-22,23-diol.Thus, the chiral ligand has been employed in the present synthesis. Castasterone 1 was synthesized in 80% yield by the AD of the 2,22-dien-6-one 9. As the transformation of 1 into brassinolide 2 is known,10 the formal synthesis of 2 was achieved. In conclusion, we have developed a convenient method for synthesizing castasterone 1 and brassinolide 2. The present synthesis provided castasterone 1 in 22% yield by 13 steps from stigmasterol 3, which is superior to the method recently reported by McMorris and co-workers.10d After submitting our paper, a concise and improved synthesis of brassinolide in 8% overall yield from stigmasterol by 12 steps has been published by Back et al.11 Although our route is the longer, our synthesis has merits of easier experimental manipulation and the expected better overall yield of brassinolide, inferred from the previous preparations of brassinolide from castasterone or its derivatives.2,10 Experimental Mps were determined under a hot-stage microscope (Yanaco micro melting point apparatus) and are uncorrected. 1H and 13C NMR spectra were recorded on a Varian XL-VXR 300 or JEOL a-400 spectrometer in a CDCl3 solution with tetramethylsilane as internal standard. HR-MS were recorded on a JEOL HX-110 mass spectrometer. Silica gel (Kieselgel 60, 70–230 mesh, Merck) was used for column chromatography.Reactions were monitored by TLC on silica gel plates (Kiesel gel 60F254, 0.25 mm thickness, Merck). Spots were visualized with 10% H2SO4, followed by heating. All purified compounds showed a single spot by TLC analysis. ( 2 2 S , 2 3 Z ) - 6 , 6 - E t h y l e n e d i o x y - 3 a, 5 - c y c l o- 2 6 , 2 7 - d i n o r - 5 a- c h o l e s t - 23-en-22-ol 5.·As described in our previous paper,3 (Z)-prop- 1-enylmagnesium bromide was prepared from (Z)-1-bromoprop- 1-ene (9.23 g, 76.3 mmol) and Mg (11.20 g, 0.461 mol).A solution of the 22-aldehyde 44 (24.30 g, 65.3 mmol) in THF (250 cm3) was added to the Grignard reagent at 0 °C under an argon atmosphere. The mixture was stirred at room temperature for 1 h. Work-up (hexane) gave a crude product, which was analysed by TLC, showing three spots with RF=0.33, 0.29 and 0.21 (hexane–EtOAc, 5:1), as described in the Grignard reaction of (20S)-20-formyl- 6b-methoxy-3a,5-cyclo-5a-pregnane.3 The product was applied to a column of silica gel (7.0 cm i.d.Å100 cm).Elution with hexane– EtOAc (100:5) separated the three products. The major product (15.35 g, 57%) with RF=0.29 was identified as the title compound 5, oil; dH (300 MHz): 0.73 (3 H, s, 18-H3), 0.96 (3 H, d, J 6.5 Hz, 21-H3), 1.01 (3 H, s, 19-H3), 1.66 (3 H, d, J 5 Hz, 25-H3), 3.75 (1 H, m, ethylene ketal), 3.87 (2 H, m, ethylene ketal), 4.02 (1 H, m, ethylene ketal), 4.57 (1 H, br d, J 6 Hz, 22-H) and 5.48–5.69 (2 H, m, 23-H and 24-H); dC (75 MHz): 7.3, 12.1, 12.3, 13.4, 19.0, 22.6, 23.1, 24.2, 24.9, 27.8, 33.3, 34.2, 39.3, 40.1, 40.2, 41.9, 42.8, 45.6, 47.4, 52.6, 56.2, 64.6, 64.9, 69.7, 109.9, 125.1 and 133.2.HR-MS (EI) (Found: M+, 414.3143. C27H42O3 requires Mr 414.3134). Ethyl (22E,24R)-6,6-Ethylenedioxy-3a,5-cyclo-5a-ergost-22-en- 26-oate 6.·A mixture of the allylic alcohol 5 (4.5 g, 10.86 mmol), triethyl orthopropionate (20 cm3, 0.160 mol), propionic acid (10 drops) and xylene (30 cm3) was refluxed under argon atmosphere for 2 h.MeOH was added and the solvent was removed in vacuo to give a residue which was applied to a column of silica gel (4.0 cm i.d.Å35 cm). Elution with hexane–EtOAc (30:1) afforded the title compound 6 (5.30 g, 98%) as an oil; TLC: hexane–EtOAc (10:1) RF=0.65; dH (300 MHz): 0.72 (3 H, s, 18-H3), 0.96 (3 H, d, J 6.5 Hz, *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem.Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Fig. 1 Structures of castasterone and brassinolideHO 3 CHO 4 O O 5 O O OH 6 O O CO2Et i ii iii iv, v, vi 7 O O 8 O 9 O 1 2 vii viii ix x H J. CHEM. RESEARCH (S), 1997 361 28-H3), 0.99 (3 H, d, J 6.5 Hz, 21-H3), 1.00 (3 H, s, 19-H3), 1.07 (3 H, d, J 7 Hz, 27-H3), 1.26 (3 H, t, J 7 Hz, OCH2CH3), 3.74 (1 H, m, ethylene ketal), 3.86 (2 H, m, ethylene ketal), 4.01 (1 H, m, ethylene ketal), 4.12 (2 H, q, J 7 Hz, OCH2CH3) and 5.05–5.30 (2 H, m, 22-H and 23-H).HR-MS (FAB) (Found: M++H, 499.3785. C21H51O4 requires Mr 499.3787). ( 2 2 E , 2 4 S ) - 6 , 6 - E t h y l e n e d i o x y - 3 a, 5 - c y c l o - 5 a- e r g o s t - 2 2 - e n e 7.— The ester 6 (2.24 g, 4.50 mmol) in THF (100 cm3) was treated with LiAlH4 (1.0 g, 26.35 mmol) at reflux temperature under argon for 2 h. Work-up (hexane) gave a corresponding 26-ol, which was dissolved in toluene (50 cm3) and Et3N (5 cm3) and then treated with methanesulfonyl chloride (0.5 cm3, 6.46 mmol) at 0 °C for 2 h.Work-up (toluene) gave a corresponding sulfonate (2.25 g), which in THF (50 cm3) was treated with LiAlH4 (1.0 g, 26.35 mmol) at room temperature overnight. Work-up (hexane) followed by chromatography on silica gel (3.0 cm. i.d.Å30 cm) eluting with toluene afforded the title compound 7 (1.76 g, 89% in three steps) as an oil; TLC: toluene RF=0.70; dH (300 MHz): 0.73 (3 H, s, 18-H3), 0.83 (3 H, d, J 6.5 Hz, 28-H3), 0.84 (3 H, d, J 6.5 Hz, 26-H3), 0.91 (3 H, d, J 7 Hz, 27-H3), 1.00 (3 H, d, J 6.5 Hz, 21-H3), 1.01 (3 H, s, 19-H3), 3.75 (1 H, m, ethylene ketal), 3.87 (2 H, m, ethylene ketal), 4.02 (1 H, m, ethylene ketal) and 5.16 (2 H, m, 22-H and 23-H).HR-MS (FAB) (Found: M++H, 441.3736. C30H49O2 requires Mr 441.3733). (22E,24S)-3a,5-Cyclo-5a-ergost-22-en-6-one 8.·A solution of the compound 7 (1.76 g, 4.00 mmol) in acetone (75 cm3) was treated with 1 M H2SO4 (1 cm3) at room temperature for 2 h. Workup (hexane) and chromatography of a crude product on silica gel (3.0 cm i.d.Å30 cm) eluting with hexane–EtOAc (20:1) afforded the known compound 8 (1.57 g, 99%), mp 105–106 °C (from MeOH) (lit.,5 mp 105–108 °C).Its spectral data are in agreement with the reported data.5 (22E,24S)-5a-Ergosta-2,22-dien-6-one 9.·A mixture of compound 8 (505.6 mg, 1.277 mmol), pyridinium toluene-p-sulfonate (65 mg, 0.259 mmol), LiBr (52.6 mg, 0.606 mmol) and N,N-dimethylacetamide (30 cm3) was heated at 160 °C under argon for 5 h.Work-up (hexane) followed by chromatography on silica gel (1.6 cm i.d.Å25 cm) eluting with hexane–toluene–EtOAc (120:2:1) afforded the known compound 9 (416.3 mg, 82%), mp 110-111 °C (from acetone) (lit.,5 mp 111–112 °C). Its spectral data are in agreement with the reported data.5 ( 2 2 R , 2 3 R , 2 4 S ) - 2 a , 3 a, 2 2 , 2 3 - T e t r a h y d r o x y - 5 a- e r g o s t a n - 6 - o n e , Castasterone 1.·A mixture of the compound 8 (319.3 mg, 0.806 mmol), K3[Fe(CN)6] (2.0 g, 6.07 mmol), K2CO3 (0.84 g, 6.08 mmol), methanesulfonamide (1.15 g, 12.09 mmol), 1,4-bis(9-O-dihydroquinidinyl) phthalazine (400.3 mg, 0.514 mmol) and OsO4 (2.83 mg, 0.011 mmol) in ButOH–H2O (50 cm3, 1:1) was stirred at room temperature in the dark for 15 d.NaHSO3 (1.0 g, powder) was added and the mixture was stirred further for 1 h. Work-up (EtOAc) gave a crude product, which was analysed by TLC, showing two spots with RF=0.53 and 0.42 (CHCl3–EtOH, 9:1).The product was applied to a column of silica gel (1.8 cm i.d.Å40 cm). Elution with CH2Cl2–EtOH (30:1) separated the two products and castasterone 1 (300.4 mg, 80%) with RF=0.42 was obtained, mp 253–254 °C (from EtOAc) (lit.,5 mp 252–255 °C, lit.,10d mp 251–253 °C). Its spectral data are in agreement with the reported data.5,10 We thank Professor T. Yoshikawa and Dr Y. Orihara of Kitasato University for the measurements of 1H and 13C NMR and mass spectra.Received, 24th April 1997; Accepted, 3rd June 1997 Paper E/7/02805I References 1 (a) S. Fujioka and A. Sakurai, Nat. Prod. Rep., 1997, 1; (b) S. Takatsuto, J. Chromatogr., 1994, 658, 3; (c) Brassinosteroids: Chemistry, Bioactivity and Applications, ed. H. G. Cutler, T. Yokota and G. Adam, ACS Symposium Series 474, American Chemical Society, Washington, D.C., 1991. 2 T. G. Back, in Studies in Natural Products Chemistry, ed. Attaur- Rahman, Elsevier, Amsterdam, The Netherlands, 1995, vol. 16, pp. 321–364. 3 S. Takatsuto, T. Watanabe, S. Fujioka and A. Sakurai, J. Chem. Res., 1997, (S) 134; (M) 0901. 4 K. Okada and K. Mori, Agric. Biol. Chem., 1983, 47, 89. 5 M. Anastasia, P. Ciuffreda, M. D. Puppo and A. Fiecchi, J. Chem. Soc., Perkin Trans. 1, 1983, 383. 6 T. Watanabe, H. Kuriyama, T. Furuse, K. Kobayashi and S. Takatsuto, Agric. Biol. Chem., 1988, 52, 2117. 7 L.-Q. Sun, W.-S. Zhou and X.-F. Pan, Tetrahedron: Asymmetry, 1991, 2, 973. 8 J. P. Marino, A. Dedios, L. J. Anna and R. F. Delapradilla, J. Org. Chem., 1996, 61, 109. 9 W. Amberg, Y. L. Bennani, R. K. Chadha, G. A. Crispino, W. D. Davis, J. Hartung, K.-S. Jeong, Y. Ogino, T. Shibata and K. B. Sharpless, J. Org. Chem., 1993, 58, 844. 10 (a) S. Fung and J. B. Siddall, J. Am. Chem. Soc., 1980, 102, 6580; (b) S. Takatsuto, N. Yazawa, M. Ishiguro, M. Morisaki and N. Ikekawa, J. Chem. Soc., Perkin Trans. 1, 1984, 139; (c) K. Mori, M. Sakakibara and K. Okada, Tetrahedron, 1984, 40, 1767; (d) T. C. McMorris, R. G. Chavez and P. A. Patil, J. Chem. Soc., Perkin Trans. 1, 1996, 295. 11 T. G. Back, D. L. Baron, W. Luo and S. K. Nakajima, J. Org. Chem., 1997, 62, 1179. Scheme 1 Reagents and conditions: i, ref.4; ii, BrMgCH�CHCH3, THF, 0 °C to room temp., 1 h; iii, Et(OEt)3, propionic acid, xylene, reflux, 2 h; iv, LiAlH4, THF, reflux, 2 h; v, MeSO2Cl, Et3N, toluene, room temp., 2 h; vii, LiAlH4, THF, room temp., overnight; vii, 1 M H2SO4, acetone, room temp., 2 h; viii, PPTS, LiBr, DMA, 160 °C, 5 h; ix, OsO4, K3[Fe(CN)6], 1,4-bis(9-O-dihydroquinidinyl)phthalazine, K2CO3, methanesulfonamide, ButOH–H2O, room temp., 15 d; x, ref. 1

ISSN:0308-2342    

DOI:10.1039/a702805i

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

Cl Pt NH2R NH2R Cl 1 R = alkyl, aryl O O R1 2 R1 = H 3 R1 = SO2C6H4- p-Me O HN R2 4 R2 = C6H4- p-Me 5 R2 = CH2Ph 6 R2 = c-C6H11 i,ii OMe N R2 7 R2 = C6H4- p-Me 8 R2 = CH2Ph 9 R2 = c-C6H11 iii 2 1 iv N HNR2 R3O 10 R2 = C6H4- p-Me, R3 = H 11 R2 = CH2Ph, R3 = H 12 R2 = C6H4- p-Me, R3 = Me 13 R2 = CH2Ph, R3 = Me 14 R2 = c-C6H11, R3 = Me OMe N OR3 15 R3 = H 16 R3 = Me + 362 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 362–363† Synthesis of 2-Aminotropone Oximes and 2-Alkoxytropone Imines† Tetsuo Nozoe,1‡ Lung Ching Lin,*ab Chih-Hsien Hsu,a Shwu-Chen Tsay,b Gholam H.Hakimelahib and Jih Ru Hwu*b,c aDepartment of Chemistry, National Taiwan University, Taipei, Taiwan 10671, Republic of China bInstitute of Chemistry, Academia Sinica, Nankang, Taipei, Taiwan 11529, Republic of China cDepartment of Chemistry, National Tsing Hua University, Hsinchu, Taiwan 30043, Republic of China A synthetic route was developed for preparation of 2-aminotropone oximes 10–14, a new class of compounds, from tropolone 2; 2-methoxytropone imines 7–9 and tropylium salts 17 were generated as the key intermediates.cis-Diamminedichloroplatinum analogues 1 are used as drugs for clinical cancer chemotherapy.2,3 In order for 1 to exhibit significant biological activity, the two amino groups must be in a cis configuration in 1.4,5 Here we report the preparation of 2-aminotropone oximes (e.g., 10–14), in which the two adjacent nitrogen atoms are attached to a planar nucleus and could coordinate to Pt to form cis-platinum complexes.Reaction of tropone with NH2OH.HCl and pyridine in methanol generates tropone oxime and 2-aminotropone.6 Under the same conditions, 2-alkyltropones can also be converted to 2-alkyltropone oximes and 2-alkyl-7-aminotropones, 7 yet tropolone 2 remains intact.8 By replacement of pyridine with various bases, including NaOH, NaOMe, NaOAc, Na2CO3 and Et3N, we were also unable to convert tropolone to the corresponding oximes by using NH2OH.HCl.The unusual resonance phenomenon associated with tropolone and an inherent intramolecular hydrogen bonding between the OH and the C�O groups9 may decrease its reactivity towards oxime formation. Furthermore, our attempts to oximate 2-(p-tolylsulfonyl)tropone and 2-aminotropone were also unsuccessful. Herein we report an indirect way to convert tropolone 2 to the desired 2-aminotropone oximes 10–14. To the best of our knowledge, this provides the only available up-to-date route for the preparation of 2-aminotropone oximes, an unprecedented class of compounds.After tosylation of 2,10 the resultant toluene-p-sulfonate 3 was treated with various amines,11 including p-toluidine, benzylamine and cyclohexylamine, in BuOH under reflux to give the corresponding 2-aminotropones 4–6 in 65–76% yields (Scheme 1). Methylation11 of 4–6 with dimethyl sulfate in toluene under reflux followed by treatment with NaHCO3 afforded the 2-methoxytropone imines 7–9 in 60–65% overall yields.Upon reaction with NH2OR.HCl (R=H or Me) and NaOMe in MeOH, 7–9 were converted to the desired oximes 10–14 in 24–54% yields. The spectroscopic data are summarized in Table 1. In these reactions, an unexpected by-product (i.e., 2-methoxytropone oxime 15 or 16) was generated and its structure was determined with the aid of single-crystal X-ray diffraction analysis.§ Formation of oximes 10–14 came from a nucleophilic attack of 7–9 by NH2OR (R=H or Me) at the C-2 position and formation of oximes 15 and 16 came from an attack at the C-1 position.Furthermore, we found that reactions of 2-aminotropones 4–6 with methyl fluorosulfonate gave the corresponding isolable tropylium salts 17 (Scheme 2).12 The desired oximes 10–14 can be obtained by treatment of 17 with NH2OH.HCl or NH2OMe.HCl. Moreover, we were able to synthesize 2-aminotropone imines 18–20 in high yields (a80%) by treating tropylium salts 17 with primary amines, including p-toluidine and benzylamine.13 These 2-aminotropone imines were also obtained in excellent yields (91–98%) by the reactions of 2-methoxytropone imines 7 and 8 with amines (Scheme 2 and Table 1).11 In conclusion, 2-methoxytropone imines 7–9 and tropylium salts 17 were prepared readily from tropolone 2 via toluene-p-sulfonate 3 and 2-aminotropones 4–6.These key intermediates (i.e., 7–9 and 17) were successfully converted to the 2-aminotropone oximes (10 and 11) and oxime methyl ethers (12–14) upon treatment with NH2OR.HCl (R=H or Me), and to 2-aminotropone imines 18–20 with primary amines.Use of the resultant new nitrogen-containing planar compounds to form cis-diamminedichloroplatinum analogues and to test their biological activity are under investigation in our laboratory. Experimental General Procedure for the Conversion of 2-Methoxytropone Imines (7–9) to 2-Aminotropone Oximes 10–14.·To a clear solution of NH2OH.HCl or NH2OMe.HCl (2.30 mmol) and NaOMe (2.30 mmol) in MeOH (20 mL) was added a 2-methoxytropone imine (7–9, 2.22 mmol).The reaction mixture was stirred at room temperature for 4.0 h. After the solvent was removed under reduced *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). ‡Deceased April 4, 1996. §Details of the X-ray crystal-structure determination will be reported elsewhere. Scheme 1 Reagents and conditions: i, for 2h3: p-MeC6H4SO2Cl, pyridine, 0 °C (96%); ii, for 3h4: p-MeC6H4NH2, BuOH, reflux (72%); for 3h5: PhCH2NH2, BuOH, reflux (76%); for 3h6: cyclohexylamine, BuOH, reflux (65%); iii, for 4–6h7–9: Me2SO4, toluene, reflux, NaHCO3 (aq) (60–65%); iv, for 7h10+15 and 8h11+15: NH2OH.HCl, NaOMe, MeOH; for 7–9h12–14+16: NH2OMe.HCl, NaOMe, MeOHO HN R2 OMe HN R2 SO3F– 17 MeOSO2F OMe N R2 NHR4 N R2 R4NH2 (R4 = C6H4- p-Me or CH2Ph) MeOH 10–14 + R4NH2, MeOH (R4 = C6H4- p-Me or CH2Ph) NH2OR3•HCl (R3 = H or Me) 4 R2 = C6H4- p-Me 5 R2 = CH2Ph 6 R2 = c-C6H11 7 R2 = C6H4- p-Me 8 R2 = CH2Ph 18 R2 = C6H4- p-Me, 19 R2 = C6H4- p-Me, 20 R2 = CH2Ph, R4 = CH2Ph R4 = C6H4- p-Me R4 = CH2Ph J.CHEM. RESEARCH (S), 1997 363 pressure, the residue was purified by use of column chromatography (EtOAc/hexanes=1:5 as eluent) to give a 2-aminotropone oxime (10–14) and a 2-methoxytropone oxime (15 or 16) in a pure form.The yields and spectroscopic data are listed in Table 1. This work was supported by the National Science Council of the Republic of China and Academia Sinica. Received, 7th March 1997; Accepted, 5th June 1997 Paper E/7/01621B References and notes 1 811-2-5-1, Kami-Yoga, Setagaya-Ku, Tokyo 158, Japan 2 B. Rosenberg, L. VanCamp, J. E. Trosko and V. H. Mansour, Nature (London), 1969, 222, 385. 3 K. R. Harrap, Cancer Treat.Rev., 1985, 12, 21. 4 S. J. Lippard, H. M. Ushay, C. M. Merkel and M. C. Poirier, Biochemistry, 1983, 22, 5165. 5 M. V. Keck and S. J. Lippard, J. Am. Chem. Soc., 1992, 114, 3386. 6 T. Machiguchi, T. Hasegawa, M. Ohno, Y. Kitahara, M. Funamizu and T. Nozoe, J. Chem. Soc., Chem. Commun., 1988, 838. 7 T. Nozoe, T. Mukai and I. Murata, Proc. Jpn. Acad., 1953, 29, 169. 8 T. Nozoe, T. Mukai, K. Takase and T. Nagase, Proc. Jpn. Acad., 1952, 28, 477. 9 W. von E. Doering and L.H. Knox, J. Am. Chem. Soc., 1951, 73, 828. 10 W. von E. Doering and C. F. Hiskey, J. Am. Chem. Soc., 1952, 74, 5688. 11 A. Zask, N. Gonnella, K. Nakanishi, C. J. Turner, S. Imajo and T. Nozoe, Inorg. Chem., 1986, 25, 3400. 12 P. Beak, J.-K. Lee and B. G. McKinnie, J. Org. Chem., 1978, 43, 1367. 13 cf. W. R. Brasen, H. E. Holmquist and R. E. Benson, J. Am. Chem. Soc., 1961, 83, 3125; K. Kikuchi, Y. Maki and K. Sato, Bull. Chem. Soc. Jpn., 1978, 51, 2338. Table 1 Conversion of 2-methoxytropone imines 7–9 to a mixture of oximes 10–16 or to 2-aminotropone imines 18–20 by the use of various nitrogen-containing reagents Found (calcd) (%) Products Mp Imine Reagent (% in yield)a dH (CDCl3) dC (CDCl vmax/cm–1 (T/°C) C H N 7 NH2OH.HCl 10 (28)+15 (50) 10: 2.31 (s, 3 H), 6.12–7.20 (m, 10 H), 7.46 (br s, 1 H); 15: 3.72 (s, 3 H), 5.80–7.11 (m, 5 H), 9.83 (br s, 1 H) 10: 21.9, 106.3, 117.6, 121.6, 125.8, 130.9, 132.9, 133.1, 135.8, 137.6, 145.8, 151.0; 15: 55.6, 104.9, 120.7, 124.2, 129.0, 131.1, 149.9, 157.0 10: 3315 (OH, NH), 1583 (C�N); 15: 3298 (OH), 1599 (C�N) 10: liq.; 15: 132–133 10: 74.26 (74.31) 15: 63.48 (63.57) 6.55 (6.24) 5.99 (6.00) 12.26 (12.38) 9.38 (9.27) 8 NH2OH.HCl 11 (24)+15 (50) 11: 4.43 (d, 2 H), 5.82–7.33 (m, 12 H) 11: 47.4, 103.4, 115.6, 119.1, 127.2, 127.4, 128.7, 132.0, 132.4, 137.4, 146.2, 150.1 11: 3352 (OH, NH), 1584 (C�N) 11: liq. 11: 74.18 (74.31) 6.31 (6.24) 12.49 (12.38) 7 NH2OMe.HCl 12 (54)+16 (30) 12: 2.33 (s, 3 H), 4.00 (s, 3 H), 6.11–7.28 (m, 9 H), 7.62 (br s, 1 H); 16: 3.84 (s, 3 H), 4.01 (s, 3 H), 5.82–6.94 (m, 5 H) 12: 20.9, 62.1, 105.3, 117.3, 120.7, 124.9, 129.9, 132.0, 132.2, 134.8, 136.6, 144.8, 148.4; 16: 560, 62.0, 105.2, 120.9, 124.3, 129.0, 131.0, 151.0, 151.2 12: 3152 (NH), 1583 (C�N); 16: 1590 (C�N) 12: liq.; 16: liq. 12: 74.88 (74.97) 16: 65.45 (65.44) 6.73 (6.71) 6.84 (6.71) 11.57 (11.66) 8.40 (8.48) 8 NH2OMe.HCl 13 (47)+16 (25) 13: 4.02 (s, 3 H), 4.49 (d, 2 H), 5.82–7.43 (m, 10 H), 7.87 (br s, 1 H) 13: 47.2, 62.0, 103.3, 116.5, 119.2, 127.2, 127.4, 128.8, 132.0, 132.5, 134.9, 137.8, 146.3, 148.6 13: 3360 (NH), 1584 (C�N) 13: liq. 13: 75.09 (74.97) 6.63 (6.71) 11.77 (11.66) 9 NH2OMe.HCl 14 (51)+16 (31) 14: 0.92–2.00 (m, 11 H), 3.43 (br s, 1 H), 3.96 (s, 3 H), 5.81–7.06 (m, 5 H) 14: 24.7, 25.7, 32.4, 50.8, 61.9, 115.4, 118.0, 131.8, 132.5, 145.4, 148.5 14: 3338 (NH), 1583 (C�N) 14: liq. 14: 72.44 (72.38) 8.63 (8.68) 12.15 (12.06) 7 p-MeC6H4NH2 18 (98) 18: 2.41 (s, 3 H), 2.49 (s, 3 H), 6.19–7.32 (m, 14 H) 18: 20.9, 114.5, 121.5, 122.6, 130.0, 133.2, 133.4, 142.5, 152.1 18: 3059 (NH), 1587 (C�N) 18: 143–144 18: 83.83 (83.96) 6.71 (6.71) 9.25 (9.33) 7 PhCH2NH2 19 (91) 19: 2.32 (s, 3 H), 4.54 (s, 2 H), 6.10–7.32 (m, 15 H) 19: 20.8, 47.2, 105.4, 119.9, 120.7, 120.9, 127.2, 127.4, 130.0, 131.9, 133.0, 133.7, 137.4, 148.4, 150.8, 155.1 19: 3265 (NH), 1582 (C�N) 19: 113–114 19: 84.09 (83.96) 6.80 (6.71) 9.24 (9.33) 8 PhCH2NH2 20 (95) 20: 4.62 (br s, 4 H), 6.27–7.33 (m, 16 H) 20: 50.0, 111.6, 119.1, 126.8, 127.2, 128.4, 133.8, 139.3, 153.2 20: 3055 (NH), 1591 (C�N) 20: 81–82 20: 84.03 (83.96) 6.56 (6.71) 9.38 (9.33) aAll data are satisfactory for the high- and low-resolution mass sp

ISSN:0308-2342    

DOI:10.1039/a701621b

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

364 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 364–365† Kinetics and Mechanism of Chromium(III)-catalysed Oxidation of Formic Acid by Cerium(IV) in Aqueous Sulfuric Acid Media† Premendra Nath Saha, Sudhin K. Mondal, Dalia Kar, Mahua Das, Asim K. Das* and Rajani K. Mohanty* Department of Chemistry, Visva-Bharati, Santiniketan - 731 235, West Bengal, India In the CrIII-catalysed oxidation of formic acid by CeIV in aqueous sulfuric acid media, an intermediate involving the oxidant, substrate and catalyst is formed and a CrIII/CrIV catalytic cycle operates.The kinetics and mechanism of RuIII- and IrIII-catalysed oxidation of formic acid in aqueous sulfuric acid media have been reported1,2 by us recently. CrIII is known3 to catalyse the title reaction and this prompted us to carry out the present investigation in detail in continuation of our studies1,2,4 on metal-ion catalysis in CeIV oxidation. In fact, there are only a very few cases where the kinetics and mechanistic aspects of CrIII catalysis in CeIV oxidation have been reported5 so far.Here we report the kinetics and mechanism of the title reaction in 1.0 mol dmµ3 H2SO4 under the conditions [CeIV]T=(2.5–4.5)Å10µ3 mol dmµ3, [Cr]T=(0.25– 7.0)Å10µ2 mol dmµ3 and [HCO2H]T=(0.25–3.0) mol dmµ3 in the temperature range 40–60 °C. Experimental Materials and Reagents.·Standard stock solutions of CeIV and HCO2H were prepared as reported1 earlier. The CrIII catalyst was in the form of chromium(III) potassium sulfate (BDH, AR), Cr2(SO4)3.K2SO4.24H2O, and the stock solution in aqueous sulfuric acid media was standardised as usual.All other reagents were of reagent grade. Procedure and Kinetic Measurements.·The method employed for following the progress of the reaction has been discussed earlier.1 The reactions were followed up to 80–85% completion and the pseudo-first-order rate constants (kobs) were computed from the linear plot (ra0.99) of log [CeIV] vs.time. The rate constants (kobs) were reproducible within �3–5%. Stoichiometry and Product Analysis.·Stoichiometry determination of the title reaction under the experimental conditions was carried out as reported earlier.1 The observation conforms to: CrIII 2CeIV+HCO2Hh2CeIII+CO2+2H+ (1) The concentration of CrIII remains unchanged after the reaction. Results and Discussion Dependence on [CeIV].·The rate of disappearance of CeIV shows a first-order dependence on [CeIV] up to 80-85%, then the plot (ln [CeIV] vs.t) slightly deviates. The pseudo-firstorder rate constant (kobs) is independent of the initial concentration of CeIV in the range (2–6)Å10µ3 mol dmµ3. µ d[CeIV] dt =k[CeIV] or µ d ln [CeIV] dt =kobs (2) Dependence on [CrIII].·The pseudo-first-order rate constant (kobs) at fixed [HCO2H] (=1.0 mol dmµ3) increases sharply with increasing [CrIII] but levels off at higher values of [CrIII]. It can be represented as: kobs= A[Cr]T B+C[Cr]T (3) or 1 kobs = B A[Cr]T + C A (4) At fixed [HCO2H] in 1.0 mol dmµ3 H2SO4, A, B and C are constants and expressed in terms of different rate constants as discussed later on.[Cr]T gives the total concentration of chromium added as catalyst. The constants are estimated from linear plots (ra0.98) of 1/kobs vs. 1/[Cr]T. Dependence on [HCO2H].·At fixed [Cr]T, kobs shows a first-order dependence on [HCO2H] in 1.0 mol dmµ3 H2SO4. kobs=ks[HCO2H]T (5) The values of ks are: 104 ks/dm3 molµ1 sµ1=2.2�0.1 (45 °C), = 3.5�0.1 (50 °C), =7.0�0.1 (60 °C) at [Cr]T=[K+] =0.01 mol dmµ3, [CeIV]T=4Å10µ3 mol dmµ3, [H2SO4] =1.0 mol dmµ3, [HCO2H]T=(0.25–3.0) mol dmµ3.Dependence on [HSO4 µ].·For variations in [HSO4 µ] over the range (0.3–1.75) mol dmµ3 at a fixed [H+], the composition of the mixture [H2SO4]+[HClO4]3[H+] =1.75 mol dmµ3 was varied.4 This leads to [HSO4 µ]3[H2SO4], ignoring the dissociation of HSO4 µ. [HSO4 µ] shows a rate-retarding effect on kobs (see Table 1).The plot of 1/kobs vs. [HSO4 µ] is linear (r=0.99) with positive intercept and slope. Dependence on [H+].·For variations in [H+] over the range (0.3–1.75) mol dmµ3 at a fixed [HSO4 µ], the composition of the mixture, [H2SO4]+[NaHSO4]3[HSO4 µ] =1.75 mol dmµ3, was varied6 assuming [H+]3[H2SO4]. The dependence on [H+] is expressed from an experimental fit as: kobs=k0+kHp[H+]+kHP[H+]2 (6) Because of the existence of so many proton-dependent equilibria4a among the reactants, the said approximation can be called into question.4a In fact, because of this complexity4a in the present reaction media, no attempt was made to explain the observed [H+] dependence from the proposed reaction scheme.Acrylonitrile Polymerisation Test.·When acrylonitrile was added to the reaction mixture under a nitrogen atmosphere, on prolonged standing polymerisation starts very slowly. However, in the absence of the title catalyst, addition of acrylonitrile under identical conditions leads very rapidly to the reaction mixture becoming viscous.Effect of MnSO4, Products and Other Factors.·MnSO4 (ca. 0.01 mol dmµ3) can itself catalyse the reaction. CrIII (ca. 0.01 *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Table 1 Dependence of kobs on [HSO4 µ] for CrIII-catalysed oxidation of formic acid by CeIV.[HCO2H]T=1.0 mol dmµ3, [CeIV]T=4Å10µ3 mol dmµ3, [H+] =1.75 mol dmµ3, [Cr]T=[K+] =0.01 mol dmµ3, 50 °C [HSO4 µ]/mol dmµ3 10µ2 kobs µ1/s 0.3 6.6 0.5 8.4 0.75 10.8 1.0 13.2 1.5 18.6 1.75 22.2J. CHEM. RESEARCH (S), 1997 365 mol dmµ3) which is a catalyst in the title investigation has been found to antagonise the catalytic activity of MnSO4. No discernible effects of [Na+] and/or [K+] (up to 0.07 mol dmµ3) or of the product, [CeIII] (up to 4Å10µ3 dmµ3), were observed.Ambient light and aerial oxygen had no effect on kobs. Mechanism of the Reaction.·The observations in 1.0 mol dmµ3 H2SO4 can be mathematically represented as: kobs= a[Cr]T[HCO2H]T b+c[Cr]T (7) The following reaction scheme (S=HCO2H) can explain the experimental findings: k1 CeIV+SMCeIV(S) (complex C1) (8) kµ1 k2 C1+CrIIIMCeIV(S)µCrIII (outer-sphere complex, C2) (9) kµ2 k3 C2hCeIII(S) CrIV (inner-sphere complex, C3) (10) fast C3hCeIII(S.)CrIII+H+ (11) fast CeIII(S.)CrIII+CeIVh2CeIII+CO2+H++CrIII (12) Under the steady-state conditions of the species C1 and C2, the above scheme under the reasonable approximation [Cr]T2[CrIII] leads to the rate equation: kobs=µ d ln [CeIV] dt = 2k1k2k3 f[HCO2H]T[Cr]T {kµ1kp+k2k3[Cr]T} (13) where f gives the fraction of the total cerium(IV), [CeIV]T, which is kinetically active, and kp=kµ2+k3.Combining eqns. (3)–(7) and (13) gives A=2k1k2k3 f[HCO2H]T. B=b=kµ1kp, C=c=k2k3, a=2k1k2k3 f and k5= 2k1k2k3 f[Cr]T {kµ1kp+k2k3[Cr]T} (14) In the given scheme, C2 is an outer-sphere complex due to the inherent inertness7 of CrIII, but C3 is an inner-sphere complex where the CrIV centre generated is a labile7 one.In C3, electron transfer occurs rapidly to produce an intermediate complex in which a formate radical (S.), being tightly bound to CrIII, is not available in the bulk sufficiently to initiate polymerisation. This can explain qualitatively the sluggish rate of polymerisation in the presence of CrIII. From the plot of 1/kobs vs. 1/[Cr]T at fixed [HCO2H]T the composite constants, kn (=2k1 f ) and Km=k2k3/kµ1kp were evaluated. The values are: 104 kn/sµ1=2.4�0.2 (40 °C), 3.4�0.2 (45 °C), =4.4�0.1 (50 °C), with activation parameters DH‡=144 kJ molµ1 and DS‡=1µ174 J Kµ1 molµ1; and 10µ2 Km/dm3 molµ1=0.95�0.15�0.1 (45 °C), =3.6�0.1 (50 °C), at [HCO2H]T=[H2SO4] =1.0 mol dmµ3. The antagonistic activity of the mixed catalyst system, MnII- +CrIII, indirectly supports the involvement of CrIV in CrIII catalysis.It is known8 that MnSO4 rapidly removes CrIV thus hindering the catalytic activity of CrIII. In fact, participation of the catalytic cycle CrIII/CrIV in CeIV oxidation in aqueous sulfuric acid media has also been reported5 previously. CrIII is an inert centre7 while CeIV is a relatively more labile one.7 Consequently, the equilibria leading to different sulfato species of CeIV are only important in the present kinetics to explain the [HSO4 µ] dependence.Under the experimental conditions of aqueous sulfuric acid media, the important CeIV species are9 Ce(SO4)2+, Ce(SO4)2 and HCe(SO4)3 µ. By considering the relative values9 of Q1, Q2 and Q3 which are the successive formation equilibrium constants for the species Ce(SO4)2+, Ce(SO4)2 and HCe(SO4)3 µ, respectively, [Ce(SO4)2] can be reasonably given4b by eqn. (15). [Ce(SO4)2]2 [CeIV]T 1+Q3[HSO4 µ] =f[CeIV]T (15) Use of eqn. (15) in eqn.(13) affords eqn. (16) after rearrangement. 1 kobs = 1 p + Q3[HSO4 µ] p (16) where p= 2k1k2k3[HCO2H]T[Cr]T kµ1kp+k2k3[Cr]T Eqn. (16) explains the hydrogensulfate dependence. From the plot of 1/kobs vs. [HSO4 µ] (r=0.99), where [HSO4 µ] =(0.3–1.75) mol dmµ3 at fixed [HCO2H]T=1.0 mol dmµ3, [Cr]T=[K+] =0.01 mol dmµ3, the estimated Q3=3.1 at 50 °C conforms well to the reported values.4b,9b Previously, in many cases, Ce(SO4)2 has been identified4b,9b as the kinetically active CeIV species.Thanks are due to CSIR, New Delhi, for financial assistance. Received, 20th January 1997; Accepted, 9th June 1997 Paper E/7/00449D References 1 A. K. Das and M. Das, J. Chem. Soc., Dalton Trans., 1994, 589. 2 A. K. Das and M. Das, Indian J. Chem., 1995, 34A, 866. 3 (a) N. N. Sharma and R. C. Mehrotra, Anal. Chim. Acta, 1954, 11, 417; 1955, 13, 419; (b) N. N. Sharma and R. C. Mehrotra, Z. Anal. Chem., 1960, 173, 395. 4 (a) A. K. Das, J. Chem. Res., 1996, (S) 185; (M) 1023; (b) A. K. Das and M. Das, Int. J. Chem. Kinet., 1995, 27, 7. 5 (a) A. Chimatadar, S. T. Nandibewoor, M. I. Sambrani and J. R. Raju, J. Chem. Soc., Dalton Trans., 1987, 573; (b) S. R. Kampli, S. T. Nandibewoor and J. R. Raju, Indian J. Chem., 1990, 29A, 908. 6 G. Arcoleo, G. Calvaruso, F. P. Cavasino and C. Sbriziolo, Inorg. Chim. Acta, 1977, 23, 227. 7 cf. R. G. Wilkins, in The Study of Kinetics and Mechanism of Reactions of Transition Metal Complexes, Allyn & Bacon, Boston, 1974. 8 (a) W. Watanabe and F. H. Westheimer, J. Chem. Phys., 1949, 61, 17; (b) L. Kaplan, J. Am. Chem. Soc., 1955, 77, 5469. 9 (a) L. T. Bugaenko and H. Kuan-Lin, Russ. J. Inorg. Chem., 1963, 8, 1299 and references cited therein; (b) S. K. Misra and Y. K. Gupta, J. Chem. Soc. A, 1970, 2

ISSN:0308-2342    

DOI:10.1039/a700449d

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

366 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 366–367† Selective Oxidation of Toluene over Complex Fe–Mo Oxides in the Absence of Molecular Oxygen Wenxing Kuang,* Yining Fan, Kaidong Chen and Yi Chen Department of Chemistry, Institute of Mesoscopic Solid State Chemistry, Nanjing University, Nanjing 210093, China Fe–Mo catalysts prepared by a sol–gel method for selective oxidation of toluene are studied in the absence of molecular oxygen; a high benzaldehyde yield and high specific activity are achieved at an atomic ratio (Mo:Fe) of about 1.0.Over the past forty years, iron molybdates have been widely used in industry for the selective oxidation of hydrocarbons, and the active component has been found to be defective iron(III) molybdate.1–3 In general, the optimum specific activity is achieved at high Mo:Fe atomic ratio (ca. 1.70 to 4.05); at lower Mo:Fe ratios the excess of Fe2O3 may lead to complete oxidation and thus reduce the catalytic activity for selective oxidation.In 1981, Germain et al.4 first reported that iron molybdates can be used as catalysts for selective oxidation of toluene to benzaldehyde. Later Zhang et al.5 pointed out that the catalyst has the highest specific activity for selective oxidation of toluene to benzaldehyde at an Mo:Fe atomic ratio of 3.45. Since all the above reactions are studied in the presence of molecular oxygen, various kinds of oxygen species may co-exist on the surface of the catalyst, which eventually results in the formation of products other than benzaldehyde. 6 In contrast to the widespread applications of iron molybdates, little is known about the fundamental nature and catalytic properties of these catalysts in the absence of molecular oxygen. In this work, we report an iron molybdate of low Mo:Fe atomic ratio (1.0) which has a high benzaldehyde yield and specific activity for selective oxidation of toluene to benzaldehyde in the absence of molecular oxygen.Besides Fe2(MoO4)3, highly dispersed Fe2O3 is also found to be an active component participating in the reaction and to be responsible for the high benzaldehyde yield and high specific activity for selective oxidation of toluene. The total amount of benzaldehyde yield and the corresponding specific activity for selective oxidation of toluene to benzaldehyde (benzaldehyde yield per BET surface area) over various Fe–Mo samples in the absence of molecular oxygen are shown in Fig. 1. For pure Fe2O3 and MoO3 samples, no product is detected under our reaction conditions, while the Fe–Mo samples exhibit high yields of benzaldehyde, indicating that iron molybdate species are the main catalytic active components. It is also pertinent to note that of these Fe–Mo samples, both the highest yield of benzaldehyde and the optimum specific activity appear at an Mo:Fe atomic ratio of 1.0. This result is different from that obtained in the presence of molecular oxygen,5 suggesting that the catalytic properties of Fe–Mo samples can be influenced by the reaction conditions.Compared to the case in the presence of molecular oxygen, only lattice oxygen exists on the surface of the oxides in the absence of molecular oxgyen. This may lead to changes in the catalytic active phase and reaction mechanism. XRD and M�ossbauer spectroscopic techniques are used to study the catalytic active phase and the relationship between structure and catalytic properties of the Fe–Mo oxide with an Mo:Fe atomic ratio of 1.0.M�ossbauer parameters of the sample are listed in Table 1. For the fresh sample, only XRD lines of Fe2(MoO4)3 are observed in the XRD pattern, while a singlet corresponding to an Fe2(MoO4)3 phase and a doublet assigned to superparamagnetic Fe3+ ions are shown in the M�ossbauer spectrum, suggesting that the fresh sample is composed of an Fe2(MoO4)3 phase and highly dispersed Fe2O3. After the reaction, XRD lines for crystalline b-FeMoO4 and Fe2(MoO4)3 are both observed in the XRD pattern.In the M�ossbauer spectrum two new doublets, which can be assigned to b-FeMoO4, are found in addition to the singlet for Fe2(MoO4)3 and the doublet for Fe3+ ions. As shown in Table 1, the amount of Fe2(MoO4)3 decreases after the reaction and, surprisingly, that of the highly dispersed superparamagnetic Fe2O3 decreases. Moreover, the amount of newly produced b-FeMoO4 species is much larger than the decrease in the amount of Fe2(MoO4)3 species.All these results suggest that the highly dispersed Fe2O3 may also parti- *To receive any correspondence (e-mail: physchem@nju.edu.cn). †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Fig. 1 The catalytic properties for selective oxidation of toluene to benzaldehyde over Fe–Mo samples in the absence of molecular oxygen Table 1 M�ossbauer parameters of the Fe–Mo sample (Mo:Fe=1:1) M�ossbauer parameters Relative Sample IS (mm Sµ1) QS (mm Sµ1) H (kOe) Iron species area (%) Fresh 0.39 0.40 0.90 0 00 Fe2O3 Fe2(MoO4)3 34 66 After reaction 1.12 1.11 0.39 0.40 0.96 2.54 0.90 0 0000 b-FeMoO4 b-FeMoO4 Fe2O3 Fe2(MoO4)3 36 34 11 19J.CHEM. RESEARCH (S), 1997 367 cipate in the reaction, so that both Fe2(MoO4)3 and the highly dispersed Fe2O3 are the catalytic active species.The first stage in the reduction of Fe2(MoO4)3 with H2 was reported to be7 4Fe2(MoO4)3+5H2h8b-FeMoO4+Mo4O11+5H2O As mentioned above, both Fe2(MoO4)3 and the highly dispersed Fe2O3 phases participate in the reaction, the mechanism for which may then be suggested as 4Fe2(MoO4)3h8b-FeMoO4+Mo4O11+5[O] (1) 2Fe2O3+Mo4O11h4b-FeMoO4+[O] (2) where [O] is lattice oxygen. The total reaction equation can be written as 4Fe2(MoO4)3+2Fe2O3h12b-FeMoO4+6[O] (3) It is easy to find from eqn.(3) that the optimum atomic ratio of n(Fe2O3):n[Fe2(MoO4)3] is 1:2, i.e., Mo:Fe=1.0, which is well supported by our experimental results. Experimental The complex Fe–Mo oxides were prepared by a sol–gel method. Iron(III) nitrate, ammonium molybdate and citric acid (the molar ratio of citric acid to metallic ions was 1:3) were dissolved in water and mixed together, then nitric acid solution was added under constant stirring until the precipitates had completely dissolved.The above solutions were kept in a water batch at 333 K for gelation. The gels thus prepared were first dried at 393 K and then calcined at 673 K to afford the oxides. The oxides (250 mg) were located in a pulse microreactor and the catalytic properties were determined under the conditions of 623 K, 0.2 MPa, helium flow-rate 40 ml minµ1, and 1.45 mmol toluene/pulse. All samples were pretreated in a helium flow at 673 K for the removal of adsorbed oxygen species. The reaction products, detected by using an on-line gas chromatography, were found to be chiefly benzaldehyde and H2O. The support of the National Natural Science Foundation of China and SINOPEC is gratefully acknowledged. Received, 6th May 1997; Accepted, 17th June 1997 Paper E/7/04247G References 1 G. D. Kolovertnov, G. K. Boreskov, V. A. Dzis’Ko, B. I. Popov, D. V. Tarasova and G. G. Belugina, Kinet. Catal., 1965, 6, 950. 2 J. M. Leroy, S. Peirs and G. Tridot, C. R. Acad. Sci., Ser. C, 1971, 218. 3 I. De La Torre, G. Acosta and M. Hernandez, Rev. Inst. Mex. Pet., 1979, 11, 68. 4 J. E. Germain and R. Laugier, C. R. Acad. Sci., Ser. C, 1973, 276, 1349. 5 H. Zhang, Z. Li and X. Fu, Cuihua Xuebao, 1988, 9, 331. 6 S. L. T. Andersson, J. Catal., 1986, 98, 138. 7 H. Zhang, J. Shen and X. Ge, J. Solid State Chem., 199

ISSN:0308-2342    

DOI:10.1039/a704247g

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

368 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 368–369† Investigation into the Nature of the Oxoruthenate Species used to Mediate the Oxidation of an Organic Substrate by Hypochlorite in a Biphasic System† Andrew Mills* and Carolyn Holland University of Wales Swansea, Singleton Park, Swansea, Wales, UK Hydrophilic sodium perruthenate, rather than lipophilic ruthenium tetraoxide, is the mediator in the oxidation of octan-2-ol by sodium hypochlorite in a water–carbon tetrachloride (or dichloromethane) biphasic system; as a consequence, oxidation occurs at the phase boundary and is promoted by stirring or ultrasound.Ruthenium tetraoxide, RuO4, is a popular selective oxidant1 for, amongst other things, primary alcohols (to aldehydes and carboxylic acids), secondary alcohols (to ketones), olefins (to aldehydes), aldehydes (to carboxylic acids), amines (to imides), ethers (to esters) and sulfides (to sulfones). RuO4 is, however, expensive if used in stoichiometric amounts and nowadays it is commonplace to employ it in catalytic amounts, often in a biphasic system in which an excess of a cheaper inorganic oxidant is in the aqueous phase and the lipophilic organic substrate is in the organic phase, usually carbon tetrachloride or dichloromethane.1,2 Such a system works because RuO4 is more soluble in organic solvents such as carbon tetrachloride and dichloromethane, than it is in water; typical partition coefficients are a50 for such solvents. 3 In a biphasic system involving RuO4, a catalytic amount of RuO4 is generated by adding ruthenium trichloride, RuCl3 .nH2O or ruthenium dioxide hydrate, RuO2 .xH2O, to the aqueous layer containing an excess of the inorganic oxidant. As noted by Fieser4 and others1,2,5,6 ‘in catalytic procedures with RuO4, periodate or hypochlorite, are generally used as the stoichiometric oxidants’. The RuO4 rapidly partitions into the organic phase where it effects the selective oxidation of the organic substrate; the RuO2 generated as a result of this latter reaction eventually comes into contact with the inorganic oxidant in the aqueous phase and is then re-oxidised back to RuO4, so allowing the catalytic cycle to begin again.This process continues until the organic substrate has been completely oxidised, or the reaction is stopped. Recent work by Bailey et al.7 has identified many cases where the nature of the active catalyst in such biphasic systems was either not identified or the identification was questionable. In particular, these workers were able to show7 that the actual oxoruthenate catalyst was usually RuO4, [RuO4]µ (perruthenate), or trans-[Ru(OH)2O3]2µ (ruthenate) when the pH of the aqueous solution as s8, 9.8–10.1, a12, respectively. Previous work carried out by our group8 on the oxidation of octa-2-ol using a {(RuO2 .xH2O:NaBrO3) H2O/CCl4} biphasic system has also highlighted that RuO4 is stable below pH 8, but at higher pHs first [RuO4]µ, then trans-[Ru(OH)2O3]2µ are the stable oxoruthenate species in aqueous solution.Most work on such RuO4 catalytic biphasic systems employs sodium periodate in neutral solution as the inorganic oxidant: however, the latter is considered expensive and problems can be encountered with the precipitation of voluminous amounts of sodium iodate as the reaction proceeds. 9 Prompted by these problems, in 1970 Wolfe and his co-workers9 suggested that household bleach, i.e., sodium hypochlorite in alkali solution (typically 0.67 mol dmµ3 NaOCl), acts as a suitable replacement for sodium periodate.NaOCl is not stable below pH 8, decomposing with the liberation of chlorine. Thus in household bleach, and most other commercial forms of NaOCl in aqueous solution, NaOH is added to stabilise the product; typically the final pH of household bleach10 is E11, but can be as high as 14. Wolfe and co-workers9 appear to have assumed, mistakenly, that RuO4 is as stable in household bleach as it is in neutral aqueous solution and, as a result, that the active oxoruthenate species in the {RuCl3 .nH2O (or, RuO2 .xH2O): NaOCl}/{organic phase (organic substrate)} biphasic system is RuO4.In fact, RuO4, a yellow-coloured species, is very unstable in alkali solution and is reduced by OHµ ions to perruthenate, RuO4 µ, a yellow-green species, which, in turn, is reduced much more slowly by OHµ ions to ruthenate, trans- [Ru(OH)2O3]2µ, an orange species.The UV–visible absorption spectra of RuO4, [RuO4]µ and trans-[Ru(OH)2O3]2µ are well known:11–13 thus, in a simple set of experiments we recorded, after 20 min, the UV–visible absorption spectra of a range of RuO4 aqueous solutions set at different pHs. From these spectra we were able to calculate the fractions of RuO4 [RuO4]µ and trans-[Ru(OH)2O3]2µ present in each of the solutions at the different pHs tested. The results of this work are illustrated in Fig. 1 and show that in household bleach (typical pHE11) RuO4 is not stable and will be readily reduced to trans-[Ru(OH)2O3]2µ by OHµ. However, further work showed that when RuCl3 .nH2O, or RuO2 .xH2O, is added to a well defined NaOCl solution (0.1 mol dmµ3 in 0.1 mol dmµ3 NaOH), or household bleach, the solution turns yellow-green and not orange in colour; the latter colour would be expected if trans-[Ru(OH)2O3]2µ were the major oxoruthenate species present, as seems reasonable given the high pH of the aqueous NaOCl solution.The colour of the final solution gives the appearance that RuO4 is produced, although, in contrast to RuO4, the yellow-green *To receive any correspondence (e-mail: A-mills@seansea.ac.uk). †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Fig. 1 Proportions (%) of RuO4 (d), [RuO4]µ (s) and trans- [Ru(OH)2O3]2µ (n) present in a series of aqueous solutions at different pHs, 20 min after the adjustment of the pH of an aqueous solution of RuO4 (3.8Å10µ4 mol dmµ3)J.CHEM. RESEARCH (S), 1997 369 species did not partition into the organic layer when the solution was shaken with CCl4. From an examination of its UV–visible absorption spectrum the yellow-green species was identified as [RuO4]µ. The results of the above work show that the major highoxidation- state species of ruthenium in the aqueous {RuCl3 .nH2O (or, RuO2 .xH2O):NaOCl}/{organic phase (organic substrate)} biphasic system is [RuO4]µ, and not RuO4, as assumed by Wolfe9 and others.4,5,14,15 The reason why [RuO4]µ, and not trans-[Ru(OH)2O3]2µ, is the major oxoruthenate species present in NaOCl even at pH 14 is because the oxidation of trans-[Ru(OH)2O3]2µ by the excess NaOCl present is much more rapid than the reduction of [RuO4]µ to trans-[Ru(OH)2O3]2µ by the OHµ ions present.13 Further work showed that when the amount of NaOH in the aqueous layer is increased markedly, from 0.1 to 5 mol dmµ3, the position of this dynamic equilibrium is altered and trans-[Ru(OH)2O3]2µ becomes the major highoxidation- state ruthenium species present.The different processes operating in the {RuCl3 .nH2O (or, RuO2 .xH2O): NaOCl}/{organic phase (organic phase (organic substrate)} biphasic system are summarised in Scheme 1. Since [RuO4]µ, a hydrophilic species, is responsible for the oxidation of the organic substrate in the aqueous {RuCl3 .nH2O (or, RuO2 .xH2O):NaOCl}/{organic phase (organic substrate)} biphasic system, then the reaction must occur at or near the phase boundary and any process, such as stirring or ultrasound, which increases the extent of this boundary will lead to an increase in reaction rate.In a study using this biphasic system, in which octan-2-ol was the lipophilic organic substrate, the rate of its oxidation was studied as a function of stirrer speed, both with and without ultrasound, and the results are illustrated in Fig. 2 and show that the rate of oxidation of octan-2-ol to octan-2-one increases with increasing agitation through stirring and that further enhancement in rate was possible if the reaction mixture was also subjected to agitation through the use of ultrasound. Experimental The RuCl3.nH2O and RuO2.xH2O were obtained from Johnson Matthey and all other chemicals from Aldrich.Aqueous solutions of RuO4 set at different pHs were prepared using the method of Bailey et al.7 The oxidation of octan-2-ol by hypochlorite in a biphasic system was monitored by gas chromatography using a procedure and equipment described by Giddings and Mills.8 We thank the EPSRC for supporting this work and Johnson Matthey for the loan of ruthenium trichloride and ruthenium dioxide hydrate. Received, 16th June 1997; Accepted, 20th June 1997 Paper E/7/04210H References 1 E.S. Gore, in Studies in Organic Chemistry vol. 11: Chemistry of the Platinum Group Metals, ed. F. R. Hartley, Elsevier, Amsterdam, 1991, ch. 8. 2 A. H. Haines, Methods for the Oxidation of Organic Compounds, Academic Press, London, 1988, pp. 55–64. 3 F. S. Martin, J. Chem. Soc., 1952, 2683. 4 M. Fieser, in Fieser and Fieser’s Reagents for Organic Synthesis, Wiley–Interscience, 1984, 11, p. 462. 5 U. A. Spitzer and D. G. Lee, J. Org. Chem., 1974, 39, 2468. 6 W. P. Griffith, Chem.Soc. Rev., 1992, 179. 7 A. J. Bailey, L. D. Cother, W. P. Griffith and D. M. Hankin, Trans. Met. Chem., 1995, 20, 590. 8 S. Giddings and A. Mills, J. Org. Chem., 1988, 53, 1103. 9 S. Wolfe, S. K. Hasan and J. R. Campbell, J. Chem. Soc., Chem. Commun., 1970, 1420. 10 N. N. Greenwood and A. Earnshaw, Chemistry of the Elements, Pergamon, Oxford, 1984, p. 1006. 11 R. E. Connick and C. R. Hurley, J. Am. Chem. Soc., 1952, 74, 5012. 12 J. L. Woodhead and J. M. Fletcher, J. Chem. Soc., 1961, 5039. 13 R.P. Larsen and L. E. Ross, Anal. Chem., 1959, 31, 176. 14 Y. Sasson, G. D. Zappi and R. Neumann, J. Org. Chem., 1986, 51, 2880. 15 T.A. Foglia, P. A. Barr and A. J. Malloy, J. Am. Oil Chem. Soc., 1977, 54, 858A. Scheme 1 Fig. 2 First-order rate constant, k1, measured over the first half-life, for the oxidation of octan-2-ol (0.4 mmol) to octan- 2-one (100% conversion) using a typical aqueous {RuO2.xH2O:NaOCl}/{organic phase (organic substrate)} biphasic system. In this system, the [RuO4]µ was generated through the addition of 2.1 mg of RuO2.xH2O to the aqueous solution (30 cm3), containing 0.1 mol dmµ3 NaOCl and 0.1 mol dmµ3 NaOH; the organic phase (30 cm3) was CCl4. Agitation was achieved either through stirring (j) or stirring and ultrasound (s). The ultrasound was generated using a 20 kHz soniprobe (Lucas Dawe Ultrsonics; model 7534A) fitted with a standard ultrasonic horn with a titanium tip (1.1 cm diameter), operated on a 30% duty cycle at output control level 2. The whole reaction system was thermostatted at 25 °C

ISSN:0308-2342    

DOI:10.1039/a704210h

出版商:RSC    

年代:1997

数据来源: RSC