|
81. |
Synthesis and Structure of 7-Methyl-2-(4′-methyl-2′,3′-dihydro-1′H-inden-1′-yl)-1H-indene |
|
Journal of Chemical Research, Synopses,
Volume 0,
Issue 9,
1997,
Page 606-607
Albertina G. Moglioni,
Preview
|
|
摘要:
Synthesis and Structure of 7-Methyl-2-(4'-methyl- 2',3'-dihydro-1'H-inden-1'-yl)-1H-indene$ Albertina G. Moglioni, Dora G. Tombari and Graciela Y. Moltrasio Iglesias* Departamento de Quý� mica Orga� nica, Facultad de Farmacia y Bioquý� mica, Universidad de Buenos Aires, Juný� n 956, (1113), Buenos Aires, Argentina We report research to find better conditions for the dehydration of 4-methylindan-1-ol to render 4-methylindene and 7-methyl-2-(4'-methyl-2',3'-dihydro-1'H-inden-1'-yl)-1H-indene. A suitable starting material for the preparation of several pterosines1 is the 4-methylindene 1.We have previously reported the synthesis of 5,6-dimethoxyindene from 5,6- dimethoxyindan-1-ol with thionyl chloride in benzene at 0 8C,2 so the same reaction was performed with 4-methyl- indan-1-ol 2, but the reactions products were a complex mixture from which a compound of molecular weight 260 was isolated. Bearing in mind that a dimeric compound had been obtained when 5,6-dimethoxyindan-1-ol was treated with toluene-p-sulfonic chloride or mesityl chloride,2 and comparing MS and NMR spectra, the structure of 7-methyl-2-(4'-methyl-2',3'-dihydro-1'H-inden-1'-yl)-1H-indene 3 was assigned tentatively to the compound of Mw 260.The formation of such a product was rationalized within the framework of the previously proposed mechanism for similar compounds (see Scheme 1).3 But, taking into account that the benzylic carbocations involved in the reaction could be transposed, several other isomers are possible (e.g. 4±7). Structure 3 was con®rmed by employing 2D NMR techniques (Fig. 1). The 1H±1H and 1H±13C correlation spectra were measured using COSY and HSQC procedures J. Chem. Research (S), 1998, 606±607$ Scheme 1 Fig. 1 *Interchangeable respectively. With these techniques were elucidated the connectivity of the carbon atoms to which the protons were attached. The HH NOESY experiment showed the proximity of the two methyl-H atoms (at d 2.31 and 2.33) to the benzylic methylene protons.This con®rmed the substitution system of 3. The position of the double bond was also evaluated with an HH NOESY experiment. The lack of spatial connectivity between the ole®nic proton and the benzylic methylene H-atom let us rule out isomer 7. Smooth conditions have been described for the dehy- dration of indan-1-ols.4 In 1963, Elvidge and Foster,5 suggested the preparation of indenes from the reaction of indan-1-ols with a few crystals of toluene-p-sulfonic acid (PTSA).However, when we repeated the procedure only the dimeric product 3 was obtained. In 1977, Woodward et al.6 quanti®ed the amount of PTSA for several tetrasubstituted indan-1-ols, but when we employed their conditions with the 4-methylindan-1-ol 2, the alcohol was recovered without modi®cation. $This is a Short Paper as de®ned in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there- fore no corresponding material in J.Chem. Research (M). *To receive any correspondence. 606 J. CHEM. RESEARCH (S), 1998Table 1Experiment M (PTSA)/mga Benzene/ml Reflux time Products (%)1 30 75 10 min Polymers2 20 75 10 min 3 (35), 2 (25), 1 (14)3 4 100 10 min 2 (100)4 4 100 100 min 2 (40), 3 (40)5 4 200 150 min 1 (60)6 10 100 180 min 1 (80)7 100 100 24 h 3 (90)aFor each reaction 1 g of 4-methylindan-1-ol was used.We now report research to nd better conditions underwhich the yields of the dimeric compound and the indenecould be maximized and Table 1 summarizes our results.ExperimentalMelting points are uncorrected, and were determined on aThomas Hoover apparatus. 1H NMR and 13C NMR were recordedon a Bruker AC400 spectrometer. The mass spectrum was recordedon a Varian CH7A. Satisfactory microanalysis was obtained forcompound 3.4-Methylindene 1.4-methylindan-1-ol (1 g), PTSA (10 mg) andbenzene (100 ml) were heated at reux for 180 min. Benzene wasthen distilled o (30 8C, 30 mmHg) and the residual product wasisolated by distillation in vacuo (64¡Ó66 8C, 2 mmHg, lit.,5 88 8C,13 mmHg).dH (CDCl3) 2.50 (3 H, s, CH3); 3.40 (2 H, br s, HC-3); 6.65 (1 H,br d, J1,2 5.60, HC-2); 7.00¡Ó7.60 (4 H, m, HC-1 and ArH).dC(CDCl3) 18.4; 37.7; 118.5; 125.6; 126.4; 132.6; 133.4; 142.1; 144.3.7-Methyl-2-(4'-methyl-2',3'-dihydro-1'H-inden-1'-yl )-1H-indene 3.To a solution of 4-methylindan-1-ol (1 g, 6.75 mmol) in benzene(100 ml), PTSA (100 mg) was added.The solution was stirred atreux for 24 h, then washed with 5% aqueous NaHCO3 (230 ml)and water (230 ml), dried (Na2SO4) and evaporated to dryness.The residue was puried by ash chromatography (hexane: ethylacetate, 4:1) to give 790 mg (yield 90%). Mp (ethanol) 98¡Ó99 8C./cm£¾1 (neat): 2900, 1580 and 1450. MS, EI 261 (M1, 11.4); 260(M, 50.5); 259 (2.0), 131 (100) (Found: C, 92.40; H, 7.91. C20H20requires C, 92.26; H, 7.74%).We express our sincere gratitude to Dr Teodor Parellafrom Universitat Autonoma de Barcelona, Spain, for theNMR spectra.This work is part of a Research Project sup-ported by the CONICET and SECYT (UBA).Received, 9th December 1997; Accepted, 1st June 1998Paper E/7/08862KReferences1 (a) D. G. Tombari, A. G. Moglioni and G. Y. Moltrasio Iglesias,Org. Prep. Proc. Int., 1995, 27, 679; (b) A. G. Moglioni and G. Y.Moltrasio Iglesias, An. Asoc. Quim. Argent., 1997, 85, 77.2 (a) W. Huckel, M. Sachs, J. Yantschulewitsch and F. Nerdel,Liebigs. Ann. Chem., 1935, 518, 155. (b) Z. Gorin, M. J. Heegand S. Mobashery, J. Org. Chem., 1991, 56, 7186. (c) D. G.Tombari, A. G. Moglioni and G. Y. Moltrasio Iglesias, An.Quim. de la Real Sociedad Espanula de Quimca., 1992, 88, 722.3 (a) W. E. Noland, L. L. Landucci and J. C. Darling, J. Org.Chem., 1979, 44, 1358; (b) B. R. Davies, S. J. Johnson and P. D.Woodgate, J. Chem. Soc., Perkin Trans. 1, 1985, 2545.4 (a) M. Braun and C. Bernard, Liebigs. Ann. Chem., 1985, 435;(b) F. McCapra, P. D. Leeson, V. Donovan and G. Perry,Tetrahedron, 1986, 42, 3223.5 (a) J. A. Elvidge and R. G. Foster, J. Chem. Soc., 1963, 590;(b) 1964, 981.6 R. B. Woodward and T. R. Hoye, J. Am. Chem. Soc., 1977, 99,8007.J. CHEM. RESEARCH (S),
ISSN:0308-2342
DOI:10.1039/a708862k
出版商:RSC
年代:1998
数据来源: RSC
|
82. |
Unusual Reactions of the Tricyclo[5.3.1.05,11]undecane Ring System of the Decipiane Diterpenes |
|
Journal of Chemical Research, Synopses,
Volume 0,
Issue 9,
1997,
Page 608-609
Yana M. Syah,
Preview
|
|
摘要:
Unusual Reactions of theTricyclo[5.3.1.05,11]undecane Ring System ofthe Decipiane Diterpenes$Yana M. Syah and Emilio L. Ghisalberti*Department of Chemistry, University of Western Australia, Nedlands, Western Australia, 6907,AustraliaThe tricyclo[5.3.1.05,11]undecane ring system of the decipiane diterpenes has been converted to the 1,4-disubstitutedtetralin system of the serrulatane diterpenes in two steps.Members of the serulatane 1 and decipiane 2 classes ofditerpenes have been encountered frequently as metabolitesof species of the plant genus Eremophila (Myoporaceae).1Determination of their absolute stereochemistry has shownthat they share the same absolute conguration at C1but are epimeric at C4.1,2 In attempts to convert the deci-piane skeleton to the 4-epi-serrulatane skeleton, we haveuncovered two unusual reactions of the decipiane skeleton,details of which are described in this report.Hydroboration of the acetate 3, a compound readilyderived from a metabolite of Eremophila decipiens,3 aordedmainly two compounds in addition to trace amounts ofthe dihydro derivative.The minor component could beassigned the expected structure 4 on the basis of spectro-scopic analysis. The major compound on the other handlacked a secondary hydroxy group and was shown to be thetertiary alcohol 5 as follows. The 1H NMR spectrumincluded a doublet for a secondary methyl (d 1.00) whichreplaced the vinyl methyl at d 1.61 in the spectrum of 3.The signals for the protons at C10 and C5, observed atd 2.59 (appar.q, J 9.3 Hz) and 2.45 (d, J 9.1 Hz) in 3, werereplaced by a doublet of doublets at d 2.29 (J 11.9 and8.6 Hz; H-10). The 13C NMR spectrum included a singletfor an oxygenated carbon at d 80.0 (C5).An explanation for the formation of 5 requires the iso-merisation of the double bond at C6, under the inuenceof diborane, to give the compound 6 with a tetra-substituted double bond at C5. Such isomerisations havebeen reported before4 and are known to occur even at lowtemperature.5 Nevertheless, the formation of 5 is surprisingin view of the fact that dehydration of the tertiary alcohol7 has been reported6 to provide mainly the compoundwith a tetrasubstituted double bond 8 which could becompletely isomerised with sulfur dioxide to the less strainedtrisubstituted counterpart 9.Molecular mechanics energyminimization techniques7 indeed show that 8 is lessstable than 9 (74.5 kcal mol£¾1 compared to 70.6 kcal mol£¾1;1 cal 4.184 J) due, in part, to an extra close contact inter-action between C5¡ÓC8 (2.805 A ).In contrast, similar mini-mization techniques on 3 and 6, the acetate derivative of 5show that the former (78.5 kcal mol£¾1) is less stable thanthe latter (74.4 kcal mol£¾1) with an extra close contactinteraction between C6¡ÓC9 (2.848 A ).The tertiary alcohol 10, obtained by acetylation of 5, ontreatment with Pb(OAc)4¡ÓCaCO3 at room temperatureyielded a new compound 11 which was shown by HRMSto have the molecular formula C22H32O3. The presence ofthe 1,2,3,4-tetrasubstituted benzene ring was evident fromthe NMR spectral data (4 singlets and 2 doublets for sp2carbons; dH 6.62 and 6.68, AB system, J 7.7 Hz), which alsoindicated the presence of an oxygen substituent (dC 154.9)and an aromatic methyl group (dH 2.15).The appearanceof two multiplets at dH 3.26 and 2.96 were reminiscent ofthe signals observed for the benzylic hydrogens at C1 andC4 in the serrulatane system 2,8 and homonuclear COSYtechniques conrmed the connectivity of the isolated systemC20¡ÓC1 to C4.Signals for the C12¡ÓC17 side chains andan acetoxy group could also be identied, thus leavingtwo carbons to be assigned. Both of these carried an oxygensubstituent, and comprised a fully substituted carbon (dCJ. Chem. Research (S),1998, 608¡Ó609$$This is a Short Paper as dened in the Instructions for Authors,Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-fore no corresponding material in J.Chem. Research (M).*To receive any correspondence.608 J. CHEM. RESEARCH (S), 199893.0 s) and a methyleneoxy carbon (dC 67.0, t; dH 4.38 and 4.43, AB system, J 11.6 Hz). This information leads to two possible structures 11 and 12 and a choice in favour of 11 could be made since the 1H NMR spectrum of the hydro- lysis product showed the AB system of the methyleneoxy group at dH 3.46, a consequence of the conversion of the C18-acetate to a primary hydroxy group.The stereo- chemistry at C11 was tentatively assigned from the obser- vation that the C4 methine proton had undergone a down¢çeld shift to dH 3.48, presumably a result of the removal of the shielding e€ect of a syn-acetate. The near identity of the chemical shift for the protons at C18 and C4 precluded con¢çrmation of this through NOE measurements. The formation of 11 and 10 can be rationalised by assuming that the ketone produced from fragmentation of the C5¡¾C11 bond undergoes aromatization through a- acetoxylation, a process for which there are precedents.8 The apparent formation of a single diastereoisomer, explain- able by involvement of the 18-acetoxy group in stabilizing a developing radical or carbocation at C11, is probably a consequence of the puri¢çcation process.Smaller amounts of a C11-stereoisomer could have been lost in the chromato- graphic steps. Experimental 1H and 13C NMR spectra were measured for CDCl3 solutions at either 300 MHz (Bruker AM-300) or 500 MHz (Bruker AMX-500).J values are in Hz. Hydroboration of the acetate 3.�¢The acetate 3 (900 mg, 2.7 mmol) in dry diethyl ether was mixed with an excess of BH3. (CH3)2S (2.0 ml) at 0 8C under N2. The solution was allowed to warm to room temperature for 3 h. After cooling to 0 8C, ethanol (0.3 ml) was added followed by 30% NaOH (4 ml) and 35% H2O2 (3.5 ml) solutions. The mixture was stirred at 40 8C for 1 h, diluted with water and extracted with diethyl ether.Separation by radial chromatography (Si gel; EtOAc¡¾light petroleum, 1:9) of the residue gave the 6,7-dihydro alcohol (34 mg, 4%), the 7,18-diol 4 (105 mg, 13%) and the 5,18-diol 5 (340 mg, 41%) as oils. Decipiane-6,7-dihydroalcohol.�¢Oil, H (300 MHz, CDCl3), 3.64 and 3.48 (each 1 H, d, J 10.6, H2-18), 2.45 (1 H, m, H-10); 2.20 (1 H, dd, J 10, 4.5, H-5); 0.97 (3 H, d, J 6.7, H3-20), 0.88 (3 H, d, J 6.6, H3-19), 0.84 (6 H, d, J 6.6, H3-16 and H-17); C (75 MHz, CDCl3): 71.2, d; 48.6, s; 43.9, d; 40.2 t; 34.3, d; 32.6, d; 30.5, t; 30.2, d; 28.8, d; 28.0, d; 27.4, t; 25.7, d; 23.0, t; 22.7, q; 22.6, q; 21.1, q; 20.2, d; 18.8, q.m/z 292 (Ma) (41), 261 (33), 189 (46), 163 (59), 135 (29), 122 (100). Decipiane-7,18-diol 4.�¢Oil, H (300 MHz, CDCl3), 3.64 and 3.45 (each 1 H, d, J 10.6, H2-18), 1.09 (3 H, d, J 7.1, H3-20), 0.88 (3 H, d, J 6.6, H3-19), 0.84 and 0.83 (each 3 H, d, J 6.6, H3-16 and H3-17); C (75 MHz, CDCl3): 71.8, d; 71.1, t; 48.5, s; 45.3, d; 40.1, t; 38.7, d; 33.9, t; 31.8, d; 29.9, d; 29.6, d; 29.2, t; 28.0, d; 25.4, t; 23.0, t; 22.7, q; 22.5, q; 20.2, q; 18.6, d; 17.1 q.Decipiane-5,18-diol 5.�¢Oil, H (300 MHz, CDCl3); 3.90 and 3.87 (each 1 H, d, J 11.1, H2-18), 2.55 (br s, OH), 2.33 (1 H, dd, J 10.8, 8.3, H-17), 1.06 (3 H, d, J 6.9, H3-20), 0.85 (3 H, d, J 6.6, H3-19), 0.84 (6 H, d, J 6.6, H3-16 and H3-17); C (75 MHz, CDCl3): 80.0, s; 67.7, t; 53.2, s; 44.6, d; 40.4, d; 40.2, t; 29.9, d; 29.4, d; 29.0, t; 28.8, d; 28.0, d; 28.0, t; 25.4, t; 23.3, t; 22.7, q; 22.5, q; 20.0, q; 19.5, t; 18.2, t; 16.4, q; EIMS, m/z 308 (Ma) (3), 290 (50), 205 (97), 171 (62), 149 (100).Lead tetraacetate treatment of 10.�¢The diol 5 was acetylated with Ac2O¡¾pyridine and the monoacetate alcohol 10 (170 mg, 0.48 mmol) was treated with Pb(OAc)4 (0.49 mmol) in the presence of CaCO3 for 20 h. Radial chromatography (Si gel, EtOAc¡¾light petroleum; 1:19 to 1:4) of the reaction product a€orded the 4-epi- serrulatane 5,11-ether 11 (40 mg) as an oil; max/cm¢§1 1748, 1604, 1227; H (500 MHz, CDCl3): 0.82 (6 H, d, J 6.6, H3-16 and H3-17), 1.05 (2 H, m, H2-14), 1.18 (3 H, d,-20), 1.50 (1 H, m, H-15), 1.55 (1 H, m, Ha-3), 1.74 (1 H, m, Hb-3), 2.12 (3 H, s, OAc), 2.15 (3 H, br s, H3-19), 2.96 (1 H, dq, J 7.2, 7.2, H-1), 3.26 (1 H, dd, J 4.7, 11.9, H-4), 4.38 (1 H, d, J 11.6, Ha-18), 4.43 (1 H, d, J 11.6, Hb-18), 6.62 (1 H, d, J 7.7, H-8), 6.88 (1 H, d, J 7.7, H-7); assignments were aided by COSY techniques; C (75 MHz, CDCl3): 14.7 (C19), 19.2 (C3), 20.7 (C2), 20.9 (CH3CO), 22.4, 22.5 (C16, C17), 23.9 (C20), 27.7 (C15), 29.3 (C1), 31.2, 31.1 (C13, C14), 39.3 (C12), 45.6 (C4), 67.0 (C18), 93.0 (C11), 116.3 (C6), 119.1 (C8), 127.3 (C10), 129.6 (C7), 138.0 (C9), 154.9 (C5), 170.9 (CH3CO) (FABMS: found: MaaH, 345.2407.C22H33O3 requires: MaaH, 345.2430); CIMS, m/z: 345 (MaaH), 285 (51), 205 (10), 175 (11), 121 (100). Received, 22nd May 1998; Accepted, 2nd June 1998 Paper E/8/03890B References 1 E. L. Ghisalberti, Phytochem., 1994, 35, 7. 2 E. L. Ghisalberti, in Studies in Natural Products Chemistry, ed. Atta-ur-Rhaman, Elsevier Science B. V., Amsterdam, 1995, vol. 15, p. 255. 3 E. L. Ghisalberti, P. R. Je€eries and P. N. Sheppard, Tetrahedron, 1980, 36, 3253. 4 G. M. L. Cragg, Organoboranes in Organic Synthesis, Marcel Dekker Inc., New York, 1973, pp. 68¡¾74. 5 A. M. Krubiner, N. Gottfried and E. P. Oliveto, J. Org. Chem., 1968, 33, 1715. 6 M. L. Grenlee, J. Am. Chem. Soc., 1981, 103, 2425. 7 U. Berkert and N. L. Allinger, Molecular Mechanics, ACS, Washington DC; as implemented in CS Chem3D Pro with Ponder's TINKER additions, 1985. 8 P. G. Forster, E. L. Ghisalberti, P. R. Je€eries, V. M. Poletti and N. J. Whiteside, Phytochemistry, 1986, 25, 1377. 9 M. Lj. Mihailovic, J. Forsek and Lj. Lorenc, J. Chem. Soc., Chem. Commun., 1978, 916. J. CHEM. RESEARCH (S), 1998 609
ISSN:0308-2342
DOI:10.1039/a803890b
出版商:RSC
年代:1998
数据来源: RSC
|
83. |
Selective Oxidation of Toluene Catalysed by Ultrafine Fe–Mo Oxide Particles |
|
Journal of Chemical Research, Synopses,
Volume 0,
Issue 9,
1997,
Page 610-611
Wenxing Kuang,
Preview
|
|
摘要:
Selective Oxidation of Toluene Catalysed byUltrafine Fe¡ÓMo Oxide Particles$Wenxing Kuang,* Yining Fan, Chibiao Liu, Kaidong Chen andYi ChenDepartment of Chemistry, Institute of Mesoscopic Solid State Chemistry, Nanjing University,Nanjing 210093, ChinaIt has been found that by decreasing the size of both Fe2O3 and Fe2(MoO4)3 particles in complex Fe¡ÓMo oxide tonanometric order, the catalytic activity of the mixed oxide in toluene oxidation is remarkably improved.Selective oxidation of hydrocarbons over metal oxide cata-lysts is currently the main method for the synthesis oforganic oxygenate compounds.It has been found1¡Ó8 thatthe nature of lattice oxygen ions is one of the most import-ant parameters inuencing catalytic selectivity. In pastdecades, considerable attention has been devoted to thedesign of highly selective oxidation catalysts, and greateort has been made to improve the reactivity of latticeoxygen ions by adjusting the composition and structure ofoxide catalysts.In the past decade, ultrane oxide particles have attractedconsiderable research interest in the eld of heterogeneouscatalysis due to their unique physical and chemical proper-ties, and many eorts have been devoted to the preparationand application of single-phase or supported oxides.9¡Ó11However, studies on ultrane mixed-phase oxides are ratherlimited, although most important industrial catalysts aremixed-phase oxides.In our previous study,12 it was found that forselective oxidation of toluene in the absence of molecularoxygen over complex Fe¡ÓMo oxides prepared by thesol¡Ógel (sg) technique, both the highest yield forbenzaldehyde and the optimum specic activity are achievedat a Fe :Mo atomic ratio of 1:1.The aim of this workis to study the behavior of complex Fe¡ÓMo oxides withdierent particle sizes for the selective oxidation of toluenein the absence of molecular oxygen and to discover theeect of oxide particle size on the reactivity of lattice oxygenions.The results of TEM, XRD and Mo ssbauer spectroscopyare presented in Table 1.It can be seen that the size of pureFe2O3 and Fe2(MoO4)3 particles is in the range 10¡Ó20 and20¡Ó40 nm, respectively. The size of Fe2O3 and Fe2(MoO4)3particles in Fe¡ÓMo (sg) is about the same as that of pureFe2O3 and Fe2(MoO4)3 particles, respectively. The BETsurface area of the Fe¡ÓMo (sg) is 46.3 m2 g£¾1. Due to themolecular homogeneous distribution of various componentsin the sol¡Ógel process,13¡Ó18 it is possible to form ultraneFe2O3 and Fe2(MnO4)3 particles from the Fe¡ÓMo gel.PureFe2O3, Fe2(MoO4)3 and Fe¡ÓMo (sg) are actually ultraneoxide particles (<100 nm). As shown in Table 1, Fe2O3particles in a pure sample or in Fe¡ÓMo (sg) exist in thehighly dispersed superparamagnetic state. It can also beshown that the particle size of Fe¡ÓMo (cp) prepared by thecoprecipitation method is much larger than that of Fe¡ÓMo(sg) prepared by the sol¡Ógel process.The correspondingBET surface area is 2.7 m2 g£¾1, smaller than that of Fe¡ÓMo(sg).Table 1 also shows the total yield of benzaldehydeover various samples in the pulse microreactor. It can beseen that the benzaldehyde yield of Fe¡ÓMo (sg) is muchhigher than that of pure Fe2(MoO4)3 and Fe2O3 samples,suggesting that the eect of the particle size on the reac-tivity of lattice oxygen ions of mixed-phase oxides ismore marked than that of single-phase oxides. This maybe correlated with the interaction between ultraneFe2(MoO4)3 and Fe2O3 in Fe¡ÓMo (sg).It is also noteworthythat for complex Fe¡ÓMo oxides, with increasing size ofFe2O3 and Fe2(MoO4)3 particles, the benzaldehyde yielddecreases rapidly, indicating that the particle size of themixed-phase oxides has great inuence on the reactivityof lattice oxygen ions. In particular, the specic activity ofFe¡ÓMo (sg) is found to be much higher than that of Fe¡ÓMo(cp). This reveals that the lattice oxygen ions in the ultraneoxide particles have unique reactivity for selective oxidationof toluene to benzaldehyde.For pure Fe2O3, Fe2(MoO4)3 and Fe¡ÓMo (cp), no newspecies appear in the XRD patterns or in the Mo ssbauerspectra after the reaction.This indicates that only the latticeoxygen ions on the surface of these samples participate inthe reaction. However, for Fe¡ÓMo (sg), newly appearedXRD patterns and two doublets in Mo ssbauer spectra areobserved and can be assigned to crystalline b-FeMoO4.12Since the various components of Fe¡ÓMo (sg) have a homo-geneous distribution and the particles are of ultrane size,the interaction between Fe2O3 and Fe2(MoO4)3 may begreatly increased, resulting in both the lattice oxygen ionson the surface and those in the bulk phase of Fe¡ÓMo (sg)J.Chem. Research (S),1998, 610¡Ó611$Table 1 The reactivity of lattice oxygen ions of various samplesParticle size/nmSampleStructure analysis by XRDand Mo ssbauer spectroscopy Fe2(MoO4)3 Fe2O3Total benzaldehydeyield/mmol g£¾1Specific activity(a.u.)cFe2O3 Fe2O3a 10¡Ó20 0 0.0Fe2(MoO4)3 Fe2(MoO4)3 20¡Ó40 1.0 0.2Fe¡ÓMo (sg) Fe2(MoO4)3, Fe2O3a 20¡Ó40 10¡Ó20 23.2 1.9Fe¡ÓMo (cp) Fe2(MoO4)3, Fe2O3b 200¡Ó400 40¡Ó80 0.7 1.0aSuperparamagnetic Fe2O3.bMagnetic Fe2O3. cBenzaldehyde per BET surface area.participating in the reaction. The reaction mechanism forFe¡ÓMo (sg) is reported to be:122Fe2MoO43 Fe2O3 4 6b-FeMoO4 3O$This is a Short Paper as dened in the Instructions for Authors,Section 5.0 [see J.Chem. Research (S), 1998, Issue 1]; there is there-fore no corresponding material in J. Chem. Research (M).*To receive any correspondence.610 J. CHEM. RESEARCH (S), 1998The above results reveal that the oxide particle size exerts great in¡¥uence on the reactivity of lattice oxygen ions. By decreasing the size of both Fe2O3 and Fe2(MoO4)3 particles in complex Fe¡ÀMo oxide to nanoscale, the reactivity of lattice oxygen ions can be markedly improved.Experimental Fe2O3, Fe2(MoO4)3 and Fe¡ÀMo (sg) were prepared by the sol¡Àgel method using citric acid as the complexing agent, and were calcined at 673 K for 4 h to a€ord the oxides.12 Fe¡ÀMo (cp) was prepared by the coprecipitation method. The precipitates formed were dried and calcined at 773 K for 8 h. The Fe:Mo atomic ratio of both Fe¡ÀMo (sg) and Fe-Mo (cp) was 1:1. The pulse reactions of toluene over complex Fe¡ÀMo oxide in the absence of molecular oxygen were carried out under the conditions of 623 K, 0.2 MPa, helium ¡¥ow-rate 40 ml min¡¦1, and 1.45 mmol toluene per pulse.12 The support of the National Natural Science Foundation of China and SINOPEC is gratefully acknowledged.Received, 27th May 1998; Accepted, 2nd June 1998 Paper E/8/03987I References 1 A. Bielanski and J. Haber, Catal. Rev.-Sci. Eng., 1979, 19, 1. 2 R. K. Grasselli and J. D. Burrington, Adv. Catal., 1981, 30, 133. 3 R. Pitchai and K. Klier, Catal. Rev.-Sci. Eng., 1986, 28, 13. 4 T. P. Snyder and C. G. Hill, Catal. Rev.-Sci. Eng., 1989, 31, 43. 5 V. D. Sokolovskii, Catal. Rev.-Sci. Eng., 1900, 32, 1. 6 W. Kuang, Y. Fan and Y. Chen, Catal. Lett., 1998, 50, 31. 7 W. Kuang, Y. Fan and Y. Chen, J. Mater. Chem., 1998, 8, 19. 8 W. Kuang, Y. Fan, L. Dong and Y. Chen, J. Chem. Res. (S), 1998, 276. 9 K. R. Barnard, J. Catal., 1990, 125, 265. 10 W. C. Conner, G. M. Pajonk and S. J. Teichner, Adv. Catal., 1986, 34, 1. 11 M. Lacroix, G. M. Pajonk and S. J. Teichner, J. Catal., 1986, 101, 314. 12 W. Kuang, Y. Fan, K. Chen and Y. Chen, J. Chem. Res. (S), 1997, 366. 13 G. M. Pajonk, Appl. Catal., 1991, 72, 217. 14 D. A. Ward and E. I. Ko, Ind. Eng. Chem. Res., 1995, 34, 421. 15 M. Schneider and A. Baiker, Catal. Rev.-Sci. Eng., 1995, 37, 515. 16 Z. Fen, L. Liu and R. G. Anthony, J. Catal., 1992, 136, 423. 17 C. D. E. Lakeman and D. A. Payne, Mater. Chem. Phys., 1994, 38, 305. 18 B. J. J. Zelinski and D. R. Uhlmann, J. Phys. Chem. Solids, 1984, 45, 1069. J. CHEM. RESEARCH (S), 1998 611
ISSN:0308-2342
DOI:10.1039/a803987i
出版商:RSC
年代:1998
数据来源: RSC
|
84. |
Regio- and Stereo-selective Reaction of Chiral Alkoxy- and Aminomethyl-substituted α-Silylallyl Carbanions with Aldehydes |
|
Journal of Chemical Research, Synopses,
Volume 0,
Issue 9,
1997,
Page 612-613
Li Liu,
Preview
|
|
摘要:
Regio- and Stereo-selective Reaction of Chiral Alkoxy- and Aminomethyl-substituted a-Silylallyl Carbanions with Aldehydes$ Li Liu and Dong Wang* Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100080, PR China The reactions of chiral alkoxy- and aminomethyl-substituted -silylallyl carbanions with aldehydes gave 1-silylhomoallylic alcohols with high -regioselection and E-stereoselection, as well as a diastereomeric excess of 8¡¾69%, depending on the chiral substituents on silicon, the aldehydes and the base used.a-Silylallyl carbanons1 have been used extensively as syn- thetic intermediates, since the silyl group can be sub- sequently transformed to other electrophile equivalents thus enhancing its usefulness in synthesis.2 When the carbanions are allylic in nature, the reactions of silylallyl anion 1 with various electrophiles can occur at either the a- or the g-position giving the a-product 2 or the g-product 3 respect- ively. In the case of the g-product 3, there is an additional complexity in terms of the stereochemistry of the double bond produced which can have either the E- or the Z- con¢çguration.It was found that changing the substituents on silicon showed some promise in the control of regio- and stereo-selectivity. If a chiral allylsilane was used to generate chiral a-silylallyl carbanion, asymmetric induction of the chiral substituent on silicon should be observed. Herein, we wish to report regio- and stereo-selectivity of the reactions of chiral alkoxy- and aminomethyl-substituted a-silylallyl carbanions with aldehydes.The parent compounds, chiral alkoxyallyldimethylsilanes 4a¡¾c, were prepared through the condensation of allyl- chlorodimethylsilane 5 with chiral alcohols, ( ¢§ )-menthol 6a or N-methyl-(1R,2S)-( ¢§ )-ephedrine 6b,3 while chiral allyl- (aminomethyl)dimethylsilanes 7a,b were obtained via the condensation of allyl(chloromethyl)dimethylsilane 8 with chiral amines, O-methyl-(¢§)-ephedrine 9a or (S)-(a)-2- (methoxymethyl)pyrrolidine 9b.4 The reactions of chiral allylalkoxysilanes 4a¡¾c in the presence of Lewis base, Schlosser's base (BunLi¡¾ButOK)5 or lithium diisopropylamide (LDA), generated the anions 10a¡¾c, which reacted with aldehydes giving g-(E) products 11¡¾13 exclusively in high yield (Table 1, Scheme 1).The E-con¢çguration of the double bond formed was deduced by 1H NMR: a double triplet at d 6.2 and a doublet at d 5.7 with J 18.2.It is interesting that the high g-regioselection6 in the reactions of alkoxy-substituted a-silylallyl anion 10a¡¾c with aldehydes contrasts the favorable a-regioselection for halides under the same Lewis base conditions.7 Diastereo- selectivities (de) of the reactions of 10a,b with aldehydes are low (8¡¾16%), which was determined by the diastereomeric proton, and carbon resonances and the use of a chiral shift reagent [(a)-Eu(hfc)3]. When 2-methylallylsilane 4c was used, the de of the product 13 was improved slightly to 26%.An aminomethyl substituent on silicon leads to another type of e€ective regio- and stereo-controlling group. Chan and coworkers4 reported that the asymmetric alkylation of chiral aminomethyl-substituted a-silylallyl anions with alkyl halides exhibited high a-selection and dia- stereoselectivity (de>90%). These results encouraged us to investigate the regio- and stereo-chemistry of the reactions of chiral aminomethyl-substituted a-silylallyl carbanions with aldehydes. Chiral (aminomethyl)allylsilanes 7a,b were deprotonated to the corresponding chiral aminomethyl- substituted silylallyl carbanions 14a,b in the presence of Schlosser's base. 14a,b reacted with aldehydes to give 1-silyl-homoallylic alcohols 15 and 16. In contrast to the a-selection of the alkylation,4 all the reactions of amino- methyl-substituted a-silylallyl carbanions with aldehydes produced the g-isomer exclusively, with the exception of the case of use of BunLi¡¾TMEDA as Lewis base, in which the a-isomer (a-15a, 20% yield) was isolated from the product mixture (entry 7).On the other hand, the g-products are a mixture of E- and Z-isomers (Table 1, Scheme 1). The Z-con¢çguration of the double bond formed was proved by 1H NMR: a double triplet at d 5.6 and a doublet at d 5.3 with J 15.4, while the E-con¢çguration was shown by a double triplet at d 6.05 and a doublet at d 5.73. As Chan and Labrecque8 have demonstrated, the a-silylallyl anion can exist as three species: exo-17, endo-18 and an open form 19.9 The aminomethyl group on silicon may coordinate with a neighbouring metal ion, leading to exo-17, which e€ected J.Chem. Research (S), 1998, 612¡¾613$ Table 1 Regio- and stereo-selection of silylallyl anions with aldehydes Entry Silane ([a]D) Basea Anion Aldehyde (R) Product Yield (%)b (gE a gZ) gE (de, %) : gZ (de, %) 1 4a (¢§59.7) A 10a C5H11 11 g-(E) 92 (8) .c 2 4a B 10a C5H11 11 g-(E) 60 (12) . 3 4b (¢§37.2) A 10b Ph 12a g-(E) 82 (16) . 4 4b A 10b C5H11 12b g-(E) 75 (14) . 5 4c (¢§50.3) A 10c C5H11 13 g-(E) 70 (26) . 6 7a (¢§44.8) A 14a Ph 15a g-(E) 90 (54) . 7 7a C 14a Ph 15a g-(E a Z) a a-d 70 7 (48) : 1 8 7a A 14a C5H11 15b g-(E a Z) 75 1 (21) : 1.5 (8) 9 7b (¢§78.2) A 14b Ph 16a g-(E a Z) 90 8 (69) : 1 10 7b A 14b C5H11 16b g-(E a Z) 87 1.2 (52) : 1 (14) 11 7b A 14b C2H5 16c g-(E a Z) 82 1 : 2 (11) aLewis base: A, BunLi¡¾ButOK; B, LDA; C, BunLi¡¾TMEDA; bisolated yield; cexclusive -E isomer; d -isomer in 20% isolated yield.the attack of the alkyl cation of alkyl halides occurring at the a-position. However, the aldehydic carbonyl would participate in coordination with the counterion (transition state 20), so the attack of the carbonyl group took place at $This is a Short Paper as de¢çned in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there- fore no corresponding material in J.Chem. Research (M). *To receive any correspondence. 612 J. CHEM. RESEARCH (S), 1998the g-position via an SE2' type process, leading to g-selec-tion. Meanwhile, the species endo-18 would be responsiblefor the formation of the Z-isomer and the open form 19 forboth g- and a-isomers, depending on the base used as in thecase of entry 7. The E/Z ratios also depend on the structureof the aldehydes. For benzaldehyde, E/Z is larger than thatfor the aliphatic aldehydes (entries 6 and 9 cf. 8 and 10).For propionaldehyde (entry 11), the E/Z ratio of the pro-duct 16c is even reversed (1:2).Change of the substituent on silicon from a chiral alkoxygroup to a chiral aminomethyl group led to an increase inthe de of the g-(E) isomer produced of up to 69% (Table 1).Comparing the de of g-(E)-12a (entry 3) with that ofg-(E)-15a (entry 6), it is worth noting that although theconguration of the chiral ephedrine moiety is the same(1R,2S) in 4b and 7a, and dierent only in the mode ofconnection of the chiral group with silicon, Si¡ÓO*R andSi¡ÓC¡ÓN*R, the de of the products is markedly dierent:16% for 4b and 54% for 7a.This is ascribed to the fact thatthe aminomethyl group on silicon could coordinate with themetal ion forming a ve-membered ring, which is morestable than the four-membered ring formed in the case ofalkoxyallyl silanes. At the same time, the stereocontrolability of the more rigid (S)-2-(methoxymethyl)pyrrolidinemoiety is better (de of 16a up to 69%) than that of theO-methyl-(£¾)-ephedrine moiety.ExperimentalGeneral Procedure.To an ice-cooled suspension of KOBut(22 mmol) in dried hexane (15 ml) BunLi solution (1.6 M in hexane,22 mmol) was added dropwise. The mixture was cooled to £¾70 8C.Diethyl ether (10 ml) was added, followed by a solution of 7a(20 mmol) in diethyl ether (10 ml).The mixture was allowed towarm to room temperature for 4 h and cooled to £¾78 8C beforeaddition of benzaldehyde (20 mmol) in ether (10 ml).The mixturewas stirred at this temperature for 6 h, and then at room tempera-ture for 12 h. Then, the mixture was poured into an aqueous satu-rated solution of ammonium chloride (50 ml). The organic layerwas dried (MgSO4) and evaporated to produce crude product whichwas puried by ash chromatography (neutral Al2O3 column; elu-ent: light petroleum¡Óethyl acetate, 10:1) to give as a colorless liquid-(E)-15a (Found: C, 72.72; H, 8.87; N, 3.52.C24H35NO2Si requiresC, 72.49; H, 8.86; N, 3.52%); max/cm£¾1 (lm) 3350, 2940, 1610,1250. H 0.00 (6 H, s, SiCH3), 1.02 (3 H, d, J 6.2, CH3), 1.45 (1 H,br s, OH), 2.02 (2 H, d, J 8.2, NCH2), 2.20 (3 H, s, NCH3), 2.4¡Ó2.9(2 H, m), 3.24 (3 H, s, OCH3), 4.22 (1 H, d, J 6.0, PhCH), 4.6¡Ó4.8(1 H, m, PhCH), 5.73 (1 H, d, J 18.6, 1-H), 6.05 (1 H, dt, J 18.6, 6,2-H), 7.1¡Ó7.6 (10 H, m, Ar-H); C £¾ 3.0 ( £¾ 3.1), 7.4, 41.3, 44.8(44.7), 47.0, 56.6, 66.3, 72.8 (72.9), 85.7, 128.5¡Ó125.7 (2C6H5),133.7, 144.0 (143.1), The NMR data in parentheses are for the sec-ond diastereoisomers (as below).g-(E)-15b, colorless liquid (Found: C, 70.51; H, 10.71; N, 3.46.C23H41NO2Si requires C, 70.59; H, 10.48; N, 3.58%).max/cm£¾1(lm) 3420, 2920, 1620, 1500. dH 0.01 (6 H, s, SiCH3), 0.6¡Ó1.8 (16 H,m), 2.02 (2 H, d, J 8.0, NCH2), 2.20 (3 H, s, NCH3), 2.3¡Ó2.8 (2 H,m), 3.20 (3 H, s, OCH3), 3.6 (1 H, m, OCH), 4.15 (1 H, d, J 5.8,PhCH), 5.68 (1 H, d, J 18.8, 1-H), 6.15 (1 H, dt, J 18.8, 6.2, 2-H),7.1¡Ó7.5 (5 H, m, PhH).dC £¾3.0, 22.8, 25.8, 27.3, 41.3, 44.7, 46.0,47.2, 56.6, 66.0, 72.1, 85.7, 125.0¡Ó128.5 (2C6H5), 132.8, 142.0(143.6).g-(E)-16a, colorless liquid (Found: C, 68.61; H, 9.52; N, 4.55.C19H31NO2Si requires C, 68.42; H, 9.36; N, 4.20%); max/cm£¾1(lm) 3400, 2950, 1610, 1240. dH 0.03 (6 H, s, SiCH3), 1.4¡Ó2.0 (7 H,m), 2.0¡Ó2.2 (1 H, m), 2.3¡Ó2.7 (3 H, m), 3.0¡Ó3.3 (2 H, m), 3.33 (3 H,s, OCH3), 3.4¡Ó3.5 (1 H, m), 4.6¡Ó4.8 (1 H, m, PhCH), 5.82 (1 H, d,J 19.0, 1-H), 6.12 (1 H, dt, J 19.0, 7.2, 2-H), 7.1¡Ó7.4 (5 H, m,Ar-H).dC £¾3.0, £¾2.2, 22.9, 28.0, 46.0, 47.2, 57.8, 59.1, 67.5, 72.5(72.7), 75.7, 124.0¡Ó128.5 (2C6H5), 132.4, 143.8 (144.1).We thank the National Natural Science Foundation ofChina for nancial support of this research and ProfessorT. H. Chan for his helpful suggestions.Received, 17th April 1998; Accepted, 2nd June 1998Paper E/8/02886IReferences1 R. J. P. Corriu and J. Masse, J. Organomet. Chem., 1973, 57, C5;R. J. P. Corriu, J. Masse and D. Samate, J. Organomet. Chem.,1957, 93, 71.2 T. H. Chan and D. Wang, Chem. Rev., 1995, 95, 1279 andreferences cited therein.3 Z. Y. Wei, D. Wang, J. S. Li and T. H. Chan, J. Org. Chem.,1989, 54, 5768.4 R. F. Horvath and T. H. Chan, J. Org. Chem., 1989, 54, 319;S. Lamothe and T. H. Chan, Tetrahedron Lett., 1991, 32, 1847.5 M. Schlosser, R. Dahan and S. Cotterns, Helv. Chim. Acta.,1984, 67, 284.6 For similar results see: K. Takaku, H. Shinokubo and K. Oshima,Tetrahedron Lett., 1997, 38, 5189.7 L. H. Li, D. Wang and T. H. Chan, Tetrahedron Lett., 1991, 32,2879; L. Liu and D. Wang, Chin. Chem. Lett., 1996, 7, 1069.8 T. H. Chan and D. Labrecque, Tetrahedron Lett., 1992, 33, 7997.9 G. Fraenkel, A. Chow and W. R. Winchester, J. Am. Chem. Soc.,1990, 112, 1382; 2582.Scheme 1Scheme 2J. CHEM. RESEARCH (S), 1998 613
ISSN:0308-2342
DOI:10.1039/a802886i
出版商:RSC
年代:1998
数据来源: RSC
|
85. |
A Facile Preparation of 4-Arylidene-4,5-dihydrooxazol-5-ones using Zeolite as a Cyclodehydrating Agent |
|
Journal of Chemical Research, Synopses,
Volume 0,
Issue 9,
1997,
Page 614-615
Anima Boruah,
Preview
|
|
摘要:
A Facile Preparation of 4-Arylidene-4,5- dihydrooxazol-5-ones using Zeolite as a Cyclodehydrating Agent$ Anima Boruah, Partha P. Baruah and Jagir S. Sandhu* Regional Research Laboratory, Jorhat-785 006, India An efficient new method for the azlactonisation of acylamino acids using zeolite under mild conditions is described; the method is fairly general as well as providing high yields. 4,5-Dihydrooxazol-5-ones (2-oxazolin-5-ones) are important intermediates in organic synthesis and there is continu- ing interest in the exploration of their chemistry.1 The 5-oxazolone derivatives are reported to exhibit biological activity such as anticancer activity2 and the dehydro- peptides, N-substituted amides obtained by their aminolysis, are claimed to have antitumour3 and central nervous system inhibiting4 properties.There are several chemical methods reported for the cyclodehydration of N-acylamino acids, e.g. acetic anhydride�}sodium acetate, acetic anhydride�}lead acetate,5 polyphosphoric acid,6 perchloric acid7 and carbodiimides.8 All these methods have several drawbacks, i.e.the need for a large amount of dehydrating agent, and poor yields caused by the formation of undesirable side products. In addition, side products are formed by the reaction of the reagents used with other functional groups in the substrate: e.g. amino and phenolic groups are acetylated when acetic anhydride is used in this azlactonization. Also, these methods are not so environment friendly. Moreover, in recent years there has been increased interest in the area of zeolite induced organic transformations9 in view of their remarkable catalytic properties.Several methods using such catalysts, e.g. thioacetalization of carbonyl compounds, sulfoxidation of thioethers, de- ketalisation, tetrahydropyranylation of alcohol, oxidative cleavage of tosylhydrazones and methoxymethylation of alcohols, have been investigated.10 However, the cyclo- dehydration of a-acylamino acids in Erlenmeyer azlactone synthesis has not been reported. We disclose here a new mild, convenient and heterogeneous catalytic procedure for the synthesis of various 4,5-dihydrooxazol-5-ones.The reaction is fairly general, facile and ecient and is devoid of any side products emanating from functional groups present as formed in the known methods employing anhydrides. Typically, HY-zeolite was impregnated with melted hippuric acid (heated under microwave oven operating at 2450 MHz frequency for 6 min) to incipient wetness and then a hydrocarbon solvent was added to extract the lactone products out of the zeolite cavities as the amino acid is insoluble in hydrocarbon but the lactone 3 is soluble.The catalyst was separated by Rltration and the hydrocarbon solvent was evaporated to dryness. To the residue, benz- aldehyde (10 mmol) was added and then triethylamine (30 mmol) in dichloromethane (10 ml) was added dropwise.The resulting mixture was stirred at room temperature for 6 h (monitored with TLC), washed with water and the organic solvent was dried over anhydrous sodium sulfate. Evaporation of the solvent and recrystallisation of the residue from ethanol yielded the corresponding 4-arylidene- 4,5-dihydrooxazol-5-one 4a in 80% yield. Similarly other 4,5-dihydrooxazol-5-ones were prepared; see Table 1. It is remarkable that the above reaction did not proceed when J. Chem. Research (S), 1998, 614�}615$ Table 1 Preparation of 4-arylidine-2-oxazolin-5-one 4a Mp/8C Entry R1 R2 Yield (%)b Found Lit. 4a Ph Ph 80 166�}167 165�}16611a 4b Me Ph 73 149�}150 147�}14811b 4c Ph 4-NMe2Ph 85 214�}215 213�}21411c 4d Ph 3-OMe,4-HOC6H4 72 158�}159 15811d 4e Ph 2-Furyl 73 170-171 17111e 4f PhCH1CH Ph 75 132�}133 133�}13411f 4g Me 4-AcOC6H4 70 136�}138 138�}13911g 4h Me 3-OMe, 4-AcOC6H4 72 143�}145 144�}14811h 4i Me 3-OMe, 4-OMe 78 164�}165 16711i aAll products were characterised by their IR and 1H NMR spectroscopic data and also by comparison with authentic samples.bYields refer to isolated pure products. performed in the absence of the catalyst under microwave irradiation, also the reaction is not as e€ective when conven- tional heating is employed without microwave energy the conversion is only 50% after 6�}7 h of heating. $This is a Short Paper as deRned in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there- fore no corresponding material in J.Chem. Research (M). *To receive any correspondence. 614 J. CHEM. RESEARCH (S), 1998In conclusion, the results described herein demonstrate the novelty of zeolite catalysts which exercises unique selectivity in the lactonisation of hippuric acid to 4,5- dihydrooxazol-5-ones. The present method also o€ers signiRcant improvements over the existing procedures and constitutes a useful and important addition to the present methodologies.Experimental Melting points were recorded in open capillary tubes on a Buchi apparatus and are uncorrected. All chemicals were puriRed by distillation or crystallisation prior to use. General procedure for the preparation of 4-arylidene-4,5-dihydro- 5-ones using zeolite-HY under microwave irradiationDIn a typical procedure, about 1 g of zeolite-HY was impregnated with the melted hippuric acid (1.8 g, 10 mmol) in a commercial microwave oven (operating at 2450 MHz) for 6 min and then benzene (20 ml) was added to extract the lactone.The catalyst was separated by Rltration and the benzene was evaporated to dryness. To the residue, benzaldehyde (1.06 ml, 10 mmol) was added and then dry triethylamine (4.03 ml, 30 mmol) in dichloromethane (10 ml) drop- wise. The resulting mixture was stirred at room temperature for 6 h, washed with water (250 ml) and the organic solvent was dried over anhydrous sodium sulfate. Evaporation of the solvent and recrystallisation of the residue from ethanol yielded the 2-phenyl- 4-phenylmethylene-4,5-dihydrooxazol-5-one 4a in 80% yield.Similarly other acylamino acids and aldehydes were reacted and the corresponding 4,5-dihydrooxazol-5-ones were obtained in 75�}85% yields. All the products obtained were characterised by IR and 1H NMR spectroscopy and Rnally by comparison with authentic samples. Received, 16th April 1998; Accepted, 2nd June 1998 Paper E/8/02863J References 1 Y. S. Rao and R.Filler, Synthesis, 1975, 749; Y. S. Rao and R. Filler, Adv. Heterocycl. Chem., 1977, 21, 175; A. K. Mukherjee and P. Kumar, Heterocycles, 1981, 16, 1995. 2 K. H. E. Boltze, E. Etschenberg, W. Opitz, S. Raddatz and O. Vollbrecht, Ger. Pat., 1978, 2659543; E. Etschenberg, W. Opitz and S. Raddatz, Ger. Pat., 1978, 2659114. 3 E. Etschenberg, W. Opitz and S. Raddatz, Ger. Pat., 1979, 2745584; E. Etschenberg, H. Jacobi and W. Opitz, Ger. Pat., 1980, 2904512; E. Etschenberg, W.Opitz and S. Raddatz, US Pat., 1982, 4310517. 4 I. Lupsa and C. Bilegan, Rev. Chim. (Bucharest), 1974, 25, 95. 5 E. Baltazzi and R. Robinson, Chem. Ind. (London), 1954, 191. 6 Y. S. Rao, J. Org. Chem., 1976, 41, 722. 7 G. V. Boyd and P. H. Wright, J. Chem. Soc., Perkin Trans. 1, 1972, 909. 8 F. M. F. Chen, K. Kuroda and N. L. Benoiton, Synthesis, 1979, 230. 9 (a) M. E.Davis, Acc. Chem. Res., 1993, 26, 111; (b) W. Holderich, M. Hesse and F. Naumann, Angew. Chem., Int. Ed. Engl., 1988, 27, 226; (c) S.L. Suib, Chem. Rev., 1993, 93, 803; (d) W. M. H. Sachtler, Acc. Chem. Res., 1993, 26, 383. 10 P. Kumar, R. S. Reddy, A. P. Singh and B. Pandey, Tetrahedron Lett., 1992, 33, 825; R. S. Reddy, J. S. Reddy, R. Kumar and P. Kumar, Chem. Commun., 1992, 84; P. Kumar, C. U. Dinesh, R. S. Reddy and B. Pandey, Synthesis, 1993, 1069; P. Kumar, V. R. Hegde, B. Pandey and I. Ravindranathan, J. Chem. Soc., Chem. Commun., 1993, 1553; P. Kumar, S. V. N. Raju, R. S. Reddy and B. Pandey, Tetrahedron Lett., 1994, 35, 1289. 11 (a) H. B. Gillespie and H. R. Snyder, Org. Synth. Coll. Vol. II, 1943, 489; (b) R. Glaser and M. Twaik, Tetrahedron Lett., 1976, 1219; (c) C. Bodea and I. Oprean, Rev. Roum. Chim., 1968, 13, 1647; (d) E. Baltazzi and E. A. Davis, Chem. Ind. (London), 1962, 929; (e) M. Crawford and W. T. Little, J. Chem. Soc., 1959, 729; ( f ) J. M. Riordan and C. H. Stammer, J. Org. Chem., 1974, 39, 654; (g) H. D. (h) K. N. F. Shaw, A. McMillan and M. D. Armstrong, J. Org. Chem. 1958, 23, 27; (i ) J. Niedert and A. Ziering, J. Am. Chem. Soc., 1942, 64, 885. J. CHEM. RESEARCH (S), 1998 615
ISSN:0308-2342
DOI:10.1039/a802863j
出版商:RSC
年代:1998
数据来源: RSC
|
86. |
First Example of Alkynyliodonium Tosylates coupling with 1,1-Bimetalloalkenes of Selenium and Zirconium |
|
Journal of Chemical Research, Synopses,
Volume 0,
Issue 9,
1997,
Page 616-617
Ai-Ming Sun,
Preview
|
|
摘要:
First Example of Alkynyliodonium Tosylates coupling with 1,1-Bimetalloalkenes of Selenium and Zirconium$ Ai-Ming Sun and Xian Huang* Department of Chemistry, Hangzhou University, Hangzhou, 310028, P.R. China Hydrozirconation of internal acetylenic selenides afforded 1,1-bimetalloalkenes, (E)- -selanylvinylzirconium, which can cross-couple with alkynyliodonium tosylates directly in the presence of Pd(PPh3)4 as the catalyst. The stereoselective synthesis of conjugated enynes is of great importance in organic chemistry because of many natural compounds containing their structural skeletons.1 A number of methods for the preparation of conjugated enynes have been previously reported, particularly transition-metal- catalyzed processes.1 Coupling of stereodeRned alkenyl metallic compounds include vinylboron,2 vinylcopper,3,4 vinylzinc,5,6 vinylaluminium7 or vinylmagnesium reagents8 with haloalkynes.Recently, the synthesis of conjugated functionalized enynes have received more attention.Although various methods for the synthesis of vinylic selenides have been studied intensively,9 the synthesis of 1,3-enynylselenides has been little explored.10 In a previous paper, we reported the coupling of diaryliodonium salts and vinylzirconium compounds in the presence of Pd(PPh3)4,11 compared with the cross-coupling of vinylzirconium com- pounds with arylhalides, which has the advantages of lower reaction time and mild reaction conditions. As an extension of our studies, herein we report the stereoselective formation of selanyl-substituted 1,3-enynes via a new carbon�}carbon bond-forming reaction, involving the coupling of alkynyl- iodonium tosylates 1 and (E)-a-selanylvinylic zirconium compounds 4 in the presence of Pd(PPh3)4.Alkynyliodonium tosylates 1 are readily available in reasonable yields by interaction of Koser's reagent, PhI(OH)OTs, with terminal alkynes.12 (E)-a-Selanylvinylic zirconium compounds 4 are readily made by hydrozircona- tion of internal acetylenic selenides 2, 3; hydrozirconation of phenylacetylenic selenides 3 can not be directly performed even over extended times or at a raised tempera- ture, however, in the presence of 5% mmol Pd(PPh3)4, 3 can react with Cp2Zr(H)Cl rapidly in about 1 h at room temperature (Scheme 1).Alkynyliodonium tosylate 1 was added to a mixture of (E)-a-selanylvinylic zirconium com- pound 4 and 5% mmol Pd(PPh3)4 in THF and stirred for about 3 h, which resulted in the stereoselective synthesis of conjugated enynylselenides 5 (Scheme 2).As the data in Table 1 show, this method a€ords a variety of 1,3-enynylselenides stereoselectively in good yields, and more importantly, the reaction can be performed at room temperature in about 2 h. The conRguration of selenoenyne 5a could be conRrmed from compound 6 which was obtained by treatment of 5a with n-butyllithium in THF followed by hydrolysis; the reaction occurs stereo- selectively (Scheme 3).13 Particularly diagnostic for the stereochemistry of 6 was the coupling constant between the vicinal protons Ha and Hb which show a typical value of JHH of 16 Hz which is consistent with an E conRguration. Conjugated enynylselenides are important synthetic inter- mediates and are e€ective precursors for synthesizing conju- gated enynes, for example, 5a at room temperature in THF can be coupled with PhZnBr in the presence of 5 mmol% NiCl2(PPh3)2 for 3 h to give 7 in an isolated yield of 60% (Scheme 4).In summary, we have combined vinylzirconium com- pounds and hypervalent iodine salts to synthesize conju- gated enynes. Compared to other methods that have been reported, this method has the advantages of mild conditions, simple procedure and lower reaction time. Experimental 1H NMR spectra were recorded on an AZ-300 MHz with TMS as internal standard. Mass spectra were determined using a Finigan 8230 mass spectrometer.IR spectra were obtained in neat capillary cells on a Shimadzu IR-408 instrument. The reactions were carried out in pre-dried glassware (150 8C, 4 h) and cooled under a stream of dry nitrogen. All solvents were dried, deoxygenated and re- distilled before use. General Procedure for the Synthesis of 1,3-Enynylselenides 5a�}f.D To a freshly prepared suspension of Cp2Zr(H)Cl (2 mmol) in THF (15 ml) at r.t. was injected acetylenic selenides 2 (2 mmol) in THF (2 ml) [for added phenylacetylenic selenides 3, Pd(PPh3)4 (25% mmol) must be added simultaneously].The reaction mix- ture was stirred for ca. 30 min and turned green, then Pd(PPh3)4 (25% mmol) and alkynyliodonium tosylates 1 (2 mmol) in THF (2 ml) were added to the solution at r.t. and stirred for 2 h. The J. Chem. Research (S), 1998, 616�}617$ Scheme 1 Scheme 2 Scheme 3 Scheme 4 $This is a Short Paper as deRned in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there- fore no corresponding material in J.Chem. Research (M). *To receive any correspondence. 616 J. CHEM. RESEARCH (S), 1998Table 1 Alkynyliodonium/(E)-a-selanylvinylzirconium compound couplingsEntry Alkynyliodonium salt (E)-a-Selanylvinylzirconium Enzyne Yielda (%)5a 805b 755c 855d 835e 755f 70aIsolated yield. bIn the presence of Pd(PPh3)4.product was washed with saturated aq. NH4Cl (10 ml) thenextracted into diethyl ether, dried with MgSO4, ltered and concen-trated in vacuo.The residue was puried by ash chromatographyon a 3 ft1 in column with light petroleum (bp 30¡Ó60 8C) eluent togive 5a¡Óf.5a: 1H NMR d 7.70¡Ó7.20 (m, 5H), 6.10 (t, J 6.6 Hz, 1H), 2.18(s, 3H), 1.96¡Ó2.34 (m, 2H), 1.14¡Ó1.49 (m, 4H), 0.81 (t, 3H). MS:m/z 278 (M1) (Found: C, 64.93; H, 6.44. C15H18Se requiresC, 64.98; H, 6.54%).5b: 1H NMR d 7.69¡Ó7.18 (m, 5H), 6.08 (t, J 6.6 Hz, 1H), 2.53(q, 2H), 1.94¡Ó2.30 (m, 2H), 1.47 (t, 3H), 1.12¡Ó1.50 (m, 4H), 0.79(t, 3H).MS: m/z 292 (M1) (Found: C, 65.65; H, 6.46. C16H20Serequires C, 65.97; H, 6.92%).5c: 1H NMR d 7.65¡Ó7.10 (m, 5H), 6.10 (t, J 6.7 Hz, 2H), 3.80(d, 2H), 3.24 (s, 3H), 2.17 (s, 3H), MS: m/z 265 (M1) (Found:C, 58.53; H, 5.02. C13H14SeO requires C, 58.87; H, 5.32%).5d: 1H NMR d 7.66¡Ó7.12 (m, 5H), 6.12 (t, J 6.7 Hz, 1H), 3.83(d, 2H), 3.25 (s, 3H), 2.55 (q, 2H), 1.52 (t, 3H). MS: m/z 279(M1) (Found: C, 59.74; H, 5.35. C14H16SeO requires C, 60.22;H, 5.78%).5e: 1H NMR d 7.50¡Ó7.0 (m, 5H), 6.78 (s, 1H), 4.12 (s, 2H), 3.29(s, 3H), 2.15 (s, 3H), MS: m/z 266 (M1) (Found: C, 58.40;H, 4.86.C13H14SeO requires C, 58.88; H, 5.32%).5f: 1H NMR d 7.49¡Ó7.02 (m, 5H), 6.77 (s, 1H), 4.14 (s, 2H), 3.30(s, 3H), 2.65 (q, 2H), 1.49 (t, 3H). MS: m/z 280 (M1) (Found:C, 59.82; H, 5.40. C14H16SeO requires C, 60.22; H, 5.78%).Addition of BunLi to 1,3-Enynylselenide 5a 4Enyne 6.BuLi(1.6 M hexane solution, 1.1 mmol) was added to a THF (5.0 ml)solution of 5a (1.0 mmol) at £¾78 8C.After stirring for 30 min, themixture was hydrolyzed with saturated aq. NH4Cl and extractedwith CH2Cl2 (210 ml). The organic extract was dried withMgSO4, ltered and concentrated in vacuo. The residue was puriedby column chromatography over silica gel (hexane as eluent) to give6 (yield: 90%). 1H NMR 7.24 (m, 5H), 6.17 (dt, 1H, J 6.5 and16 Hz), 5.62 (d, 1H, J 16 Hz), 2.15 (q, 2H), 1.20¡Ó2.05 (m, 4H), 0.93(t, 3H).General Procedure for the Synthesis of 7.PhZnBr (1.0 mmol) inTHF (3.0 ml) was added to a THF (5.0 ml) solution of selenoenyne5a (1.0 mmol) and NiCl2(PPh3)2 (1.05% mmol) at r.t.Afterstirring for 3 h, the mixture was washed with saturated aq. NH4Cl.The product was extracted with hexane and dried over MgSO4,ltered and concentrated in vacuo. The residue was puried by ashchromatography on a 3 ft1 in column with hexane as eluentto give 8. 1H NMR 7.71¡Ó7.01 (m, 10H), 6.30 (t, 1H, J 6.8 Hz),2.45¡Ó2.10 (m, 2H), 1.43¡Ó1.22 (m, 4H), 0.84 (t, 3H).Projects 29493800, 29772007 supported by the NationalNatural Science Foundation of China.This work wasalso supported by the Laboratory of OrganometallicChemistry, Shanghai Institute of Organic Chemistry,Academia Sinica.Received, 25th February 1998; Accepted, 11th June 1er E/8/01589IReferences1 T. Tokuyama, K. Uenoyama, G. Brown, J. W. Daly andB. Witkop, Helv. Chim. Acta., 1974, 57, 2597 and referencestherein; R. Fujimoto, Y. Kishi and J. F. Blount, J. Am. Chem.Soc., 1980, 102, 7154; G.R. Schulte, M. C. G. Chung and P. J.Scheuer, J. Org. Chem., 1981, 46, 3870; A. Guerrero, F. Camps,J. Coll, M. Riba, J. Einhorn, Ch. Descoins and J. Y. Lallemond,Tetrahedron Lett., 1981, 2013.2 N. Miyaura, K. Yamada, H. Suginome and A. Suzuki, J. Am.Chem. Soc., 1985, 107, 972.3 J. F. Normant, A. Commercon and J. Villieras, TetrahedronLett., 1975, 1465; A. Pelter, K. Smith and M. Tabata, J. Chem.Soc., Chem. Commun., 1975, 857.4 I. Rhee, M. Ryang and S. Tsutsumi, Tetrahedron Lett., 1969,4593; A.Alexakis, G. Cahiez and J. F. Normant, Synthesis,1979, 826.5 A. O. King, N. Okukada and E. I. Negishi, J. Chem. Soc.,Chem. Commun., 1977, 683.6 P. A. Magriotis, M. E. Scott and K. D. Kim, Tetrahedron Lett.,1991, 32, 6085; M. Abarbri, J. L. Parrain, J. C. Cintrat andA. Duchene, Synthesis, 1996, 82.7 S. Negishi and A. O. King, J. Chem. Soc., Chem. Commun.,1976, 17; M. Kobayashi, L. F. Valente and E. Negishi,Synthesis, 1980, 1034.8 H. P. Dang and G. Linstrumelle, Tetrahedron Lett., 1978, 191.9 (a) D. Y. Yang and X. Huang, J. Organomet. Chem., 1996, 523,139; (b) D. Y. Yang and X. Huang, Tetrahedron Lett., 1997,62; (c) D. Y. Yang and X. Huang, J. Chem. Res. (S), 1996,470; (d) D. Y. Yang and X. Huang, Synth. Commun., 1996, 26,4369.10 (a) J. V. Coamsseto and C. A. Brandt, Synthesis, 1987, 146;(b) L. S. Zhu, Z. Z. Huang and X. Huang, Tetrahedron, 1996,52, 9819.11 X. Huang and A. M. Sun, Synth. Commun., 1998, 28, 773.12 P. J. Stang, B. W. Surber, Z. C. Chen and K. A. Roberts, J. Am.Chem. Soc., 1987, 109, 228.13 B. T. Grobel and D. Seebach, Chem. Ber., 1977, 110, 867.J. CHEM. RESEARCH (S), 1998 617
ISSN:0308-2342
DOI:10.1039/a801589i
出版商:RSC
年代:1998
数据来源: RSC
|
87. |
Mild and Selective Phase Transfer Catalysed Bromination of Terminal Acetylenes Using Carbon Tetrabromide as Reagent |
|
Journal of Chemical Research, Synopses,
Volume 0,
Issue 9,
1997,
Page 618-619
Edgars Abele,
Preview
|
|
摘要:
Mild and Selective Phase Transfer CatalysedBromination of Terminal Acetylenes Using CarbonTetrabromide as Reagent$Edgars Abele, Kira Rubina, Ramona Abele, Aleksandr Gaukhmanand Edmunds Lukevics*Latvian Institute of Organic Synthesis, 21 Aizkraukles Str., Riga, LV-1006, LatviaTerminal acetylenes were successfully brominated under phase transfer conditions using a CBr4/solid KOH/18-crown-6/benzene system.Brominated terminal acetylenes are of interest as potentialbiologically active substances or intermediates.Usuallythis type of organic compound is obtained from terminalacetylenes by bromination in BunLi/N-bromosuccinimide,1BunLi/Br2,2 NaOH/Br23 and DBU/Cl3CBr4 systems as wellas by treating with hypobromite solution.5¡Ó7 It is alsoknown that phenylacetylene is successfully chlorinated in thecarbon tetrachloride/50% aq. NaOH/TEBA PTC system.8We have developed a new, simple and selective PTCbromination method for a variety of terminal acetylenes.The inuence of catalyst, base and amounts of brominatingagent (CBr4) was studied in the bromination reaction ofphenylacetylene (1).Surprisingly, the PTC system CBr4(0.75 equiv. to phenylacetylene)/solid KOH/18-crown-6 inbenzene was found to be the most active (Table 1). In thepresence of this system phenylbromoacetylene was obtainedin 79% yield. Increase in the amount of carbon tetra-bromide to e1 equiv. diminishes the desired product (12)yield owing to brominated product side reactions.ThePTC systems solid CBr4/KF/18-crown-6 and CBr4/50%KOH/triethylbenzylammonium chloride (TEBAC) were lessactive in bromination of 1. Interestingly, bromination ofphenylacetylene also proceeds in the presence of the PTCsystem bromoform (1 equiv.)/solid KOH/18-crown-6 andproduct 12 was obtained in 6% yield. This suggests that aswell as carbon tetrabromide, bromoform can also serve asa source of Br ion. The PTC system CBr4/solid K2CO3/18-crown-6 was inactive in phenylacetylene bromination.The PTC system carbon tetrabromide (0.75 equiv.)/solidKOH/18-crown-6/benzene being the most active was thenused in bromination of terminal acetylenes of dierenttypes.All reactions proceed selectively and aord the corre-sponding bromoacetylenes 13¡Ó22 in 16¡Ó84% yield (Table 2,Scheme 2).Double bond bromination in compounds 8¡Ó11as well as formation of addition products of dibromo-carbene generated from CHBr3 or CBr4 to C.N doubleand C/C triple bonds was not observed.Bromination ofE-ketoxime and aldoxime O-propargyl ethers 8¡Ó11 proceedsstereoselectively giving only E-isomers of brominated pro-ducts 19¡Ó22 (Table 2). PTC bromination of terminalacetylenes 2¡Ó11 with carbon tetrabromide in the systemsolid KOH/18-crown-6/benzene takes place at roomtemperature.Experimental1H NMR spectra were recorded with a Bruker WH-90/DS(90 MHz) spectrometer using CDCl3 as solvent and Me4Si asinternal standard. Mass spectra were recorded on a MS-25 spec-trometer (Kratos, 70 eV).GC analysis was performed on a Chrom-5instrument equipped with a ame-ionization detector using a glasscolumn packed with 5% OV-101/Chromosorb W-HP (80¡Ó100mesh), 1.2 m3 mm.Typical Procedure. Synthesis of 13.Finely powdered KOH(0.336 g, 6 mmol) was added to a solution of 2 (0.29 g, 2 mmol),CBr4 (0.498 g, 1.5 mmol) and 18-crown-6 (26 mg, 0.1 mmol) in2 ml of benzene. The reaction mixture was stirred for 2 h at roomtemperature until the substrates disappeared (GC and GC¡ÓMS).The solid substance was ltered o and the ltrate evaporatedunder reduced pressure.The residue was puried by column chro-matography using light petroleum (bp 45¡Ó60 8C)¡Óbenzene (2 :1) aseluent. Isolated yield was 0.164 g (37%).1H NMR (CDCl3, 90MHz) and MS Data for Isolated Com-pounds.13. 1H NMR: 4.11 (s, 2H, CH2), 4.53 (s, 2H, CH2), 7.27(m, 5H, Ph). MS: m/z 225 (M, 1), 119 (12), 117 (36), 116 (22), 115(100), 105 (14), 92 (14), 91 (60), 89 (10), 79 (26), 77 (38), 65 (19), 51(21), 50 (10), 39 (23), 38 (11).14. 1H NMR: d 4.22 (s, 2H, OCH2), 4.74 (s, 2H, CH2), 7.11¡Ó7.69(m, 4H, Ph). MS: m/z 293 (M, <1), 193 (12), 185 (31), 184 (20),J. Chem. Research (S),1998, 618¡Ó619$Table 1 PTC bromination of phenylacetyleneaBase (equiv.) CatalystCBr4(equiv.)Reactiontime/hYield (%)(GLCdata)KOH (3) 18-crown-6 0.5 13 58KOH (3) 18-crown-6 0.75 11 79KOH (3) 18-crown-6 1.0 11 67KOH (2) 18-crown-6 1.5 8 42KOH (3) 18-crown-6 1.5 8 36K2CO3 (3) 18-crown-6 1.0 9 0KF (3) 18-crown-6 1.0 9 2250% KOH (4 ml) TEBAC 1.5 8 41KOH (3) 18-crown-6 1.0b 11 6aReaction conditions: phenylacetylene (0.11 ml, 1 mmol),catalyst (0.05 mmol), base and brominating agent (see table) inbenzene (1 ml), 20 8C.bCHBr3 as a bromination agent.Scheme 1Table 2 PTC bromination of terminal acetylenes 2¡Ó11 withcarbon tetrabromide in the system solid KOH/18-crown-6/benzene at room temperatureRReactiontime/h ProductIsolatedyield (%) Mp/8C2 2 13 37 ¡Va3 2.5 14 53 ¡Va4 1 15 16 ¡Va5 4 16 66 ¡Va6 7 17 60 ¡Va7 12 18 42 123¡Ó1268 4 19 59 107¡Ó1109 4 20 64 61¡Ó6310 4 21 42 129¡Ó13111 2 22 84 ¡VaaOil, boiling point was not determined.$This is a Short Paper as dened in the Instructions for Authors,Section 5.0 [see J. Chem.Research (S), 1998, Issue 1]; there is there-fore no corresponding material in J. Chem. Research (M).*To receive any correspondence (e-mail: kira@osi.lanet.lv)618 J. CHEM. RESEARCH (S), 1998183 (75), 173 (19), 165 (17), 164 (12), 160 (14), 159 (100), 158 (17), 155 (16), (32), 137 (11), 133 (12), 127 (77), 125 (10), 120 (16), 119 (52) 118 (18), 117 (39), 109 (54), 107 (12), 95 (10), 91 (22), 89 (13), 77 (12), 75 (16), 63 (12), 55 (12), 51 (15), 50 (12), 49 (49), 37 (11). 15. 1H NMR: d 3.76 (s, 3H, OCH3), 4.04 (s, 2H, OCH2), 4.56 (s, 2H, CH2), 6.71±7.36 (m, 4H, Ph). MS: m/z 255 (Má, 2), 211 (68), 209 (67), 146 (10), 145 (54), 135 (13), 131 (11), 121 (30), 119 (20), 117 (27), 115 (35), 109 (13), 107 (17), 94 (15), 93 (10), 92 (20), 91 (100), 79 (10), 78 (42), 65 (28), 63 (15), 52 (11), 51 (22), 50 (11), 39 (26), 38 (15). 16. 1H NMR: d 7.16 (m, 1H, H-5), 7.34 (m, 1H, H-3), 7.61 (m, 1H, H-4), 8.49 (m, 1H, H-6). MS: m/z 181 (Má, 100), 154 (11), 130 (25), 128 (23), 102 (95), 75 (48), 74 (37), 61 (10), 51 (31), 50 (30), 37 (14). 17. 1H NMR: d 7.16 (m, 1H, H-5), 7.27 (m, 1H, H-4), 7.48 (m, 1H, H-6), 8.49 (m, 1H, H-2). MS: m/z 181 (Má, 100), 154 (10), 130 (20), 128 (27), 102 (90), 76 (40), 74 (33), 51 (23), 50 (19), 37 (12). 18. 1H NMR: d 2.54 (s, 3H, CH3), 7.09 (m, 1H, H-3), 7.59 (m, 1H, H-4), 8.51 (m, 1H, H-6). MS: m/z 195 (Má, 89), 130 (17), 128 (20), 116 (23), 89 (100), 74 (22), 63 (25), 62 (19), 50 (14), 40 (21), 39 (16). 19. 1H NMR: d 4.83 (s, 2H, OCH2), 7.15±7.35 (m, 1H, H-5), 7.55±7.89 (m, 2H, H-3,4), 8.19 (s, 1H, CH), 8.54±8.67 (m, 1H, H-6). MS: m/z 239 (Má, 10), 210 (30), 209 (10), 208 (30), 131 (12), 129 (44), 119 (32), 117 (34), 104 (10), 79 (19), 78 (100), 66 (16), 64 (12), 63 (16), 52 (20), 51 (44), 50 (15), 39 (14), 38 (25). 20. 1H NMR: d 4.76 (s, 2H, OCH2), 7.13±7.36 (m, 1H, H-5), 7.91 (dt, 1H, J1=7.6, J2=1.6 Hz, H-4), 8.07 (s, 1H, CH), 8.54 (dd, 1H, J1=6.0, J2=1.6 Hz, H-6), 8.67 (d, 1H, J à 2.0 Hz, H-2). MS: m/z 239 (Má, 46), 238 (12), 237 (48), 159 (13), 131 (27), 130 (11), 129 (72), 119 (92), 117 (100), 106 (11), 105 (20), 104 (27), 103 (12), 91 (15), 79 (12), 78 (69), 77 (17), 76 (12), 66 (23), 64 (36), 63 (49), 52 (27), 51 (74), 50 (35), 39 (23), 38 (48), 37 (16). 21. 1H NMR: d 4.76 (s, 2H, OCH2), 7.38 (dd, 2H, J1=6.2, J2=2.0 Hz, H-3,5), 7.97 (s, 1H, CH), 8.56 (dd, 2H, J1=6.2, J2=2.0 Hz, H-2,6). MS: m/z 239 (Má, 13), 237 (13), 131 (30), 130 (15), 129 (100), 119 (84), 117 (90), 105 (16), 104 (21), 78 (44), 77 (12), 66 (15), 64 (18), 63 (29), 52 (14), 51 (66), 50 (33), 39 (26), 38 (29), 37 (12). 22. 1H NMR: d 2.20 (s, 3H, CH3), 4.67 (s, 2H, CH2), 6.87 (m, 1H, H-4), 7.11 (m, 1H, H-3), 7.20 (m, 1H, H-5). MS: m/z 259 (Má, 15), 148 (49), 110 (82), 109 (66), 99 (100), 84 (21), 66 (27), 57 (13), 39 (36). We thank the Latvian Council of Science for ®nancial support (Grant N 707). Received, 29th April 1998; Accepted, 12th June 1998 Paper E/8/03272F References 1 E. J. Corey and T. Ravindranathan, J. Am. Chem. Soc., 1972, 94, 4013. 2 E. Kloster-Jensen, Tetrahedron, 1966, 22, 965. 3 G. Eglington and W. McCrae, J. Chem. Soc., 1963, 2295. 4 Y. Hori, Y. Nagano, H. Uchiyama, Y. Hamada and H. Taniguchi, Chem. Lett., 1978, 73. 5 F. Straus, L. Kollek and H. Hauptmann, Ber. Deutsch. Chem. Ges., 1930, 63, 1886. 6 H. Normant and T. Cuvigny, Bull. Soc. Chim. Fr., 1957, 1447. 7 G. R. Ziegler, C. A. Welch, C. E. Orzech, S. Kikkawa and S. I. Miller, J. Am. Chem. Soc., 1963, 85, 1648. 8 M. Makosza and M. Fedorynski, Rocz. Chem., 1975, 49, 1779. Scheme 2 J. CHEM. RESEARCH (S), 1998 619
ISSN:0308-2342
DOI:10.1039/a803272f
出版商:RSC
年代:1998
数据来源: RSC
|
88. |
Direct Oxidative Deprotection using Montmorillonite Supported Bis(trimethylsilyl)chromate |
|
Journal of Chemical Research, Synopses,
Volume 0,
Issue 9,
1997,
Page 620-621
M. M. Heravi,
Preview
|
|
摘要:
Direct Oxidative Deprotection using Montmorillonite Supported Bis(trimethylsilyl)chromate$ M. M. Heravi,* D. Ajami, K. Tabar-Heydar and M. M. Mojtahedi Chemistry & Chemical Engineering Research Center of Iran, Tehran, P.O. Box 14335-186, Iran Direct oxidative deprotection of different trimethylsilyl ethers to their corresponding carbonyl compounds has been achieved using montmorillonite K-10 supported bis(trimethylsilyl)chromate in dichloromethane. The protection of functional groups is a useful and import- ant method in organic synthesis. Hydroxy groups are one of the most abundant functional groups in organic molecules and its controlled manipulation is very important in multi- step synthesis. One of the most useful and convenient methods for protection of hydroxy groups is their trans- formation to trialkylsilyl ethers.1,2 Direct oxidation of trimethylsilyl ethers to the corre- sponding carbonyl compounds has recently found much attention.3 However some of the reported methods show limitations such as the requirement for aqueous reaction conditions,4,5 use of expensive reagents,6�}8 long reaction times, tedious work-up5 and low yields of products.9 Therefore introduction of new methods and inexpensive reagents for such functional group transformations is still in much demand.Recently we have demonstrated the use of bis(trimethyl- silyl)chromate supported on silica gel and montmorillonite K-10 as an ecient and mild oxidizing agent under classical heating10,11 or microwave irradiation.11,12 Now we wish to report a new and ecient method for the oxidative deprotection of trimethylsilyl ethers to their corresponding carbonyl compounds using bis(trimethylsilyl)chromate supported on montmorillonite K-10 in dichloromethane at room temperature.Heating chromic anhydride under re�Pux with a slight excess of hexamethyldisoloxane in dichloromethane pro- duces a nearly homogeneous solution. BTSC supported on montmorillonite K-10 is conveniently prepared simply by adding montmorillonite K-10 to a vigorously stirred solution of BTSC.10,11 A dark brown free-�Powing solid was obtained on evaporation of volatiles.This reagent can be stored in a dark brown bottle without appreciable loss of reactivity for at least three months. In a typical reaction 2�}2.2 equiv. of BTSC supported on montmorillonite K-10 was added to a stirred solution of a trimethylsilyl ether in dry CH2Cl2 (Scheme 1). The reaction mixture was stirred at room temperature until the reaction was complete, then it was Rltered and washed with dichloro- methane.Evaporation of the solvent gave the corresponding carbonyl compounds. Di€erent types of trimethylsilyl ethers were converted to their corresponding carbonyl compounds in high yield. For example benzyl trimethylsilyl ether (Table 1, entry 1) was oxidized to benzaldehyde in excellent yield. Substituted benzyl trimethylsilyl ethers (entries 2 and 3) were similarly oxidized to their corresponding aldehydes under the same conditions.No traces of benzoic acid were observed even after prolonged re�Pux of benzaldehyde with excess supported BTSC. Cinnamyl trimethylsilyl ether (entry 4) was also oxidatively deprotected to cinnamyl aldehyde in J. Chem. Research (S), 1998, 620�}621$ Table 1 Oxidative deprotection of trimethylsilyl ethers with BTSC supported on montmorillonite K10 Scheme 1 Reagents and conditions: i, CrO3, TMSOTMS, montmorillonite K-10, CH2Cl2, 258C, 25 min $This is a Short Paper as deRned in the Instructions for Authors, Section 5.0 [see J.Chem. Research (S), 1998, Issue 1]; there is there- fore no corresponding material in J. Chem. Research (M). *To receive any correspondence. 620 J. CHEM. RESEARCH (S), 1998high yield. No benzaldehyde was detected in this reaction, showing that benzylic double bonds are not prone to cleavage by this method. In conclusion, BTSC supported onto montmorillonite K-10 is a simple and inexpensive reagent for one-pot oxidative deprotection of trimethylsilyl ethers.Experimental All products were known compounds and identiRed by com- parison with authentic samples. Yields refer to GC analysis. Trimethylsilyl ethers were synthesized according to the reported procedure.13 BTSC supported on montmorillonite K-10 was also prepared according to a reported procedure.10�}12 Oxidative Deprotection of Trimethylsilyl Ethers, a Typical Pro- cedure.DIn a round bottomed �Pask (50 ml) equipped with a magnetic stirrer and a condenser a solution of trimethylsilyl benzyl ether (180 mg, 1 mmol) in CH2Cl2 (20 ml) was prepared.To this solution pre-made BTSC supported onto montmorillonite K-10 (1.66 g equiv. to 2.4 mmol of CrO3) was added. The reaction mixture was stirred at room temperature for 10 min. The progress of the reaction was monitored by TLC [eluent: light petroleum�} ethyl acetate (8:2)].The mixture was Rltered and the solid material was washed with CH2Cl2 (20 ml). The Rltrate was evaporated to dryness under reduced pressure and the resulting crude material was puriRed on a silica gel pad. After evaporation of solvent pure benzaldehyde was obtained in 93% yield (Table 1). Received, 29th April 1998; Accepted, 12th June 1998 Paper E/8/03237H References 1 T. W. Greene and P. G. M. Wuts, Protective Groups in Organic Synthesis, New York, 2nd edn., 1991. 2 M.Latonde and T. H. Chan, Synthesis, 1985, 81 and references therein. 3 I. Mohammadpoor-Baltork and S. H. Pouranshirvani, Synthesis, 1997, 7, 756. 4 R. Baker, V. B. Rao, P. D. Ravenscroft and C. J. Swann, Synthesis, 1983, 572. 5 R. Mahrwald, F. Theil, H. H. Schick, S. Sehwartz, H. J. Palme and G. Weber, J. Prakt. Chem., 1986, 328, 777. 6 H. Firouzabadi and I. Mohammadpoor-Baltork, Synth. Commun., 1995, 24, 1065. 7 H. Firouzabadi and F. Shiriny, Synth Commun., 1996, 26, 423. 8 H.Firouzabadi and F. Shiriny, Synth Commun., 1996, 26, 649. 9 H. W. Pinnick and N. H. Lajis, J. Org. Chem., 1978, 43, 371. 10 M. M. Heravi, D. Ajami and K. Tabar-Heydar, Monatsch. Chem., 1998, in press. 11 M. M. Heravi, D. Ajami and K. Tabar-Heydar, Synth Commun., 1998, submitted. 12 Preparation of Bis(trimethylsilyl )chromate Supported on Mont- morillonite K-10.DTo a solution of hexamethyldisiloxane (6.4 ml, 0.03 mol) in 20 ml of dry dichloromethane was added chromic anhydride (3 g, 0.03 mol). The reaction mixture was stirred in an oil-bath at 50 8C for 5 h. Solid chromic anhydride dissolved and the dark red mixture became a homogeneous solution. Montmorillonite K-10 (13 g) pre-dried in a 120 8C oven overnight and activated in a microwave oven for 3 min was added to the warm reaction mixture and the resulting mixture was stirred for a further 5 h. The solvent and other volatile components were distilled under reduced pressure to a€ord 19 g of supported chromium oxidant. 13 G. Maity and S. C. Roy, Synth Commun., 1993, 23, 1967. J. CHEM. RESE
ISSN:0308-2342
DOI:10.1039/a803237h
出版商:RSC
年代:1998
数据来源: RSC
|
|