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41. |
Carbon 13 NMR Spectra of Dimethyl Fumarate and its Thioderivatives: Empirical Shielding Constants for the Methyl Ester and Thioester Substituents† |
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Journal of Chemical Research, Synopses,
Volume 0,
Issue 5,
1997,
Page 270-271
Fernanda Ferraz Camilo,
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摘要:
Carbon 13 NMR Spectra of Dimethyl Fumarate and its Thioderivatives: Empirical Shielding Constants for the Methyl Ester and Thioester Substituents$ Fernanda Ferraz Camilo,a Ivan P. de Arruda Campos*b and Jonas Gruber*a aInstituto de Qu�Ê mica, Universidade de Sa o Paulo, Cx. P. 26077, S. Paulo, SP, 05599-970, Brazil bInstituto de CieA ncias Exatas e Tecnologia, Universidade Paulista, Av. Alphaville, 3500, Santana de Parna�Ê ba, SP, 06500-000, Brazil The assigned 13C NMR spectroscopic data from O,S-dimethyl thiofumarate, S,S-dimethyl bis(thio)fumarate and the novel S-methyl p-methoxythiocinnamate are presented and the empirical shielding constants for the methoxycarbonyl and methylsulfanylcarbonyl groups determined for the first time.Our continued interest in the chemistry of organic sulfur compounds led us to prepare some thioderivatives (1a, b) of dimethyl fumarate (1c). When their 13C NMR spectra were acquired (Table 1), as part of the characterization process, we were struck by the amazing similarity between the oleRnic carbon's (C-2 and C-3) chemical shifts of compounds 1a and 1c, which hinders the assignment of the signals arising from C-2 and C-3 in compound 1b.To assign dC-2 and dC-3 in the spectrum of 1b and in the hope of better understanding the results already obtained, we decided to calculate the expected chemical shifts of those signals, by using empirical shielding constants (Zi). To our surprise, however, we have been unable to Rnd the Zi values for either the methylsulfanylcarbonyl or methoxycarbonyl substituent groups in the literature.Thus, we decided to determine these values by comparing the 13C NMR data (Table 2) from a series of p-substituted styrenes (2) with the data from the corresponding series of p-substituted thio- cinnamates (3) and cinnamates (4). The results (Table 3) for �}C(1O)OMe are consistent with the reported2 empirical shielding constants for the carboxyl group (Z1=4.2; Z2=8.9), albeit less so with those for the ethoxycarbonyl substituent (Z1=6.3; Z2=7.0). No such comparisons are possible for �}C(1O)SMe owing to the lack of previously published data.Hence, to test the accuracy of the newly determined Zi values, we calculated the 13C NMR chemical shifts for the oleRnic carbons in p-nitrostyrene, using data both from the corresponding cinnamate and thio- cinnamate and found the calculated values to be in good agreement with the experimental3 values (Table 4).We then calculated dC-2 and dC-3 for 1b, using the experimental values of the chemical shifts owing to the oleRnic carbons of 1a (Table 1), by adding the Zi values for �}C(1O)OMe (Table 3) and subtracting those for �}C(1O)SMe. Similarly, we obtained another pair of dC-2/3 estimates from 1c. Furthermore, as the above estimates are mutually independent, we assumed that their average should be the best estimated values available for dC-2/3. These results (Table 5) led us to the assignments of dC-2/3 for 1b shown in both Tables 1 and 5.Moreover, from a com- parison of the best calculated estimates of dC-2/3 with the measured values of the same chemical shifts, we were able to determine the corresponding non-additivity corrections (NA i) for dC-2/3 of 1b. The non-zero value of these corrections suggests that there are subtle di€erences in the rotameric preferences of the �}C(1O)OMe and �}C(1O)SMe sub- stituents, not taken into account by the model underlying the idea of empirical shielding constants.The fact that these NA i are small enough to permit the application of Zi to the assignment of 13C NMR data is a triumph of this elegantly straightforward model. In conclusion, it should be pointed out that the similarity of dC-2/3 in compounds 1a and 1c is not accidental, but J. Chem. Research (S), 1998, 270�}271$ Table 1 d13C of dimethyl fumarate and its thioderivativesa Compound X Y C-1 C-2 C-3 C-4 C-5 C-6 1a S S 189.2 133.4 133.4 189.2 12.0 12.0 1b O S 189.2 138.7 128.3 165.5 11.9 52.4 1cb O O 165.3 133.5 133.5 165.3 52.2 52.2 a5% v/v CDCl3 solutions (TMS a 0 ppm), observed at 50 MHz.bAlthough the 13C NMR spectrum of 1c (in CCl4) is published in ref. 1, we acquired it in CDCl3, to ascertain that the observed similarity of C-2/3 in 1a and 1c was not owing to any spurious solvent effect. We found that both solvents led to identical spectra. traceable, as we have shown, to a capricious combination of the e€ects governing the chemical shifts, the very same e€ects that lead to the di€erent values of dC-2 and dC-3 observed for compound 1b.$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. 270 J. CHEM. RESEARCH (S), 1998ExperimentalMaterials.Deuterochloroform and compounds 1c and 4awere used as-received from Aldrich, after being checked forpurity.Compounds 1a, 1b, 3a, 3b, 3d, 3e and 4b¡Óe were preparedby literature4¡Ó8 procedures; all liquid compounds were distilledunder reduced pressure, while the solids were recrystallized, untilthe nal purity attained for each of these compounds was at least98% (both by GLC and 1H NMR). The complete assigned 13CNMR dataset for compounds 3a¡Óe is presented in Table 6.Methyl p-methoxythiocinnamate 3c.Thionyl chloride (6.5 cm3,91 mmol) was added dropwise to a stirred solution of p-methoxy-thiocinnamic acid (8.0 g; 45 mmol) in 50 cm3 of anhydrous diethylether, the resulting mixture being held under reux during 5 h.Thesolvent and excess thionyl chloride were removed by evaporationunder reduced pressure and the greyish solid obtained was re-dissolved in a further 50 cm3 of anhydrous diethyl ether. Thissolution was cooled in a dry-ice/acetone bath, 5.5 cm3 (10 mmol)of liqueed methanethiol was added to it, in a single portion,followed by 4.0 cm3 (50 mmol) of pyridine, added dropwise.Afterremoving the cooling bath, the reaction mixture was boiled underreux for 5 h (NB. all preceding operations were performed under amoisture-free atmosphere) and then quenched with water andextracted with dichloromethane. The combined extracts were driedover anhydrous magnesium sulfate, the solvent removed and thecrude product recrystallized from ethanol. Compound 3c (3.93 g,18.9 mmol) was obtained as a colourless microcystalline solid ofmp 82¡Ó85 8C (Found: C, 63.0; H, 5.7.C11H12O2S requires C,63.44; H, 5.81%). Yield: 42%, purity: 99% (both by GLC and1H NMR). H (CDCl3) 2.42 (s, 3 H, H-5), 3.84 (s, 3 H, H-9), 6.63(d, 1 H, J23 16 Hz, H-2), 6.91 (d, 2 H, J76 8 Hz, H-7, H-6), 7.50(d, 2 H, J67 8 Hz), 7.58 (d, 1 H, J32 16 Hz, H-3).Instruments and Methods.See ref. 9.We thank FAPESP and CNPq for nancial support. Wealso gratefully acknowledge Mr L.C. Roque for technicalassistance in the NMR experiments.Received, 17th November 1997; Accepted, 15th January 1998Paper E/7/08244DReferences1 Sadtler Standard Carbon-13 NMR Spectra, Sadtler ResearchLaboratories, Inc: Philadelphia 1976, S229C [1c]; S4006C [2a];S12461C [2b]; S1965C [2c]; S12345C [2d].2 E. Pretsch, T. Clerc, J. Seibl and W. Simon, in Tablas para laElucidacion Estructural de Compuestos Organicos por MetodosEspectroscopicos, Alhambra Longman, Madrid, 1996, p.C90.3 K. S. Dhami and J. B. Stothers, Can. J. Chem., 1965, 43, 510.4 P. G. Campbell, G. Sumrell and C. H. Schramm, J. Org. Chem.,1961, 26, 697.5 G. Sumrell, M. Zief, E. J. Huber, G. E. Ham and C. H.Schramm, J. Am. Chem. Soc., 1959, 81, 4313.6 S. Rondestvedt, Jr and C. D. Ver Nooy, J. Am. Chem. Soc.,1955, 77, 4878.7 B. Myrboh, H. Ila and H. Junjappa, J. Org. Chem., 1983, 48,5327.8 J. Bestmann, G. Schmid and D. Sandmeier, Chem. Ber., 1980,113, 912.9 A. de B. Rezende, M. R.Alcantara, I. P. de Arruda Campos,V. G. Toscano, G. Ebeling and J. C. D. Lopes, Tetrahedron,1997, 53, 10113.Table 3 Calculated values of Dd13Ca (ppm) andthe Zib,c of esters and thioestersDd13C¡ÓC(1O)OMe ¡ÓC(1O)SMeY C-2 C-3 C-2 C-3H 7.7 4.6 3.1 11.2Me 7.9 4.1 3.4 11.3MeO 8.0 3.9 3.5 11.3Cl 7.7 5.2 3.0 11.0Zib,c 7.8 4.5 3.3 11.2a13C 13C (4 or 3) £¾ 13C (2). bZi avg. (1 thus: i 2 for C-2 and i 1 for C-3.Table 2 d13C for signals of olefinic carbonsa of substituted styrenesb (2), methyl thiocinnamates (3)and methyl cinnamates (4)d13C d13C d13CY Comp. C-2 C-3 Comp.C-2 C-3 Comp. C-2 C-3H 2a 137.0 113.5 3a 140.1 124.7 4a 144.7 118.1Me 2b 136.9 112.5 3b 140.3 123.8 4b 144.8 116.6MeO 2c 136.5 111.3 3c 140.0 122.5 4c 144.5 115.2Cl 2d 135.7 114.2 3d 138.7 125.2 4d 143.4 119.4a5% (v/v) CDCl3 solutions (TMS 0 ppm), observed at 150 MHz. bRef. 1.Table 4 Calculated and experimental d13C for the olefiniccarbons in p-nitrostyrene (2e)Compound d13Ca d13C(2e)No Z C-2 C-3 C-2 C-33e NO2 137.0 128.4 133.7b 117.2b4e NO2 141.8 122.0 134.0c 117.5c2e NO2 Exptl.d values 134.8 117.9aAt 50 MHz, 5% (v/v) CDCl3 solutions (TMS 0 ppm).b13C(3e) £¾ Zi [¡ÓC(O)SMe].c13C(4e) £¾Zi [¡ÓC(O)OMe].dAt 15 MHz, in 1,4-dioxane (CS2 192.6 ppm), cf. ref. 3.Table 5 Calculated and experimental d13C for theolefinic carbons in compound 1b and the values forthe corresponding non-additivity correction (N i)d13C(1b) N iaC-2 C-3 C-2 C-3137.9b 126.7b 0.8 1.6140.2c 129.0c £¾1.5 £¾0.7139.1d 127.9d £¾0.4 0.4138.7e 128.3e ¡Ó ¡ÓaN i 13C(exptl.)£¾13C(calcd.). b13C(1a)£¾Zi[¡ÓC(O)SMe] Zi [¡ÓC(O)OMe]. c13C(1c) £¾ Zi[¡ÓC(O)OMe] Zi[¡ÓC(O)SMe]. dAverage estimates. eExperimental values,see Table 1.Table 6 d13C of methyl thiocinnamatesaCompound Y C-1 C-2 C-3 C-4 C-5 C-6 C-7 C-8 C-93a H 133.9 140.1 124.7 190.0 11.5 ¡Ób ¡Ób ¡Ób ¡Ó3b Me 131.3 140.3 123.8 190.3 11.6 128.4 129.7 141.0 21.53c OMe 126.9 140.0 122.7 190.2 11.6 129.0 114.3 161.6 55.43d Cl 132.6 138.7 125.2 190.0 11.7 129.2 129.5 138.4 ¡Ó3e NO2 140.3 137.0 128.5 189.6 11.9 129.0 124.2 148.6 ¡Óa5% (v/v) CDCl3 solutions (TMS 0 ppm), observed at 50 MHz. b127.7 or 130.8.J. CHEM. RESEARCH (S), 1998 271
ISSN:0308-2342
DOI:10.1039/a708244d
出版商:RSC
年代:1998
数据来源: RSC
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42. |
Microwave-induced One-pot Synthesis ofN-carboxyalkyl Maleimides and Phthalimides† |
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Journal of Chemical Research, Synopses,
Volume 0,
Issue 5,
1997,
Page 272-273
Harsha N. Borah,
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摘要:
Microwave-induced One-pot Synthesis ofN-carboxyalkyl Maleimides and Phthalimides$Harsha N. Borah, Romesh C. Boruah and Jagir S. Sandhu*Organic Chemistry Division, Regional Research Laboratory, Jorhat-6, Assam 785006, IndiaMaleic and phthalic anhydride condenses with amino acids and alkylamines under microwave irradiation to affordN-substituted maleimides and phthalimides in excellent yields.Maleimides constitute an important class of chemically andbiologically signicant compounds.1 Reagents containing amaleimido ligand tethered to an active ester group are inhigh demand in modern chemistry and biotechnology.2In addition, N-alkylphthalimides have received renewedinterest as a source of functionalized b-lactams.3 In general,most methods of cyclic imide synthesis involve Lewis-acid-mediated condensation of an amine with maleic anhydrideor n-alkylation of maleimide using Mitsunobo reactionconditions.4 Maleimide-linked esters are prepared by cyclo-condensation of maleimino acids in the presence of aceticanhydride and sodium acetate or from N-(ethoxy-carbonyl)maleimide and amino acids.5 However, thesemethods have limitations of general applicability owingto low yield, extensive by-product formation and harshreaction conditions.6There has been a growing interest in the use of microwaveirradiation for heating in organic synthesis.7 This resultsin better selectivity, rate enhancement and reduction ofthermally degradative products when compared withconventional heating. In addition, microwave-mediated syn-thesis without a solvent oers advantages for reducinghazardous explosions and the removal of high boilingaprotic solvents from the reaction mixture.8 Recently micro-wave irradiation has been utilized for N-alkylation ofphthalimide in dry media under phase-transfer catalysis.9Although the synthesis of N-arylmaleimides proceeds inexcellent yields, the synthesis of N-alkylmaleimides underidentical conditions is less satisfactory.10 In this report wedescribe a microwave-induced fast synthesis of potentiallybiologically active carboxyalkyl maleimides in a one-potreaction by condensing functionalized amines with maleicanhydrides.Equimolecular amounts of maleic anhydride (1) andamino acid (3, R2=H, Me, Ph; R3=CO2H, CO2Me) wereplaced in an open Erlenmeyer ask and heated in a domesticmicrowave oven for an appropiate time (Table 1) toobtain N-carboxyalkyl maleimides (4¡Ó6) in excellent yields(90¡Ó96%). Under identical conditions phthalic anhydride (2)reacted with alkylamine (3, R2=H, R3=Ph) and aminoacids (3, R2=H, R3=CO2H) aording N-substitutedphthalimides (9 and 10, respectively) in 89¡Ó95% yields.Interestingly, our procedure of microwave heating excludespolymerization.6 Further, alkylamines (3, R2=H, R3=Ph,vinyl) eciently undergo one-pot condensation with 1 and2, aording 7 and 8, respectively.All the products wereidentied by spectral and microanalytical analysis.In conclusion we have described a microwave-mediatedfacile and fast synthesis of N-carboxyalkyl- and N-alkyl-maleimides that may be biologically active.The reportedone-pot procedure is economical because of its high selec-tivity, solvent-less condition and absence of dehydratingagent.ExperimentalMps were uncorrected and recorded on a Buchi apparatus.IR spectra were obtained on a Perkin-Elmer 237B and 580B infra-red spectrometer in KBr discs. The 1H NMR spectra were recordedon Varian T-60 and JEOL JNM FX90Q spectrometers using Me4Sias internal standard (d/ppm).Mass spectra were recorded ona AEIMS-30 spectrometer at 70 eV. Microanalytical data were per-formed on a Perkin-Elmer Series II 2400 instrument. Reactionswere conducted in a commercial microwave oven model ER 5054 Dof Microwave Products (India) Ltd.General Procedure.A mixture of either maleic anhydride (1) orphthalic anhydride (2, 0.02 mol) and glycine (3, R2=H, R3=CO2H,0.02 mol) was placed in an Erlenmeyer ask tted with a loose topcap and heated in a commercial microwave oven operating at2450 MHz by setting the power range to medium high (70% oftotal power).The reaction mixture turned red. After cooling, thereaction mixture was extracted with chloroform (230 ml) andwshed with cold water (210 ml), dried (Na2SO4), ltered and thesolvent removed.N-Carboxymethylmaleimide 4: yield 94%, mp 112¡Ó13 8C; max/cm£¾1 (KBr) 3050, 1710; dH (CDCl3) 6.70 (s, 2 H, olenic), 3.75 (s, 2H, methylene); m/z 111 (M£¾ CO2) (Found: 46.5; H, 3.15; N, 9.1.C6H5NO4 requires C, 46.44; H, 3.25; N, 9.01%).N-(a-Carboxyethyl )maleimide 5: yield 90%, mp 97¡Ó98 8C; max/cm£¾1 (KBr) 3060, 1710; dH (CD3COCD3) 6.85 (s, 2 H, olenic),3.80 (q, 1 H, methine), 2.1 (d, 3 H, methyl); m/z 125 (M£¾ CO2)(Found: C, 49.8; H, 4.2; N, 8.2.C7H7NO4 requires C, 49.69; H,4.17; N, 8.25%).N-(a-Methoxycarbonylbenzyl )maleimide 6: yield 95%, mp 87¡Ó89 8C (lit.4(c), 88 8C); max/cm£¾1 (KBr) 3010, 1725, 1710; dH (CDCl3)7.25¡Ó8.25 (m, 5 H, aromatic), 6.90 (s, 2 H, olenic), 4.85 (s, 1 H,methylene), 3.75 (s, 3 H, ester methyl); m/z 221 (M).N-Benzylmaleimide 7: yield 96%, mp 69¡Ó70 8C (lit.,4(c) 69.5¡Ó70.5 8C); max/cm£¾1 (KBr) 3050, 1705; dH (CDCl3) 7.20¡Ó7.40 (m,5 H, aromatic), 6.70 (s, 2 H, olenic) 4.68 (s, 2 H, methylene); m/z237 (M).N-Allylmaleimide 8: yield 82%, mp 42¡Ó43 8C (lit.,4(c) 42.5¡Ó43 8C);max/cm£¾1 (KBr) 3000, 1710; dH(CDCl3) 6.72 (s, 2 H, olenic), 5.80(m, 1 H, vinylc), 5.12¡Ó5.24 (m, 2 H, vinylic), 4.10 (dt, 2 H, J5.6 Hz, vinylic); m/z 137 (M).N-Benzylphthalimide 9: yield 89%, mp 119¡Ó20 8C (lit.,4(c) 118.5¡Ó119.5 8C); max/cm£¾1 (KBr) 3060, 1700; dH (CDCl3) 7.65¡Ó7.88 (m, 4H, aromatic), 7.20¡Ó7.45 (m, 5 H, aromatic), 4.80 (s, 2 H, olenic);m/z 237 (M).N-Carboxymethylphthalimide 10: yield 95%, mp 110¡Ó11 8C; max/cm£¾1 (KBr) 3040, 1720; dH (CD3COCD3) 7.60¡Ó7.95 (m, 4 H,aromatic), 4.70 (s, 2 H, methylene); m/z 161 (M£¾CO2). (Found:C, 58.6, H, 3.3, N, 6.9.C10H7NO4 requires C, 58.52, H, 3.44,N, 6.83%).J. Chem. Research (S),1998, 272¡Ó273$$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.272 J. CHEM. RESEARCH (S), 1998Received, 5th December 1997; Accepted, 19th January 1998 Paper E/7/07961C References 1 J. E. T. Corrie, J.Chem. Soc., Perkin Trans 1, 1994, 2975. 2 T. Kitagawa, T. Kawasaki and H. Munechika, J. Biochem., 1982, 92, 585. 3 D. D. Pietro, R. M. Borzilleri and S. M. Weinreb, J. Org. Chem., 1994, 59, 5856. 4 (a) G. B. Gill, G. B. James, K. V. Oates and G. J. Pattenden, J. Chem. Soc., Perkin Trans. 1, 1993, 2567; (b) M. A. Walker, J. Org. Chem., 1995, 60, 5352; (c) P. Y. Reddy, S. Kondo, T. Toru and Y. Ueno, J. Org. Chem., 1997, 62, 2652. 5 O. Nielsen and O. Buchardt, Synthesis, 1991, 819 and references cited therein. 6 M. P. Stevens, J. Polym. Sci. Polym. Lett. Ed., 1984, 22, 467. 7 (a) R. Laurent, A. Leporterie, J. Dubac, J. Berlan, S. Lauverie and F. M. Audhuy, J. Org. Chem., 1992, 57, 7099 and references cited therein; (b) S. Caddick, Tetrahedron, 1995, 51, 10403. 8 (a) G. Bram, A. Loupy and D. Villemerin, in Solid Supports and Catalysts in Organic Chemistry, Ellis Horwood, London, 1992; (b) A. Boruah, M. Baruah, D. Prajapati and J. S. Sandhu, Chem. Lett., 1996, 965. 9 D. Bogda and J. Pielichiowski, Synlett, 1996, 873. 10 (a) N. B. Metha, A. P. Phillips, F. F. Lui and R. E. Brooks, J. Org. Chem., 1960, 25, 1012; (b) D. H. Rich, P. D. Gesellchen, D. Paul, A. Tong, T. A. Cheung and C. K. Buckner, J. Med. Chem., 1975, 18, 1004. Table 1 Condensation of maleic and phthalic anhydrides with amines Entry Substrate Product Reaction time (t/min) Solvent of crystallization 1 Glycine N-Carboxymethylmaleimide (4) 3 Water 2 Alanine N-(a-Carboxyethyl)maleimide (5) 3 Water 3 2-Phenylglycine methyl ester N-(a-Methoxycarbonylbenzyl)maleimide (6) 2 Methanol 4 Benzylamine N-Benzylmaleimide (7) 2 Chloroform 5 Allylamine N-Allylmaleimide (8) 2 Methanol 6 Benzylamine N-Benzylphthalimide (9) 3 Water 7 Glycine N-(Carboxymethyl)phthalimide (10) 3 Chloroform J. CHEM. RESEARCH (S), 1998 273
ISSN:0308-2342
DOI:10.1039/a707961c
出版商:RSC
年代:1998
数据来源: RSC
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43. |
Oxidation of Carbon Monoxide and Methane over CeO2-supported Palladium Catalysts† |
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Journal of Chemical Research, Synopses,
Volume 0,
Issue 5,
1997,
Page 274-275
Meng-Fei Luo,
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摘要:
Oxidation of Carbon Monoxide and Methane overCeO2-supported Palladium Catalysts$Meng-Fei Luo* and Xiao-Ming ZhengInstitute of Catalysis, Hangzhou University, Hangzhou 310028, P.R. ChinaDispersed PdO which interacts with CeO2 is the active site for CO oxidation, while the large PdO particles which do notinteract strongly with CeO2 are the active site for methane oxidation.Complete oxidation of carbon monoxide and gaseoushydrocarbons to carbon dioxide and water by catalysis hasbeen used to reduce toxic emissions from car exhausts.Precious metals (Pt, Pd) are well known complete oxidationcatalysts with high activity and stability.In the past severalyears, much interest has arisen in the use of ceria, CeO2, asa precious and transition metal oxide support. For example,Pt/CeO2 has been used for oxidation of CO1 and ethylene,2and in the water-gas shift reaction.3 However, virtuallyno study on CeO2 as a support for palladium catalysts ofcarbon monoxide and methane oxidation has been reported.The present work is concerned with the oxidation activity ofPdO¡ÓCeO2 for carbon monoxide and methane.ExperimentalPreparation of Catalysts.The CeO2 was prepared by thermaldecomposition of cerium(III) nitrate, Ce(NO3)3, for 4 h at 650 8C inair.Its BET surface area is 55 m2 g£¾1. The supported PdO¡ÓCeO2catalysts were prepared by the conventional wet impregnationmethod using an aqueous solution of H2PdCl4, dried overnightin an oven at 120 8C and then heated in air at 650 8C for 4 h.The loading of Pd was 0.25, 0.75, 1.5, 2.0, and 5.0%, respectively.The catalyst is denoted as PdO¡ÓCeO2 (X%).The amount ofchlorine included in the catalyst was too small to be detected byspectrophotometry.4Activity Measurement.Catalytic activity measurements werecarried out in a xed bed reactor (0.6 cm i.d.) using 150 mg of cata-lyst mesh size 20¡Ó60. The total gas ow rate was 80 (ml min£¾1). ForCO oxidation, the gas consisted of 2.4% CO and 1.2% O2 in N2,for methane oxidation, 2.8% CH4 and 8% O2 in N2.The catalystswere directly exposed to 80 ml min£¾1 of reaction gas as the reactortemperature stabilized at reaction temperature, without any pre-treatment. The products were analysed by gas chromatography withMolecular Sieves 13X and Porapak Q columns both operatingat 50 8C.Results and DiscussionFig. 1 shows the catalytic activity of the PdO¡ÓCeO2 cata-lyst in the oxidation of CO and methane. The activity wascompared on the basis of T20 (the temperature for 20%conversion).None of these catalysts was pretreated beforereaction. This is particularly important in applicationswhere pretreatment is not possible or when the catalystsmust be stored in air before use. The T20 of pure PdO forCO oxidation is 250 8C. The activity of pure PdO and CeO2is much lower than that of PdO¡ÓCeO2 catalysts. The activityof the latter increases with palladium loading from 0.25 to2%, but larger amounts of Pd (from 2 to 5%) do not aectthe activity.Since the activity of pure PdO and the CeO2support is very low, a synergistic interaction between thetwo is responsible for the high activity for carbon monoxideoxidation at low temperature. On the basis of the results,only a small amount of palladium (2%) is needed to formthe active site for CO oxidation, and the excess of Pd formsbulk PdO particles contributing little to the activity. Inother words, the dispersed PdO which interacts with CeO2 isthe active site for CO oxidation.From Fig. 1, it can be seenthat the activity of the catalyst at low palladium loading(0.25 and 0.75%) for methane oxidation is lower than thatJ. Chem. Research (S),1998, 274¡Ó275$Fig. 1 Effect of palladium loading in PdO¡ÓCeO2 catalyst onactivity for CO and methane oxidationFig. 2 Effect of amount of palladium in a physical mixture ofPdO¡ÓCeO2 on the activity for CO and methane oxidation$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.274 J. CHEM. RESEARCH (S), 1998of the CeO2 support. As the loading increases from 1.5 to 5% the activity of the PdO±CeO2 catalyst increases. We think that ®nely dispersed PdO is not active, and that the large particles of PdO are the active site for methane oxidation. This is consistent with the SiO2, Al2 O3 and SiO2±Al2O3 supported palladium catalysts for methane oxidation reported by Muto et al.5 To clarify that the active site for CO and methane oxidation reaction is the ®nely dispersed PdO and the large particles of PdO respectively, the activity of a physical mixture of PdO±CeO2 was investigated, as shown in Fig. 2. It is well known that the crystal particle size of PdO in a physical mixture is larger than that of a catalyst prepared by impregnation methods. Compared to Fig. 1, it is clear that the activity of the mixture for CO oxidation is much lower than that of the PdO±CeO2 catalyst. Thus, we con- clude that the ®nely dispersed PdO which interacts with CeO2 mainly contributes to the catalytic activity for CO oxi- dation at low temperature, and the large particles of PdO contribute little to the activity. However, for methane oxi- dation, the catalytic activity of the mixture is much higher than that of the PdO±CeO2 catalyst as the palladium load- ing increases from 0.25 to 2%, while the activity of the PdO±CeO2 (5%) catalyst for methane oxidation is slightly higher than that of the PdO±CeO2 (5%) mixture.The activity of the mixture obviously increases as the amount of Pd increases from 0.25 to 2%. This indicates that the large particles of PdO are the active site for methane oxidation. In order to con®rm the active site of the catalyst for CO and methane oxidation, we selected a low surface area CeO2 support (22 m2 g¡1).The T20 of this supported PdO catalyst (2%) for CO and methane oxidation is 55 and 420 8C, respectively. This indicates that the activity of the low sur- face area catalyst for CO oxidation is lower than that of the high surface area catalyst, while the activity of the former for methane oxidation is higher than that of the latter. We further conclude that the ®nely dispersed PdO is the active site for CO oxidation, the large particles of PdO that for methane oxidation. The project was supported by the Zhejiang Provincial Science Foundation of China and Education Commission of Zhejiang Province. Received, 20th October 1997; Accepted, 27th January 1998 Paper E/7/07542A References 1 T. Jin, T. O. Kuhara, G. J. Mains and J. M. White, J. Phys. Chem., 1987, 91, 3310. 2 L. Mendelevici and M. Sdeinberg, J. Catal., 1985, 93, 353. 3 L. Mendelevici and M. Sdeinberg, J. Catal., 1985, 96, 285. 4 A. Tomonari, Nippon Kagaku Zasshi, 1961, 82, 864. 5 K-I. Muto, N. Katada and M. Niwa, Appl. Catal. A, 1996, 134, 203. J. CHEM. RESEARCH (S), 1998 275
ISSN:0308-2342
DOI:10.1039/a707542a
出版商:RSC
年代:1998
数据来源: RSC
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44. |
Highly Efficient and Single Step Synthesis of 4-Phenylcoumarins and 3,4-Dihydro-4-phenylcoumarins Over Montmorillonite K-10 Clay, Under Microwave Irradiation† |
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Journal of Chemical Research, Synopses,
Volume 0,
Issue 5,
1997,
Page 280-281
Jasvinder Singh,
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摘要:
Highly Efficient and Single Step Synthesis of4-Phenylcoumarins and 3,4-Dihydro-4-phenylcoumarins Over Montmorillonite K-10 Clay,Under Microwave Irradiation$Jasvinder Singh,* Jasamrit Kaur, Sandeep Nayyar andGoverdhan L. KadDepartment of Chemistry, Panjab University, Chandigarh-160 014, IndiaA simple, elegant and one-pot synthesis of 3,4-dihydro-4-phenylcoumarins, 4-phenylcoumarins and their derivatives bymaking use of solid support, montmorillonite K-10 clay in conjunction with microwave irradiation is described.Coumarins and dihydrocoumarins are an important class oforganic compounds, used in the pharmaceutical industryand as intermediates in the synthesis of useful pesticides andbioactive compounds. A number of syntheses of coumarinsare available which oer a variety of intermediates andreaction conditions.1¡Ó7 Some of the problems which arisewith these have been avoided by employing solid supportsunder microwave conditions.8¡Ó10We have found that some 3,4-dihydro-4-phenylcoumarinsand 4-phenylcoumarins can be obtained in a single step andin good yield.Phenol (or its derivatives) and cinnamicacid (or its derivatives) impregnated on activated mont-morillonite K-10 clay (by heating under vacuum for 2 h),when subjected to microwave irradiation (MWI), in anopen vessel and employing optimized conditions of 640 Wpower output in a domestic microwave oven, for 8¡Ó10 min,furnished 3,4-dihydro-4-phenylcoumarin and its derivatives1¡Ó5, Scheme 1.The results of this reaction are summarizedin Table 1.The methodology adopted has a few advantages (i) nosolvent is required and (ii) since an open vessel is used thereis no question of excessive accumulation and consequentdanger of explosion. The exact role of the microwaveradiation is not known, that is whether it provides a thermaleect or in some way decreases the activation barrier, so thatthe reaction proceeds quickly. Montmorillonite KSF-claypredoped with or without ZnCl2 was also used, howeverJ.Chem. Research (S),1998, 280¡Ó281$Scheme 1Table 1 Reaction between phenols and cinnamic acids to form 3,4-dihydro-4-phenylcoumarins13C NMR 300 MHz MassSolid Yield (d)/phase 1H NMR spectrum Mp (lit.)/Compound R R' support t/min (%) on DEPT (d) max/cm£¾1 m/z M/% 8C1 H p-OMe K-10 8 85 167.827/£¾ 2.94¡Ó3.09(m, 2 H)1760, 1160,1240254/100 98a37.21/ £¾ ve 4.28¡Ó4.32(t, 1 H)39.90/ ve 3.79 (s, 3 H)2 m-OH H KSF/ZnCl2(no acid)20 79 167.001/£¾ 2.83¡Ó3.00(m, 2 H)1760, 1210,3200¡Ó3400240/24 140¡Ó142(1401)36.54/ £¾ ve 4.06¡Ó4.24(t, 1 H)38.93/ ve 6.45 (br s, OH)K-10 8 75 38.93/ ve 6.45 (br s, OH) 240/223 m-OMe H K-10 8 81 167.741/£¾ 2.96¡Ó3.10(m, 2 H)1760, 1130,1220254/100 110¡Ó114(1121)37.404/ £¾ ve 4.26¡Ó4.31(t, 1 H)40.192/ ve 3.80 (s, 3 H)4 H m,p-OCH2O- K-10 10 65 167.683/£¾ 2.94¡Ó3.09(m,2 H)1770, 1230,1260268/100 118b37.32/ £¾ ve 4.25¡Ó4.29(t, 1 H)39.89/ ve 5.95 (s, 2 H)5 H H K-10 10 82 167.645/£¾ 2.98¡Ó3.13(m, 2 H)1780, 1140,1240224/65 80¡Ó82(831)37.063/ £¾ ve 4.32¡Ó4.37(t,1 H)KSF(no acid)22 74 40.749/ veaFound: C, 75.43; H, 5.59.C16H14O3 requires C, 75.58; H, 5.55%. bFound: C, 71.69; H, 4.55. C16H12O4 requires C, 71.64; H, 4.51%.greater exposure time to MWI was required. When a mix-ture of phenol, cinnamic acid and one drop of H2SO4 wasreuxed in dimethylformamide for 10 h, with or withoutK-10 clay, no reaction was observed.$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.280 J. CHEM. RESEARCH (S), 1998Similarly, when phenol (or its derivatives) and phenyl-propynoic acid (or its derivatives) were subjected to MWIin the presence of montmorillonite K-10 clay with one dropof H2SO4 and placed in a silica bath, coumarins 6¡Ó8(Scheme 2) were obtained in good yield as shown in Table 2.The results of the spectral data were compared with thedata for analogs or similar systems.11 The most relevantresonance in the 13C NMR spectrum is at d 167¡Ó168, corre-sponding to the carbonyl carbon.Condensation reactionsinvolving resorcinol or its monomethyl ether with cinnamicacid, resulting in products 2, 3 and 7, proceed at the 4 notat the 2 position: thus the product available through thisroute will exclusively be the 7- and not the 5-substitutedderivative.12ExperimentalMontmorillonite K-10 clay was purchased from Fluka.Typical Procedure.To activated montmorillonite K-10 clay (2 g)in a 100 ml Erlenmeyer ask was added a mixture of freshly distilledphenol (0.50 g, 5.3 mmol) and recrystallized p-methoxycinnamicacid (0.94 g, 5.3 mmol) dissolved in CH2Cl2 (5 ml) along with onedrop of concentrated H2SO4.The solvent was evaporated and theresultant free-owing solid placed on a silica bath and subjectedto MWI at 640W for 10 min. Dichloromethane (20 ml) was added,the reaction mixture ltered and the ltrate washed with saturatedNaHCO3 solution, brine and dried over Na2SO4.Evaporation ofthe solvent in vacuo yielded the product, 1.05 g (82%). 1H NMR(300 MHz, CDCl3): 7.29¡Ó7.26 (d, J 4, 1 H), 7.11¡Ó7.08 (t, J 4,4 H), 6.99¡Ó6.97 (d, J 4, 1 H), 6.89¡Ó6.86 (d, J 4, 2 H), 4.32¡Ó4.28(t, J 6 Hz, 1 H), 3.79 (s, 3 H) and 3.09¡Ó2.94 (m, 2 H). Massspectrum (m/z, % base): 255/24 (M1), 254/100 (M), 253/5(M£¾1), 149/4 and 148/17. 13C NMR (CDCl3/phase on DEPT): 167.827, 159.005, 151.681, 132.240, 128.643/ve, 128.310/ve,126.250, 124.659/ve, 117.097/ve, 114.502/ve, 55.320/ve,39.900/ve and 37.210/£¾ve. IR (CCl4, cm£¾1): 1760, 1240, 1160and 750¡Ó710.We are grateful to the CSIR, New Delhi, for providingnancial assistance for this work.Received, 11th November 1997; Accepted, 27th January 1998Paper E/7/08103KReferences1 J.D. Simpson and H. Stephen, J. Chem. Soc., 1956, 1382.2 P. Sebok, J. Jeko, T. Timar and J.Cs. Jaszberenyi, TetrahedronLett, 1992, 33, 2791.3 J. E. Pickett and P. C. Van Dort, Tetrahedron Lett., 1992, 33,1161.4 A. J. Hoefnagel, E. A. Gunnewegh, R. S. Downing and H. VanBekkum, J. Chem. Soc., Chem. Commun., 1995, 225.5 L. Crombie, R. C. F. Jones and C. J. Palmer, J. Chem. Soc.,Perkin. Trans. 1, 1987, 317.6 S. Setha and R. Phadke, Org. React. (N.Y.), 1953, 7, 1.7 D. D. Chaudhari, Chem. Ind., 1983, 568.8 G. L. Kad, J. Kaur, P. Bansal and J. Singh, J. Chem. Res. (S),1996, 188.9 G. L. Kad, I. R. Trehan, J. Kaur, S. Nayyar, A. Arora and J. S.Brar, Indian J. Chem., Sect. B, 1996, 35, 734.10 V. Singh, J. Singh, K. P. Kaur and G. L. Kad, J. Chem. Res.(S), 1997, 58.11 K. K. Chan, Tetrahedron, 1977, 33, 899.12 N. S. Narasimhan and R. S. Mali, Synthesis, 1983, 957.13 F. Bergmann, M. Weizmann, E. Dimant, J. Patai andJ. Szmuskowicz, J. Am. Chem. Soc., 1948, 70, 1612.Table 2 Reactions of phenols and phenylpropynoic acid to form coumarinsMain peak in MassYield 300 MHz spectrum Mp (lit.)/Compound R0 R000 t/min (%) 1H NMR (d) max/cm£¾1 m/z M/% 8C6 H H 10 69.5 6.42 (s, 1 H) 1710, 1620, 1240 222/60 102¡Ó104(10513)7 m-OMe H 10 55.0 6.28 (s, 1 H) 1700, 1630, 1220 252/54 138a8 H p-OMe 10 67.0 6.20 (s, 1 H) 1690, 1620, 1260 252/46 101¡Ó103baFound: C, 76.29, H, 4.51. C16H12O3 requires C, 76.18; H, 4.79%. bFound: C, 76.06, H, 4.70. C16H12O3 requires C, 76.17; H, 4.77%.Scheme 2J. CHEM. RESEARCH (S), 1998 281
ISSN:0308-2342
DOI:10.1039/a708103k
出版商:RSC
年代:1998
数据来源: RSC
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45. |
Synthesis of Some Substituted Adamantanetriones |
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Journal of Chemical Research, Synopses,
Volume 0,
Issue 5,
1997,
Page 282-282
Mohammed Giasuddin Ahmed,
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摘要:
Synthesis of Some Substituted Adamantanetriones Mohammed Giasuddin Ahmed,*a Syed M. Iqbal Moeiz,a Syeda Asghari Ahmed,a Mohammed Abu Hena,a Yoshisuke Tsudab and Paul Sampsonc aDepartment of Chemistry, University of Dhaka 1000, Bangladesh bFaculty of Pharmaceutical Sciences, Kanazawa University, 13-1 Takara-Machi, Kanazawa 920, Japan cDepartment of Chemistry, Kent State University, P.O. Box No. 5190, Kent, Ohio 44242-0001, USA Following the same general procedure employed for the synthesis of substituted adamantane-2,4-diones which we reported previously6,7 we now herein report the synthesis of substituted adamantane-2,4,6-triones 6a and 6b.The morpholine enamine 4 of ethyl 1-phenyl-4-oxocyclo- hexane-1-carboxylate 3 prepared following the reported procedure,9 reacted with acryloyl and crotonoyl chlorides giving 1-phenyladamantane-2,4,6-trione 6a and 10-methyl-1- phenyladamantane-2,4,6-trione 6b$ respectively in good yields. The structures of the adamantane derivatives were established from their spectral properties.Preparation and characterization of oximes 10 and 11 of compounds 6a and 6b a€orded additional evidence for their structures (Scheme 1). The crystalline compounds 6a and 6b gave informative 1H NMR spectral data in CDCl3. It was possible to assign all the protons by running two-dimensional (1H01H COSY) NMR spectra and the coupling constants were determined from the one-dimensional spectra. In both the compounds 6a and 6b the bridgehead protons at positions 3 and 5 appeared downReld due to the adjacent carbonyl groups.The protons at these positions in 6b were shifted slightly upReld in comparison to 6a due to the anisotropic e€ect of the CH3 group in the 10 position. The methylene protons of positions 8 and 9 individually appeared as singlets in each of 6a and 6b. In each of these compounds the protons at position 8 were more deshielded than those at position 9 due to the phenyl group at position 1 (d 0.16 in the case of 6a and d 0.13 in the case of 6b).The stereo- chemistry at position 10 in 6b is evident from the relatively high d value of the protons at this position which is indica- tive of its equatorial conformation.6,7 This in turn indicates the axial conformation of the 10-CH3 group in 6b. Similar observations were made for the shielding and deshielding e€ects on carbon at di€erent positions of compounds 6a and 6b. The chemical shifts and substituent pattern of carbons in 6b were assigned with the help of 1H013C COSY and DEPT NMR spectroscopy.By analogy with 6b the positions of the carbon atoms in 6a were ascertained. The shielding and deshielding of di€erent carbons were explained on the basis of the substitution chemical shift e€ect and the g-anti e€ect.8 This further conRrmed the stereochemistry at position 10 for compound 6b. In their mass spectra compounds 6a and 6b showed molecular ions at m/z 254 and 268 respectively.Techniques used: IR, 1H and 13C NMR, and mass spectrometry References: 10 Schemes: 2 Table 1: Proton NMR spectral data for compounds 6a and 6b Table 2: Carbon-13 NMR spectral data for compounds 6a and 6b Table 3: Carbon-13 NMR spectral data for compound 3 Received, 24th September 1997; Accepted, 14th January 1998 Paper E/7/06921I References cited in this synopsis 6 A. K. M. F. Huque, M. Mosihuzzaman, S. A. Ahmed, M. G. Ahmed and R. Andersson, J. Chem. Res., 1987, (S) 214; (M) 1701 and references cited therein. 7 M. G. Ahmed, A. K. M. F. Huque, S. A. Ahmed, M. Mosihuzzaman and R. Andersson, J. Chem. Res., 1988, (S) 362; (M) 2815 and references cited therein. 8 H. Duddeck and H. Klein, Tetrahedron, 1977, 33, 1971. 9 G. Stork, A. Brizzolara, H. Landesman, J. Szmuskovicz and R. Terral, J. Am. Chem. Soc., 1963, 85, 207. 10 G. Snatzke and D. Marquarding, Chem. Ber., 1967, 100, 1710. J. Chem. Research (S), 1998, 282 J. Chem. Research (M), 1998, 1082�}1095 Scheme 1 *To receive any correspondence. $In deRning axial and equatorial positions in these polycyclic com- pounds the Snatzke10 convention was followed. 282 J. CHEM. RESEARCH (S), 19
ISSN:0308-2342
DOI:10.1039/a706921i
出版商:RSC
年代:1998
数据来源: RSC
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