摘要:

C O + O 1 hn O 6 • O hn 5 3 • + CO CN O 2 hn CN 4a CN 4b + J. CHEM. RESEARCH (S), 1997 345 J. Chem. Research (S), 1997, 345† Photodecarbonylation of 2,2,6,6-Tetrasubstituted Cyclohex- 3-enones to Vinylcyclopropanes† Sven Andresen and Paul Margaretha* Institute of Organic Chemistry, University of Hamburg, D-20146 Hamburg, Germany On irradiation (l=300 nm), 2,2,6,6-tetramethylcyclohex-3-enone (1) is cleanly converted into 1-(2,2-dimethylcyclopropyl)- 2-methylpropene (3); similarly, 6-oxo-1,5,5-trimethylcyclohex-2-ene-1-carbonitrile (2) affords a mixture of (Z)- and (E)-3-(2,2-dimethylcyclopropyl)-2-methylpropenonitriles 4a and 4b.The photorearrangement of bicyclooct-2-en-5-ones or bicyclohept-2-en-5-ones by a 1,3-acyl migration to yield (bicyclic) cyclobutanones occurs efficiently for a variety of systems, while subsequent photodecarbonylation has only been observed in a few cases.1–5 Here we report the first examples of the light-induced conversion of monocyclic cyclohex-3-enones to vinylcyclopropanes. 2,2,6,6-Tetramethylcyclohex-3-enone (1) and 6-oxo-1,5,5- trimethylcyclohex-2-ene-1-carbonitrile (2) were obtained by methylation of 2,6,6-trimethylcyclohex-2-enone and 5,5-dimethyl- 6-oxocyclohex-1-ene-1-carbonitrile, respectively. Irradiation of 1 in pentane up to total conversion affords 3 selectively in 75% yield, while irradiation of 2 affords a 4:1 mixture of 4a and 4b.Monitoring the irradiation of 1 in CD3CN by 1H NMR and GC–MS at a low degree of conversion (s20%) indicated the formation of 3 (2/3) and an additional product 5 (1/3), the latter disappearing at higher degrees of conversion of 1.Spectroscopic evidence allows the assignment of a cyclobutanone structure, i.e. the expected 1,3-acyl migration product, to 5. From these findings it becomes evident that 5 is efficiently (photo)reconverted to its precursor, i.e. the biradical 6, which undergoes only decarbonylation and subsequent 1,3-cyclization, to the exclusion of b-cleavage to dimethylketene and 4-methylpenta-1,3-diene (Scheme 1).This selectivity in the behaviour of 6 is most probably due to its (alkyl)substitution pattern,6 the a-cleavage process (leading to 3) being facilitated by the methyl groups on C(2) of the acyl–allyl biradical. Experimental NMR spectra (Bruker WM 400 spectrometer: 1H, 400 MHz; 13C, 100.62 MHz) were recorded in either CDCl3 or CD3CN as solvent. High-resolution mass spectra were recorded at 70 eV on a 311A (Varian MAT) spectrometer.Photolyses were run in a Rayonet RPR-100 photoreactor equipped with 300 nm lamps. Cyclohex-3-enones.·Treatment of 2,6,6-trimethylcyclohex- 2-enone7 with LDA–HMPT and MeI in THF,8,9 and subsequent chromatography (SiO2, pentane–diethyl ether, 15:1) afforded 1 in 47% yield as a colourless liquid, 1H NMR and UV-spectrum identical to those reported;10,11 dC (CDCl3) 219.5 (C-1), 136.1 (C-4), 122.7 (C-3), 44.1 and 43.4 (C-2 and C-6), 38.5 (C-5), 27.0 and 25.6 (CH3).Similarly, treatment of 5,5-dimethyl-6-oxocyclohex-1-ene-1-carbonitrile12 and subsequent chromatography (SiO2, pentane–ethyl acetate, 10:3) afforded 2 in 13% yield as a colourless oil; dH (CDCl3) 6.02 (1 H), 5.76 (1 H), 2.38 (2 H), 1.58, 1.36 and 1.19 (CH3); dC 206.2 (CO), 128.8 and 127.0 (CH=CH), 118.9 (CN), 44.2 and 42.3 (aCs), 39.2 (CH2), 26.0, 25.2 and 23.8 (CH3) (Found: M+, 163.0997. C10H13NO requires Mr 163.0996). Preparative Irradiations.·An Ar-degassed solution of 1 (760 mg, 5 mmol) in pentane (50 ml) was irradiated for 6 h.After distillation of the solvent through a Vigreux column the residue was bulbto- bulb distilled at 130 °C to give 1-(2,2-dimethylcyclopropyl)- 2-methylpropene (3), 465 mg (75%), with 1H and 13C NMR spectra identical with those reported.13 Similarly, an Ar-degassed solution of 2 (815 mg, 5 mmol) in pentane (50 ml) was irradiated for 8 h. After distillation of the solvent as above the residue, a 4:1 mixture of 4a and 4b, was separated by chromatography (SiO2, pentane– diethyl ether 15:1) to afford first (Z)-3-(2,2-dimethylcyclopropyl)- 2-methylpropenonitrile (4a), Rf=0.47, as a colourless liquid, dH (CDCl3 5.79 (1 H), 1.93 (3 H), 1.73 (ddd, J 5.1, 8.4, 10.4 Hz), 1.30 and 1.10 (CH3), 0.97 (dd, J 4.6, 8.4 Hz), 0.56 (t, J 4.8 Hz) (Found: M+, 135.1041.C9H13N requires Mr 135.1040), and then the Ediastereoisomer (4b), Rf=0.37 as a colourless liquid, dH (CDCl3) 6.00 (1 H), 1.91 (3 H), 1.44 (ddd, J 4.9, 8.1, 10.2 Hz), 1.23 and 1.21 (CH3), 0.96 (dd, J 4.8, 8.1 Hz), 0.61 (t, J 4.9 Hz) (M+, 135.1039.C9H13N requires Mr 135.1040). Detection of 2-(2-Methylprop-1-enyl)-4,4-dimethylcyclobutanone (5).·An Ar-degassed solution of 1 (1.52 mg, 1Å10µ2 mmol) in CD3CN (1 ml) was irradiated for 10 min. Besides 1 (80%) and 3 (12%) there were 1H NMR signals for 5, dH 5.15 (1 H), 4.25 (1 H), 2.18 (t, J 11.7 Hz), 1.71 and 1.63 (CH3), 1.58 (dd, J 8.1, 11.7 Hz), 1.22 (6 H).GC–MS analysis gave (M+, 152.1341. C10H16O requires Mr 152.1340). Financial support by Deutsche Forschungsgemeinschaft and Fonds der Chemischen Industrie is gratefully acknowledged. Received, 6th May 1997; Accepted, 29th May 1997 Paper E/7/03094K References 1 J. Sala�un, in Methods of Organic Chemistry (Houben-Weyl), ed. A. de Meijere, Thieme, Stuttgart, 1997, vol. E17, p. 1156. 2 V. Singh, B. Thomas and U. Sharma, Tetrahedron Lett., 1995, 36, 3421. 3 S. Katayama and M. Yamauchi, Chem. Lett., 1995, 311. 4 J. Meinwald and P. J. van Vuuren, J. Chem. Soc., Chem. Commun., 1971, 1460. 5 H. D. Scharf and W. K�usters, Chem. Ber., 1971, 104, 3016. 6 K. Hobel and P. Margaretha, Res. Chem. Intermed., 1989, 12, 263. 7 M. Baumann, W. Hoffmann and A. N�urrenbach, Liebigs Ann. Chem., 1979, 1945. 8 G. Stork and R. l. Danheiser, J. Org. Chem., 1973, 38, 1775. 9 G. M. Rubottom and H. D. Juve Jr, J. Org. Chem., 1983, 48, 422. 10 W. Cocker, K. J. Crowley and K. Srinivasan, J. Chem. Soc., Perkin Trans. 1, 1973, 2485. 11 R. K. Murray Jr. and D. L. Goff, J. Chem. Soc., Chem. Commun., 1973, 881. 12 S. Andresen and P. Margaretha, J. Chem. Res. (S), 1994, 332. 13 B. J. Fahie and W. J. Leigh, Can. J. Chem., 1989, 67, 1859. *To receive any correspondence. †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Sc

ISSN:0308-2342    

DOI:10.1039/a703094k

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

N N O HO O Me Me R2 X R1 + N N O O O Me Me R2 R1 1 2 3 R2 Br Br Cl Cl H H CH2OH CH2Cl H Me H H a b c d 2,3 X R1 i N N O O O Me Me R2 R1 3a–d N N O O Me Me O R1 R2 N N O O Me Me O 4a–d 5a–c R2 R1 i ii J. CHEM. RESEARCH (S), 1997 309 J. Chem. Research (S), 1997, 309 J. Chem. Research (M), 1997, 2062–2067 Regioselective Synthesis of 6H-Pyrano[3,2-d]pyrimidine- 2,4(1H)-diones and Furo[3,2-d]pyrimidine-2,4(1H)-diones Krishna C. Majumdar* and Udayan Das Department of Chemistry, University of Kalyani, Kalyani 741235, W.B. India A number of 1,3-dimethyl-6H-pyrano[3,2-d]pyrimidine-2,4(1H)-diones (4a–d) and 1,3-dimethylfuro[3,2-d]pyrimidine- 2,4(1H)-diones (5a–c) have been regioselectively synthesised in 88–94% and 80–90% yields respectively from the thermal [3s,3s] sigmatropic rearrangement of 1,3-dimethyl-5-(prop-2-ynyloxy)uracils (3a–d). We have recently reported1 the regioselective synthesis of pyrano[2,3-c]coumarins from aryloxybut-2-ynyloxy coumarins. There we established that it is possible to cyclise regioselectively the intermediate allenyl enol from the [3s,3s] sigmatropic rearrangement of the propynyl ethers of 3-hydroxycoumarin exclusively either to furo[2,3-c]coumarin or pyrano[2,3-c]coumarin simply by manipulating the reaction conditions.Literature reports2 revealed that Otter et al. studied the Claisen rearrangement of 5-(prop-2-ynyloxy)- uracil under a variety of conditions. Although they succeeded in obtaining a mixture of varying proportions of furo[3,2-d]- pyrimidine-2,4-dione and 6H-pyrano[3,2-d]pyrimidine- 2,4-dione they failed to isolate exclusively either of the products.This prompted us to undertake a study based on our recent experiences with subsequent cyclisation of the o-allenyl enol.3 Here we report the results of this investigation. The starting materials, 1,3-dimethyl-5-(prop-2-ynyloxy)- uracils (3a–d) were prepared in 88–94% yields by the alkylation of 1,3-dimethyl-5-hydroxyuracil4 1 with various prop- 2-ynylic halides (2a–d) in refluxing acetone in the presence of anhydrous potassium carbonate (Scheme 1).The 1,3-dimethyl-5-(prop-2-ynyloxy)uracil 3a was refluxed in purified chlorobenzene (bp 132 °C) to give 1,3-dimethyl- 6H-pyrano[3,2-d]pyrimidine-2,4(1H)-dione 4a as a white crystalline solid (88% yield), mp 202 °C. Other substrates (3b–d) were also similarly treated to furnish products (4b–d) in 90–94% yields (Scheme 2). The exclusive formation of products 4a–d from the ethers 3a–d is explicable4 by a [3s,3s] sigmatropic shift of the propynyl vinyl ether moiety of substrates 3a–d followed by enolisation, a 1,5-H shift and electrocyclic ring closure to give 4a–d.The ethers 3a–d were also heated in basic solvents, e.g., N,N-diethylaniline at 115 °C for 1.5 h to give exclusively the furo[3,2-d]pyrimidine-2,4(1H)-diones (5a–c) in 80–90% yields (Scheme 2). This conversion may also be completed in boiling pyridine (1.5 h).Substrates 3d showed a tendency to decompose when heated in N,N-diethylaniline and no tractable product could be obtained. A mixture of products 4 and 5 was obtained when the reaction was conducted in chlorobenzene in the presence of a small amount of N,N-diethylaniline. The ethers decomposed completely when heated in chlorobenzene in the presence of toluene-4-sulfonic acid. The formation of product 4 was unaffected when a radical initiator, azoisobutyronitrile (AlBN), was added to the reaction mixture.Only the one example each of the furo[3,2-d]pyrimidinedione 5a and the 6H-pyrano[3,2-d]pyrimidinedione 4a in a mixture of varying amounts was reported earlier by Otter et al.,2 the maximum yields reported for the compounds from different experiments being only 49% for 4a and 66% for 5a. The simple reaction conditions reported here seem to be general, as a number of furo- and pyrano-pyrimidines have been synthesised regioselectively in excellent yields, in each case exclusively one product being obtained.In addition the dimer of 4a reported by Otter et al. was not detected in the reaction mixture. We thank the CSIR (New Delhi) for financial assistance. One of us (U. D.) is grateful to U.G.C. (New Delhi) for a fellowship. Techniques used: UV, IR, 1H NMR, mass spectrometry References: 5 Schemes: 2 Received, 2nd January 1997; Accepted, 3rd June 1997 Paper E/7/00009J References 1 (a) K. C. Majumdar, R. N. De, A. T. Khan, S. K. Chattopadhyay, K. Dey and A. Patra, J. Chem. Soc., Chem. Commun., 1988, 777; (b) K. C. Majumdar and R. N. De, J. Chem. Soc., Perkin Trans. 1, 1989, 1901. 2 B. A. Otter, S. S. Saluja and J. J. Fox, J. Org. Chem., 1972, 37, 2858. 3 (a) K. C. Majumdar, A. T. Khan and R. N. De, Synth. Commun., 1988, 18, 1589; (b) K. C. Majumdar, D. P. Das and A. T. Khan, Synth. Commun., 1988, 18, 2027; (c) K. C. Majumdar, P. K. Choudhury and A. T. Khan, Synth. Commun., 1989, 19, 3249. 4 J. Zsindely and H. Schmid, Helv. Chim. Acta, 1968, 51, 1510. *To receive any correspondence (e-mail: kcm@klyuniv.ernet.in). Scheme 1 Reagents and conditions: i, Me2CO–K2CO3, reflux Scheme 2 Reagents and conditions: i, PhCl, reflux; ii, PhNEt2, 115 °C

ISSN:0308-2342    

DOI:10.1039/a700009j

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

N O NO2 Me 1 N O NH2 Me 2 N O NH Me 3 Ts i ii NO NH Me 5 N O N Me 4 Me iv Me Ts iii N O N R Me Me Cl R 5 + i 6(a–i) 7(a–i) PhOCH2 4-ClC6H4OCH2 4-MeC6H4OCH2 2,4-Cl2C6H3OCH2 2,4-Me2C6H3OCH2 3,5-Me2C6H3OCH2 4-NO2C6H4OCH2 H HOCH2 a b c d e f g h i R N O N Me R Me 7(a–g) N O Me 8(a–g) N R O Cl Me i O N O Me N Me R O – + 10 N O Me 12 8 N Me OH R Cl O O • • N O Me 11 H O R N Me N O Me 10a O N Me 7 • R 310 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 310–311 J. Chem. Research (M), 1997, 2068–2079 Studies on Amine Oxide Rearrangements: Regioselective Synthesis of Pyrrolo[3,2-f]quinolin-7-ones Krishna C.Majumdar,* Paritosh Biswas and Gour H. Jana Department of Chemistry, University of Kalyani, Kalyani 741 235, W.B., India A number of derivatives of the hitherto unreported pyrrolo[3,2-f]quinolin-7-one tricyclic system have been synthesised from 6-nitroquinolone by successive reduction, tosylation, methylation, detosylation, prop-2-ynylation and treatment with m-chloroperoxybenzoic acid.Earlier, Thyagarajan and co-workers reported a one-step process for the construction of the five-membered heterocyclic ring in benzo[b]thiophenes1 and indoles.2 The nitrogen heterocycles are obtained in almost quantitative yield by simply stirring a solution of the arylprop-2-ynylamine in dichloromethane at room temperature with 1 mol equiv. of m-chloroperoxybenzoic acid (m-CPBA). We subsequently reported3 the synthesis of 5,6-dihydro-4H-pyrrolo[3,2,1- ij]quinoline via this amine oxide rearrangement and more recently decided to see whether the five-membered pyrrole ring of the pyrroloquinolone system with a 3,4-double bond in the quinolone portion could be constructed via the aforesaid amine oxide rearrangement route.Here we report the results of this latter investigation. The 6-[N-(4-aryloxybut-2-ynyl)-N-methylamino]-1-methyl- 2-quinolones 7a–g required for this study were prepared in good yields from the reaction of 1-methyl-6-(N-methylamino)- 2-quinolone 5 with 1-aryloxy-4-chlorobut-2-ynes 6 (Scheme 2). Substrates 7h and 7i were similarly prepared from compound 5 by its reaction with propargyl bromide and 4-chlorobut-2-yn-1-ol respectively.Compound 5 was in turn prepared from 6-nitroquinolone4 through the sequence of reactions shown in Scheme 1. Treatment of the tertiary amine 7a with 1 mol equiv. of m-CPBA in dichloromethane at room temperature for 12 h afforded the pyrroloquinolone derivative 8a.Similar subjection of the remaining substrates 7b–i to the amine oxide rearrangement furnished the pyrroloquinolone derivatives 8b–g (Scheme 3). We failed to obtain any tractable product from substrate 7h. Substrate 7i also did not provide any pure product. The formation of the pyrroloquinolone derivatives 8 from the amines 7 is explicable2 by the initial formation of an N-oxide 10 which undergoes a [2s,3s] sigmatropic rearrangement [similar to a Meisenheimer rearrangement in a tertiary allyl (aryl) amine]5 to give an intermediate 10a (Scheme 4).*To receive any correspondence (e-mail: kcm@klyuniv.ernet.in). Scheme 1 Reagents and conditions: i, Fe powder and NH4Cl, heat; ii, toluene-4-sulfonyl chloride, pyridine, heat; iii, MeI, Me2CO, K2CO3, reflux; iv, glacial acetic acid, conc. H2SO4, heat Scheme 2 Reagents and conditions: i, Me2CO, K2CO3, NaI, reflux, 12 h Scheme 3 Reagents and conditions: i, m-CPBA, CH2Cl2, room temp., 12 h Scheme 4N N MeO R Me O Me 9(a–g) 8(a–g) i N O N OH Me Me N O Me N MeO OAc Me N O N OAc Me Me N O Me N O OAc Me O Cl 7i 15 14 13 i ii iii J.CHEM. RESEARCH (S), 1997 311 This undergoes a [3s,3s] sigmatropic rearrangement followed by ketol formation to give the ketol 12, acid-catalysed allylic rearrangement of which gives the final product 8. The m-chlorobenzoate group of the pyrroloquinolone derivatives 8a–g is easily replaced by a methoxy group (SN2 displacement) when compounds 8a–g are refluxed in absolute methanol for 2 h, providing a series of methoxy derivatives 9a–g (Scheme 5).Only a single product was obtained from the amine oxide rearrangement of each of the substrates studied, and in some cases it was possible to conclude from the 1H NMR spectra that this was the expected angularly fused product. However, in other cases the structures were difficult to confirm as the aromatic protons were not well separated. All the substrates except 7h and 7i studied so far contained an aryloxybut-2-ynyl group and consequently the rearranged product 8 as well as the methanolysis product 9 contained aryloxy aromatic protons.Substrates 7h and 7i did not give any isolable pyrroloquinolone. Thus in an attempt to synthesise a pyrroloquinolone devoid of any aryloxy appendage, compound 7i was converted into the methoxy derivative 15 by the route shown in Scheme 6. The 1H NMR spectrum of 15 exhibited two well separated ortho-coupled aromatic 1 H doublets (J 9.5 Hz) centred at d 7.32 asnd 7.55 as well as two 1 H doublets (J 10 Hz) at d 6.82 and 8.44 due to the quinolone p-bond protons.The presence of the two ortho-coupled aromatic protons at d 7.32 and 7.55 conclusively shows this product to be the angularly fused pyrroloquinolone. To our knowledge this is the first report of the synthesis of the pyrrolo[3,2-f ]quinolin-7-one ring system. The method described is extremely facile and mild, and its generality has been tested by the successful conversion of eight substrates (7a–g and 13) into the corresponding derivatives 8a–g and 14 regioselectively and in excellent yields.It is notable that the 3,4-double bond of the quinolone is totally unaffected by the peracid. The quinolone nitrigen is also unaffected, as the lone-pair availability is lowered by the adjacent carbonyl function. The present report is also an example of the application of an amine oxide rearrangement in heterocyclic substrates leading to polyheterocycles.We thank the CSIR (New Delhi) for financial assistance. One of us (P. B.) is grateful to U.G.C. (New Delhi) for a Junior Research Fellowship. Techniques used: UV, IR, 1H NMR, mass spectrometry, elemental analysis References: 8 Received, 9th April 1997; Accepted, 3rd June 1997 Paper E/7/02432K References cited in this synopsis 1 (a) K. C. Majumdar and B. S. Thyagarajan, J. Chem. Soc., Chem. Commun., 1972, 83; (b) K. C. Majumdar and B. S. Thyagarajan, Int. J. Sulfur Chem., 1972, 2A, 93; (c) K. C. Majumdar and B. S. Thyagarajan, Int. J. Sulfur Chem., 1972, 2A, 67; (d) B. Elosta, K. C. Majumdar and B. S. Thyagarajan, J. Heterocycl. Chem., 1973, 10, 107. 2 (a) J. B. Hillard, K. V. Reddy, K. C. Majumdar and B. S. Thyagarajan, Tetrahedron Ltt., 1974, 1999; (b) J. B. Hillard, K. V. Reddy, K. C. Majumdar and B. S. Thyaragajan, J. Heterocycl. Chem., 1974, 11, 369; (c) B. S. Thyagarajan and K. C. Majumdar, J. Heterocycl. Chem., 1975, 12, 43; (d) K. C. Majumdar and S. K. Chattopadhyay, J. Chem. Soc., Chem. Commun., 1987, 524. 3 K. C. Majumdar, S. K. Chattopadhyay and A. T. Khan, J. Chem. Soc., Perkin Trans. 1, 1989, 1285. 4 H. Balli and D. Schelz, Helv. Chim. Acta, 1970, 53, 1903. 5 K. C. Majumdar and G. H. Jana, J. Org. Chem., 1997, 62, 1506. Scheme 5 Reagents and conditions: i, MeOH, reflux Scheme 6 Reagents and conditions: i, Ac2O, NaOAc, heat; ii, m-CPBA, CH2Cl2, room temp., 12 h; iii, MeOH, reflux

ISSN:0308-2342    

DOI:10.1039/a702432k

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

OH CHO 1 O CN O 2 O N NH2 NC CN CN NH2 O N N NC CN NH2 CNCH2CN NH4OH 1 or 2 3 4 NH2 OH CN NH OH O NC O NH O O NC 9 11 H+ 2 CH3CO2NH4 CNCH2CO2R NH2 O CN OH CN N NH2 NH2 NC 8 10 CH3CO2NH4 NH2 NC CN H+ O N NH2 NH2 NC 12 NH O N NH2 NH2 NC 13 O 312 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 312–313 J. Chem. Research (M), 1997, 2101–2122 Reactions of 2-Oxo-2H-1-benzopyran-3-carbonitrile Conor N. O’Callaghan,* T. Brian H. McMurry, John E. O’Brien and Sylvia M. Draper University Chemical Laboratory, Trinity College, Dublin 2, Ireland Synthetic reactions of 2-oxo-2H-1-benzopyran-3-carbonitrile afford products which establish that partial or complete cleavage of the starting material occurs in the course of reaction.Benzopyran derivatives are useful starting materials for the preparation of polyheterocyclic compounds,2–4 but the products vary considerably according to the structure and reactivity of the parent benzopyran. The use in synthesis of the stable compound 2-oxo-2H-1-benzopyran-3-carbonitrile 2 (which is formed by reaction of salicylaldehyde 1 with alkyl cyanoacetates5) is now described.Some synthetic reactions of the bicyclic compound 2 have already been reported in the literature. Most of these reactions were carried out in the pre-NMR era; in some cases it was not possible to formulate the products, while in others the products were formulated incorrectly. It is now clear that the basic mistake was the assumption that, during reaction, the 2-oxo-2H-1-benzopyran structure remained essentially intact (as happens, for example, when 2-oxo-2H-1- benzopyran-3-carboxamide undergoes reaction4).In fact, our results show that the nitrile derivative 2 usually undergoes ring-opening (by fission of the 1,2 bond) and that fission of the 3,4-bond may also occur, resulting in cleavage of the molecule. This is well illustrated by the reaction of 2-oxo- 2H-1-benzopyran-3-carbonitrile 2 with malononitrile and ammonium acetate.A previous report states that this affords an inseparable mixture of (unformulated) products.6 The products formed are now identified as the tri- and tetra-cyclic compounds 3 and 4, both of which have been shown to be formed directly from the reaction of salicylaldehyde with malononitrile.2 The reaction of the bicyclic compound 2 with methyl cyanoacetate in the presence of ammonia or ammonium acetate affords the tricyclic product 11. (This product is also obtained from the reaction of 2 with ammonia or ammonium acetate alone, when the mechanism must involve disproportionation of 2.) Prior to purification of 11, when the crude product is first obtained, the 1H NMR spectrum shows that a monocyclic impurity is also present.This is presumed to be the pyridine derivative 9 but it is not isolable; in [2H6]dimethyl sulfoxide solution it slowly changes into the tricyclic product 11 (a change which takes place more rapidly in the presence of mineral acid).In the course of examining the reaction 2h9h11, we studied also the related reaction of ammonium acetate with the benzopyran derivative 8 (which represents the first isolable product formed by reaction of salicylaldehyde with malononitrile in 1:2 ratio). This reaction follows a similar pathway 8h10h12h13, but in this case it is possible to isolate the monocyclic pyridine intermediate 10. This is also converted, in the presence of acid, into a tricyclic product 13; presumably the imino group in the postulated intermediate 12 is hydrolysed during formation of 13.The reaction of 2 with 2-aminoprop-1-ene-1,1,4-tricarbonitrile 14 in the presence of ammonia has been reported to afford the simple addition compound 15,11 but the NMR spectrum is not reconcilable with the structure, and in fact the correct formulation of the product is 16. In a different type of reaction, the benzopyran 2 reacts with ketones and ammonium acetate to afford the bridged structure 20.Thus, with 3-oxobutanamide 17 (R=H, Rp=CONH2) and ammonium acetate, the amide derivative 20 (R=H, Rp=CONH2) is formed. In a related reaction, when the benzopyran 2 reacts with methyl acetoacetate and ammonium acetate, the main product is the ester derivative 20 (R=CO2Me, Rp=H). The molecular structure of this compound, as determined by X-ray diffraction, is shown in Fig. 1. This appears to be the first published example of an X-ray determination of a bridged structure of this general type.Crystal Structure Determination of 20 (R=CO2Me, Rp=H).·Data were collected on an Enraf-Nonius CAD-4 *To receive any correspondence.NC NH2 CN CN 14 2 + O O CN NC NH2 NC CN O O NC NH NC CN NH2 15 16 2 + RCH2COCH2R¢ O NH R¢CH2 R H CN O 20 17 J. CHEM. RESEARCH (S), 1997 313 diffractometer (Mo radiation, graphite monochromator, w–2y scans) at 20 °C. The crystal data and experimental parameters are given in Table 1. The final cell parameters were determined using the Celdim routine.It was not found necessary to apply decay or absorption corrections to the data. The data were reduced to give the number of unique reflections and those with |F|E4s|F| were used in structure solution and refinement. The structure was solved by automatic direct methods using SHELXS-86.15 The structure was refined by full-matrix least-squares analysis on F2 with SHELXL.16 The non-hydrogen atoms were refined anisotropically and all the hydrogen atoms were located from subsequent difference Fourier maps and refined with individual temperature factors to a final R value of 4.4%. Techniques used: IR, 1H NMR, 13C NMR, X-ray crystallography, elemental analysis References: 17 Appendix: Tables of atomic coordinates and equivalent isotropic displacement parameters, bond lengths and angles, anisotropic displacement parameters, and hydrogen coordinates and isotropic displacement parameters for 20 (R=CO2Me, Rp=H) Received, 3rd March 1997; Accepted, 3rd June 1997 Paper E/7/01462G References cited in this synopsis 2 C.N. O’Callaghan, T. B. H. McMurry and J. E. O’Brien, J. Chem. Soc., Perkin Trans. 1, 1995, 417. 3 C. N. O’Callaghan, T. B. H. McMurry, J. E. O’Brien, S. M. Draper and D. J. Wilcock, J. Chem. Soc., Perkin Trans. 1, 1996, 1067. 4 C. N. O’Callaghan, T. B. H. McMurry and J. E. O’Brien, J. Chem. Res., 1995, (S) 490; (M) 3001. 5 B. B. Dey and H. Dalal, J. Chem.Soc., 1923, 123, 3384. 6 H. Junek and F. Frosch, Z. Naturforsch., Teil B., 1971, 26, 1124. 11 H. Junek, Monatsh Chem., 1964, 95, 234. 15 G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467. 16 G. M. Sheldrick, SHELXL 93, Program for Crystal Structure Refinement, University of G�ottingen, G�ottingen, 1993. Table 1 Crystal data and structure refinement for 20 (R=CO2Me, Rp=H) Empirical formula C15H14N2O4 Formula weight 286.28 Temperature 293(2) K Wavelength 0.71069 Å Crystal system monoclinic Space group P21/c Unit cell dimensions a=13.445(2) Å a=90° b=12.449(2) Å b=108.57° c=8.918(3) Å g=90° Volume 1415.0(5) Å Z 4 Density (calculated) 1.344 g cmµ3 Absorption coefficient 0.099 mmµ1 F(000) 600 Crystal size 0.3Å0.5Å0.4 mm Theta range for data collection 1.60–21.98° Index ranges µ13shs13, 0sks13, 0sls9 Reflections collected 1866 Independent reflections 1728 [R(int)=0.0189] Refinement method Full-matrix least-squares on F2 Data/restraints/parameters 1728/0/246 Goodness-of-fit on F2 1.219 Final R indices [Ia2s(()] R1=0.0444, wR2=0.1074 R indices (all data) R1=0.0600, wR2=0.1132 Largest diff. peak and hole 0.198 and µ0.205 e ŵ3 Fig. 1 Molecular structure of methyl 12-cyano-9-methyl-11-oxo- 8-oxa-10-azatricyclo[7.3.1.02,7]trideca-2,4,6-triene-13-carboxylate 20 (R=CO2Me, Rp=H), showing the crystallographic numbering sy

ISSN:0308-2342    

DOI:10.1039/a701462g

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

S OHC R N S S R ortho-aminobenzenethiol DMSO, reflux 7 6 5 4 3a 7a 2 2¢ 3¢ 4¢ 5¢ 1 2 aR = H b R = Me c R = OMe d R = Br e R = Ph f R = NO2 2g R = CN S CI CHO 1i OHC S CHO 1h O2N N S CH2Ph Vilsmeier Haack N S R2 R1 N S N S R2 3 R1 = CHO, R2 = CH2Ph 4 R1 = CHO, R2 = H 5 R2 = CH2Ph 6 R2 = H ortho-aminobenzenethiol DMSO, reflux 2¢ 4¢ 1¢ 6¢ 9¢ 7¢ 8¢ 314 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 314–315 J. Chem. Research (M), 1997, 2001–2013 New Fluorescent 1,3-Benzothiazoles by the Reaction of Heterocyclic Aldehydes with ortho-Aminobenzenethiol Susana P.G. Costa,a Jo�ao A. Ferreira,b Gilbert Kirschc and Ana M. F. Oliveira-Campos*a aDepartamento de Qu�ýmica, Universidade do Minho, Campus de Gualtar, 4700 Braga, Portugal bDepartamento de F�ýsica, Universidade do Minho, Campus de Gualtar, 4700 Braga, Portugal cLaboratoire de Chimie Organique, Facult�e des Sciences, Universit�e de Metz, 57045 Metz, France Fluorescent thienyl-1,3-benzothiazoles 2 and phenothiazinyl-1,3-benzothiazoles 5 are synthesised in 60–80% yields, characterised by spectroscopic means and their fluorescence properties evaluated.Following our interest on synthesising reactive dyes1 and applying them to fibres or analogous systems, we decided to prepare fluorescent compounds, which are largely used in scientific and industrial areas, as fluorescent brightening agents for textiles and plastics, additives in textile dyeing, lasers and biological stains.2 The 1,3-benzothiazole moiety is present in many of the compounds currently used for these purposes. 1,3-Benzothiazoles are usually prepared from aldehydes3 or carboxylic acids4 by condensation with o-aminobenzenethiol and it was decided to follow this approach in the present work. The first series started with formylthiophenes 1 which were heated with ortho-aminobenzenethiol in DMSO for 30–60 min to afford the corresponding 2-(2-thienyl)- 1,3-benzothiazoles 2a–f in good yields (60–80%).The starting formylthiophenes were either commercially available (1a, 1b, 1d) or had to be prepared. From the nitration of 2-formylthiophene 1a, 5-nitro-2-formylthiophene 1f was obtained in 13% yield along with the 4-nitro derivative 1h (46%) as the major compound and they were separated by column chromatography. Formylation of 2-methoxythiophene under Vilsmeier–Haack conditions5 gave derivative 1c in 27% yield. Another compound was isolated from the reaction in 26% yield and was identified as compound 1i.6 5-Phenyl-2-formylthiophene 1e was obtained in 35% yield from 3-chloro- 3-phenylprop-2-enal by condensation with sodium sulfide and chloroacetaldehyde in DMF.7 Compound 2g was obtained by heating 2d with copper cyanide in DMF (15% yield).Using the same procedure we also investigated the reactivity of formylphenothiazines. For this purpose, formylation of N-benzylphenothiazine led to the aldehyde 3 in 45% yield, together with a by-product, the phenothiazine 4.Deprotection was observed during the formylation. Usually hydrogenation is the method of choice for debenzylation, but this has not previously been successful in this case.8 Condensation of the aldehydes with ortho-aminobenzenethiol gives the desired compounds 2a–f, 5, 6 and 9a–c in good yields. The 1H NMR spectra of the benzothiazoles showed the characteristic pattern corresponding to the homocyclic ring. The proton chemical shifts are not much influenced by the structure of the rest of the molecule and the observed chemical shifts are 0.4–0.6 ppm higher for 4- and 7-H as compared to 5- and 6-H.In the UV–VIS spectra, a bathochromic shift was observed for the thiophene series when R=H was replaced by a substituent, this effect being more pronounced when R=NO2. There is also an increase in the absorption intensity (e) as the substituents change from electron-withdrawing to electrondonating. The fluorescence properties of the benzothiazoles, namely fluorescence spectra, wavelengths of maximum fluorescence and fluorescence quantum yields were obtained.The quantum yields (f) were calculated using 9,10-diphenylanthracene in ethanol as standard (f=0.95)10 (Table 2). The best fluorescence quantum yields in ethanol were observed for 2-(2-thienyl)-1,3-benzothiazoles substituted at the 5p-position with phenyl (2e) or methoxy (2c) groups. These compounds show fluorescence in the blue region. The phenothiazinylbenzothiazoles 5 and 6, although having lower *To receive any correspondence.Table 2 UV absorption and fluorescence data for the 1,3-benzothiazoles 2a–g, 5, 6, 8 and 9a–c Absorption Fluorescence 1,3-Benzothiazole lmax/nm e lmax/nm e 2a 2b 2c 2d 2e 2f 2g 568 9a 9b 9c 316 331 347 329 359 376 342 304 307 282 297 302 318 22 800 23 200 23 200 23 100 31 800 18 900 20 200 28 000 22 600 30 900 19 800 22 200 24 800 397 406 417 400 426 454 402 527 534 315 365 371 369 0.14 0.39 0.55 0.05 0.63 0.007 0.10 0.22 0.19 0.004 0.01 0.02 0.12J.CHEM. RESEARCH (S), 1997 315 fluorescence quantum yields, show exceptionally large Stokes’ shifts with the wavelength of maximum fluorescence being displaced to the green region. To see how the introduction of a heterocyclic nucleus on the benzothiazole ring would affect the quantum yields, as opposed to a phenyl and a methyl substituent, 2-methyl-1,3-benzothiazole 8 and a series of known 2-substituted 1,3-benzothiazoles 9a–c [a R=H; b R=OMe; c R=Br) were prepared.Replacement of the methyl group in the 2-methyl-1,3-benzothiazole moiety by a phenyl or thienyl nucleus causes an increase in the quantum yield (0.004h0.01h0.14) and there is also a difference in the quantum yields of the substituted phenyl- and thienyl-1,3-benzothiazoles, as seen in Table 2. Compounds which exhibit fa0.5 can be considered interesting for further synthetic studies. This work was supported by JNICT (Portugal) through IBQF-UM and PRAXIS XXI (Portugal), project 2/2.1/QUI/ 44/94. A scholarship from JNICT/PRAXIS XXI to S.P. G. C. (Ci�encia/BD/2567/93-RM) and a grant for invited scientists (G. K.) from PRAXIS XXI are gratefully acknowledged. Techniques used: 1H and 13C NMR spectroscopy, mass spectrometry, UV–VIS, fluorescence spectrophotometry, elemental analysis Table 1: 13C NMR chemical shifts of the 1,3-benzothiazole ring for 2a–g Schemes: 3 References: 17 Figure 1: Fluorescence spectra of 2a–e and g Received, 17th April 1997; Accepted, 13th May 1997 Paper E/7/02605F References cited in this synopsis 1 J. N. I. R. Gomes, J. Griffiths, J. L. S. Maia, J. C. V. P. Moura and A. M. F. Oliveira-Campos, Dyes Pigm., 1991, 17, 269. 2 B. M. Krasovitski and B. M. Bolotin, Organic Luminescent Materials, VCH, Weinheim, 1988. 3 T. G Deligeorgiev, Dyes Pigm., 1990, 12, 243. 4 P. Savarino, G. Viscardi, E. Barni and R. Carpignano, Dyes Pigm., 1988, 9, 295. 5 S. Alumni, P. Linda, G. Marino, S. Santini and G. Savelli, J. Chem. Soc., Perkin Trans. 2, 1974, 1610. 6 O. Meth-Cohn and B. Narine, J. Chem. Res., 1977, (S) 294; (M) 3262 (Chem. Abstr., 1977, 88, 105040h). 7 G. Kirsch, D. Prim, F. Leising and G. Mignani, J. Heterocycl. Chem., 1994, 31, 1005. 8 R. J. Hall, A. H. Jackson, A. M. F. Oliveira-Campos and P. V. R. Shannon, J. Chem. Res., 1990, (S) 314; (M) 2501. 10 J. V. Morris, M. A. Mahaney and J. R. Huber, J. Phys. Chem., 19

ISSN:0308-2342    

DOI:10.1039/a702605f

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

O CH2R O R CH2R NC CN [H] 7 R NC CN O R NC CN N N NC OR¢ R OR¢ CN R HO N N NC OR¢ R OR¢ CN R 3 2 5 4 6 R¢OH–KOH O + R CH C CN CN –2H –H2O –2H R¢O– R¢O– CH2(CN)2 R¢OH–KOH a R = Ph b R = 4-ClC6H4 c R = 4-FC6H4 d R = 4-MeOC6H4 e R = 2-thienyl f R = 2-furanyl 1a R = Ph b R = 4-ClC6H4 c R = 4-FC6H4 d R = 4-MeOC6H4 e R = 2-thienyl f R = 2-furanyl CH2(CN)2 [H] Ph Ph 4-ClC6H4 4-ClC6H4 4-FC6H4 4-FC6H4 4-MeOC6H4 4-MeOC6H4 2-thienyl 2-thienyl 2-furanyl 2-furanyl Et Me Et Me Et Me Et Me Et Me Et Me a bc def ghij kl R R¢ 8a R = Ph b R = 4-ClC6H4 c R = 4-FC6H4 d R = 4-MeOC6H4 e R = 2-thienyl 316 J.CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 316–317 J. Chem. Research (M), 1997, 2014–2025 Synthetic Approaches towards 5H-Indeno[1,2-b]pyridines Nawal Mishriky,*a Fahmy M. Asaad,a Yehia A. Ibrahimb and Adel S. Girgisa aNational Research Centre, Dokki, Cairo, Egypt bChemistry Department, Faculty of Science, Cairo University, Giza, Egypt Reaction of the 2-arylmethylidene-2,3-dihydro-1H-inden-1-ones 1a–f with malononitrile in alcoholic KOH affords 2-alkoxy- 4-aryl-5H-indeno[1,2-b]pyridine-3-carbonitriles 2a–l and (2-arylmethyl-2,3-dihydro-1H-inden-1-ylidene)dicyanomethanes 6a–f.The reactions of a,b-unsaturated ketones with methylene compounds activated by a nitrile function, particularly malononitrile, have been the subject of many publications. Although the reaction was first investigated using sodium methoxide,1 other organic basic catalysts such as morpholine2 –4 or piperidine5,6 have been found to be useful in allowing the isolation of the mono-Michael adducts.Depending on the reaction conditions many interesting products were obtained. Thus, the reaction was used to synthesize 2-amino- 3-cyano-4H-pyrans,5,6 cyclohexane derivatives2,6–9 and pyridine analogues.6,9,10 *To receive any correspondence. Scheme 1J. CHEM. RESEARCH (S), 1997 317 In the present work the reaction of a number of 2-arylmethylideneindan- 1-ones 1a–f with malononitrile as a possible route for the synthesis of indenopyridinecarbonitrile derivatives was investigated.Thus, 1a–f were reacted with malononitrile in alcoholic KOH to give colourless products. Based on analytical and spectral data, the structure of these products was assigned either as 5H-indeno[1,2-b]pyridines 2a–l or the isomeric 9H-indeno[2,1-c]pyridines 3a–l. The isolated pyridines were established as being 2 rather than 3 on the basis of their independent synthesis via base catalysed addition of indan-1-one to arylmethylidenemalononitriles 8 in alcoholic KOH solution.The formation of 2a–l, presumably, takes place via Michael addition of the active methylene compound to the b-carbon of the unsaturated system affording the intermediate adducts 4. Alkoxide attack on one of the nitrile groups, followed by dehydration and subsequent dehydrogenation, affords the condensed pyridines 2. A by-product 6a–f was isolated in each case, the structure of which was based on IR, 1H and 13C NMR spectral and elemental analytical data.The formation of 6 presumably takes place through the reduction of the arylmethylidenes 1 or 5 and may be concerted with the dehydrogenation process that gives the indenopyridines 2 or 3. Techniques used: Elemental analysis, IR, 1H and 13C NMR References: 19 Table 1: Physical properties of the products Table 2: Spectroscopic properties of the products Received, 10th December 1996; Accepted, 28th May 1997 Paper E/6/08311K References cited in this synopsis 1 P.A. Kohler and B. L. Souther, J. Am. Chem. Soc., 1922, 44, 2093. 2 J. Mirek, Chem. Scr., 1988, 28, 295. 3 A. M. Shestopalov, V. K, Promonenkov, Yu. A. Sharanin, L. A. Rodinovskaya and S. Yu. Sharanin, Zh. Org. Khim., 1984, 20, 1517. 4 P. Victory, J. I. Borrell, A. V. Ferran, C. Seoane and J. L. Soto, Tetrahedron Lett., 1991, 32, 5375. 5 J. L. Soto, C. Seoane, N. Martin and L. A. Blanco, Heterocycles, 1983, 20, 803. 6 J. L. Soto, C. Seoane and J. A. Ciller, An. Quim., Ser. C, 1980, 76, 281 (Chem. Abstr., 1981, 94, 192085s). 7 S. K. El-Sadany, S. M. Sharaf, A. I. Darwish and A. A. Youssef, Indian J. Chem., 1991, 30B, 567. 8 M. M. Al-Arab, H. D. Tabba, B. S. Ghanem and M. M. Olmstead, Synthesis, 1990, 1157. 9 N. Mishriky, F. M. Asaad, Y. A. Ibrahim and A. S. Girgis, Recl. Trav. Chim. Pays-Bas, 1994, 113, 35. 10 M. M. Al-Arab, J. Heterocycl. Chem., 1989, 26, 1665.

ISSN:0308-2342    

DOI:10.1039/a608311k

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

N N NH2 Me Ph 1 O Ph X NMe2 2 N N Me NH Ph O Ph X 3 N N Me NH2 Ph X 4 Ph O N N Me N Ph Ph X 5 N N Me Ph X 6 Ph N a X = H b X = CN 2–6 N N Me NH2 Ph 1 PhCH C CN CN 7 CN CN EtO N N Me N Ph CN 8 N N Me N NH2 Ph CN 9 H H Ph NH2 or N N Me NH2 CN Ph CN 10 N N Me NH NC Ph CN 11 or N N Me N Ph CN 12 N N Me N NH2 Ph CN 13 NH2 N N NH2 Me Ph 1 N N NH2 Me Ph 14 NaNO2 HCl ON CH2(CN)2 EtOH/pip H2N CN CN CN N N N N N Me Ph NH2 NH2 N N NH2 CN N N Me Ph NH2 15 16 17 CN CN 318 J. CHEM. RESEARCH (S), 1997 J.Chem. Research (S), 1997, 318–319 J. Chem. Research (M), 1997, 2026–2038 Studies with Condensed Azines: New Routes to Pyrazolo[3,4-b]pyridines and Pyrrolo[3,2-b]pyridines Saleh M. Al-Mousawi, Kamini Kaul, Mohammad A. Mohammad and Mohamed H. Elnagdi* Department of Chemistry, Faculty of Science, University of Kuwait, P.O. Box 5969, Safat 13060, Kuwait Several condensed pyrazole derivatives are obtained from the reaction of 3-methyl-1-phenylpyrazol-5-amine (1) with a,b-unsaturated ketones, a,b-unsaturated nitriles and isothiocyanates.In conjunction with our previous interest in the chemistry of azoloazines,5,6,7 we report here the novel syntheses of pyrazolo[ 3,4-b]pyridines and pyrrolo[3,2-b]pyridines. We found that 3-methyl-1-phenylpyrazol-5-amine (1) reacts with 1-phenyl-3-dimethylaminoprop-2-en-1-ones 2a,b in the presence of zinc chloride and pyridine, respectively, to yield addition products with the elimination of dimethylamine and water.The products can thus be formulated as 5 or the isomeric structure 6. Structure 6 was established based on 1H NMR data and NOE experiments. NOE difference experiments showed that the methyl group and pyridine H-4 interact through space. Thus, irradiating the methyl signal at d 2.62 and 2.68 enhanced the pyridine H-4 signal at d 8.45 and 9.07 in 6a and 6b respectively. Moreover, when 1 and 2a were refluxed in ethanol, compound 4a was isolated in good yield. It could then be cyclised to 6a on fusion with ZnCl2.Compound 1 also reacted with benzylidenemalononitrile (7) in refluxing pyridine to yield an addition product which then underwent auto-oxidation to give 8 or the isomeric structure 9. Again, structure 8 was established based on the shielding effect of the methyl signal by the aromatic ring current and by NOE experiments. Thus irradiating the methyl signal at d 1.86 little enhanced the phenyl protons at d 7.21 while no enhancement of the NH2 protons was observed.The observed small effect is perhaps due to the existence of phenyl o-H’s out of plane as shown in structure (8). The observation that the methyl protons are shifted upfield to d 1.86 (expected position is ca. d 2.45) further supports this conclusion. Compound 1 also reacted with ethoxymethylidenemalononitrile to yield a product that may be formulated as acyclic 10 and 11 or cyclic 12 and 13. 1H NMR revealed an absence of any signal for a pyrazole H-4 and thus the acyclic form 11 was excluded. 13C NMR indicated the presence of only one CN carbon at d 109.85 and thus the acyclic form 10 could also be excluded. NOE difference experiments showed no interaction between the methyl protons at d 2.45 and the 6-H pyridine proton at d 8.48. It showed in contrast that the methyl protons and amino protons are proximal. Thus irradiating the methyl signal at d 2.45 enhanced the amino proton signal at d 5.8 and vice versa. Hence structure 12 was excluded and structure 13 was established.When the same reaction was carried out in refluxing ethanol for 2 h, compound 11 was formed instead of 13. 1H NMR revealed the presence of the pyrazole H-4 signal at d 6.33. Compound 11 was cyclised to give 13 on refluxing in ethanol for a few more hours. Thus structure 13 was further established. *To receive any correspondence.N N Me NH2 Ph 1 O Ph N C S MeCN N N Me Ph NH NH O Ph S N N Me Ph N S NHCOPh 18 19 Br2 AcOH N N Me Ph NH X Y Z X = OEt X = NMe2 20a Me OEt O O N O OR Me H NH2 N MeO O Me H N H Ph CN O a R = Me b R = Et 21 H2NCH2CN NaOMe N MeO O Me H N H O CN Ph 23 24 CN CO2Et Ph 2 N MeO O Me Me N OMe CN Ph 25 J. CHEM.RESEARCH (S), 1997 319 Attempted diazotisation of 1 gave the nitroso derivative 14 which reacted with malononitrile to yield a product of molecular formula C16H12N8. The same product was also obtained by reacting 14 with the malononitrile dimer 15. It was thus assumed that malononitrile first dimerises under the reaction conditions, which then condenses with 14 to yield a product that can be formulated as 16 or isomeric 17.Structure 17 was established on the basis of 13C NMR which revealed the presence of only one CN signal. Moreover, compound 17 was recovered almost unreacted when boiled in acetic acid: a condition expected to effect cyclisation of 16 into 17. Compound 1 also reacted with benzoyl isothiocyanate (prepared in situ) in acetonitrile to give the thiourea derivative 18.Compound 18 on treatment with bromine in acetic acid gave pyrazolo[3,4-d]thiazole 19. The fact that 1 reacted with 2a,b, 7 and nitrous acid at C-4 while reaction with benzoyl isothiocyanate and ethoxymethylidenemalononitrile occurred preferentially at the exocyclic amino group can be interpreted as follows. Firstly reaction with nitrous acid was conducted in acid solution. Under such conditions, the exocyclic amino group is protonated and the attacking reagent is thus directed to C-4.For the reactions with 2a,b, ethoxymethylidenemalononitrile and benzoyl isothiocyanate, we believe that both the exocyclic amino and C-4 are potential sites for attack, with the former being more reactive. Thus in reaction with benzoyl isothiocyanate, the addition at the exocyclic amino is irreversible, and thus the reaction product with the amino function was isolated. In reactions with 2a,b and 7, the reaction at the exocyclic amino group is reversible while the one at C-4 is irreversible.Thus the reaction is thermodynamically controlled and the products are exclusively those of addition at C-4. Although adducts 20a,b seem to be structurally related, the fact that EtOµ is a better leaving group than NMe2 has resulted in ready elimination of EtOµ from the adduct 20a, leading to the formation of 11, while reaction leading to 3 will revert to the starting material. Methyl 4-amino-2-methyl-1H-pyrrole-3-carboxylate (21a) was generated in situ via reacting ethyl acetoacetate with aminoacetonitrile in sodium methoxide solution as has been described earlier8 (21a was formed instead of 21b due to transesterification in methanol).The pyrroleamine 21a reacted with ethyl benzylidenecyanoacetate 22 to yield a product that may be formulated as 23 or the isomeric 24. This compound underwent methylation with methyl iodide to give the dimethyl derivative 25, the structure being confirmed by NOE which revealed steric interaction between the methyl signal at d 2.66 and the N-methyl signal at d 3.08 and the phenyl protons at d 7.53. This work was financed by the University of Kuwait under research grant Sc 080. We are grateful to the general facility projects in the Department of Chemistry for the analytical and spectral measurements. Techniques used: IR, NMR, (1H, 13C, NOE) and microanalysis References: 8 Received, 3rd April 1997; Accepted, 30th May 1997 Paper E/7/02276J References cited in this synopsis 5 M. H. Elnagdi, M. R. H. Elmoghayer and K. U. Sadek, Adv. Heterocycl. Chem., 1990, 48, 223. 6 M. H. Elnagdi, N. Al-Awadi and A. W. Erian, Comprehensive Heterocyclic Chemistry II, ed. A. R. Katritzky and C. W. Rees, Elsevier, Amsterdam, 1996, volume 7, p. 431 and references cited therein. 7 A. El-Enzy, B. Al-Saleh and M. H. Elnagdi, J. Chem. Res., 1997, (S) 4; (M) 0110. 8 G. H. Birnberg, W. J. Fanshawe, G. D. Francisco and J. W. Epstein, J. Heterocycl. Chem., 1995, 32, 1293.

ISSN:0308-2342    

DOI:10.1039/a702276j

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

OH Cl CH C CN X Ar + Cl O NH2 X Ar Cl O N Ar NH O HCO2H Cl O N CN Ar Cl O NHCOMe CN Ar Cl O N Ar NH O Me 4 5 COMe COMe + 6 1 2 3 7 3 h Ac2O 30 min 3b MeCN HCl gas HCONH2 a Ar = C6H4Me- p, X = CN b Ar = C6H4Me- p, X = CO2Et O NH2 CN Ar Cl 3a (Ar = C6H4Me- p) O N CN Ar Cl 8 HC(OEt)3 O N Ar Cl 10 O N CN Ar Cl 9 piperidine NH3 O N Ar Cl 11 c 4-MeC6H4NH2 d NH2NH2•H2O a BunNH2 b PhCH2NH2 N R NH a R = Bun b R = PhCH2 c R = C6H4Me- p d R = NH2 HCONH2 1 2 3 4 6 10 CH OEt N NH2 CH NH2 EtOH 320 J.CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 320–321 J. Chem. Research (M), 1997, 2039–2048 Activated Nitriles in Heterocyclic Synthesis: Synthesis of Pyrano[2,3-d]pyrimidine and Pyrano[3,2-e][1,2,4]triazolo[1,5-c]pyrimidine Derivatives Ahmed M. El-Agrody,* Hussein A. Emam, Mamdouh H. El-Hakim, Mohsen S. Abd El-latif and Ashraf H. Fakery Department of Chemistry, Faculty of Science, Al-Azhar University, Nasr City, Cairo, Egypt Several new naphtho[2p,1p:5,6]pyrano[2,3-d]pyrimidines have been synthesized via hydrazinolysis of a 2-ethoxymethylideneaminonaphtho[1,2-b]pyran; polysubstituted pyrano[3,2-e][1,2,4]triazolo[1,5-c]pyrimidines have also been prepared.The considerable biological and medicinal activity of fused 4H-pyrans has stimulated much research in this field.1–3 In continuation of our previous work4–6 on the synthesis of fused pyrans using enaminonitriles, we report here the synthesis of a variety of new heterocyclic compounds.Thus condensation of various substituted a-cyanocinnamonitriles 1a,b with 4-chloro-1-naphthol 2 in ethanolic piperidine afforded 1:1 adducts.5,7,8 Structure 3 (Scheme 1) was established on the basis of the 1H NMR spectra which showed 7-H at d 5.1 (3a) and at d 5.4 (3b).5 The increased chemical shift for this signal, compared to the expected value (d 4.0–5.0) for such protons, can be attributed to the deshielding effect of the diamagnetic current of the naphthyl, aryl and allylic p-electrons.8–10 The UV spectrum of 3a revealed a weak shoulder,11 characteristic for a 4H-pyran at lmax (CHCl3) 275 (log e 4.7).Interaction of 2-amino-6-chloro-4-(p-tolyl)-4H-naphtho- [1,2-b]pyran-3-carbonitrile 3a with acetic anhydride for 30 min afforded the N-acetyl 4 and N,N-diacetyl derivatives 5, while heating of 3a with acetic anhydride under reflux for 3 h afforded the naphthopyranopyrimidin-8-one derivative 6. Structure 6 is supported by an independent synthesis of the same product from 3b and acetonitrile in the presence of HCl gas12 (Scheme 1).Structures 4–6 were established by spectral data and analogy with our previous work.5 An attempted cyclization of 4 in ethanolic piperidine to give 6 failed.5 Treatment of 3a with formic acid gave the naphthopyranopyrimidin- 8-one derivative 7. The structure of 7 was supported by an independent synthesis from 3b and formamide (Scheme 1). Treatment of 3a with triethyl orthoformate in acetic acid at reflux gave the corresponding ethoxymethylideneamino derivative 8 (Scheme 3), ammonolysis of which in methanol at room temperature afforded the open-chain product 9.Treatment of 9 with ethanolic piperidine caused cyclization to yield the pyrimidine derivative 10, the structure of which was supported by its independent synthesis from 3a and formamide (Scheme 3). Reaction of 8 with various amines in ethanol at room temperature yielded the pyrimidine derivatives 11a–c, while with hydrazine hydrate, the naphtho- [2p,1p:5,6]pyrano[2,3-d]pyrimidine derivative 11d was obtained (Scheme 3).When 8 was treated with phenylhydrazine in ethanol at room temperature, an addition product formed, from which elimination of ethyl formate phenylhydrazone gave the enaminonitrile 3a,14 while, with hydrogen sulfide, an addition product 12 formed, in which the hydrogen sulfide added into the cyano group only. Attempted cyclization of 12 in ethanolic piperidine to give 13 failed (Scheme 4).*To receive any correspondence. Scheme 1 Scheme 3O N CN Ar Cl CH OEt 8 (Ar = C6H4Me- p) O Cl N H CH N H NH OEt Ph CN PhNHNH2 O NH2 CN Ar Cl 3a O N C Ar Cl CH OEt 12 NH2 S O N Ar Cl 13 NH S H2S Ar –PhNHN CH-OEt J. CHEM. RESEARCH (S), 1997 321 Interaction of 11d with triethyl orthoformate or formic acid afforded the naphtho[2p,1p:5,6]pyrano[3,2-e][1,2,4]triazolo[ 1,5-c]pyrimidine derivative 14a, while with acetic acid or acetyl chloride the respective 2-methyl derivative 14b was obtained.Reaction of 11d with chloroacetyl chloride and trichloroacetonitrile at reflux yielding the corresponding 2-chloromethyl 14c and 2-trichloromethyl 14d derivatives respectively, while with ethyl cyanoacetate and benzoyl chloride the 2-cyanomethyl 14e and 2-phenyl 14f derivatives were obtained (Scheme 5). Treatment of 11d with diethyl oxalate in ethanol at reflux yielded the 2-ethoxycarbonyl derivative 14g (Scheme 5). Treatment of 11d with ethyl chloroformate in dry benzene afforded a 1:1 adduct 16, while heating of 11d with ethyl chloroformate under reflux for 3 h yielded a 1:2 adduct 18.The formation of 16 is assumed to proceed via interaction of 11d with ethyl chloroformate with elimination of HCl to yield 15, which then cyclizes into 16 with elimination of ethanol. However, 18 is assumed to be obtained via formation of a bis(ethoxycarbonyl) derivative 17, which cyclizes into 18 with elimination of ethanol (Scheme 6).Techniques used: IR, UV, 1H NMR, 13C NMR, MS, microanalysis References: 14 Schemes: 6 Table 1: Characterization data for newly synthesized compounds Received, 12th December 1996; Accepted, 2nd June 1997 Paper E/6/08348J References cited in this synopsis 1 J. Bloxham, C. P. Dell and C. W. Smith, Heterocycles, 1994, 38, 399. 2 A. A. Elagamey and F. M. A. El-Taweel, Indian J. Chem., 1990, 29B, 885. 3 G. M. Cingolani, F. Gualtieri and M. Pigini, J. Med. Chem., 1969, 12, 531. 4 A. M. El-Agrody, J. Chem. Res. (S), 1994, 50. 5 A. M. El-Agrody, J. Chem. Res. (S), 1994, 280. 6 A. M. El-Agrody and S. M. Hassan, J. Chem. Res. (S), 1995, 100. 7 A. A. Elagamey, S. Z. Swillim, F. M. A. El-Taweal and M. H. Elnagdi, Collect. Czech. Chem. Commun., 1988, 53, 1534. 8 M. H. Elnagdi, A. H. H. Elghandour, M. K. A. Ibrahim and I. S. A. Hafiz, Z. Naturforsch., Teil B, 1992, 47, 572. 9 P. Ropiteau and P. Maitte, Bull. Soc. Chim. Fr., 1969, 1715. 10 A. M. Islam, A. M. Sh. El-Sharief, F. A. Aly, A. H. Bedair and A. M. El-Agrody, Indian J. Chem., 1981, 20B, 924. 11 J. Walinsky and H. S. Hauer, J. Org. Chem., 1969, 34, 3169. 12 K. G. Dave, C. J. Shishoo, M. B. Devani, R. Kalyanaraman, S. Ananthan, G. V. Ullas and V. S. Bhadit, J. Heterocycl. Chem., 1980, 17, 1497. 13 B. Willhalm, A. F. Thomas and F. Gautschi, Tetrahedron, 1964, 20, 1185. 14 G. Tacconi, G. Gatti, G. Desimoni and V. Messori, J. Prakt. Chem., 1980, 322, 831. Scheme 4 Scheme 5 Scheme 6

ISSN:0308-2342    

DOI:10.1039/a608348j

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

N N Me N N N N H R¢ R N N Me N N O N H Ph N N Me N N NH R R R¢ N N Me N N NH2 R N N Me NHNH2 1 3 5 2 8 N N Me N N R 7 S HN O R¢ R¢CHO RCOCl AcOH HCHO R¢–HN2 HSCH2CO2H RCOCH2CN N N Me N N NHSO2R C6H4Me- p 4 N N Me N N N R 6 R¢ RSO2Cl EtOH Ph C6H4Br- p C6H4Cl- p C6H4Me- p 2 R a b c d e H Me Et CH2Cl Ph 3 R Ph C6H4Me- p 4 R a b c d a b c d Ph C6H4Br- p C6H4Cl- p C6H4Me- p 5-7 R C6H4Cl- p Ph C6H4OMe- p C6H4Cl- p R¢ a b a b c d e Ph Ph Ph C6H4Br- p C6H4Br- p 8 R Me Ph C6H4Me- p Ph C6H4NO2- p R¢ RCO2H R¢CHO 322 J.CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 322–323 J. Chem. Research (M), 1997, 2049–2061 Studies on the Synthesis and Cyclization Reactions of 2-(5-Amino-3-arylpyrazol-1-yl)-3-methylquinoxalines Hassan A. El-Sherief,* Abdalla M. Mahmoud and Ahmed A. Ismaiel Chemistry Department, Faculty of Science, Assiut University, Assiut, 71516, Egypt A series of 2-(5-amino-3-arylpyrazol-1-yl)-3-methylquinoxalines (2a–d) has been synthesized by the condensation of 2-hydrazino-3-methylquinoxaline (1) with substituted benzoylacetonitriles and converted into the corresponding 3,4-diaryl-1-(3-methylquinoxalin-2-yl)-4,8-dihydro-1H-pyrazolo[3,4-e][1,4]thiazepin-7(6H)-ones (7a–d) and 2-(3-aryl- 4,5,6,7-tetrahydro-5-alkyl/aryl-1H-pyrazolo[3,4-d]pyrimidin-1-yl)-3-methylquinoxalines (8a–e).Quinoxaline derivatives have been found to be biologically active compounds having antibacterial, antifungal, anticancer, antiinflammatory, antidepressant, anthelmintic and herbicidal properties.1–3 Likewise, pyrazole derivatives are reported to have antibacterial, antifungal and other biological activity.4–7 In view of the above interest in these compounds and in continuation of our studies on the cyclization of hydrazino heterocyclic compounds we have investigated 2-hydrazino-3-methylquinoxaline in ring-closure reactions with substituted benzoylacetonitrile under different reaction conditions.Condensation of 2-hydrazino-3-methylquinoxaline (1) with substituted benzoylacetonitriles either in boiling ethanol or by fusion led to the formation of 2-(5-amino-3-arylpyrazol- 1-yl)-3-methylquinoxalines (2) (Scheme).Condensation of the 3-phenylpyrazolyl derivative 2a with formic, acetic or propionic acid afforded the corresponding N-acyl derivatives 3a–c. Compounds 3b,d,e were also obtained on treatment of 2a with acetyl, chloroacetyl and benzoyl chloride11 respectively. Refluxing of the p-tolyl derivative 2d with arenesulfonyl chlorides12 in chloroform containing anhydrous K2CO3 provided the corresponding N-arylsulfonyl derivatives 4a,b.Condensation of 2 with aromatic aldehydes either in acetic acid or in toluene gave 2-(4-arylmethylidene - 5-imino-3-arylpyrazol-1-yl)-3-methylquinoxalines (5a–d), while in ethanol containing a few drops of piperidine, as a catalyst, the corresponding Schiff’s bases (6a–d) were the sole isolable products.15 Condensation of 5 with sulfanylacetic acid in boiling toluene gave 3,4-diaryl-1-(3-methylquinoxalin-2-yl)-4,8- dihydro-1H-pyrazolo[3,4-e][1,4]thiazepin-7(6H)-ones (7a–d).Interestingly, condensation of 6 with sulfanylacetic acid under the same reaction condition gave the same products 7. We also investigated the behaviour of 2 as a bifunctional nucleophile with formaldehyde and appropriate amines in order to study the reactivity at the 4- and 5-positions of the pyrazole moiety. When 2a,b were treated with formaldehyde and primary amines in boiling ethanol only one pure product *To receive any correspondence (e-mail: assiut@frcu.eun.eg). SchemeJ.CHEM. RESEARCH (S), 1997 323 8 was obtained. This could be formed via a double Mannich reaction.17 Techniques used: Elemental analysis, IR, 1H NMR, mass spectrometry, TLC References: 17 Schemes: 3 Tables: 3 (Yields, mps, spectral and analytical data for 2–8) Received, 5th June 1996; Accepted, 2nd June 1997 Paper E/6/03951K References cited in this synopsis 1 Y.Kurasawa and A. Takad, Heterocycles, 1986, 24, 2321. 2 Y. Kurasawa, M. Muramatsu, K. Yamazaki, S. Tajima, Y. Okamoto and A. Takada, J. Heterocycl. Chem., 1986, 23, 1379, 1391. 3 G. Skata, K. Makino and Y. Kurasawa, Heterocycles, 1988, 27, 2481. 4 G. Vertuani, P. Giori, M. Guarneri and G. P. Sarto, J. Pharm. Sci., 1985, 74, 1013. 5 P. Giori, T. Poli, C. B. Vicentini, M. Manfrini, M. Guarneri and V. Brandolini, Farmaco, Ed. Sci., 1985, 40, 795. 6 C. B. Vincentini, T. Poli, M. Manfrini, M. Guarnerim, P. Giori and V. Brandolini, Farmaco, Ed. Sci., 1987, 42, 133. 7 C. B. Vicentini, T. Poli, A. C. Veronese, V. Brandolini, M. Manfrini, M. Guarneri and P. Giori, Pestic. Sci., 1989, 27, 77. 11 C. B. Vicentini, A. C. Veronese, P. Giori, B. Lumachi and M. Guarneri, Tetrahedron, 1990, 46, 5777. 12 G. Szilagyi and P. Dvortsak, Monatsh. Chem., 1989, 120, 131. 15 L. Jennig, J. Hofmann, M. Alva-Astudillo and G. Mann, J. Prakt. Chem., 1990,l 332, 351. 17 M. Tramontini and L. Angiolini, Tetrahedron, 1990, 46, 1791.

ISSN:0308-2342    

DOI:10.1039/a603951k

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

NH2 Et C Me NH2 C N H Me C N Me MeCN(g) NH2 Et 1 2 3 4 5 6 C Me NH • C Me NH 7 8 324 J. CHEM. RESEARCH (S), 1997 J. Chem. Research (S), 1997, 324–325† The Enthalpy Changes in the Course of Ethylamine Decomposition on a Ni(111) Surface† Fereydoon Gobal* and Saied Azizian Department of Chemistry, Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran The BOC-MP method is capable of calculating the enthalpies of various adsorbates in the catalytic decomposition of ethylamine on Ni(111) with results in good agreement with the experiments and superior to the extended H�uckel approximation predictions.Surface-sensitive spectroscopic methods are capable of providing extensive information regarding the structure of observed intermediates and reaction mechanisms. However, little information about the energies involved in these processes is provided. The present study applies the method of bond order conservation–Morse potential analysis1 (BOCMP) to investigate the heat of adsorption of ethylamine and the enthalpies of the possible intermediates in the decomposition of this species to acetonitrile and hydrogen on a Ni(111) surface.This process has been studied in some detail by Somorjai et al.2 where the methods of temperature programmed desorption (TPD) and high resolution electron energy loss spectroscopy (HREELS) were employed. It has been concluded that the dehydrogenation starts by an a-H·C cleavage, and the subsequent dehydrogenation of the ensuing MeCNH2 (2) and MeCNH (4) species gives rise to MeCN.On the basis of the TPD and HREELS results, the enthalpies of all the species were calculated (Table 1). In a further endeavour, Somorjai et al.3 attempted to calculate the enthalpies by the extended H�uckel method with the inclusion of a repulsive correction4 for various pairs of adsorbate atoms but ignoring the repulsion between the metal and adsorbate (Table 1). Although the treatment reproduces the trend, it largely over-estimates the enthalpies.We have employed the BOC-MP method to calculate the heats of adsorption of the surface species proposed by Somorjai.2,3 Table 2 shows the values of the gas phase bond energies (D) and the heats of atomic and molecular chemisorption (Q) calculated using the equations in the appendix of ref. 5 neglecting the destabilizing/stabilizing effects of the changes of the surface coverages of the adsorbates.6 From these results and using eqn.(1) the enthalpies were calculated and the results are presented in Table 1. In eqn. (1), P and R refer to the products and the reactant [MeCH2NH2(g)] respectively. DH=µ[S(Q+D)PµS(Q+D)R] (1) The agreement with the experimental results is very good and the deviations never exceed 0.3 eV except for the case of the acimidoyl group 4 where the BOC-MP analysis gives a highly under-estimated value. It must be emphasized that the reported enthalpy of 4 is not an experimental finding and is calculated on the basis of bond energies.On the basis of the BOC-MP analysis it seems that 4 is unlikely to be the intermediate. This intermediate has been proposed2 on the basis of the HREELS peaks at 1350 and 3300 cmµ1 assigned to the C�N·H structure adsorbed on the surface via C and N and by comparison with the corresponding organometallic compound. 2 Although this structure with the C�N ‘softened’ by adsorption may be present on the surface, it is probably not the one taking part in the reactions and desorbing as MeCN in the course of a TPD run.It seems that the interaction with the surface which relaxes the double bond should strengthen the N·H bond and shift it to higher wavenumbers, yet the reverse has been observed. Assuming structure 7, the enthalpy of adsorption was calculated (Table 1). Considering the structure 8 where the C·N bond has been somewhat strengthened, the enthalpy is around µ1.41 eV which is far better than the H�uckel value.In this structure the C·N bond order is certainly higher than that in 7 and could possess the stretching frequency around 1350 cmµ1, midway between that of C·N (ca. 1100 cmµ1) and that of C�N (ca. 1650 cmµ1). In fact, owing to the exothermicity of the surface reactions, the enthalpy of this species must lie in *To receive any correspondence (e-mail: Gobal@alborz.sharif.ac.ir). †This is a Short Paper as defined in the Instructions for Authors, Section 5.0 [see J.Chem. Research (S), 1997, Issue 1]; there is therefore no corresponding material in J. Chem. Research (M). Table 1 Enthalpies of the gas phase (g) and adsorbed (a) species Species DH (BOC-MP)/ eV DH (exp·)/ eVa DH (ext· H�uckel)/ eVa 123 +2H(a) 4+3H(a) 5+4H(a) 6+4H(a) 6+2H(a)+H2(g) 6+2H2(g) 0.00 µ0.86 µ1.12 0.66 (µ1·86) µ1.85 µ1.03 µ0.08 0.87 0.00 µ0.78 µ1.04 µ1.65b µ1.72 µ0.82 0.17 1.17 0.00 µ1.71 µ2.00 µ4.08 µ4.79 µ2.37 µ0.53 1.31 aRef. 3. bCalculated on the basis of experimental bond energies.2 Table 2 Heat of adsorption (Q) and total bond energies in the gas phase (D) and chemisorbed state (Q+D) on Ni(111) Species D/eV Q/eV Q+D/eV C NH2345678 H2(a) H2(g) ——— 35.43 27.36 25.93 25.54 25.54 25.93 23.93 4.51 4.51 7.42 5.85 2.73 0.86 3.73 0.65 0.82 — 3.17 2.73 0.30 — 7.42 5.85 2.73 36.29 31.09 26.58 26.36 25.54 29.10 28.66 4.81 4.51 Fig. 1J. CHEM. RESEARCH (S), 1997 325 the range µ1.12 to µ1.85 eV (Fig. 2). The calculated value for structure 8 is well within this range.Table 3 compares the heat of adsorptions of ethylamine and acetonitrile in both n1- and n2-coordinations where again the values obtained by the BOC-MP method are very close to the experimental values and the method is by far superior to the extended H�uckel approximation. We believe that the good agreement between the BOC-MP-based calculation and the experimental findings stems from the use of fairly accurate atomic heats of adsorption and dissociation energies used in the calculations. Received, 17th January 1997; Accepted, 12th May 1997 Paper E/7/00408G References 1 E. Shustorovich, Adv. Catal., 1990, 37, 101. 2 D. E. Gardin and G. A. Somorjai, J. Phys. Chem., 1992, 96, 9424. 3 P. D. Ditlevsen, D. E. Gardin, M. A. Van Hove and G. A. Somorjai, Langmuir, 1993, 9, 1500. 4 A. B. Anderson, R. W. Grimes and S. Y. Hong, J. Phys. Chem., 1987, 91, 4245. 5 E. Shustorovich, Surface Science, 1992, 279, 355. 6 S. Azizian and F. Gobal, Langmuir, submitted for publication. Fig. 2 Enthalpies of the surface reactions Table 3 Heat of adsorption (Q) Species Q (BOC-MP)/eV Q (exp.)/eV Q (H�uckel)/eV MeCH2NH2 2 MeCN-n2 MeCH-n1 0.86 0.82 0.95 ca. 0.8 ca. 0.9 &midd

ISSN:0308-2342    

DOI:10.1039/a700408g

出版商:RSC    

年代:1997

数据来源: RSC