0000000000470804
AUTHOR
R. Alan Jones
Synthesis, Characterisation, and Reactivity of 1-(1-Methylimidazol-2-yl)ethenes
Abstract Thermally labile 1-(1-methylimidazol-2-yl)-ethenes, synthesised using the Wittig reaction, have been characterised as stable picrate or N-phenacyl salts. The free bases can be regenerated from the picrates on treatment with triethylamine and their reactivity with dienophiles is described.
3-Diazopyrroles—IV. Structure determination using 13C NMR spectroscopy
Abstract On the basis of the 13 C NMR chemical shifts, it is proposed that, although b is the major canonical structure, structure c , in which a negative charge resides at C-3, provides an important contribution to the resonance stabilization of the 3-diazopyrroles, 1–4 .
The reactivity of 2-vinylindoles with dimethyl acetylenedicarboxylate
Abstract The overall rates of reaction of 1-substltuted-1- (1-methyl-2-indolyl)ethenes with dimethyl acetylenedicarboxylate are considerably lower than those of the corresponding 2-vinyl- pyrroles. Steric interaction between the N-methyl group on the indole ring and the 1-substituent on the ethenyl group prevents the diene system adopting a coplanar cisoid configuration and, thereby, inhibits the π4 + π2 cycloaddition reaction of the system with dimethyl acetylenedicarboxylate. Under such conditions, the indolylethene preferentially undergoes a Michael addition reaction at the 3-position. The π4 + π2 cycloaddition reaction is promoted at elevated temperatures. No evidence was found for a Co…
Pyrrole Studies XXVII.1Utilisation of 1-Methyl-2-pyrrolyl Lithium in the Synthesis of 1-Methyl-2-substituted Pyrroles
Abstract Although metallation of 1-substituted pyrroles with alkyl lithium reagents to give the lithiated derivatives has been recorded by several research groups,4–6 only limited use has been made of these derivatives in the synthesis of 1,2-disubstituted pyrroles. Subsequent to ourinitial studies,7 it was reported that tetrahydrofuran was the solvent of choice for the formation of the mono-lithiated pyrrole derivative and that the rate of the metallation was accelerated by the presence of TMEDA.6 We had noted,7 however, that prolonged reaction of n-butyl lithium with 1-methylpyrrole in a 2:1 mixture of tetrahydrofuran:hexaneat ca 18°C in the absence of TMEDA gave 1-methyl-2-pyrrolyl lithi…
Theoretical Study of the Reaction of Dimethyl Acetylenedicarboxylate with 1-Methyl-2-(1-substituted vinyl)pyrroles
Abstract A theoretical study of the transition structure for the electrophilic attack step of the 1-methyl-2-vinylpyrrole to dimethyl acetylenedicarboxylate is reported with analytical gradients at AM1 and PM3 semi-empirical levels and ab initio at 3-21G level. The geometry, electronic structure, and vector components are qualitatively computer level and model independent The competition of the Michael addition reactions and Diels-Alder reactions of 1-methyl-2-(1-substituted vinyl)pyrroles with dimethyl acetylenedicarboxylate has been studied at the PM3 semi-empirical level.
Protonation of 3-aminopyrroles
Abstract The protonation of 3-aminopyrroles has been investigated using H and 13C n.m.r. spectroscopy. The spectral data are compatible with predominant protonation of the amino group with no evidence for protonation of the pyrrole ring.
Thermolysis of 3-(carbazol-3-yl)-2-azidopropenoates
Abstract Thermal cyclisation of 2-azido-3-(carbazol-3-yl)propenoic esters produces the 1,6-dihydropyrrolo[3,2- c ]carbazole and not the 1,9-dihydropyrrolo[2,3- b ]carbazole whereas, in the case of the 4-methylcarbazolyl derivative, the 1,9-dihydropyrrolo[2,3- b ]-carbazole is formed in preference to the alternative pyrido[4,3- c ]carbazole.