A number of previously unknown N-isopropenyl-substituted pyrroles, indoles, and di- and -triazoles were synthesized in 20-86% yield by reaction of the corresponding azole with an equilibrium mixture of propyne with allene or pure propyne and allene in the system KOH-DMSO (105-145degreesC, 5-15 h, atmospheric or elevated pressure). The reaction is regioselective. The electronic and steric structure and the degree of conjugation between the exocyclic double bond and the azole ring are discussed on the basis of the H-1 and C-13 NMR spectra. Almost complete absence of p-pi conjugation in alpha,alpha'-disubstitutecl N-isopropenylazoles have been found.
Comparison of the electronic and steric structures of 1-vinyl-and 1-(prop-1-en-1-yl)pyrroles according to the 1H and 13C NMR data
作者:A. V. Afonin、I. A. Ushakov、D. E. Simonenko、O. A. Tarasova、M. A. Maksimova、B. A. Trofimov
DOI:10.1134/s1070428007030116
日期:2007.3
According to the H-1 and C-13 NMR data, 1-isopropenylpyrroles are characterized by larger dihedral angles between the heteroring and exocyclic double bond planes, as compared to isostructural 1-vinylpyrroles, due to steric effect of the alpha-methyl group in the propenyl fragment. As a result, p-pi conjugation with the propenyl group is weaker than with the vinyl group. The propenyl group in 1-isopropenylpyrrole having no other substituents in the heteroring is forced out from the heteroring plane, while the 1-vinylpyrrole molecule is planar. If substituents are present in positions 2 and 5 of the pyrrole ring, the propenyl group on the nitrogen atom becomes orthogonal with respect to the pyrrole ring plane, so that no p-pi conjugation is possible. The steric structures of (E)-1-(prop-1-en-1-yl)pyrrole and (Z)-1-(prop-l-en-l-yl)pyrrole are different: the propenyl group in the former is turned relative to the heteroring plane, while the latter molecule is planar.
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作者:B. A. Trofimov、O. A. Tarasova、M. A. Shemetova、A. V. Afonin、L. V. Klyba、L. V. Baikalova、A. I. Mikhaleva
DOI:10.1023/a:1025502016921
日期:——
A number of previously unknown N-isopropenyl-substituted pyrroles, indoles, and di- and -triazoles were synthesized in 20-86% yield by reaction of the corresponding azole with an equilibrium mixture of propyne with allene or pure propyne and allene in the system KOH-DMSO (105-145degreesC, 5-15 h, atmospheric or elevated pressure). The reaction is regioselective. The electronic and steric structure and the degree of conjugation between the exocyclic double bond and the azole ring are discussed on the basis of the H-1 and C-13 NMR spectra. Almost complete absence of p-pi conjugation in alpha,alpha'-disubstitutecl N-isopropenylazoles have been found.
Regioselective Cross-Coupling of 1-Vinylpyrroles with Acylbromoacetylenes on Al<sub>2</sub>O<sub>3</sub>: Synthesis of 2-(2-Acylethynyl)-1-vinylpyrroles
1-Vinyl- and 1-isopropenylpyrroles enter readily (ambient temperature) into cross-coupling reaction with acylbromoacetylenes on Al2O3 to furnish regioselectively 2-(2-acylethynyl)-1-vinyl- and 2-(2-acylethynyl)-1-isopropenylpyrroles in 39-70% yield.