Pyrroles from ketoximes and acetylene. 45. A new route to 2,2-dipyrroles

The reaction of 1-methyl-2-acetylpyrrole oxime with acetylene at atmospheric and increased pressure can be catalyzed by KOH-DMSO superbase to give 1-methyl-2-(2-pyrrolyl)pyrrole, N-vinyl-2-[1-methyl(2-pyrrolyl)]pyrrole, and the reaction intermediate methyl-2-(1-methylpyrrolyl)-O-vinyloxime.See [1] for Communication 44.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 460–463, April, 1991.     

Pyrroles from ketoximes and acetylene. 23. 2-(1-naphthyl)- and 2-(2-naphthyl)pyrroles and their 1-vinyl derivatives

2-(1-Naphthyl)- and 2-(2-naphthyl)pyrroles and their 1-vinyl derivatives were synthesized in 22–64% yields by the reaction of 1- and 2-acetylnaphthalene oximes with acetylene at both atmospheric pressure and elevated pressures in an alkali metal hydroxide-dimethyl sulfoxide system.See [1] for communication 22.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1351–1353, October, 1982.     

Selective hydrogenation of the vinyl group of 1-vinylpyrroles

The hydrogenation of 1-vinylpyrroles over Raney nickel in ethanol at 50–90°C proceeds exclusively at the 1-vinyl group and leads to the formation of 1-ethylpyrroles in 80–90% yields. The IR and PMR spectra are presented.Translated from Khimiya Geterotsilicheskikh Soedinenii, No. 2, pp. 215–216, February, 1077.     

Pyrroles from ketoximes and acetylene

2-(2-Furyl)pyrroles and 1-vinyl-2-(2-furyl)pyrroles were obtained in up to 80% yields in the reaction of ketoximes of the furan series with acetylene in MOH—dimethyl sulfoxide (M = Li, K) Superbase media.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1058–1061, August, 1981.     

Association and relative acidities of 2-substituted 5-trifluoroacetylpyrroles

The acidities of 2-substituted 5-trifluoroacetylpyrroles were studied by IR spectroscopy from the shift of the frequency of the NH stretching vibration (_NH) in the presence of dimethylformamide (DMF) relative to the band of vibrations of free NH. The existence of a correlation relationship between _NH and _I constitutes evidence that the acidities of pyrroles are determined primarily by the inductive effect of the substituents in the 2 and 5 positions of the pyrrole ring. The low probability of the formation of an intramolecular NH... O=C hydrogen bond in the investigated molecules was demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 772–774, June, 1984.     

Pyrroles from ketoximes and acetylene. 44. Methyl aryl ketoximes with reactive substituents

The Trofimov reaction was extended to methyl aryl ketoximes with substituents in the benzene ring that are unstable with respect to the action of a strongly basic medium. The corresponding pyrroles and their 1-vinyl derivatives were obtained. 4-Nitroacetophenone oxime, from which only 2-phenyl- and 1-vinyl-2-phenylpyrrole were obtained, and 4-bromoacetophenone oxime, the reaction of which leads to the formation of 1-vinyl-2-(4-vinyloxyphenyl)pyrrole in addition to the principal 2-(4-bromophenyl)pyrrole, constituted exceptions.For communication 43, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 187–191, February, 1991.     

Pyrroles from ketoximes and acetylene

The respective 2-aryl- and N-vinyl-2-arylpyrroles were obtained by the reaction of the oximes of alkyl aryl ketones with acetylene in the superbasic medium MOH (M=Li, K)-DMSO. Their yields depended largely on the structure of the ketoximes and on the reaction conditions.For Communication 41, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 609–613, May, 1992.     

NMR spectra and structures of protonated 1-vinylpyrroles

Stable 1-vinylpyrrolium fluorosulfonates were prepared by the reaction of 1-vinylpyrroles with excess HSO₃F at –50°C in CD₂Cl₂ and their ¹H and ¹³C NMR spectra were obtained. Despite its overall positive charge, the pyrrole ring remains an electron donor relative to the vinyl group. Delocalization of the positive charge onto substituents decreases in the order 2-heteroaryl > 2-aryl > 2-alkyl.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 48–57, January, 1993.