3x-pyrrolizin-3-ones

Condensation of pyrrole-2-dithiocarboxylates with CH acids containing ester groups, in the KOH-DMSO system, was used to prepare previously unknown 1-alkylthio-3H pyrrolizin-3-ones. The latter, treated with secondary amines, are readily converted to the corresponding 1-amino derivatives.     

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.     

Pyrroles from ketoximes and acetylene

The ¹³C NMR spectra of eight 2-alkyl- and 2,3-dialkyl-1-vinylpyrroles were studied. The ¹³C chemical shifts of all of the carbon atoms of the ring and the vinyl group depend substantially on the position and structure of the alkyl substituent. As the branched character of the alkyl group in the 2 position increases, the signal of the -carbon atom of the vinyl group is shifted to weak field due to weakening of the p- conjugation in the N-vinyl group because of disruption of its coplanarity with the pyrrole ring. The conjugation between the double bond and the pyrrole system involves competition for possession of the p electrons of the nitrogen atom.See [16] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 350–354, March, 1978.     

Pyrimidines

A new method was developed for the synthesis of substituted pyrazolo[3,4-d]pyrimidines by the condensation of 1-alkyl(aryl)-3- and 5-aminopyrazoles with arylidenebisureas.See [1] for communication XXVIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 535–539, April, 1971.     

Easy α- to β-migration of an enol moiety on a pyrrole ring

Functionalized pyrrolic enols, 2-(2,2-dicyano-1-hydroxyethenyl)-1-methylpyrroles, synthesized from 2-ethenylpyrroles by a nucleophilic SEt-OH exchange, upon heating (75-142 °C) are readily rearranged to their 3-isomers in near to quantitative yield. The inter or intramolecular auto-protonation of a pyrrole ring by the acidic enol hydroxyl to form a mesomeric pyrrolium cation or zwitterion is suggested to be a key step in the rearrangement.     

Strong intramolecular hydrogen bond N—H...O in 2-(2-acyl-1-phenylethenyl)-5-phenylpyrroles

The molecular structure of 2-(2-benzoyl-1-phenylethenyl)-5-phenylpyrrole and 2-(2-furoyl-1-phenylethenyl)-5-phenylpyrrole was studied by X-ray diffraction analysis at 110 K and quantum chemistry methods (B3LYP/6-31G*). In the crystalline state, both compounds have cyclic structures closed by strong intramolecular hydrogen bond N—H...O. Canonic zwitterionic structure contributes largely to the ground state of the molecules. This is probably due to synergism of the H-bonding and -electron interactions.     

Pyrimidines

The reaction of substituted 3-methyl-5-pyrazolones with arylidenebisureas has been studied. Substituted spiro[pyrazole-4, 5-pyrimidines] have been obtained from 1-phenyl- and 1-benzyl-3-methyl-5-pyrazolones. When only one hydrogen atom was present in the ring of the 3-methyl-5-pyrazolone, the corresponding -ureidobenzyl derivative was obtained.For communication XI see [1].     

Pyrimidines

The reaction of 1-phenyl-3-methyl-4-benzal-5-pyrazolone with urea does not lead to closing of a pyrazolo[3,4-d]pyrimidine ring because of the reduced tendency of the carbonyl group of the pyrazolone to participate in cyclization reactions. The expected 1,4-diphenyl-3-methyl-6-oxo-4,5,6,7-tetrahydropyrazolo[3,4-d]pyrimidine was obtained by condensation of 1-phenyl-3-methyl-5-aminopyrazole with benzalbisurea and was dehydrogenated to the dihydro derivative.     

3-H-pyrrolizin-3-ones

Previously unknown 1-alkylthio-3H-pyrrolizin-3-ones have been obtained by the condensation of pyrrole-2-dithiocarboxylates with CH acids containing ester groupings in the KOH-DMSO system. On treating the products with secondary amines they are readily converted into the corresponding 1-amino derivatives.Irkutsk Branch of the Russian Academy of Sciences, Irkutsk 664033. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 919–924, July, 1996. Original article submitted May 2, 1996.