Ring contraction of thia(seleno)diazine rings into pyrazoles in the reaction of 3-aryl-10-methyl-2H-1,3,4-thia(seleno)diazino[3, 2-a]benzimidazolium salts with bases |
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Authors: | T A Kuz'menko V V Kuz'menko O V Kryshtalyuk A F Pozharskii |
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Institution: | (1) Physical and Organic Chemistry Research Institute, Rostov State University, 344006 Rostov-on-Don |
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Abstract: | Reaction of 3-aryl-10-methyl-2H-1,3,4-thiadiazino3,2-a]benzimidazolium salts with triethylamine led to ring contraction of the thiadiazine ring to a pyrazole ring with the formation of a mixture of derivatives of 3-mercaptopyrazolobenzimidazole and di(pyrazolo1,5-a]benzimidazolyl-3) disulfide. The disulfides were formed exclusively when these salts react with ethanolic alkali. The reaction with potassium carbonate in acetic anhydridegave3-acetylthiopyrazolo1,5- a]benzimidazoles. 2-Aryl-4- alkylpyrazolo1, 5- a]benzimidazoles were formed by heating thiadiazino3,2-a]benzimidazolium salts in formamide and by treating selenodiazino3,2-a]benzimidazolium salts with potassium carbonate in acetic anhydride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1698–1705, 1992. |
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