Heterocycles containing a bridge nitrogen atom. 11. Recyclization of 5-methyloxazolo[3,2-apyridinium cation under the action of nucleophiles containing NH2 group. Crystal structure of 3-(p-nitrophenyl)-1,4-dihydropyrido-[2,1-c]-as-triazinium perchlorate

Reactions of 5-methyl-2-(p-nitrophenyl)oxazolo3,2-a]pyridinium perchlorate with ammonia and hydrazine, in contrast to the reaction with secondary amines, do not produce indolizines. The reaction with ammonia produces 5-methyl-2-(p-nitrophenyl)imidazo1,2-a]pyridine; with hydrazine, 3-(p-nitrophenyl)-1,4-dihydropyrido2,1-c]-as-triazinium semiperchlorate (2 moles of base per one mole of acid). The structure of the latter is solved by X-ray structural studies. Dedicated to Professor Henk van der Plas on his 70th birthday. For No. 9, see 1]. M. V. Lomonosov Moscow State University, Moscow 119899, Russia Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 550–556, April, 1999.