Transformations of tetrahydro-pyrido[4,3-d]pyrimidines [b]-condensed with isoxazole, thiazole, thiadiazole, and triazole units under the action of activated alkynes

It has been established that 5-vinyl-substituted (N-R,N-vinylaminomethyl)isoxazolo(thiazolo, thiadiazolo)pyrimidines are formed when tetrahydropyrido[3,4-d]pyrimidines, annelated with isoxazole, thiazole, and thiadiazole units are treated with terminal alkynes as a result of opening of the tetrahydropyridine ring. 7-Methoxymethyl-substituted [N-R,N-(dimethoxycarbonylvinyl)]aminoethyl-isoxazolo- and thiazolopyrimi-dines were obtained by reaction with dimethyl acetylenedicarboxylate (ADCE). Triazolo-pyrimidoazocine was obtained for the first time from tetrahydrotriazolopyrimidine and methyl propiolate.