Synthesis and some properties of N-unsubstituted pyrrolo[2,1-c]-1,3-diazacycloalkano[1,2-a]pyrazinones

Reactions of methyl 2-(2-formyl-1H-pyrrol-1-yl)alkanoates with unsubstituted aliphatic 1,2-, 1,3-, and 1,4-diamines gave N-unsubstituted pyrrolo2,1-c]-1,3-diazacycloalkano1,2-a]-pyrazinones. Some of them show ring-chain tautomerism. Transformations of these compounds led to a number of novel heterocyclic systems: 2,10-dihydro-3H,5H-imidazo1,2-a]-pyrrolo1,2-d]pyrazines, 2,3,4,11-tetrahydro-6H-pyrrolo1??,2??:4,5]pyrazino1,2-a]pyrimidines, 1,2,3,5,6,10b-hexahydroimidazo1,2-a]pyrrolo2,1-c]pyrazines, 1,3,4,6,7,11b-hexahydro-2H-pyrrolo2??,1??:3,4]pyrazino1,2-a]pyrimidines, and 2,3,4,5,6,7-hexahydro-1H-pyrrolo2,1-c]-1,4,7]triazacycloundecin-8(9H)-one.