Pseudo-Michael Reaction of 2-hydrazinoimidazolines: New Synthetic Approach to Imidazo[2,1-c][1,2,4]triazepine System

In a two-step reaction (pseudo-Michael/acylation) of 1-aryl-2-hydrazinoimidazolines with DEEM (diethyl ethoxymethylenemalonate) formation of 2,3-dihydroimidazo[2,1--c][1,2,4]triazepine system was observed. This type of reaction usually lead to formation of 5:6 or 6:6 membered fused hetero-cyclic systems whereas reaction of hydrazine derivatives (alkyl or aryl) or hydrazides and DEEM give pyrazoline carboxylates. In the literature formation of fused 1,2,4-tri-azepines in reaction of a-hydrazinoazoheterocycles is not mentioned. In first step of reaction of 1-aryl-2-hydrazinoimidazolines with Michael reagents chain enamine is formed.