Conversion of coumarins accompanied by opening and recyclization of the lactone ring. 1: Study of the reaction of 3-ethoxycarbonyl(3-acyl)coumarins with cyanoacetylhydrazine and its derivatives

A stepwise sequence for the interaction of 3-ethoxycarbonyl(acyl)coumarins with cyanoacetylhydrazine, its N-acetyl and N-isopropylidene derivatives, leading to the formation of 3-cyanocoumarins, is proposed and demonstrated. It was established that the 3-cyanocoumarins formed are also able to participate in further conversions by a type of Michael reaction.