Ammonium acetate as a catalyst and/or reactant in the reaction of dimedone, aromatic aldehyde, and malononitrile: synthesis of tetrahydrobenzo[b]pyrans and hexahydroquinolines

摘要

The reaction of aromatic aldehydes, dimedone, and malononitrile in the presence of ammonium acetate has afforded tetrahydrobenzo[b]pyrans instead of polyhydroquinolines under both grinding and reflux conditions; thus ammonium acetate acts as a catalyst for this transformation instead of a reactant. Polyhydroquinoline derivatives were also synthesized via a one-pot condensation of aromatic aldehydes, malononitrile and an enaminone, which was prepared by the reaction of dimedone and ammonium acetate, in refluxing ethanol in high yields.