Efficient Synthesis of 1,3-Disubstituted 1,3-Dihydro-2H-imidazo[5,1-b]quinazolin-9-ones by an Intramolecular Mannich-Type Reaction

A general and efficient method has been developed for the synthesis of 1,3-disubstituted 1,3-dihydroimidazo[5,1- b ]quinazolin-9-ones. The process involves an intramolecular Mannich­-type reaction of a 2-aminomethylquinazolin-4-one derivative with an aldehyde, and gives diastereomeric mixtures of the minor cis - and major trans -cycloadducts.