Facile synthesis of oxaspirobicyclic butenolides via a domino Michael addition/aldol reaction/γ-lactonization sequence

A three-component domino reaction approach between a primary amine, a dialkyl acetylenedicarboxylate, and 1,3-dimethylalloxan that affords novel oxaspirobicyclic γ-butenolidobarbiturate derivatives is reported. The reaction sequence consists of an initial Michael-addition of primary amines to dialkyl acetylenedicarboxylates, followed by aldol-like reaction with 1,3-dimethylalloxan, and then γ-lactonization to afford the products. This cascade reaction sequence represents a rapid and unprecedented route to the described biologically interesting molecules.