Phosphine-catalyzed [4+3] cycloaddition reaction of aromatic azomethine imines with allenoates

An efficient phosphine-catalyzed [4 + 3] cycloaddition of aromatic azomethine imines with allenoates has been developed, providing dinitrogen-fused heterocyclic compounds in moderate to excellent yields. The reaction proceeds smoothly under mild conditions, providing an expedient access to highly valuable heterocyclic compounds with isoquinoline, quinoline and phenanthridine skeletons.