Thermal [3+2] Cycloaddition Reaction of N-Acyliminophenanthridinium Betaine with Allenoates: Facile Access to Phenanthridine-fused Tetracyclic Heterocycles
The thermal [3+2] cycloaddition reaction of N-acyliminophenanthridinium betaines with various allenoates has
been investigated. The reaction was operationally simple and proceeded smoothly under mild reaction conditions, providing
a variety of aromatic tetracyclic heterocycles in moderate to excellent yields.
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.