Synthesis of cyclopentacarbazolones via palladium-catalyzed annulation of internal alkynes

Abstract

A simple and efficient protocol for the synthesis of highly substituted cyclopentacarbazolones (50-82%) was developed by employing internal alkynes with 2-bromo-3-formylcarbazoles in the presence of palladium catalyst under ligand-free condition. High regioselectivity was observed for unsymmetrical (alkyl-, aryl-substituted) internal alkynes. © Georg Thieme Verlag Stuttgart - New York.