Regioselective Iridium(III)-Catalyzed C-H Cyclization Using Acetylene Surrogate: Direct Access to Hydroxylated Polycyclic Phthalazinones

Abstract

An iridium(III)-catalyzed C-H cyclization between N-arylphthalazinones and 2-chloroacetaldehyde has been developed. This reaction provides efficient access to tetracyclic phthalazine derivatives with broad substrate scope. 2-Chloroacetaldehyde serves as an alkyne equivalent, with its dual electrophilic sites being selectively activated. A series of hydroxylated tetracyclic phthalazine intermediates was also prepared. Notably, the process displays excellent regioselectivity, placing substituents exclusively at the meta-position relative to the nitrogen directing group in the products.