Organophosphine-Catalyzed Intramolecular Hydroacylation of Activated Alkynes

We present the details of an organophosphine-catalyzed Morita–Baylis–Hillman-type reaction of activated alkynes. The outcome is an intramolecular hydroacylation of α,β-ynones leading to the formation of 1,3-cyclopenta-, cyclohepta-, and cyclooctadione-fused arenes and heteroarenes. In addition, during the course of the investigation, a phosphine-catalyzed intramolecular aldol reaction of keto-ynones via δ′[C­(sp3)-H]-functionalization was discovered, and a new annulation event comprising of a ω′[C­(sp3)-H]-functionalization of α,β-ynones was also uncovered. The mechanisms governing these processes have been thoroughly elucidated.