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.