Sequential Ring Opening/In Situ SO 2 -Capture/Alkynylation of Cyclopropanols with Alkynyl Triflones Initiated by Energy Transfer.

A visible-light-triggered ring opening/in situ SO 2 -capture/alkynylation sequence of cyclopropyl alcohols with alkynyl triflones using 4CzIPN as a triplet energy transfer photocatalyst is herein described. This metal-free protocol provides a straightforward and atom-economical approach to alkynyl-substituted γ-keto sulfones with a broad scope of substituents. In this transformation, alkynyl triflones could be used as both radical acceptors and SO 2 donors. Preliminary experimental mechanistic studies and synthetic utility are also demonstrated.