Photoredox catalytic phosphine-mediated deoxygenative alkynylation of carboxylic acids with alkynyl sulfones for alkynone synthesis†

Ynones are essential scaffolds in a diverse array of active molecules, and also serve as important synthetic intermediates. Herein, we describe a visible light-induced photoredox strategy for the synthesis of ynones using carboxylic acids and alkynyl sulfones. The synthetic protocol features mild reaction conditions and good tolerance with respect to functional groups. Mechanistic studies have demonstrated that the deoxygenative ynonylation proceeds via acyl radical formation, followed by the capture of an alkynylation reagent to generate internal ynones with the loss of a sulfonyl radical. The synthetic utility of this methodology is demonstrated by the utilization of the synthesized ynones in the preparation of diverse important heterocycles.