Sulfonylative Pauson-Khand Reaction

The Pauson-Khand reaction is a landmark transformation in organic synthesis, enabling the rapid assembly of cyclopentenone frameworks through a (2+2+1) cycloaddition of alkenes, alkynes, and carbon monoxide. Despite its long-standing impact, the conceptual framework of Pauson-Khand chemistry has remained largely restricted to carbon monoxide incorporation. Here we report a fundamentally distinct sulfonylative Pauson-Khand-type protocol enabled by interception of a photoinduced energy-transfer-mediated (2+2) cycloaddition pathway. The reaction proceeds under mild, energy-efficient conditions, exhibits broad substrate scope across diverse 1,6-enynes, and delivers products in good to excellent yields. A complementary photocatalyst-free variant relying on direct triplet excitation of alkynyl cyclohexadienones is also disclosed. Mechanistic studies, supported by Density Functional Theory calculations reveal the origin of reactivity and selectivity and establish this process as a mechanistically orthogonal alternative to classical Pauson–Khand chemistry.