From ynones to alkynes via nickel catalyzed decarbonylative reconstructive C-C bond coupling.

A distinct nickel-catalyzed intramolecular decarbonylative reconstructive C-C coupling of unstrained ynones into alkynes is described. The directing group-free protocol accommodates diverse ynones bearing (hetero)aryl, alkenyl, alkyl, and alkynyl substituents, delivering the desired products in good to excellent yields under simple conditions with low catalyst loadings and excellent functional-group tolerance. Importantly, alkyl-substituted ynones undergo efficient C(sp3)-C(sp) coupling, offering a complementary approach to alkyne synthesis beyond traditional Sonogashira-type methodologies that commonly suffer from β-hydride elimination. The synthetic utility of the method is demonstrated through late-stage modification, diynone-to-diyne formation, and preparative-scale reactions. Computational studies provide mechanistic insight into a reaction pathway that proceeds through C-C bond activation, cleavage and subsequent C-C bond formation.