Ring Expansion of Alkynylcyclopropanols Catalyzed by Ruthenium

Significance

This paper described a novel ruthenium-catalyzed ring expansion of alkynylcyclopropanols. Depending on the electronic properties of substrates, the ruthenium catalyst can selectively mediate a dual ring expansion to either four- or five-membered cyclic ketones. For example, exclusive (Z)-alkylidene cyclobutanones were obtained with silyl and electron-withdrawing substrates. Moreover, for electron-neutral substrates, β-substituted cyclopentenones were obtained exclusively through direct two-carbon homologation.