Photochemical Radical Ring-Opening Alkylation of Cyclopropanols with Katritzky Salts.

Ring-cleavage reactions of cyclopropyl alcohols are a valuable tool for the synthesis of linear and α- or β-branched ketones. Here, we describe a visible light-induced ring-opening alkylation of these substrates with benzyl, allyl, and secondary alkyl Katritzky salts. The reaction proceeds under dual photoredox and nickel catalysis in the presence of a titanium(IV) isopropoxide additive. Mechanistically, the ring-opening step starts with generation of the cyclopropoxy radical and is followed by its isomerization to the β-carbonyl radical. This enables the regioselective preparation of β-branched ketones from 1,2-disubstituted hydroxycyclopropanes.