Dialkylation of 1,3-Dienes with Aldehydes and Cyclopropanols toward Homoallylic Alcohols by Dual Photoredox and Chromium Catalysis

A visible-light-induced three-component coupling of aldehydes, 1,3-dienes, and cyclopropyl alcohols using dual photoredox and chromium catalysis is herein described. This efficient protocol achieves the dialkylation of 1,3-dienes toward 1,4-disubstituted homoallylic alcohols in moderate to good yields with excellent regioselectivity, featuring mild reaction conditions, good functional group tolerance, and gram-scale synthesis. Mechanistic study suggests that photoinduced sequential ring opening of cyclopropyl alcohol and radical and nucleophilic cascade addition are involved in the catalytic cycle.