Nickel/Photoredox Three-Component Coupling of 1,3-Butadiene, Aldehydes, and Aryl Bromides to Homoallylic Alcohols.

Homoallylic alcohols are valuable motifs, but three-component syntheses from butadiene, carbonyl compounds, and organic electrophiles often require stoichiometric metal reductants. We report a nickel/photoredox-catalyzed coupling of 1,3-butadiene, aldehydes, and aryl bromides using Hantzsch ester as an organic reductant. The reaction proceeds under mild conditions with high regio- and stereoselectivity and broad functional-group tolerance. Control experiments and DFT calculations support a pathway involving nickel photoreduction, butadiene insertion, and carbonyl addition of a nucleophilic π-allylnickel intermediate.