Photoredox Ni-Catalyzed Branch-Selective Reductive Coupling of Aldehydes with 1,3-Dienes

We report here a Ni-catalyzed reductive coupling of aldehydes with widely available 1,3-dienes under visible-light photoredox dual catalysis. The homoallyic alcohols are obtained in broad scope with complete branched regioselectivity. Hantzsch ester is used as the hydrogen radical source to oxidize low-valent nickel salt affording Ni–H species. Preliminary mechanistic studies indicate a successive single-electron transfer (SET) pathway and the generation of a key π-allylnickel intermediate via Ni–H insertion of 1,3-diene in this synergistic catalytic process.