Nickel-Catalyzed Enantioselective Synthesis of Bishomoallylic Alcohols

Significance

The first catalytic enantioselective intermolecular reductive coupling of 1,3-dienes with aldehydes is described using catalytic Ni(II), a spirobiindane phosphoramidite ligand, and a stoi­chiometric Zn reducing agent. A wide range of aryl aldehydes couple with 1,4-diphenylbuta-1,3-diene in excellent yields, anti/syn selectivities, and enantioselectivities. Electron-donating substituents on the aryl ring give higher ee, and electron-withdrawing substituents and aliphatic aldehydes lead to lower ee. Heteroaryl aldehydes such as furyl and thiophyl can be used with excellent selectivities and yields. An unsymmetrically substituted diene, ethyl 5-phenylpenta-2,4-dienoate, coupled with benzaldehyde in excellent yield and anti/syn selectivity, but gave only moderate ee.