Nickel(0)‐Catalyzed Hydrocyanation of Terminal Allenes: A Regio‐ and Enantioselective Approach to Branched Allylic Nitriles

Abstract

AbstractA highly branched regioselective nickel(0)‐catalyzed hydrocyanation of mono‐ and 1,1‐disubstituted allenes as well as an asymmetric hydrocyanation of 1,1‐disubstituted allenes are reported herein, giving access to branched tertiary and quaternary β,γ‐allylic nitriles. For the regioselective hydrocyanation of terminal allenes, a nickel(0)/Biphephos catalytic system applicable to a substrate scope containing functional groups such as ester, THP‐group, primary aliphatic iodide, and a free carboxylic acid, provides yields up to 96%. By applying a catalytic system of Ni(0)/TADDOL‐based bisphosphite catalyst to 1,1‐disubstituted allenes, branched quaternary allylic nitriles are obtained in yields up to 99% and enantioselectivities up to 86%. Both protocols take advantage of a manageable HCN source and evidence good atom economy. In addition, the reaction's synthesis utility is highlighted by gram‐scale reactions with subsequent assorted transformation of the nitrile group as well as alkylation of the tertiary nitriles in α‐position.magnified image