Nickel Photocatalyzed Reductive 1,4-Dicarbofunctionalization of 1,3-Enynes with -Methylamines and Organohalides Enabled by Site-Selective C(sp)-H Functionalization.

A cooperative nickel and photoredox reductive catalysis for 1,4-dicarbofunctionalization of 1,3-enynes with tertiary -methylamines and organohalides to produce tetrasubstituted allenes is presented. This method enables the generation of the aminoalkyl C(sp)-centered radicals by site selective cleavage of the -methyl C(sp)-H bonds in tertiary -methylamines and is extended to alkyl bromides as the electrophilic terminating regents. Mechanistic studies indicate that the reaction involves a radical process and a Ni/Ni/Ni catalytic cycle.