Enantio- and Regioconvergent Synthesis of γ-Stereogenic Vinyl Germanes and Their Use as Masked Vinyl Halides

A nickel-catalyzed enantio- and regioconvergent alkylation of regioisomeric mixtures of racemic germylated allylic electrophiles with alkyl nucleophiles is reported. Key to success is a newly developed hept-4-yl-substituted Pybox ligand that enables accessing various chiral γ-germyl α-alkyl allylic building blocks in excellent yields and enantioselectivities. The reason for the regioconvergence is the steering effect of the bulky germyl group. The resulting vinyl germanes can be easily halodegermylated without racemization of the allylic stereocenter to afford synthetically valuable γ-stereogenic vinyl halides.