Benzyltriboronates: Building Blocks for Diastereoselective Carbon-Carbon Bond Formation

摘要

A highly diastereoselective carbon—carbon bond-forming reaction involving the tandem coupling of benzyltriboronates, enoates, and alkyl halides is described. This method was enabled by the discovery of a-dümine nickel catalysts that promote the chemoselective tribor-ylation of benzylic C(sp~3)—H bonds using B_2Pin_2 (Pin = pinacolate). The C—H functionalization method is effective with methylarenes and for the diborylation of secondary benzylic C—H bonds, providing direct access to polyboron building blocks from readily available hydrocarbons. Combination of the benzylic perborylation with a new deborylative conjugate addition—alkylation method enables a one-pot procedure in which multiple simple precursors are combined to generate diastereopure products containing quaternary stereocenters.