Journal of the American Chemical Society, Vol.143, No.5, 2441-2455, 2021
Enantioselective Synthesis of N-Alkylamines through beta-Amino C-H Functionalization Promoted by Cooperative Actions of B(C6F5)(3) and a Chiral Lewis Acid Co-Catalyst
We disclose a catalytic method for beta-C(sp(3))-H functionalization of N-alkylamines for the synthesis of enantiomerically enriched beta-substituted amines, entities prevalent in pharmaceutical compounds and used to generate different families of chiral catalysts. We demonstrate that a catalyst system comprising of seemingly competitive Lewis acids, B(C6F5)(3), and a chiral Mg- or Sc-based complex, promotes the highly enantioselective union of N-alkylamines and alpha,beta-unsaturated compounds. An array of delta-amino carbonyl compounds was synthesized under redox-neutral conditions by enantioselective reaction of a N-alkylamine-derived enamine and an electrophile activated by the chiral Lewis acid co-catalyst. The utility of the approach is highlighted by late-stage beta-C-H functionalization of bioactive amines. Investigations in regard to the mechanistic nuances of the catalytic processes are described.