Pentanidium-Catalyzed Direct Assembly of Vicinal All-Carbon Quaternary Stereocenters through C(sp³)–C(sp³) Bond Formation

The stereoselective construction of vicinal all-carbon quaternary stereocenters has long been a formidable synthetic challenge. Direct asymmetric coupling of a tertiary carbon nucleophile with a tertiary carbon electrophile is the most straightforward approach, but it is sterically and energetically disfavored. Herein, we describe a catalytic asymmetric substitution, where racemic tertiary bromides coupled directly with racemic secondary or tertiary carbanion, creating a series of congested C(sp3)–C(sp3) bonds, including isolated all-carbon quaternary stereocenters, vicinal tertiary/all-carbon quaternary stereocenters and vicinal all-carbon quaternary stereocenters. Using pentanidium as a catalyst, this double stereoconvergent process afforded substituted products in good enantioselectivities and diastereoselectivities.