Synthesis of β-Substituted γ-Aminobutyric Acid Derivatives through Enantioselective Photoredox Catalysis.

β-Substituted chiral γ-aminobutyric acids feature important biological activities and are valuable intermediates for the synthesis of pharmaceuticals. Herein, an efficient catalytic enantioselective approach for the synthesis of β-substituted γ-aminobutyric acid derivatives through visible-light-induced photocatalyst-free asymmetric radical conjugate additions is reported. Various β-substituted γ-aminobutyric acid analogues, including previously inaccessible derivatives containing fluorinated quaternary stereocenters, were obtained in good yields (42-89 %) and with excellent enantioselectivity (90-97 % ee). Synthetically valuable applications were demonstrated by providing straightforward synthetic access to the pharmaceuticals or related bioactive compounds (S)-pregabalin, (R)-baclofen, (R)-rolipram, and (S)-nebracetam.