Isothiourea-Catalyzed Atroposelective O-Boc Protection for the Kinetic Resolution of NOBINs

While existing kinetic resolution strategies of 2-amino-2′-hydroxy-1,1′-binaphthyls (NOBINs) predominantly rely on atroposelective N-functionalization, O-functionalization remains largely unexplored. Herein, we report an isothiourea-catalyzed atroposelective O-Boc protection for the kinetic resolution of NOBINs, recovering unreacted ( R )-NOBINs in 42% to >99% ee with selectivity factors ( s ) of up to 19. Although the resulting ( S )-O-Boc NOBINs are obtained in moderate enantioselectivities (30–62% ee), they can be facilely transformed into enantioenriched ( S )-NOBINs through deprotection, reprotection, and a second kinetic resolution sequence.