Organocatalytic asymmetric tandem reaction for the enantioselective synthesis of chiral oxindoles to construct CyK dyes

Abstract

We report an efficient method for the synthesis of chiral 3-trifluoromethyl-3-hydroxy oxindoles through the asymmetric [3 + 2] cascade cyclization of simple 2-naphthylamine derivatives with ethyl trifluoropyruvate. This catalytic asymmetric strategy enables the efficient construction of a series of enantioenriched CF₃-quaternary carbon oxindoles with high yields and excellent stereoselectivities. The innovative synthetic approach has been applied to the synthesis of trifluoromethylated Cy-ketone fluorescent dyes with circularly polarized luminescence (CPL) properties. In situ infrared and density functional theory calculations indicate that our catalytic system can overcome background reactions to achieve effective enantioselective annulation.