Development of N-centered radical scavengers that enables photoredox-catalyzed transition-metal-free radical amination of alkyl pinacol boronates
Changlei Zhu, Jiaxin Lin, Xiaoguang Bao, Jingjing Wu
Abstract
In recent years, amination of alkylboronates through ionic copper catalysis or boron-ate complex 1,2-metalation has been well established, but complementary radical processes remain less studied before. Herein, based on rational design, we develop several imine-type N-centered radical scavengers and apply them to the radical amination of alkylboronates. The reaction proceeds under mild photoredox-catalyzed transition-metal-free conditions and features excellent functional group tolerance. It also enables the preparation of a range of medicinally valuable amine derivatives from complex natural products. Further application of this reagent in C-H amination, deoxygenative amination, decarboxylative amination and three component trifluoromethylative/sulfonylative aminations are also realized. Further mechanistic studies and DFT calculations are conducted to provide detailed evidence for the mechanism. Amination of alkylboronates through ionic copper catalysis or boron “ate” complex 1,2-metalation has been well established, but complementary radical processes remain less studied. Here, the authors report the synthesis of imine-type N-centered radical scavengers and the application in the visible-light photoredox-catalyzed transition-metal-free radical amination of alkyl pinacol boronates.