Enantio- and Regioselective Electrooxidative Cobalt-Catalyzed C-H/N-H Annulation with Alkenes.

Abstract

In recent years, the merging of electrosynthesis with 3d metal-catalyzed C-H activation has emerged as a sustainable and powerful technique in organic synthesis. Despite the impressive advantages, the development of an enantioselective version remains elusive and pose a daunting challenge. Herein, we reported the first electrooxidative cobalt-catalyzed enantio- and regioselective C-H/N-H annulation with olefins in a simple undivided cell at room temperature(up to 99% ee). t Bu-Salox, a rationally designed Salox ligand bearing a bulky tert-butyl group at the ortho-position of phenol based on the mechanistic understanding, was found to be crucial for this asymmetric annulation reaction. A strong cooperative effect of t Bu-Salox and 3,4,5-trichloropyridine enabled the highly enantio- and regioselective C-H annulation with the more challenging α-olefins without secondary bond interaction (up to 96% ee and 97:3 rr). Cyclovoltametric studies, the preparation, characterization, and transformation of cobaltacycle intermediates shed light on the mechanism of this reaction.