Regiocontrol in the Oxidative Heck Reaction of Indole by Ligand-Enabled Switch of the Regioselectivity-Determining Step.

Abstract

Efficient control of regioselectivity is a key concern in transition-metal-catalyzed direct C-H func-tionalization reactions. Various strategies for regiocontrol have been established by tuning the selectivity of the C-H activation step as a common mode. Herein, we present our study on an alternative mode of regiocontrol, in which the selectivity of the C-H activation step is no longer a key concern. We found that, in a reaction where the C-H activation step exhibits a different re-gio-preference from the subsequent functionalization step, a ligand-enabled switch of the regi-oselectivity-determining step could render efficient regiocontrol. This mode has been exempli-fied by the Pd(II)-catalyzed aerobic oxidative Heck reaction of indoles, in which a ligand-controlled C3-/C2-selectivity was achieved for the first time by the development of sulfoxide-2-hydroxypyridine (SOHP) ligands.