Photocatalytic Direct Para-Selective C-H Amination of Benzyl Alcohols: Selectivity Independent of Side Substituents.

Aminoarenes are important molecules for broad applications in nearly all modern industries that involve chemicals. Direct and site-selective C-H bond amination of arenes provides the most efficient and convenient method to prepare aminoarenes. A main challenge is to selectively install the amino group (or other functional groups) to the distal para-carbon of arenes (especially multi-substituted arenes) during the C-H bond functionalization events. Herein, we address this problem by designing a new strategy via a sequential radical dearomatization/radical amination/rearomatization process for para-selective amination of benzyl alcohols. The para-selectivity of our reaction is completely independent of the electronic and steric properties of the other substituents of the arene substrates. Aminoarenes with many substituents (up to full substitution) and diverse substitution patterns, including those difficult to synthesize previously, could be readily prepared using our protocols. Further exploration of the current strategy shall lead to other challenging C-H functionalization of arenes.