Directing group assisted para-selective C–H alkynylation of unbiased arenes enabled by rhodium catalysis

Abstract

Regioselective C–H alkynylation of arenes via C–H activation is challenging yet a highly desirable transformation. In this regard, directing group assisted C(sp²)–H alkynylation of arenes offers a unique opportunity to ensure precise regioselectivity. While the existing methods are mainly centered around ortho-C–H alkynylation and a few for meta-C–H alkynylation, the DG-assisted para-selective C–H alkynylation is yet to be reported. Herein we disclose the first report on Rh-catalyzed para-C–H alkynylation of sterically and electronically unbiased arenes. The para-selectivity is achieved with the assistance of a cyano-based directing template and the selectivity remained unaltered irrespective of the steric and electronic influence of the substituents. The post-synthetic modification of synthesized para-alkynylated arenes is also demonstrated. The mechanistic intricacies of the developed protocol are elucidated through experimental and computational studies.