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

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. A first work on rhodium-catalyzed para-selective C-H alkynylation has been reported and its mechanistic insights were gleaned from experimental and computational studies.

Automated summary

A method for directing group-assisted para-selective C-H alkynylation using Rh catalyst has been reported. The para-selectivity was achieved with the assistance of a cyano-based directing template, and remained unaltered regardless of the steric and electronic influence of the substituents. The study provides insights into the mechanistic intricacies and shows potential applications for post-synthetic modification.