Transition metal catalyzed C–H bond activation by exo-metallacycle intermediates

Abstract

exo-Metallacycles have become the key reaction intermediates in activating various remote C(sp²)–H and C(sp³)–H bonds in the past decade and aided in achieving unusual site-selectivity. Various novel exo-chelating auxiliaries have assisted metals to reach desired remote C–H bonds of different alcohol and amine-derived substrates. As a result, a wide range of organic transformations of C–H bonds like halogenation, acetoxylation, amidation, sulfonylation, olefination, acylation, arylation, etc. were accessible using the exo-metallacycle strategy. In this review, we have summarized the developments in C–H bond activation via four-, five-, six-, seven- and eight-membered exo-metallacycles and the key reaction intermediates, including the mechanistic aspects, are discussed concisely.