Transition metal catalysed direct sulfanylation of unreactive C-H bonds: an overview of the last two decades.

Transition metal catalysed direct sulfanylations of unreactive C-H bonds have become a unique and straightforward synthetic strategy in late-stage C-S bond formation of relevant complex molecules. Such transformations represent a breakthrough in modern synthetic organic chemistry, as they offer unusual reactivity patterns and avoid pre-functionalization of the starting materials. Despite inherent challenges in activating/functionalizing unreactive C-H bonds, a considerable number of different transition metals have shown the ability to selectively catalyze these processes toward C-S bond formation. In this sense, this review article covers the development and mechanistic analysis of the direct sulfanylation of Csp 3 -H and Csp 2 -H bonds through transition metal catalysed reactions in the last two decades, providing an essential guide for organic chemists working on this research area.