Metal-catalysed non-directed C(sp²)-H bond activation

The field of non-directed C-H activation, whether catalyzed by transition metals or carried out through metal-free methods, has emerged as a transformative strategy for functionalizing organic molecules. This contemporary approach creates new retrosynthetic disconnections and complements traditional methods that utilize directing groups, enabling the direct functionalization of arenes and heteroarenes without the need for these groups. This strategy enhances synthetic flexibility and creates distinct retrosynthetic pathways, thereby enriching established methodologies. This review covers the latest advancements in catalytic non-directed C(sp²)-H functionalization, with particular focus on both metal-catalyzed and metal-free systems. We examine notable progress in reaction scope, selectivity, and mechanistic insights, all of which highlight the strategic potential of these methods in the synthesis of complex molecules. Moreover, we discuss ongoing challenges, such as issues related to regioselectivity and substrate scope, while presenting potential avenues for improving the efficiency, sustainability, and applicability of non-directed C-H activation. The goal of this review is to provide a comprehensive picture of the current state of the field, aid understanding, and inspire further innovation in non-directed C-H functionalization as a versatile tool for advanced molecular design.