Recent advances in transition-metal-free C–H functionalization of imidazo[1,2-a]pyridines

Imidazo[1,2-a]pyridines are unique nitrogen-containing organic compounds with wide applications in pharmaceuticals, natural products, material science and organometallics. Due to their significant biological and synthetic value, the construction of imidazo[1,2-a]pyridine scaffolds has been a highly intriguing research topic, and substantial progress had been made in the past decades. In this review, we aim to summarize the current advances in direct C–H functionalization of imidazo[1,2-a]pyridines under transition-metal-free conditions. For the selected examples, we focused on the design and catalytic cycle mechanism, as well as on representative outcomes and applications.