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 pharma-ceuticals,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.