Metal-free, direct acylation of purines to access C⁶-acylated purine derivatives induced by TBHP via Minisci-type reaction

A metal-free C-H functionalization of purines with aldehydes was developed to access C-6-acylated purines via green radical reactions. Theoretically, there are many competitive reactions due to the three C-H bonds (C-2-H, C-6-H, C-8-H) in the purine, and the acylation only happens at the purinyl C-6-position. This method avoids a metal catalyst and provides a green approach to construct C-C (sp(2)) bonds at the purinyl C-6-position, while maintaining excellent compatibility with various functional groups. Moreover, the protocol features broad substrate scope and easy scale-up. The transformation of the product demonstrates the significant practical value of the method. The primary mechanism was proposed based on controlled experiments.