Selective C3 Functionalization of 4H‐Pyrido[1,2‐a]pyrimidin‐4‐ones via Glyoxylic Acid: Tuning Products with Temperature and Solvents

Herein, we report a metal free protocol for direct and selective C3 hydroxymethylation, methylenation and formylation of 4H‐pyrido[1,2‐a]pyrimidin‐4‐ones. The protocol is achieved by using an environmental friendly, economical and naturally occurring reagent, glyoxylic acid. Selectivity of the reaction product can be achieved by simply switching the reaction medium, DMSO for hydroxymethylation/methylenation and CH3CN for formylation. The protocol is scalable, delivering good yields, reaching up to 95% across a wide range of derivatives.