Photocatalytic sequential C-H functionalization expediting acetoxymalonylation of imidazo heterocycles.

The importance of functionalized imidazo heterocycles has often been featured in several impactful research both from academia and industry. Herein, we report a direct C-3 acetoxymalonylation of imidazo heterocycles using relay C-H functionalization enabled by organophotocatalysis starring zinc acetate in the triple role of an activator, ion scavenger as well as an acetylating reagent. The mechanistic investigation revealed a sequential sp and sp C-H activation, followed by functionalization driven by zinc acetate coupled with the photocatalyst PTH. A variety of imidazo[1,2-]pyridines and related heterocycles were explored as substrates along with several active methylene reagents, all generating the products with excellent yields and regioselectivity, thus confirming excellent functional group tolerability.