Photoinduced Regioselective Chalcogenation and Thiocyanation of 4H‐Pyrido[1,2‐a] pyrimidin‐4‐ones Under Benign Conditions

Abstract A lenient approach for regioselective C3−H chalcogenation and thiocyanation of 4 H ‐pyrido[1,2‐ a ] pyrimidin‐4‐ones is developed using visible light photocatalysis. This operationally straightforward method furnishes a broad array of C‐3, Ar−S/Ar−Se and ‐SCN functionalized derivatives in moderate to high yields. This protocol employs visible light as an environmentally friendly energy source, cost effective inorganic persulfate‐based oxidant and easily procurable dichalcogenides for regioselective C−H chalcogenation of the substrate at room temperature. Further, regioselective thiocyanation of 4 H ‐pyrido[1,2‐ a ] pyrimidin‐4‐ones was also developed. Mechanistic path for these transformations has been proposed based on light on/off and Stern‐Volmer studies as well as quantum yield calculations.