Regioselective C(sp²)3-H thiocyanation of substituted 4H-pyrido[1,2-a]pyrimidin-4-ones and its derivatizations

We demonstrate herein the first example of K2S2O8 mediated direct C(sp(2))-Hthiocyanation of substituted 4H-pyrido[1,2-a]pyrimidin-4-ones at room temperature in the absence of a metal catalyst. This unique approach features a broad substrate scope with excellent functional group tolerance and substitution patterns, affording the target thiocyanated scaffolds in lucrative yields with exclusive regioselectivity. Mechanistic investigations have also been conducted for better understanding of the reaction pathway. In addition, the synthetic utility of this protocol has been showcased through the construction of biologically relevant analogues.