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A novel and efficient approach for the regioselective selenylation of 4H‐pyrido‐[1,2‐a]‐pyrimidin‐4‐ones with diselenides at room temperature has been developed. This procedure is catalyzed by N‐iodosuccinimide under metal‐free conditions with a broad range of substrate scopes and affords C3 selenylation products in good to excellent yields. Furthermore, the sulfenylation with diphenyl disulfides and 4‐methylbenzenethiol in this transformation is successful. A novel and efficient approach forthe C3 regioselective selenylation of 4H‐pyrido‐[1,2‐a]‐pyrimidin‐4‐ones employing N‐Iodosuccinimide at room temperature has been developed.

An efficient and simple protocol for silver‐catalyzed direct C3 phosphonation of 4H‐pyrido[1,2‐a]pyrimidin‐4‐ones with dialkyl phosphites has been developed. The reaction shows high regioselectivity, broad scope of substrates, and good functional group compatibility. Importantly, the phosphorylated 4H‐pyrido[1,2‐a]pyrimidin‐4‐one product 3 ucan be employed as efficient probes for Fe3+. A novel Ag‐catalyzed phosphonation of 4H‐pyrido[1,2‐a]pyrimidin‐4‐oneswith H‐phosphites exclusively affords C‐3 phosphonated 4H‐pyrido[1,2‐a]pyrimidin‐4‐one derivatives.