Metal free C-3 chalcogenation (sulfenylation and selenylation) of 4H-pyrido[1,2-a]pyrimidin-4-ones

An expeditious metal free C-3 chalcogenation of 4H-pyrido[1,2-a]pyrimidin-4-one has been devised to synthesize diversely orchestrated 3-ArS/ArSe derivatives in high yields (up to 95%). This operationally simple reaction proceeds under mild reaction conditions, can be executed in gram scale, and also highlights broad functional group tolerance. Preliminary experimental investigation suggests a radical mechanistic pathway for these transformations.