Oxidative Annulations Involving DMSO and Formamide: K2S2O8 Mediated Syntheses of Quinolines and Pyrimidines

An efficient strategy toward 4-arylquinolines and 4-arylpyrimidines from readily available precursors is described. Oxidative annulation promoted by K2S2O8 involving anilines, aryl ketones, and DMSO as a methine (═CH−) equivalent leads to 4-arylquinolines via a cascade that entails generation of a sulfenium ion, subsequent C–N and C–C bond formations, and cyclization. The application of this strategy to the activation of acetophenone–formamide conjugates toward the synthesis of 4-arylpyrimidines is also described.