A highly selective copper-catalyzed concise synthesis of 3,5-diarylpyridine and 2-(1H)-pyridone has been achieved through cascade Chichibabin-type cyclization, C(sp(3))-C(sp(3)) cleavage, and aerobic oxidation. Azide, ceric ammonium nitrate (CAN), and 2-aminopyridine are disclosed as efficient nitrogen donors in this Cu-catalysis using O2 as the oxidant. Water and molecular oxygen were employed as the oxygen source in the case of oxygenation.
A formal aza-Wacker cyclization through a synergistic Cu/TEMPO-catalyzed radical relay pathway, using Nfluorobenzenesulfonimide (NFSI) as an external oxidant, is reported. In this efficient cyclization of alkenylated carbamates or amides at room temperature, the imidyl nitrogen-centered radical (NCR) generated by NFSI induces carbamate or amido NCR from the substrate via N−H homolysis to realize the radical relay process, which was supported by results of control experiments. This work provides an effective approach toward oxazolidinones, pyrrolidones, and isoindolinones under mild conditions.
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