Redox Cyclization of Amides and Sulfonamides with Nitrous Oxide for Direct Synthesis of Heterocycles.

Herein we report a redox cyclization of amides and sulfonamides with nitrous oxide (N2O) for the direct synthesis of heterocycles. Various amides and sulfonamides could undergo directed ortho metalation (DoM) by treatment with BuLi, and the lithium intermediate could be trapped by N2O gas to achieve redox cyclization. N2O serves as a N-atom donor to mediate the intramolecular coupling of lithium species toward heterocycle formation with free external oxidant. This protocol offers a direct synthesis of heterocycles with features of readily available starting materials, simple operation, and a broad substrate scope.