A low-temperature, protecting-group-free oxidation of 2-substituted anilines has been developed to generate an electrophilic N-aryl nitrenoid intermediate that can engage in C–NAr bond formation to construct functionalized N-heterocycles. The exposure of 2-substituted anilines to PIFA and trifluoroacetic acid or 10 mol % Sc­(OTf)3 triggers nitrenoid formation, followed by productive and selective C–NAr and C–C bond formation to yield spirocyclic- or bicyclic 3H-indoles or benzazepinones. Our experiments demonstrate the breadth of these oxidative processes, uncover underlying fundamental elements that control selectivity, and demonstrate how the distinct reactivity patterns embedded in N-aryl nitrenoid reactive intermediates can enable access to functionalized 3H-indoles or benzazepinones.

A palladium-catalyzed reductive cyclization of nitroarenes has been designed to construct sp3-C–NHAr bonds from sp3-C–H bonds by using an enolizable nucleophile to intercept a nitrosoarene intermediate. Exposure of ortho-substituted nitroarenes to 5 mol % of Pd­(OAc)2 and 10 mol % of phenanthroline under 2 atm of CO constructs partially saturated 5-, 6-, or 7-membered N-heterocycles using α-pyridyl carboxylates, malonates, 1,3-dimethylbarbituric acid, 1,3-diones, or difurans as the nucleophile.