Oxidative Radical Cyclization of N‐methyl‐N‐arylpropiolamide to Isatins via Cleavage of the Carbon‐carbon Triple Bond

A radical cyclization of N‐methyl‐N‐arylpropiolamide to isatins via an oxidative cleavage of a carbon‐carbon triple bond has been developed. In the presence of oxone and NaNO2, a variety of N‐methyl‐N‐arylpropiolamides were smoothly transformed into isatins. A nitration reaction proceeded along with the oxidative cyclization; both nitrated and non‐nitrated isatins were obtained in a one‐pot reaction with moderate to good total yields. This is the first example for the synthesis of isatins via the oxidative radical cleavage of a carbon‐carbon triple bond.