TBHP/CoCl2‐Mediated Intramolec­ular Oxidative Cyclization of N‐(2‐Formylphenyl)amides: An Approach to the Construction of 4H‐3,1‐Benz­oxazin‐4‐ones

Abstract The intramolecular oxidative cyclization of N ‐(2‐formylphenyl)amides has been realized through an oxidative C(sp 2 )–O(sp 2 ) bond‐forming reaction between an aldehyde carbon and amide oxygen. This new strategy, which uses tert ‐butyl hydroperoxide (TBHP) as an oxidant and CoCl 2 as the catalyst, allows for the efficient Co‐catalyzed synthesis of useful benzoxazin‐4‐one derivatives and features readily available starting materials and mild reaction conditions.