Abstract Among sulfoximine derivatives containing a chiral sulfur center, benzothiadiazine‐1‐oxides are important for applications in medicinal chemistry. Here, we report that the combination of an achiral cobalt(III) catalyst and a pseudo‐ C 2 ‐symmetric H 8 ‐binaphthyl chiral carboxylic acid enables the asymmetric synthesis of benzothiadiazine‐1‐oxides from sulfoximines and dioxazolones via enantioselective C−H bond cleavage. With the optimized protocol, benzothiadiazine‐1‐oxides with several functional groups can be accessed with high enantioselectivity.