N-Acyl-, N-sulfonyl-, and N-arylsulfilimines are rapidly oxidized to the corresponding sulfoximines in high to virtually quantitative yields by m-chloroperoxybenzoate anion generated in situ in basic aqueous alcoholic media. In the one N-aryl case studied, S, S- dimethyl-N-(pnitropheny1) sulfilimine is converted unexpectedly to p-nitrosonitrobenzene in excellent yield by m-chloroperoxybenzoic acid but if the m-chloroperoxybenzoate anion is ...