Methylation of 5-Phenyl-1,4-benzodiazepin-2-one derivatives with N,N-dimethylformamide-dimethyl acetal

A novel method for N-methylation of the cyclic amide in the 1,4-benzodiazepine ring system is presented. Methods traditionally used involve treatment of the 1,4-benzodiazepinone anion with an alkyl halide. It has been demonstrated that these derivatives can be methylated on the amide nitrogen atom by use of dimethyl-formamide dimethyl acetal which acts as both reagent and solvent for the reaction.