The methylation of 2-amino-5-chlorobenzophenone (I) with dimethyl-sulfate affords the 5-chloro-2-methylaminobenzophenone (II), which is conden-sed with bromoacetyl bromide (A) to yieId 2-(2-bromo-N-methylacetamido)-5-chlorobenzophenone (III). The amonolysis of (III) with ammonia in methanol gives 2-(2-amino-N-methylacetamido)-5-chlorobenzophenone (IV), which is finally condensed with diketene (B) in refluxing acetone. This product can also be obtained by condensation of 7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2-one (V) with acetyl chloride (C) and triethylamine in ether or with diketene (B) in acetone.