Mechanism of Alkaline Hydrolysis of Diazepam

Article abstract of DOI:10.1002/jccs.199800044

Diazepam (1) is a frequently prescribed hypnotic/anxiolytic drug in worldwide use. Compound 1 is hydrolyzed in alkaline medium to form 2-methylamino-5-chlorobenzophenone imine (2) and 2-methylamino-5-chlorobenzophenone (3); the ratio of 2:3 increases with increasing NaOH concentration (J. Pharm. Sci. 85, 745-748, 1996). The mechanism in the conversion of 1 to 2 and 3 via various intermediates is the subject of this report. Results of hydrolysis kinetics and structural identification of some intermediate products indicated an initial hydroxide attack at the C2-carbonyl carbon of 1, resulting in the formation of a dioxide (7, 7-chloro-1,3-dihydro-1-methyl-5-phenyl-2H-1,4-benzodiazepin-2,2-dioxide). Compound 7 was characterized by proton NMR spectroscopy and via its monomethyl ether (8, 7-chloro-1,3-dihydro-2-hydroxy-2-methoxy-1-methyl-5-phenyl-2H-1,4-benzodiazepme) . The seven-member diazepine ring of 7 opened at the N1-C2 bond to form aglycinate [5, 2-methylamino-5-chloro-α-(phenylbenzylidene)glycinate]. Compound 7 (and/or 5) underwent an additional hydroxide attack at the C5-N4 imine bond to form a tetrahedral intermediate, which decomposed to form 2 and 3.