The acylation of 5H-2,3-benzodiazepines. Reactions of 4-phenyl-5H-2,3-benzodiazepine with acyl chlorides to give N-acylaminoisoquinolines and/or acylated dimers. X-Ray molecular structure of 5,14-diacetyl-4,5,8,9-tetrahydro-2,7-diphenyl-4,8-o-benzeno-3,9-imino-3H-3,5,6-benzotriazacycloundecine

Abstract

The acylation of 4-phenyl-5H-2,3-benzodiazepine (1) with acyl halides in benzene or toluene takes either or both of two reaction paths depending on the nature of the acylating reagent the order of mixing, and the reaction temperature. One pathway leads to the formation of 2-acylamino-3-phenylisoquinolinium chlorides (4) and the other to the formation of either or both of the acylated dimers (6) and (7) together with the benzodiazepine hydrochloride (8). These results are rationalised on the basis of the mechanism in Scheme 4 which involves the generation of the reactive intermediate (12) by the dehydrochlorination of the iminium chloride (11). Acylations in pyridine took a different path, similar to that followed in the acetic anhydride acylation of (1) in benzene or pyridine, and were used to prepare 1-alkoxy-2-benzoyl derivatives (10).