Pyridazines XXX VIIII. Pyridazino[4,5–e]‐1,4‐diazepine – A Novel Ring System of Potential Pharmaceutical Interest

Abstract

Since Sternbach's discovery of the benzodiazepines there has been enormous effort to optimize as well as to alter the pharmacological profile of these important drug substances3). In this context, a great number of structure modifications has been concerned with the replacement of the "benzo" moiety by heteroaromatic systems, including various N-hetero-cycles4). Despite the continuing interest in pyrido-1,4-diazepines4-'), the corresponding aza-analoguous diazino-annelated systems so far remained largely unexplored.We here report on the preparation of such a novel class of heteroareno-1,4-diazepines in which the seven-membered system is fused to positions 4,5 of a pyridazine nucleus. Previously, we had succeeded in the first synthesis of pyridazine analogues of 2-aminobenzophenone, namely 5-amino-4-pyridazinyl aryl ketones8). The latter bifunctional 1,2-diazine derivatives recently proved to be versatile starting materials in syntheses of various heterocycle-annelated pyridazines'. 9-12); they now were found to permit ready access also to the title pyridazinodiazepines 3a-c. C: X = 2-F a: X = H b: X = 4-C1 Arch. Pharm. (Weinheim) 321,309-310 (1988) 0 VCH Verlagsgesellschajl mbH, 0-6940 Weinheim, I988 0345-6233l88lOSOS-0309 02.SOlO