Ketazolam

The title compound, 11-chloro-8,12b-dihydro-2,8-dimethyl-12b-phenyl-4H-[1,3 ]oxazino[3,2-d][1,4]benzodiazepine-4,7- (6H)-dione, C20H17ClN2O3, is a benz odiazepine with an additional d-face-fused heterocyclic ring. In the molecu le, a dihedral angle of 86.2 (1)degrees is formed by the planes of the phen yl and benzo rings and the former is axially oriented from the core, i.e. t he fused 6,7,6-tricyclic system. Both heterocycles in the core suffer signi ficant deviations from planarity. The central diazepine ring is a twist-boa t and the oxazine ring exhibits a conformation intermediate between half-ch air and sofa.