2-Butyl-11-phenyl-5,10-dihydro-1H-benzo[e]imidazo[1,5-a][1,4]diazepine-1,3(2H)-dione

The title compound, C(21)H(21)N(3)O(2), was obtained following a five-step synthetic procedure yielding weakly diffracting rod and needle-shaped crystals which crystallized concomitantly. Structural analysis of a rod-shaped crystal showed that the central seven-membered heterocyclic ring adopts a conformation that is perhaps best described as a distorted boat, with the H-bearing (CH(2) and NH) atoms lying well out of the least-squares mean plane fitted through the other five atoms in the ring (r.m.s. deviation 0.075 Å). In the crystal, the compound packs as a twisted chain, which propagates along the b axis by means of an R (1) (2)(6) motif formed by one of the carbonyl O atoms acting as a bifurcated acceptor in an N—H⋯O and C—H⋯O inter­action. No diffraction was observed from the needle-shaped crystals.