Crystal structures of methyl 3-phenyl-4,5-di-hydro-1H,3H-benzo[4,5]imidazo[2,1-c][1,4]oxazepine-4-carboxyl-ate and methyl 1-methyl-3-phenyl-4,5-di-hydro-1H,3H-benzo[4,5]imidazo[2,1-c][1,4]oxazepine-4-carboxyl-ate.

The title compounds, C19H18N2O3, (I), and C20H20N2O3, (II), differ only by a methyl substituent on the seven-membered oxazepine ring in (II). In both compounds, these rings have a twist-chair conformation. The phenyl ring makes a dihedral angle of 73.42†(10)° with the benzimidazole ring system mean plane (r.m.s. deviation = 0.015†à ) in (I) and 83.07†(7)° in (II) (r.m.s. deviation = 0.026†à ). The methyl carboxyl-ate groups are planar to within 0.031†(2) in (I) and 0.003†(2)†à in (II). They are inclined to the phenyl and benzimidazole ring system by 33.78†(16) and 87.56†(14)°, respectively, in (I) and by 53.04†(12) and 60.22†(11)°, respectively, in (II). In the crystal of (I), mol-ecules stack in a herringbone fashion and are linked by C-H⋯O hydrogen bonds, forming chains along [100]. In the crystal of (II), there are no significant inter-molecular inter-actions present.