Synthesis and crystal structures of 7-bromo-5-(2′-chloro)phenyl-3-hydroxy-1-methyl-1,2-dihydro-3H-1,4-benzodiazepin-2-one and 7-bromo-5-(2′-chloro)phenyl-1-hexyl-1,2,4,5-tetrahydro-3H-1,4-benzodiazepin-2,3-dione

Treatment of 7-bromo-5-(2′-chloro)phenyl-3-hydroxy-1,2-dihydro-3H-1,4-benzodiazepin-2-one (1) with methyl or hexyl tosylate resulted in 7-bromo-5-(2′-chloro)phenyl-3-hydroxy-1-methyl-1,2-dihydro-3H-1,4-benzodiazepin-2-one (2) and 7-bromo-5-(2′-chloro)phenyl-1-hexyl-1,2,4,5-tetrahydro-3H-1,4-benzodiazepin-2,3-dione (3). As confirmed by X-ray crystallography, the two products differ not only in the identity of the alkyl substituent in position 1 of the benzodiazepine fragment but also crystallize in different molecular forms resulting from proton migration. This alteration of the molecular structure leads to a significant change in the conformation of the central molecular fragment and influences the assembly mode in the crystal. In 3, centrosymmetric dimers formed via a pair of NH⋯O hydrogen bonds are further linked into chains via CBr⋯OC halogen bond interaction. In turn in 2 there are two symmetry independent molecules, each giving a different set of intermolecular interactions. One of the molecules forms a dimer via OH⋯O interactions whereas the second one generates chain via CBr⋯OC halogen bond that is also assisted by a weak OH⋯Br hydrogen bond.