(2R,4S)-7-Bromo-2-phenyl-2,3,4,5-tetrahydro-1,4-epoxynaphtho[1,2-b]azepine, (2RS,4SR)-7-bromo-2-(4-chlorophenyl-2,3,4,5-tetrahydro-1,4-epoxynaphtho[1,2-b]azepine and (2RS,4SR)-2-(4-fluorophenyl)-2,3,4,5-tetrahydro-1,4-epoxynaphtho[1,2-b]azepine: hydrogen-bonded structures in two and three dimensions.

(2R,4S)-7-Bromo-2-phenyl-2,3,4,5-tetrahydro-1,4-epoxynaphtho[1,2-b]azepine, C(20)H(16)BrNO, (I), exhibits evidence of a modest degree (ca 10%) of inversion twinning, while both (2RS,4SR)-7-bromo-2-(4-chlorophenyl)-2,3,4,5-tetrahydro-1,4-epoxynaphtho[1,2-b]azepine, C(20)H(15)BrClNO, (II), and (2RS,4SR)-2-(4-fluorophenyl)-2,3,4,5-tetrahydro-1,4-epoxynaphtho[1,2-b]azepine, C(20)H(16)FNO, (III), crystallize as genuine racemic mixtures. The molecules of (I) are linked into sheets by a combination of one C-H...O hydrogen bond and two C-H...pi(arene) hydrogen bonds, while those of (II) are linked into sheets of pi-stacked hydrogen-bonded chains. A combination of one C-H...O hydrogen bond and four independent C-H...pi(arene) hydrogen bonds links the molecules of (III) into a three-dimensional framework. The significance of this study lies in its finding, via comparison with the structures of some closely-related epoxybenzazepine analogues, of significant changes in crystal structures consequent upon small changes in the peripheral substituents.