Four related benzazepine derivatives in a reaction pathway leading to a benzazepine carboxylic acid: hydrogen-bonded assembly in zero, one, two and three dimensions.

(2R*,4S*)-Methyl 2,3,4,5-tetrahydro-1,4-epoxy-1H-benz[b]azepine-2-carboxylate, C12H13NO3, (I), and its reduction product (2R*,4S*)-methyl 4-hydroxy-2,3,4,5-tetrahydro-1H-benz[b]azepine-2-carboxylate, C12H15NO3, (II), both crystallize as single enantiomers in the space group P212121, while the hydrolysis product (2RS,4SR)-4-hydroxy-2,3,4,5-tetrahydro-1H-benz[b]azepine-2-carboxylic acid, C11H13NO3, (III), and the lactone (2RS,5SR)-8-(trifluoromethoxy)-5,6-dihydro-1H-2,5-methanobenz[e][1,4]oxazocin-3(2H)-one, C12H10F3NO3, (IV), both crystallize as racemic mixtures in the space group P21/c. The molecules of compound (IV) are linked into centrosymmetric R2(2)(10) dimers by N-H···O hydrogen bonds, and those of compound (I) are linked into chains by C-H···π(arene) hydrogen bonds. A combination of O-H···O and O-H···N hydrogen bonds links the molecules of compound (III) into sheets containing equal numbers of R4(4)(14) and R4(4)(26) rings, and a combination of C-H···π(arene) hydrogen bonds and three-centre O-H···(N,O) hydrogen bonds links the molecules of compound (II) into a three-dimensional framework structure. Comparisons are made with some related compounds.