Structural characterization of [1,4]diazepino[6,5-b]indoles by powder diffraction

Abstract

As part of a systematic structural study of potentially pharmacologically active [1,4]diazepino[6,5-b]indoles, the crystal structures of nine compounds have been determined from laboratory powder diffraction data. The investigated compounds are: 2-oxo-1-(4-nitrophenyl)-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indole-4-oxide, C(17)H(12)N(4)O(4) (1a); 2-oxo-1-phenyl-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indole-4-oxide, C(17)H(13)N(3)O(2) (1b); 2-oxo-1-(4-ethoxyphenyl)-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indole-4-oxide, C(19)H(17)N(3)O(3) (1c); 2-oxo-1-(4-chlorophenyl)-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indole-4-oxide, C(17)H(12)N(3)O(2)Cl (1d); 2-oxo-1-(4-cyanophenyl)-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indole-4-oxide, C(18)H(12)N(4)O(2) (1e); 6-methyl-2-oxo-1-phenyl-1,2,3,6-tetrahydro[1,4]diazepino[6,5-b]indole-4-oxide, C(18)H(15)N(3)O(2) (1f); 2-formyl-3-[N'-(omega-chloracetyl)-N'-(4-nitrophenyl)]aminoindole, C(17)H(12)N(3)O(4)Cl (2a); 2-formyl-3-[N'-(omega-chloracetyl)-N'-(4-nitrophenyl)]aminoindole solvate with toluene (2:1), C(17)H(12)N(3)O(4)Cl.0.5C(7)H(8) (2as); 2-formyl-3-[N'-(omega-chloracetyl)-N'-(4-cyanophenyl)]aminoindole, C(18)H(12)N(3)O(2)Cl (2e). Compounds (1a)-(1f) crystallize in non-centrosymmetric triclinic, monoclinic and orthorhombic space groups. The three-dimensional structures of (1a)-(1e) demonstrate identical intermolecular NH(indole)...O<--N hydrogen bonds, which form linear chains of connected molecules. A comparison of the crystal structures (2a), (2e) and (2as) shows that the solvent used in the re-crystallization of (2a) and (2e), which are intermediates in the synthesis of (1a) and (1e), affects the intermolecular hydrogen-bond formation and, as a result, leads to essentially different yields of the goal products.