Dispiro[2H-benzimidazole-2,1'-cyclohexane-4',2''-[2H]benzimidazole] 1-oxide and dispiro[2H-benzimidazole-2,1'-cyclohexane-4',2''-[2H]benzimidazole] 1,1''-dioxide.
Oxidation of tetrahydrodispirobenzimidazole by m-chloroperbenzoic acid did not produce dispiro-2H-benzimidazole, which is the product obtained by oxidation with MnO(2). Instead, a mixture of two compounds was identified, namely dispiro[2H-benzimidazole-2,1'-cyclohexane-4',2''-[2H]benzimidazole] 1-oxide, C(18)H(16)N(4)O, (III), and dispiro[2H-benzimidazole-2,1'-cyclohexane-4',2''-[2H]benzimidazole] 1,1''-dioxide, C(18)H(16)N(4)O(2), (IV). In (III), the molecules are disordered about a twofold rotation axis and have 2/m site symmetry. In (IV), the crystals are triclinic and the molecules occupy crystallographic inversion centers. Although the two compounds are very similar and are arranged in layers, they adopt completely different packing modes within the layers, viz. herring-bone in (III) and parallel molecules in (IV). The molecules within the layers are held together by C-H...O and C-H...N hydrogen bonds.