Imidazole and benzimidazole addition to quinones. Formation of meso and d,l isomers and crystal structure of the d,l isomer of 2,3-Bis(benzimidazol-1'-yl)-1,4-dihydroxybenzene

Abstract

The hydroquinones obtained by addition of imidazole. 2methylimidazole and henzimidazole to 1,Cbenzoquinone and 1,Cnaphthoquinone have been isolated and identified. In the case of 1,4&enzoquinone they are monosubstituted hydroquinones la - lc, o-disubstitutcd hydroquinones 2a - 2~. and pdisubstituted derivatives 3a - 3c while in the case of 1.4-naphthoquinone, only disubstituted derivatives 5a and SC have been isolated. In solution, 2.3-bis(2’-methylimidazol-l’-yl)-l,4dihydroxybenzene (2b), 2,3-bis (benzimidazol-l’-yl)-1,4-dihydroxybenzene (2~) and 2.3-bis(benzimidazol-l’-yl)-1.4- dihydroxynaphthalene (SC) exist as mixtures of meso and d.1 isomers. NMR spectroscopy (n.0.e. experiments in lH NMR and solid-state *SC CPMAS spectra) and AM1 semiempirical calculations have been used to establish the stmctum OftbeisonErsbothinthe solid state and in solution as well as their interconversion pathways. Compound 2c-d,l crystallizes with two methanol solvate molecules as guests and it has a crystallographic twofold axis through the middle. The host molecules are linked together by means of the methanol molecules through 0-H...O/N hydrogen bonds giving rise to chains along the c axis centrosymmetrically l&ted.