A new approach to enantiomerically pure bis-imidazoles derived from trans-1,2-diaminocyclohexane

Racemic as well as enantiomerically pure trans-1,1′-(cyclohexane-1,2-diyl)bis(imidazole N-oxides) were prepared from trans-cyclohexane-1,2-bis(methylidenamine) and 1,2-dione monooximes (α-hydroxyiminoketones). The enantiomeric purity of selected products was determined by means of 1H NMR spectroscopy in the presence of (+)-(R)-(tert-butyl)(phenyl)phosphonothioic acid as a chiral solvating agent. Deoxygenation by treatment with Raney-nickel led to the corresponding chiral bis-imidazoles.

Figure optionsDownload as PowerPoint slide

(R,R)-trans-1,1′-(Cyclohexane-1,2-diyl)bis(4,5-dimethylimidazole)-3,3′-dioxideC16H24N4O2Ee = 100%[α]D20=-267.6 (c 0.98, MeOH)Source of chirality: enantiomerically pure substrateAbsolute configuration: (1R,2R)

(R,R)-trans-1,1′-(Cyclohexane-1,2-diyl)bis(5-methyl-4-phenylimidazo-le)-3,3′-dioxideC26H28N4O2Ee = 100%[α]D20=-136.3 (c 0.82, MeOH)Source of chirality: enantiomerically pure substrateAbsolute configuration: (1R,2R)

(R,R)-trans-1,1′-(Cyclohexane-1,2-diyl)bis(4-methyl-5-phenylimidazole)-3,3′-dioxideC26H28N4O2Ee = 100%[α]D20=-127.0 (c 0.84, MeOH)Source of chirality: enantiomerically pure substrateAbsolute configuration: (1R,2R)

(R,R)-trans-1,1′-(Cyclohexane-1,2-diyl)bis(4,5-diphenylimidazole)-3,3′-dioxideC36H32N4O2Ee = 100%[α]D20=+6.0 (c 1.02, MeOH)Source of chirality: enantiomerically pure substrateAbsolute configuration: (1R,2R)

(R,R)-trans-1,1′-(Cyclohexane-1,2-diyl)bis(5-methyl-4-phenylimidazole)C26H28N4Ee = 100%[α]D20=+62.5 (c 1.00, MeOH)Source of chirality: enantiomerically pure substrateAbsolute configuration: (1R,2R)

(R,R)-trans-1,1′-(Cyclohexane-1,2-diyl)bis(4-methyl-5-phenylimidazole)C26H28N4Ee = 100%[α]D20=-29.8 (c 1.02, MeOH)Source of chirality: enantiomerically pure substrateAbsolute configuration: (1R,2R)

(R,R)-trans-1,1′-(Cyclohexane-1,2-diyl)bis(4,5-diphenylimidazole)C36H32N4Ee = 100%[α]D20=+72.3 (c 0.94, MeOH)Source of chirality: enantiomerically pure substrateAbsolute configuration: (1R,2R)