Chemistry of Polynuclear Compounds. IV. The Reduction of Polynuclear Quinones with cyclohexyl-p-toluene Sulphonate

In an investigation into the coking mechanism of coal, polynuclear quinones have been adopted as models. Using cyclohexyl-p-toluene sulphonate the following quinones have been reduced to their parent hydrocarbons : dibenzanthrone, isodibenzanthrone, pyranthrone, 4,10-dibromoanthanthrone, anthraquinone (and anthrone), 1,5-dimethoxyanthraquinone, and 1,8-dimethoxyanthraquinone. The reaction gave favourable yields compared with alternative methods, but had the advantage that substituent groups such as halogen and alkoxyl were unattacked. A mechanism is proposed involving complexing of cyclohexyl cations with the quinones, followed by hydrogen-transfer via a resonance-stabilized cyclic transition state.