Superacidic and HUSY-zeolite activation of 1,3-indandione: reactions with benzene and cyclohexane

1,3-Indandione condenses with benzene and undergoes selective ionic hydrogenation with cyclohexane under the action of superacids, such as CF 3 SO 3 H, AlCl 3 and AlBr 3 to give 3,3-diphenyl-1-indanone and 1-indanone, respectively. The same reactions are mediated successfully by the regenerable solid acid, HUSY-zeolite. The results obtained are interpreted in terms of key dicationic (superelectrophilic) intermediates. 1,3-Indandione ( 1 ) readily condenses with benzene and undergoes selective ionic hydrogenation with cyclohexane when activated by superacids, such as CF 3 SO 3 H, AlCl 3 and AlBr 3 to give 3,3-diphenyl-1-indanone ( 4 ) and 1-indanone ( 7 ), respectively. Combination of these reactions in ‘one-pot’ yields 3-phenyl-1-indanone ( 5 ). In addition, similar reactions have been carried out using the regenerable solid acid, HUSY-zeolite, providing an effective excess of acidic sites. The mechanism of these reactions, with potential involvement of superelectrophilic dicationic intermediates, is discussed.