Aromatic Compounds Containing Benzyl-Oxygen Linkages

3 AROMATIC COMPOUNDS CONTAINING BENZYL-OXYGEN LINKAGES 

Adkins and Covert hydrogenated benzyl alcohol using Ni-kieselguhr catalysts prepared by various procedures, but the best yield of cyclohexanemethanol was only 

It appears that the hydrogenation over Raney Ni results in lower yields of cyclohexanemethanol (usually 20%).159 The hydrogenation over an active platinized Raney Ni also gave only a 20% yield.160 

However, ruthenium, rhodium, and rhodium-platinum catalysts have been found to be highly effective for the selective hydrogenation of these benzyl-oxygen compounds without loss of the oxygen functions. Thus, benzyl alcohol is hydrogenated to cyclohexanemethanol in high yield over ruthenium dioxide with addition of a small amount of acetic acid (eq. 11.35).114 

Platinum catalysts, which usually tend to cause extensive hydrogenolysis, may be used for the selective hydrogenation of benzyl-type alcohols in the presence of a proper base. For example, benzyl alcohol can be hydrogenated to cyclohexane-methanol almost quantitatively over Adams platinum oxide in ethanol with addition of a small amount of acetic acid (eq. 11.36).160 

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