Reduction of Enols and Phenols

Since enols are generally in tautomeric equilibrium with the corresponding carbonyl compounds, the methods that apply to produce hydrocarbons are those used for the reduction of aldehydes and ketones (Chapter 9) and are discussed there. For a few stable enols (vfde5Mprfl), catalytic methods, which correspond to a direct reduction of the carbon-carbon double bond as with alkenes, yield the corresponding alcohols. 

Phenols (hydroxybenzenes) and alkyl-substituted phenols can be reduced to the corresponding cyclohexanols with hydrogen in the presence of metal catalysts such as platinum (Pt) or nickel (Ni), and it is often possible to isolate more than one isomer. Thus, as shown in Equation 8.19, the reduction of 2-methylbenzenol (2-methylphenol, ori/io-cresol) with hydrogen (H,) in the presence of platinum (Pt) under acidic conditions yields (Z)- (or cis-) 2-methylcyclohexanol, while under neutral conditions, the (F - (or tram-) isomer predominates. 

The reduction of the aromatic ring has proved valuable in the synthesis of some highly hindered cyclohexanols. For example (as will be discussed more fuUy 

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