Directed reactions hydrogenation, heterogenous

The synthetic value of this reaction should be mentioned. Thus, current production of 5p-steroids from As-3(i-ols, readily available and cheap starting materials, requires a preliminary Oppenauer oxidation or fermentation to the A4-3-keto derivative followed by catalytic hydrogenation under alkaline conditions, as direct catalytic hydrogenation with both heterogeneous and homogeneous systems gives only the 5a isomer. 

The hydrogenation of p-unsaturated alcohols is a classical example of competing reaction processes in heterogeneous catalysis. In principle, either isomerization to an enol followed by tautomerization to the ketone can occur, or direct hydrogenation to the saturated alcohol is possible (1). It is fair to state that interest in this type of chemistry is derived from both basic scientific... 

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