Raney nickel phenols, ketones from

In contrast to phenolic hydroxyl, benzylic hydroxyl is replaced by hydrogen very easily. In catalytic hydrogenation of aromatic aldehydes, ketones, acids and esters it is sometimes difficult to prevent the easy hydrogenolysis of the benzylic alcohols which result from the reduction of the above functions. A catalyst suitable for preventing hydrogenolysis of benzylic hydroxyl is platinized charcoal [28], Other catalysts, especially palladium on charcoal [619], palladium hydride [619], nickel [43], Raney nickel [619] and copper chromite [620], promote hydrogenolysis. In the case of chiral alcohols such as 2-phenyl-2-butanol hydrogenolysis took place with inversion over platinum and palladium, and with retention over Raney nickel (optical purities 59-66%) [619]. 

Numerous studies have shown that low hydrogen overpotential electrically conducting catalysts (e.g., Raney nickel, platinum and palladium on carbon powder, and Devarda copper) can be used to electrocatalyticaUy hydrogenate a variety of organic compounds including benzene and multiring aromatic compounds, phenol, ketones, nitro compounds, dinitriles, and glucose [45, 46, 54, 55, 67-71]. These reactions have been carried out in both batch and semicontinuous flow reactors in most cases, the reaction products were similar to those obtained from a traditional chemical catalytic scheme at elevated temperatures and pressures. 

Birch reduction of 12-methoxypodocarpa-8,l l,13-trien-19-ol has been investigated and methods have been developed for converting the C-12 ketones into C-13 ketones. An alternative approachhas been used to transpose the aromatic oxygen function from C-12 to C-13. The best route involved mononitration of methyl podocarpate (57), reduction of the nitrophenol toluene-p-sulphonate (58) to an amine (59) with stannous chloride and then Raney nickel, and finally diazotization with isopentenyl nitrite in cold acidic methanol to atTord the phenol ether. 

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