Oxidations Using Sodium or Potassium Alkoxides

Apart from aluminium, many other metals were tested in Meerwein-Ponndorf-Verley reductions and Oppenauer oxidations during the early years of research on hydride transfer from alkoxides.26 A consensus was 

The Woodward modification of the Oppenauer oxidation is occasionally used on substrates that fail to be oxidized under the standard protocol,27 although it possesses the serious limitation of the strongly basic medium generated by potassium f-butoxide. 

An alcohol can be quantitatively transformed into a sodium or potassium alkoxide with NaH or KH. These alkoxides can sometimes transfer a hydride to a suitable hydride-acceptor28 in a quite selective manner.29 

A selective oxidation of only one diastereomeric alcohol is achieved in a very elegant manner by forming the corresponding potassium alkoxides with excess of KH, followed by treatment with benzophenone. A hydride transfer to benzophenone occurs from the alkoxide able to deliver a hydride from a less congested location. The reverse reaction of reduction of the resulting ketone is avoided by trapping this ketone by formation of its enolate with excess of KH. 

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