Ruthenium tetroxide benzyl ethers

Ruthenium tetroxide is a potent oxidant, however, and it readily attacks carbon-carbon double bonds.19 Primary alcohols are oxidized to carboxylic acids, methyl ethers give methyl esters, and benzyl ethers are oxidized to benzoate esters. 

Oxidation of benzyl ethers. Benzyl ethers are oxidized to benzoate esters in yields of 54-96% by ruthenium tetroxide using the Sharpless conditions (11, 462). This reaction provides a useful method for cleavage of benzyl ethers, which is usually effected by hydrogenation. 

Although a number of different reagents have been discovered for the selective oxidation of ethers, e.g. halogens, iodine tris(trifluoroacetate), trichloroisocyanuric acid, UFs, A(,N-dibromobenzenesul-fonamide and lead tetraacetate, few have assumed any synthetic importance. Of these, the most significant are the metallic oxidants chromic acid and ruthenium tetroxide. DDQ has also been widely used for the oxidative d rotection of benzyl ethers. It is the aim of this chapter to review the latest developments in ether oxidation by these, and other reagents, with particular emphasis on chemo- and regio-selectivity. Several reviews on the subject have appeared previously. " The related oxidation of acetals has been reviewed recently" and will not be dealt with here. 

The oxidation products of mixed ethers may differ when different oxidants are used. Whereas ruthenium tetroxide oxidizes benzyl methyl... 

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