Benzylic halides Komblum oxidation

Known as the Komblum oxidation, this is peihaps die most widely used and best-known mediod for die oxidation of halides. It works best with activated halides such as benzyl halides, a-halocarbonyl... 

Reaction of halides with silver nitrate to give nitrate esters has been known for years, but its synthetic application is more recent. Komblum showed that the nitrate esters derived from a-bromo ketones and esters decompose smoothly with catalytic sodium acetate in DMSO to give the a-dicarbonyl compounds in high yield. It was found unnecessary to isolate the nitrate ester after reaction of the halide with silver nitrate the solution was filtered to remove AgBr, concentrated, and added to DMSO containing catalytic sodium acetate. The method complements the others for the synthesis of a-dicarbonyl compounds since it employs nonacidic, nonbasic conditions. Unfortunately, the method gave variable results with benzyl halides. The application of the method to bromo esters other than bromoacetates was not reported. Some related oxidations are shown in equations (41) and (42), and Schemes 9 and 10. The oxidation of an iminium salt is notable. 

The Komblum oxidation was the first reported oxidation reaction using DMSO. a-Bromo ketones such as 23 were converted to the corresponding glycoxals in good yield.1 Less reactive halides, such as most benzylic halides and aliphatic halides, can be oxidised by conversion to the tosylate derivative with silver tosylate and then oxidising in situ with a sodium bicarbonate-DMSO mixture.17,18... 

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