Halogen Derivatives and Tosylates

In this section, only oxidations that result in the removal of halogen substituents will be discussed. Oxidations that do not affect halogens are discussed in sections describing oxidations of individual functional groups. The exception is the oxidative cleavage of haloalkenes, which leads to carboxylic acids and which is mentioned in the section Alkenes and Cy-cloalkenes. 

Halogen compounds can be oxidized to aldehydes, ketones, or acids, depending on their structures and on the oxidants used. 

Aliphatic primary halides—chlorides, bromides, and especially iodides—are converted into aldehydes by treatment with dimethyl sulfoxide [998, 999, 1000] or trimethylaniine oxide [993], The reactivity of alkyl chlorides and bromides is increased by converting them in situ to alkyl iodides by the addition of sodium iodide into the reaction mixtures [999] (equation 188). 

A modification of the oxidation of alkyl halides to aldehydes is the transformation of the halides into alkyl tosylates on treatment with silver tosylate in acetonitrile at 0-5 °C followed by heating of the crude tosylates with dimethyl sulfoxide and sodium bicarbonate (equation 189) [1000], 

Secondary bromides such as 2-bromobutane and 2-bromooctane are oxidized by dimethyl sulfoxide in the presence of sodium iodide and sodium bicarbonate after 2 h at 115 °C to 2-butanone and 2-octanone in 65 and 56% yields, respectively (equation 190) [999]. 

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