Kornblum oxidation

What is Kornblum oxidation?

The Kornblum oxidation is a method for forming aldehydes from primary alkyl halides using dimethylsulfoxide (DMSO) and a hydrogen acceptor. It was first reported by Kornblum in 1957 and is also known as the Kornblum reaction.

Kornblum oxidation - general reaction scheme - Kornblum reaction
Kornblum oxidation

X = Cl, Br, I, Ts, Ms (see list of acronyms)

The reaction typically involves the use of bases such as triethyl amine or sodium bicarbonate as the proton acceptor. However, in some cases, such as with 4-chloro-3-methyl-2-buten-1-ol acetate, a sodium or potassium phosphate dibasic is used instead.

This reaction works well for active alkyl halides, including benzylic or allylic halides or alkyl iodides, as they undergo nucleophilic substitution into an alkoxysulphonium ion that can be transformed into an aldehyde by treatment with a base. In contrast, nonactive alkyl halides are usually converted into corresponding tosylates and then treated with DMSO and a base.

The reaction can be assisted by nonnucleophilic silver salts or zinc sulfide, which facilitate the nucleophilic substitution that is added to the reaction system. However, the Kornblum oxidation is less selective or uncontrollable when it comes to the oxidation of multibenzylic halides and typically requires high temperature treatments.

Overall, the Kornblum oxidation is a mild and effective method for the synthesis of aldehydes from primary alkyl halides.

References

Kornblum, N., Powers, J. W., Anderson, G. J., Jones, W. J., Larson, H. O., Levand, O., and Weaver, W. M. (1957). A new and selective method of oxidation. Journal of the American Chemical Society, 79(24), 6562. doi: 10.1021/ja01581a057

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