Swern oxidation

What is Swern oxidation?

The Swern oxidation, also known as Moffatt-Swern oxidation, is a chemical reaction used to oxidize primary and secondary alcohols, promoted by oxalyl chloride activation of dimethyl sulfoxide, involving the dimethyl alkoxysulfonium salts. Upon the addition of base, the intermediates rearrange intramolecularly to generate aldehydes or ketones, respectively. It was developed by Daniel Swern in the 1978 and has since become a widely used method in organic synthesis.

Swern oxidation - Moffatt-Swern oxidation - general reaction scheme
Swern oxidation

The reaction involves the use of a combination of oxalyl chloride (ClCOCOCl), dimethyl sulfoxide (DMSO), and a base, such as triethylamine (TEA) or pyridine. The alcohol is treated with these reagents, resulting in the formation of an intermediate which is then oxidized to the desired aldehyde or ketone..

One of the main advantages of the Swern oxidation is that it allows for the selective oxidation of primary and secondary alcohols, without affecting other functional groups present. It is also a useful method for synthesizing aldehydes and ketones from readily available alcohols, and can be carried out under mild reaction conditions..

However, there are also some limitations to the Swern oxidation. It requires the use of toxic and expensive reagents, such as ClCOCOCl and DMSO, and can produce undesirable by-products if not carefully controlled. In addition, it is not applicable to tertiary alcohols or those containing alpha-hydrogen atoms..

Despite these limitations, the Swern oxidation remains a valuable tool in the synthesis of aldehydes and ketones, and has been used in the synthesis of a variety of chemicals, including pharmaceuticals, fragrances, and dyes..