Organic Synthesis

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The Pfitzner-Moffatt oxidation, sometimes referred to as simply the Moffatt oxidation, is a chemical reaction for the oxidation of primary and secondary alcohols to aldehydes and ketones, respectively. The oxidant is a combination of dimethyl sulfoxide (DMSO) and dicyclohexylcarbodiimide (DCC). The reaction was first reported by J. Moffatt and his student K. Pfitzner in 1963.

The reaction requires one equivalent each of the diimide, which is the dehydrating agent, and the sulfoxide, the oxidant:

(CH₃)₂SO + (CyN)₂C + R₂CHOH ---> (CH3)₂S + (CyNH)₂CO + R₂C=O

Typically the sulfoxide and diimide are used in excess. The reaction cogenerates dimethyl sulfide and a urea. Dicyclohexylurea ((CyNH)₂CO) can be difficult to remove from the product.

In terms of mechanism, the reaction is proposed to involve the intermediary of an sulfonium group, formed by a reaction between DMSO and the carbodiimide. This species is highly reactive and is attacked by the alcohol. Rearrangement give an alkoxysulfonium ylide which decomposes to give dimethyl sulfide and the carbonyl compound.

This reaction has been largely displaced by the Swern oxidation, which also uses DMSO as an oxidant in the presence of an electrophilic activator. Swern oxidations tend to give higher yields and simpler workup; however, they typically employ cryogenic conditions