Pfitzner–Moffatt oxidation

Pfitzner–Moffatt Oxidation is a chemical reaction that involves the oxidation of alcohols to aldehydes or ketones using a dimethyl sulfoxide (DMSO) activated by a carbodiimide, typically dicyclohexylcarbodiimide (DCC). This reaction is notable for its mild conditions and broad substrate scope, making it a valuable tool in organic synthesis. The reaction was independently discovered by Hans Pfitzner and James Moffatt in the 1960s.

Mechanism

The Pfitzner–Moffatt oxidation mechanism involves several key steps. Initially, DMSO reacts with the carbodiimide (e.g., DCC) to form an activated DMSO intermediate. This intermediate then reacts with the alcohol substrate to form an alkoxysulfonium ion. Subsequent elimination of this ion leads to the formation of the desired aldehyde or ketone product, along with the release of dimethyl sulfide (DMS) as a byproduct.

Applications

The Pfitzner–Moffatt oxidation has been widely applied in organic synthesis due to its ability to selectively oxidize primary and secondary alcohols under relatively mild conditions. It is particularly useful in the synthesis of complex molecules where sensitive functional groups are present, as the reaction conditions are less likely to cause unwanted side reactions.

Advantages and Limitations

One of the main advantages of the Pfitzner–Moffatt oxidation is its mildness, allowing for the oxidation of sensitive substrates that might be incompatible with more vigorous oxidation conditions. However, the reaction does have some limitations, including the generation of dimethyl sulfide, a malodorous byproduct, and the potential for overoxidation in some cases.

Variants

Several variants of the Pfitzner–Moffatt oxidation have been developed to address its limitations and expand its utility. These include modifications to the activating agent and the use of alternative solvents or additives to improve yield, reduce byproducts, or enable the oxidation of more challenging substrates.

See Also

• Swern oxidation
• Dess–Martin periodinane
• Corey–Kim oxidation
• Alcohol oxidation