McCormack cycloaddition

What is McCormack cycloaddition?

The McCormack cycloaddition, also known as the McCormack reaction or McCormack synthesis, is a method for synthesizing phospholene oxides. It involves the cycloaddition of dihalophosphines with 1,3-dienes, followed by hydrolysis. The resulting products are referred to as McCormack adducts or McCormack cycloadducts. The discovery of this reaction is attributed to W. B. McCormack, who was a research chemist at duPont.

McCormack cycloaddition - general reaction scheme -McCormack reaction - McCormack synthesis - McCormack adducts - McCormack cycloadducts.
McCormack cycloaddition

R = alkyl, alkoxyl, aryl, halogen

This reaction is typically carried out without a solvent and can be slow for less reactive dienes. In contrast, the cycloaddition of phosphenium ion with 1,3-diene is much faster due to the highly electrophilic nature of phosphenium. Interestingly, 1,3-cyclohexadiene does not undergo this cycloaddition, while 1,3-cycloheptadiene reacts with methyldichlorophosphine to give the corresponding adduct.

The McCormack cycloaddition has been modified to react with ethylene chlorophosphite to produce chlorophosphine oxide and with phosphorus tribromide to form bromophosphine. It has also been used to prepare various bicyclic phospholene oxides.

Additionally, the reaction can be reversed, as the Diels-Alder reaction, and has been applied to the preparation of dioxyphosphoranes.