WurtzFittig

The Wurtz-Fittig reaction is a coupling reaction in which an aryl halide or alkyl halide reacts with a second alkyl or aryl halide in the presence of sodium metal to form a new carbon–carbon bond. It is a development of the Wurtz reaction extended by Julius Fittig to include aryl halides, allowing the formation of diaryl, alkyl–aryl, or dialkyl products depending on the substrates used.

Typical conditions involve a dry ether solvent such as diethyl ether or THF, under strictly anhydrous and inert conditions. Sodium metal serves as the reductant. Reactions are usually carried out with equimolar or slightly sodium-rich mixtures. The process is more effective with activated halides; aryl iodides and bromides are generally more reactive than chlorides.

Substrates compatible with the Wurtz-Fittig reaction include combinations of Ar–X and R′–X. When one partner is an aryl halide and the other an alkyl halide, cross-coupled aryl–alkyl products can form, while both partners being aryl halides can yield biaryl products. Homocoupling of each partner and formation of reduced hydrocarbon byproducts are common competing outcomes, contributing to variable yields and mixtures.

Mechanistically, the reaction proceeds via single-electron transfer from sodium to the halide to generate radical intermediates that couple to form the carbon–carbon bond, with further electron transfer and salt formation to complete the process. The reaction is often unpredictable in selectivity and efficiency.

Today the Wurtz-Fittig reaction is largely of historical and pedagogical interest, having been largely superseded by modern cross-coupling methods (such as Suzuki, Kumada, Negishi, and Stille) that offer greater selectivity and milder conditions.