McMurry coupling

What is McMurry coupling?

The McMurry coupling is a chemical reaction that involves the coupling of two alkyl or aryl halides to form a diaryl or alkyl-alkyl compound. It is named after the American chemist John E. McMurry, who first described the reaction in his research on the synthesis of organometallic compounds..

The McMurry coupling is a useful method for synthesizing diaryl and alkyl-alkyl compounds, which are important intermediates in the production of a wide range of chemicals and pharmaceuticals. It is a two-step process that involves the formation of a titanium or zirconium compound, followed by the coupling of the two alkyl or aryl halides..

McMurry reaction - general reaction scheme
McMurry coupling

The first step of the McMurry coupling involves the formation of a titanium or zirconium compound from a titanium or zirconium halide and an organometallic compound, such as an alkyl lithium or an alkyl magnesium bromide. This is typically done by reacting the titanium or zirconium halide with the organometallic compound in the presence of a solvent, such as tetrahydrofuran or hexane. The resulting titanium or zirconium compound is a strong reducing agent and can be used in the second step of the reaction..

The second step of the McMurry coupling involves the coupling of the two alkyl or aryl halides using the titanium or zirconium compound as the reducing agent. This is typically done by reacting the alkyl or aryl halides with the titanium or zirconium compound in the presence of a solvent. The resulting product is a diaryl or alkyl-alkyl compound, with the alkyl or aryl groups coupled through a titanium or zirconium bond..

The McMurry coupling has several advantages over other methods of synthesizing diaryl and alkyl-alkyl compounds. It is a straightforward and efficient process that can be easily scaled up for large-scale production. It also allows for the synthesis of a wide range of diaryl and alkyl-alkyl compounds, with good yields and good selectivity..

Despite these advantages, the McMurry coupling has some limitations. It is not suitable for the synthesis of diaryl and alkyl-alkyl compounds from alkyl or aryl halides with certain substituents, such as halogens, due to the high reactivity of the intermediates. It is also not suitable for the synthesis of diaryl and alkyl-alkyl compounds from alkyl or aryl halides with certain substituents, such as electron-withdrawing groups, due to the low reactivity of the alkyl or aryl halides..

Summary

The McMurry coupling is an important method for the synthesis of diaryl and alkyl-alkyl compounds, and it has played a significant role in the production of a wide range of chemicals and pharmaceuticals..

References

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