Chemists from Switzerland and Japan have developed a cross-coupling reaction between organosodium compounds and alkyl halides. They first discovered how to obtain organosodium dimerization products in the presence of an iron catalyst and then optimized the cross-coupling reaction. The study was published in Nature Synthesis.
April 2 marks World Autism Awareness Day, so today's news on N+1 features illustrations from students of "Anton's Here." This charitable foundation has been helping people with autism spectrum disorders in Russia for over a decade.
Organosodium compounds are rarely used. This is because they are highly reactive, making them difficult to obtain and store. Furthermore, they are poorly soluble in non-polar solvents and simply unstable in coordinating solvents.
However, back in the 19th century, chemists Charles-Adolphe Wurtz and Wilhelm Rudolf Fittig discovered several reactions involving the coupling of aryl halides and alkyl halides in the presence of excess sodium metal. These reactions are no longer used because they are not selective and only work with specially selected substrates.
However, chemists led by Eva Hevia from the University of Bern and Sobi Asako from the RIKEN Institute for Physical Chemistry and Nuclear Research have now learned to use organosodium compounds to carry out catalytic cross-coupling.
To determine whether such a reaction could occur, the chemists took a pre-prepared aryl sodium derivative and mixed it with iron acetylacetonate in the presence of di-tert-butyl peroxide. It turned out that under these conditions, the aryl sodium compound dimerizes to form a biaryl. Thus, the scientists discovered that the iron complex can catalyze the homocoupling of organosodium compounds.
The scientists then attempted a cross-coupling reaction. They combined the same aryl sodium derivative, an iron complex, and cyclohexyl bromide, hoping to obtain a product combining the aryl and cyclohexyl fragments. However, instead, a dimerization product was formed again.
To overcome this problem, the chemists conducted several reactions in the presence of various coordinating additives capable of reacting with the organosodium derivative and altering its reactivity. It turned out that the cross-coupling product formed in 41 percent yield in the presence of tetramethylethylenediamine. By further adjusting the conditions, the scientists achieved an 82 percent yield.
Thus, chemists demonstrated that the long-discovered Wurtz-Fittig reaction could be performed catalytically without the use of excess sodium metal. Moreover, both primary and secondary alkyl bromides were involved, and protected alcohol groups and tertiary amino groups in the reactants did not interfere.
We recently reported on how an iron complex catalyzed the Suzuki reaction.
