Researchers from the University of Bristol have come up with a new technique to prepare biaryls, which are compounds that function as the building blocks of various therapeutic drugs and the core component of other materials like LCD and LED.
Gold as a catalyst in biaryls preparation
The new technique involves the use of gold as a catalyst in biaryls preparation. Palladium has been traditionally used as a catalyst in the preparation of biaryls through a method known as cross coupling.
The technique involves the connection of two pre-functionalized differential benzene rings facilitated by a catalyst. Even though, the cross coupling technique was honored with the 2010 Nobel Prize for chemistry, there have been efforts for a benign alternative as the use of the precious metal palladium has an adverse impact on the environment. There has also been a need for a technique that does not require the pre-functionalizing between the coupling partners.
There has been significant interest evinced in the technique of direct coupling in which the desired benzene ring replaces one of the pre-functionalized rings. Advances in this technique notwithstanding, the processes continue to operate under toxic conditions detrimental to the environment by use of strong acidic solvents, high proportions of toxic metal catalysts, etc.
The researchers from University of Bristol generated biaryls under mild conditions at room temperature by employing gold catalyst in low concentrations to couple a non-toxic silicon component with an aromatic ring. The biaryls were then proved to be effective by applying them for the synthesis of diflunisal, a drug used in arthritis treatment. Not only is gold cheaper than palladium and free of noxious residues, the method allows biaryls generation without the need for solvent and reactant purification.