The researchers from the university's Department of Organic Chemistry II focused their efforts on diaryl sulphides, which are a key structural component of certain drugs such as antibacterials. The options for synthesising these compounds are limited, however, by non-viability at high volumes and the production of contaminant waste, the scientists (M. Carril, R. San Martin and E. Dominguez) note.

The University of the Basque Country team tackled these problems by using a catalyst of copper salt in water. As they point out water is not only available in abundance but is a "cheap solvent, easily handled and does not produce any contamination".

The initial reagents used in this method of synthesis for diaryl sulphides - arylthiols and halides - are also readily available, the researchers note. Moreover, using copper salt as a catalyst is cost-effective, while generating the reaction in an aqueous medium means "there is no need for any extreme condition such as an inert atmosphere," they comment.

The results can then be extracted from the aqueous medium and the reagents and base added to start the reaction again. With recycling of both the solvent and the copper source, "the cost savings are evident," the researchers say. As an added benefit, no safety measures are needed for storing or handling the reaction medium as the water, "unlike many solvents used in industrial processes", is neither toxic nor flammable.