Much of the time, cost and waste in a multistep process is connected with the repeated isolation and purification of products at the end of each step in a sequence. Ongoing research within the Centre aims to avoid this by developing mutually compatible catalysts which can be added sequentially to a reaction to accomplish multiple transformations without the need to isolate and purify the intermediates.
Work in this area often involves catalyst immobilisation which helps both with compatibility issues between catalysts and with final product isolation. The solvent also has a critical role to play as many catalysts are only active in a narrow range of solvents. Thus, both catalyst modification to change its solvent tolerance, so that solvents do not need to be changed between steps, and the development of new solvents are under investigation. In addition, the by-products of one step can interfere with subsequent steps as can any additives that need to be added.
Work to address this problem by developing highly atom-economical process and ‘removable’ reagents, additives and scavengers is also in progress.