Towards a holistic approach to metrics for the 21st century pharmaceutical industry

A unified metrics toolkit has been developed to evaluate sustainability of reactions, encompassing a comprehensive and holistic range of criteria for measuring how green a reaction is, covering quantitative and qualitative criteria both upstream and downstream of the reaction itself. In addition, three new metrics are proposed, optimum efficiency (OE), renewable percentage (RP) and waste percentage (WP). The structure of the toolkit is tailored to give a level of detail and complexity commensurate with the stage of research, with an initial 'light-touch' appraisal at a few mg scale through to very in-depth analyses incorporating lifecycle considerations at large (multi-kg) scale. The toolkit additionally allows benchmarking of reactions against state-of-the-art in terms of their 'green credentials'. By promoting critical thinking in the user it also lends itself to being an educational tool, and its widespread adoption will support the training of a new generation of chemists to whom the use of greener and more sustainable techniques becomes second nature.