On the usefulness of life cycle assessment in early chemical methodology development: the case of organophosphorus-catalyzed Appel and Wittig reactions†

Recently, catalytic methodologies have been developed to avoid phosphine oxide waste produced in classic phosphorus-consuming processes, i.e. Appel and Wittig reactions. For these new catalytic methods, however, the requisite stoichiometric amounts of silanes raised the question of whether net environmental improvements can be achieved. Here, we conducted a life cycle assessment (LCA), in which the classic reactions are compared with their catalytic counterparts in terms of cumulative energy demand and greenhouse gas emissions. The analysis shows that the replacement of phosphines by silanes can offer environmental improvements for the Wittig reaction, but that additional reagents and working in lower concentrations can offset these environmental improvements for the Appel reaction. These results clearly show the importance of LCA in early chemical methodology development.