Eliminating Bimolecular Decomposition to Address Sustainability in Cross-Coupling: Supported Pd-PEPPSI-IPentCl.

Fine-chemical manufacturing, with its dismal E-factors, has been known for decades as being one of the worst contributors to the well-being of the environment. Further, mining practices that pursue precious metals used in catalysis lead to considerable destruction of the environment. Further contributing to this is the necessity for high catalyst loads due to the limited mortality of organometallic complexes in solution. Bimolecular decomposition (BD), in particular, is a significant contributor to this problem. Assisting in the sustainability of chemical synthesis is flow chemistry, whose "just-in-time" nature produces chemicals as needed, eliminating vast stockpiles of chemicals associated with batch manufacturing. In this work, Pd-PEPPSI-IPentCl, a high-reactivity, high-selectivity Pd catalyst, has been mounted onto the surface of silica, of which the spacing has eliminated BD. This material has been loaded into packed beds and used in Negishi coupling and Buchwald-Hartwig amination, where the active catalyst has shown tremendous resiliency while producing valuable small-molecule products with deft selectivity and speed with residence time in the order of minutes under mild conditions (e.g., Negishi couplings conducted at room temperature).