Although there has been significant progress in mimicking nature's reaction cascade strategy over the past decades, the manipulation of sequential reactions using multiple catalysts in a single vessel is still quite rare. A primary reason is that controlling one-pot, multi-step reactions using traditional homogeneous catalysts is rather difficult since, unlike for biocatalysts, interactions between soluble catalysts can cause deactivation. Existing examples of complex reaction sequences or cascades represent carefully constructed systems that were optimized for one specific sequence. In such cases, after the reaction, standard workup procedures most often result in the used catalysts simply becoming a component of the reaction waste. Here we demonstrate for the first time the application of multiple catalysts in a variety of one-pot, multi-step catalytic reactions with catalyst recovery in essentially pure form, allowing reuse of the recovered catalysts in myriad other catalytic reactions, potentially in a combinatorial manner. This has been achieved using a combination of catalysts recovered by magnetic, gravimetric and membrane methods, allowing for exquisite control of multi-step reactions with recovery of each individual catalyst[1]. In particular, the use of magnetically separable catalysts allows for creation of a variety of versatile catalysts that can be easily recovered without the need for specialized equipment. Furthermore, the recovered catalysts can be reused in different, subsequent multi-step one pot reactions. This is an unprecedented level of control over multi-step, one-pot catalytic reactions. The new approach offers the potential of reducing the number of costly separation steps during chemical synthesis, all while facilitating recovery and reuse of multiple catalysts.

1. N. T. S. Phan, C. S. Gill, J. V. Nguyen, Z. J. Zhang, C. W. Jones, Angew. Chem. Int. Ed. 2006, 45, 2209.