Frustrated Lewis pair (FLP) chemistry has attracted a widespread attention as an unprecedented metal-free activation mode. FLPs are consisting of Lewis acid-base pairs that are prevented from the classical donor-acceptor adduct formation by steric factors. This unique feature enabled the heterolytic activation of hydrogen, which reactivity promoted the development of catalytic FLP hydrogenations. While the first generation of FLPs could be employed in metal-free hydrogenation, there were multiple synthetic limitations that inhibited the penetration of this valuable catalytic hydrogenation protocol. Most importantly, several non-orthogonal reactivity of the FLP with polar functionality and the lack of water tolerance markedly narrowed the scope of this methodology. To avoid this limitation, we have introduced the size-exclusion structural design element in FLP chemistry and developed unique frustrated Lewis acid-base pair catalysts having unprecedented functional group tolerance, orthogonal reactivity and even water tolerance.<sup>1</sup> These developments have resulted in the valorization of FLP hydrogenation and triggered to unlock even more of its potential via frustrated Lewis pair tandem catalysis. In this catalytic variant, FLP hydrogenation is coupled with additional catalytic processes, thus sequential transformation of the substrate occurs in two or more mechanistically distinct processes. Along this line, we wish disclose the development of a metal-free reductive etherification, amination, Ireland-Claisen methods that involves two mechanistically distinct catalyses, a hydrogenation and a Brønsted acid catalysis, promoted by a single FLP catalyst. Beside their metal-free nature, the synthetic merit of these processes is that they enable the simple construction of various valuable molecules that would be either difficult or even intractable to access.

Expanding the boundaries of water tolerant frustrated Lewis hydrogenation via size-exclusion catalyst design

2019 Spring National Meeting

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