Pyrrolidine-based chiral porous polymers for heterogeneous organocatalysis in water

Abstract

The properties of high stability, inherent porosity, and tunable nature of porous organic polymers (POPs) make these materials ideal catalytic nanoreactors, which can be constructed by incorporating catalytic moieties into the polymer framework. However, direct construction of chiral POPs as metal-free asymmetric catalysts still remains a challenging task. Accordingly, in this article, we report the direct synthesis of a pyrrolidine-based chiral porous polymer (Py-CPP) via a “bottom-up” strategy. Constructed from rigid three-dimensional monomers through the Sonogashira–Hagihara coupling reaction, the Py-CPP material possesses extensive porosity, and readily accessible and uniformly distributed catalytic sites. Specifically, the Py-CPP proves to be an effective heterogeneous organocatalyst for the asymmetric Michael addition of cyclohexanone to nitroolefins in pure water, affording the desired products with high yields (up to 98%) and enantioselectivities (up to 99%).