A polymer-supported Cinchona-based bifunctional sulfonamide catalyst: a highly enantioselective, recyclable heterogeneous organocatalyst

摘要

The design, synthesis, and catalytic application of a highly enantioselective and indefinitely stable polymer-supported Cinchona-based bifunctional sulfonamide is reported.rnCurrently, there is much interest in organocatalysts, as they tend to be less toxic and more environmentally friendly than traditional metal-based catalysts. They can be used with a wider range of substrates than enzymes, as well as in various organic solvents. Although much progress has been made, developing chiral organocatalysts that are as reactive and stereoselective as some of the best transition metal-based catalysts or enzymes still remains a significant challenge. In order to obtain reasonable reaction rates and stereoselectivities with organocatalysts, a large catalyst loading is often required. One way to address this difficulty is to design bifunctional or multifunctional organocatalysts, with functional groups that work cooperatively to stabilize the transition state and accelerate the rate of the reaction. It has been shown that Cinchona-based bifunctional thiourea I or sulfonamide II (Fig. 1) organocatalysts are highly effective in facilitating a variety of useful asymmetric reactions.