Biodegradable Chitosan-Derived Thioureas as Recoverable Supported Organocatalysts – Application to the Stereoselective Aza-Henry Reaction

Abstract

Eight different biodegradable chitosan-supported bifunctional chiral thioureas have been prepared as a greener and more sustainable alternative to those supported on petrochemical-derived polymers. These organocatalysts promoted an enantioselective aza-Henry reaction, which afforded good product yields with moderate to high enantioselectivity. The activity and stereodirecting ability of these materials were dependent on the accessibility of the reactants to the active site and increased with the length of the tether that connected the thiourea to the biopolymer. The best performing catalyst was able to be recovered and recycled five times without a loss of activity.