Chiral Multi-Functional Cyclopropenimine-Based Organocatalysts

This research project aims to design and synthesize multi-functional chiral organocatalysts based on the cyclopropenimine scaffold. Cyclopropenimines are defined by their unique combination of a cyclopropenyl ring and an imine group, and exhibit high Brønsted basicity through formation of the cyclopropenium cation—the smallest aromatic ion—upon interaction with electrophilic species at the imino nitrogen. By incorporating hydrogen-bond donor motifs—such as ureas or thioureas—into this strongly basic cyclopropenimine framework, we seek to achieve cooperative activation of both nucleophiles and electrophiles. These catalysts are being applied to a broad range of asymmetric transformations, including 1,2- and 1,4-additions, enantioselective fluorinations, and other stereoselective bond-forming reactions, including anionic polymerizations. Through catalyst structure tuning and mechanistic investigation, we aim to uncover general principles for enhancing selectivity and reactivity in organocatalysis.

For representative examples of our work with chiral cyclopropenimine–thiourea catalysts, see J. Am. Chem. Soc. 2024, 146, 3065.