Multi-functional thioureas were shown to catalyze enantioselective ring opening of episulfonium ions with various indole derivatives. Experimental mechanistic investigation revealed definitive evidence for a transition-state stabilization effect enabled by the thiourea in the rate- and enantio-determining step � the nucleophilic ring opening. This stabilization is achieved through a network of weak, non-covalent interactions, including hydrogen-bonding to the sulfonate anion and indole, as well as a cation-pi interaction between the extended aromatic group on the catalyst and the cationic transition-state.

Development and mechanistic investigation of an enantioselective thiourea-catalyzed nucleophilic ring opening of episulfonium ions

243rd National Meeting (2012)

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