Generation of α,β-Unsaturated Iminium Ions by Laser Flash Photolysis

摘要

Iminium activation has become one of the most important methods in enantioselective synthesis. For the optimization and the rational design of organocatalytic cycles, knowledge of the mechanism of these reactions is crucial. In previous work, we have shown that the rate constants for the reactions of unsaturated iminium ions with ketene acetals, sulfur ylides, and pyrroles can be determined by UV/Vis spectroscopy employing conventional spectrometers or stopped-flow equipment. Both methods require the mixing of the reactants, and therefore are not applicable to reactions that proceed on the sub-millisecond time scale.