Diels-Alder Reactions with Ethylene and Superelectrophiles.

Diels-Alder reactions have been accomplished with ethylene as the dienophile through the use of inverse-electron demand Diels-Alder chemistry. As a key aspect of the chemistry, the dienes are part of tri- or dicationic superelectrophilic systems. Theoretical calculations reveal that the highly charged superelectrophiles possess exceptionally low lying LUMOs, and this facilitates the cycloaddition chemistry with ethylene. The chemistry has been used to prepare a series of tetrahydroquinoline products. This represents the first application of superelectrophilic activation in a cycloaddition reaction, and a new method of utilizing ethylene as a C2 building block.