Chiral pyrrolidinium salts as organocatalysts in the stereoselective 1,4-conjugate addition of N-methylpyrrole to cyclopent-1-ene carbaldehyde

A variety of enantiopure proline derived pyrrolidinium (HX)n salts have been found to catalyse the 1,4-conjugate addition of N-methylpyrrole to cyclopent-1-ene carbaldehyde with, in some cases, high diastereo- and enantioselectivity. Parameters such as water activity, choice of acidic cocatalyst (HX)n and also the amount of cocatalyst used turned out to be crucial for the diastereo- and enantioselectivity of the reaction.