exo-Selective asymmetric Diels-Alder reaction catalyzed by diamine salts as organocatalysts

A novel binaphthyl-based diamine (R)-2 was designed and synthesized. A protonic acid-(R)-2 salt catalyst has the advantage of exhibiting unprecedented high exo selectivity in the asymmetric Diels-Alder reaction of alpha,beta-unsaturated aldehydes. For instance, the reaction between cinnamaldehyde and cyclopentadiene in the presence of 12 mol % of binaphthyl-based diamine (R)-2 and 10 mol % of p-TsOH center dot H2O in alpha, alpha, alpha-trifluorotoluene at -20 degrees C gave the corresponding exo cycloadduct with 92% ee as a major diastereomer (exo/endo = 13/1).