Diversity-based strategy for discovery of environmentally benign organocatalyst: diamine–protonic acid catalysts for asymmetric direct aldol reaction

Fifteen different diamines () and potonic acids have been screened in the catalytic asymmetric direct aldol reaction of three different aldehydes in acetone. These initial studies demonstrated that the secondary–tertiary diamine series is effective with regard to reactivity. In contrast, the primary–tertiary diamines and were proved to be a superb structural module to avoid dehydration. Further investigation led us to a new procedure for the preparation of diamine catalysts for synthetic convenience. This involves diamine–diacid salt , which acted not only as a catalyst backbone but also as a TfOH source. Salt –diamine catalyst thus prepared was found to exhibit higher reactivity and selectivity.