Different chiral 1,1’-bi-2-naphthol (BINOL)-derived acids and their analogues (see image on the right) were recently introduced as a highly efficient class of metal-free Brønsted acid organocatalysts, capable also of enantioselective (chiral) catalysis.

These catalysts have been successfully used for a wide range of reactions (hydrogenations, various addition reactions to aldimines and ketimines, Diels-Alder and [3+2] cycloaddition reactions, Nazarov cyclizations, asymmetric protonations, Mukaiyama aldol reactions, etc). In spite of their wide usage, accurate data about their acidity were not available until recently.

PhD student Karl Kaupmees (image on the left) has carried out measurement of pKa values of a number of those acids in acetonitrile and as a result, reliable acidity data are now available. Furthermore, it was possible to demonstrate for the first time that the catalytic activity of the acid in one of the reactions (Nazarov cyclization) is directly related to the acidity of the acid catalyst.

This result was so significant that it was published by one of the most prominent chemistry journals Angewandte Chemie Int. Ed. (Angew. Chem. Int. Ed. 2013, 52, 11569-11572).

_