Intramolecular Dehydrative Condensation of Dicarboxylic Acids with Bronsted Base-Assisted Boronic Acid Catalysts

Bifunctional Bronsted base-assisted boronic acid catalysts, arylboronic acids bearing two sterically bulky (N,N-dialkylamino)methyl groups at the 2,6-positions, exhibit remarkable activities for the dehydrative intramolecular condensation of dicarboxylic acids. The steric bulkiness of the (N,N-dialkylamino) methyl groups of 1, which prevents the formation of less active species such as the N -> B chelated species and triarylboroxines 3, is crucial for the high catalytic activity. This is the first successful method for the catalytic dehydrative self-condensation of di- and tetracarboxylic acids.