Axially Chiral Sulfonic Acids for Brønsted Acid Catalysis: 8-Benzoimidazolylnaphthalene-1-sulfonic Acids and Their Derivatives.

Abstract

A new type of axially chiral sulfonic acid was developed. The synthesis is based on cheap commercially available materials and a practical method for optical resolution via diastereomeric salt formation, which can provide both enantiomers. Eleven benzoimidazolylnaphthalenesulfonic acids were prepared and four of them were isolated as pure and stable atropisomers. Moreover, several of these sulfonic acids were transformed into triflyl imides to further expand the range of dissociation constants.