Design of Boronic Acid–Base Complexes as Reusable Homogeneous Catalysts in Dehydrative Condensations between Carboxylic Acids and Amines

Abstract

AbstractTwo novel boronic acid–base complexes were developed as reusable homogeneous catalysts for amide condensation. First, quaternary ammonium resin‐bound boronates were shown to be effective catalysts that might release free boronic acids during reactions and could be regenerated afterwards. Next, a 1:1 mixture of 3,5‐dinitro‐4‐tolueneboronic acid and 4‐(N,N‐dimethylamino)pyridine N‐oxide (DMAPO) or 4‐(N,N,‐dimethylamino)pyridine (DMAP) cooperatively promoted amide formation and precipitated as an acid–base solid complex after cooling. These inexpensive and reusable complexes may be useful in large‐scale process chemistry.