Investigations into the utility of aminoboronates as bifunctional catalysts

Abstract

This project has been concerned with identification and refinement of any bifunctional catalytic properties of arylaminoboronic acids and derivatives Stage one of the project was directed towards the design, synthesis and structural understanding of several series of novel and interesting bifunctional boranie acids and derivatives, including the N,N-dialkylbenzylamine-2-boronic acid series and the 1֊-dimethylaminonaphthene-8-boronic acid series, stage two involved the high-throughput testing of potential catalysts. Direct amide formation (i.e. directly from carboxylic acid and amine) was identified from stage two as an interesting reaction and was investigated further in stage three of the project. N,N-Disopropylamine-2-boronic acid was found to be an effective catalyst for this reaction. In this area in particular we made many exciting and sometimes surprising findings: the thermal direct amide bond forming reaction is effective under certain circumstances, the current industry standard catalyst - 3,4,5-trifluorobenzeneboronic acid - appears to deboronate under some of the published reaction conditions, and boric acid is frequently more effective than the significantly more expensive boronic acid catalysts for the direct amide bond forming reaction.