An Efficient Synthesis of Amides and Esters via Triacyloxyboranes

Abstract

Borane-tetrahydrofuran complex or borane-methyl ­sulfide complex is used to activate carboxylic acids to generate triacyloxyboranes. The triacyloxyboranes can be effectively reacted with various nucleophiles including alkylamines, arylamines, hydrazides, alcohols and phenols at reflux in toluene to provide the corresponding amides and esters in excellent yield. Aliphatic carboxylic acids are selectively esterified in the presence of aromatic carboxylic acids under the borane conditions.