Conversion of carboxylic acids to potassium acyltrifluoroborates (KATs) by Cu-catalyzed borylation of mixed anhydrides

We report the preparation of potassium acyltrifluoroborates (KATs) from widely-available carboxylic acids. Mixed anhydrides of carboxylic acids were prepared using isobutyl chloroformate and transformed to the corresponding KATs using a commercial copper catalyst, B2(pin)2 and aqueous KHF2. This method allows for the facile preparation of aliphatic, aromatic, and amino acid-derived KATs and is compatible with a variety of functional groups including alkenes, esters, halides, nitriles, and protected amines.