Preparation of Potassium Acyltrifluoroborates (KATs) from Carboxylic Acids by Copper‐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. Aliphatic and aromatic carboxylic acids are rapidly converted into potassium acyltrifluoroborates (KATs) by copper‐catalyzed borylation of their mixed anhydrides. This scalable method is compatible with a broad range of functional groups and allows for the facile preparation of aliphatic and aromatic KATs, including KATs derived from Fmoc‐ and Boc‐protected amino acids.