PPh₃/Selectfluor‐Mediated Transformation of Carboxylic Acids into Acid Anhydrides and Acyl Fluorides and Its Application in Amide and Ester Synthesis

By taking the advantage of PPh 3 /Selectfluor system, carboxylic acids are efficiently converted into the pivotal intermediates acyloxyphosphonium ions that can selectively react with a second carboxylic acid or fluoride to in situ yield the corresponding acid anhydrides or acyl fluorides. The developed protocol features commercially availabile reagents, no involvement of base, room temperature conditions, and simple experimental procedure. Additionally, various amides or esters are readily achieved, respectively, with the addition of amines or alcohols.