Direct Access to Acyl Fluorides from Carboxylic Acids Using a Phosphine/Fluoride Deoxyfluorination Reagent System.

A fast and simple method for deoxyfluorination of carboxylic acids is presented. The protocol employs commodity chemicals (PPh3, NBS, fluoride), affording products in excellent yields under mild conditions. Acyloxyphosphonium ion, the key reaction intermediate, was identified by NMR spectroscopic methods. Brønsted acidic conditions are essential for efficient C-F bond formation. The protocol displays scalability, high functional group tolerance, chemoselectivity, and easy purification of products. Deoxyfluorination of active pharmaceutical ingredients was established.