Cyanuric fluoride, with carboxylic acids

The acid fluoride (3 mmol), obtained from the carboxylic acid and cyanuric fluoride, and TBA-F (5 mg, 0.02 mmol) are added to the silylamine (3 mmol) in MeCN (5 ml) under N2 and the solution is stirred for 6 h at room temperature. The solvent is removed under reduced pressure and the residue is taken up in CH2Cl2. The organic solution is washed with aqueous NaHCO, (5%, 2 x 10 ml), aqueous HCI (4M, 2 x 10 ml) and H20 (20 ml), dried (Na2S04), and evaporated to yield the amide (>75%). 

The key step of the approach to 45 is the ring opening of /V-Boc p-lactam 43 with ammonia, Scheme 17. The synthesis starts from the 4-carboxy azetidin-2-one 41, which is a p-hydroxy aspartic acid form possessing the p-carboxyl group and the a-amino moiety simultaneously protected. The dipeptide unit 42 is obtained in 95% overall yield after activation of the a-carboxy group with cyanuric fluoride and... 

Olah GA, Nojima M, Kerekes I. Synthetic methods and reactions IV. 1 Huorination of carboxylic acids with cyanuric fluoride. Synthesis 1973 8 487. 

Trifluoro-l,3,5-triazine (cyanuric fluoride) is a colorless liquid, which is used mainly in dye manufacturing. Cyanuric fluoride is a mild reagent that is suitable for the preparation of acyl fluorides even when unsaturated double bonds, hydroxyl groups, or aromatic rings are found in the molecule. Carboxylic acids were converted into the corresponding acyl fluorides by treatment with cyanuric fluoride in the presence of pyridine (Equation 56). 

---