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Various carboxylic acids were converted into acyl azides in excellent yields by treating with trichloroacetonitrile, triphenylphosphine and sodium azide at room temperature. The reaction was applicable to the preparation of dipeptide without rearrangement.

Various carboxylic acids were converted into acyl fluorides in excellent yields by treatment with trichloroacetonitrile, triphenylphosphine, and TBAF(t-BuOH) 4 at room temperature. The reaction was applicable to the preparation of acid-sensitive amino acid fluorides without deprotection or rearrangement.