Reagent for the preparation of Boc-derivatives of amino acids, preferred on safety grounds to the unstable t-butyl azidoformate. In aqueous dioxane and in the presence of triethylamine as base, reaction is rapid at room temperature. The organic by-product, 2-hydroxyimino-2-phenylacetonitrile is easily removed by extraction into an organic phase: Tetrahedron Lett., 4393 (1975); Bull. Chem. Soc. Jpn., 50, 718 (1977).
