Synthesis of <i>N</i>-sulfonyl acetamidines using calcium carbide as an alkyne source

<i>N</i>-Sulfonyl acetamidine moieties are widely present in many biologically active compounds and organometallic complexes, and are particularly used as intermediates in organic synthesis. Herein, a novel and practical method for the synthesis of <i>N</i>-sulfonyl acetamidines through one-pot three-component reactions of sulfonyl azides, amines, and calcium carbide is described. This method is suitable for different amines including secondary amines, primary amines, aliphatic amines, aromatic amines, and alicyclic amines as raw materials, and various aromatic and aliphatic azides as starting materials. The notable features of this protocol include the use of inexpensive, abundant, and easy-to-handle solid calcium carbide instead of flammable and explosive gaseous acetylene as an alkyne source, the use of a low-cost catalyst, mild reaction conditions, satisfactory yield, and simple workup procedures. The method can also be extended to synthesis on a gram scale.