One‐Pot Stereoselective Synthesis of Substituted E ‐Furan‐3(2 H )‐Imines From Propargyl Amines and Acyl Chlorides via Pd/Cu‐ and t ‐BuOK‐Catalyzed Sequential Steps

A new family of aromatic (heteroaromatic) propargyl amines (available from ketimines and acetylene gas), after the reaction with (hetero)aroyl chlorides (CuI/PdCl 2 /Ph 3 P/Et 3 N, 40–45 °C, toluene, 2–3 h) and sequential treatment with t ‐BuOK (room temperature, 5–8 h), stereoselectively delivered polysubstituted E ‐furan‐3(2 H )‐imines in up to 72% yields. The latter were proved to be formed from the initially generated intermediate acylpropargyl amines, which underwent the unique base‐catalyzed rearrangement proceeding via the intermediate aziridines, products of intramolecular addition of nitrogen‐centered anion to the triple bond. In the intermediate aziridines, the cleavage of the C─N bond occurs with simultaneous formation of the C─O bond followed by deep restructuring to give the final products.