Proton‐Promoted Hydroamination of 3‐Dialkylthiomethylene‐1,4‐pentadiynes with o ‐Phenylenediamines: A Facile Route to Benzo[ b ][1,4]diazepines

The first proton‐promoted intermolecular hydroamination reaction of the enynes, α,α‐dialkynylketene S,S ‐acetals 2 , is described. A series of benzo[ b ][1,4]diazepines, with the structures of 3 and 5 , were prepared chemo‐ and regioselectively in good to high yields by reacting the readily available 1,4‐diynes 2 with both terminal and internal alkyne functions with o ‐phenylenediamines under very mild conditions.