Iron-Catalyzed Denitrogenative Annulation Reactions between α-Azido Acetamides and Cyclic Ketones.

We report an FeCl 2 -catalyzed annulation reaction between α-azido acetamides and cyclic ketones. Two types of α,β -unsaturated γ-lactam products can be obtained, depending on the reaction conditions. When α-azido acetamides were reacted with cyclohexanone, 8-amino-5,6,7,8-tetrahydro-1 H -indol-2(4 H )-ones were obtained when a primary amine was present in the reaction system; conducting the reaction in the presence of 2-aminobenzenesulfonic acid, on the contrary, resulted in the formation of 5,6-dihydro-1 H -indol-2(4 H )-ones. Cycloheptanone and cyclooctanone reacted in the same way as cyclohexanone. The reactions proceed via the intermediacy of 2-iminoacetamides, which are formed by FeCl 2 -facilitated dinitrogenation of α-azido acetamides. These reactions constitute a new strategy for expanding the synthetic dimensions of organic azides.