Chemoselective carbene insertion into the N−H bonds of NH3·H2O

AbstractThe conversion of inexpensive aqueous ammonia (NH3·H2O) into value-added primary amines by N − H insertion persists as a longstanding challenge in chemistry because of the tendency of Lewis basic ammonia (NH3) to bind and inhibit metal catalysts. Herein, we report a chemoselective carbene N − H insertion of NH3·H2O using a TpBr3Ag-catalyzed two-phase system. Weak coordination by a homoscorpionate ligand enables silver compatible with NH3and H2O and ensures the generation of electrophilic silver carbene. Water promotes subsequent [1, 2]-proton shift to generate N − H insertion mono-substituted products with high chemoselectivity. The end result of the reaction is the coupling of an inorganic nitrogen source with either diazo compounds orN-triftosylhydrazones to produce useful primary amines. Further investigations elucidate the reaction mechanism and the origin of chemoselectivity.