Stereoselective Synthesis of Functionalized Tetrahydro-1H-1,2-diazepines by N-Heterocyclic Carbene-Catalyzed [3+4] Annulation

An efficient N-heterocyclic carbene (NHC)-catalyzed asymmetric [3 + 4] annulation reaction of N-Ts hydrazones with 2-bromoenals has been developed. A series of functionalized tetrahydro-1H-1,2-diazepines with two consecutive stereocenters was obtained using NHCs as the catalyst in good yields with excellent diastereo- and enantioselectivities.