Copper-Catalyzed Enantioselective (3 + 3) Cycloaddition of Ethynyl Methylene Cyclic Carbamates with N,N′-Cyclic Azomethine Imines

A copper-catalyzed asymmetric cross 1,3-dipolar cycloaddition between 2-aminoallyl zwitterions generated in situ from ethynyl methylene cyclic carbamates and N,N'-cyclic azomethine imines has been realized. The reaction, which utilizes a commercially available chiral tridentate N-ligand, delivers a range of functionally rich chiral hexahydro-8H-pyrazolo[1,2-a][1,2,4]triazin-8-one derivatives in 51-99% yields with good to high enantioselectivities (44-95% ee).