Asymmetric Catalytic 1,3-Dipolar Cycloaddition Reaction of Nitrile Imines for the Synthesis of Chiral Spiro-Pyrazoline-Oxindoles

A new 1,3-dipolar cycloaddition of nitrile imines with 3-alkenyl-oxindoles was catalyzed by a new chiral Mg(ClO4)2 complex of an N,N′-dioxide ligand. The reaction is so far the sole catalytic synthesis of spiro-pyrazoline-oxindole derivatives. A wide variety of substrates were explored to obtain good yields (up to 98%) and excellent enantioselectivities (up to 99%). This cycloaddition expands the scope of propargyl anion type 1,3-dipole in the construction of 2-pyrazoline subunit.