Synthesis of Oxindolyl Pyrazolines and 3-Amino Oxindole Building Blocks via a Nitrile Imine [3+2] Cycloaddition Strategy

The [3 + 2] dipolar cycloaddition reaction of nitrite imines with 3-alkylidene oxindoles is described. The pyrazoline spiroadducts were obtained in high yields and with excellent regio- and diastereoselectivities. These spirocyclic intermediates have been elaborated to synthetically versatile 3-amino oxindole building blocks such as beta-amino nitrile, 1,3-diamine, and pyrrolo[2,3-b]indoline derivatives.