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 nitrile 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 β-amino nitrile, 1,3-diamine, and pyrrolo[2,3-b]indoline derivatives.