Synthesis of Oxindolyl Pyrazolines and 3‑Amino Oxindole Building Blocks <i>via</i> a Nitrile Imine [3 + 2] Cycloaddition Strategy

Abstract

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-<i>b</i>]indoline derivatives