First C-H activation route to oxindoles using copper catalysis

(Equation Presented). The preparation of 3,3-disubstituted oxindoles by a formal C-H, Ar-H coupling of anilides is described. Highly efficient conditions have been identified using catalytic (5 mol %) Cu(OAc)₂·H ₂O with atmospheric oxygen as the reoxidant; no additional base is required, and the reaction can be run in toluene or mesitylene. Optimization studies are reported together with a scope and limitation investigation based on variation of the anilide precursors. The application of this methodology to prepare a key intermediate for the total synthesis of the anticancer, analgesic oxindole alkaloid Horsfiline is also described.