Sulfonato-diketimine Copper(II) Complexes: Synthesis and Application as Catalysts in Chan–Evans–Lam Couplings

Copper complexes bearing a diketimino-sulfonate ligand, LCu­(NO₃)­(NCMe), were prepared and proved to be stable to water for several hours in solution. Prolonged standing in the presence of water or strong bases led to desulfonation of the ligand. LCu­(NO₃) was inactive in the polymerization of lactide (in the presence of benzyl alcohol), but showed high activity for the Chan–Evans–Lam coupling of a variety of amines and anilines. Couplings do not require addition of base, ligand, or molecular sieves. Mechanistic investigations indicate a catalytic cycle involving dioxygen as the required oxidant, precoordination of boronic acid to the sulfonate group, and transmetalation occurring prior to reaction with the nucleophile.