In the cross-coupling reactions of unprotected oxindoles with aryl halides, Pd- and Cu-based catalyst systems displayed orthogonal chemoselectivity. A Pd-dialkylbiarylphosphine-based catalyst system chemoselectively arylated oxindole at the 3 position, while arylation occurred exclusively at the nitrogen using a Cu-diamine-based catalyst system. Computational examination of the relevant L(1)Pd(Ar)(oxindolate) and diamine-Cu(oxindolate) species was performed to gain mechanistic insight into the controlling features of the observed chemoselectivity.
“Orthogonal Pd- and Cu-Based Catalyst Systems for C- and N-Arylation of Oxindoles”, J. Am. Chem. Soc., 2008, 130(29), 9613-9620.