Heteropoly acid-mediated reactions

Subsequently, we studied the relationship between the oxidant and the mechanism of the Pd-catalyzed oxidative cross-coupling reactions. Through an extensive study of reaction kinetics and competition reactions, we demonstrated that oxidative coupling conditions employing heteropoly acids and O2 are distinctly different from those mediated by more conventional oxidants such as Cu(OAc)2 or AgOAc (Scheme 7). We concluded that the heteropoly acid-mediated reactions proceed via a Pd(II)/Pd(IV) mechanism. To the best of our knowledge, this is the first example of a Pd(IV)-mediated oxidative coupling reaction. 

H. Nagai, S. Matsumura, and K. Toshima, A novel promoter, heteropoly acid, mediated chemo- and stereoselective sulfoxide glycosidation reactions, Tetrahedron Lett., 41 (2000) 10233-10237. 

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