OXIDATIVE FUNCTIONALIZATION OF PdII-C BONDS USING HYDROGEN PEROXIDE: EXPLORING THE POTENTIAL OF THE PdII HYDROCARBYL - DPK SYSTEM

Abstract

Previously the oxidation utilizing hydrogen peroxide and various monoarylpalladium(II) complexes supported by di-(2-pyridyl)-ketone was shown to proceed via palladium(IV) intermediates that undergo C-X reductive elimination to produce the corresponding phenols, chlorides, and bromides in protic solvents. However, the conversion of monoalkylpalladium(II) complexes using hydrogen peroxide to their monoalkylpalladium(IV) derivatives as well as the transformations of the latter to form C-X bonds (X = F, Br, Cl, and I) are yet to be established. Herein, we report palladium - mediated oxidative C(sp3)-H functionalization of 8-methylquinoline, 4-amino-2-tert-butylpyridine and C(sp2)-H functionalization of benzo[h]quinoline, with various nucleophilic sources (H2O, MeOH, LiCl, LiBr, LiI, AgF etc) and hydrogen peroxide as an oxidizing agent. Our results demonstrate that oxidation of Pd(II) precursors with hydrogen peroxide affords new Pd(IV) complexes. The observation that Pd(IV) monoalkyl complexes can react with various nucleophiles in solution opens up an opportunity to produce functionalized organic compounds containing various C-X bonds.