A series of di(2-pyridyl)ketone - supported cationic k2-C,N-2’-(N-R-amino)biphenyl-2-yl Pd(II) complexes 1 (R = H, Me, Et), neutral k2-C,N-2’-(N-R-amido)biphenyl-2-yl Pd(II) complexes 2 (R = Ac, CF3CO, MeSO2, CF3SO2) and halogen-substituted k2-C,N-2’-(2’,2’-dimethylethanediyl)-N-trifluoromethanesulfonylanilido Pd(II) complexes 3 were prepared. Reactions of 1 and 2 with H2O2 in organic solvents lead to the formation of the derived N-R-substituted carbazoles in high yield. The reaction is fast for the amido complexes 1 and does not involve any significant amounts of reaction intermediates. The oxidation of electron-poorer amido complexes 2 is slower and allows for a number of Pd(II) and Pd(IV) reaction intermediates to be isolated and fully characterized. Finally, the oxidation of the amido alkyl complexes 3 with H2O2 leads to isolable amido alkyl Pd(IV) complexes that can be involved in C-N reductive elimination of the derived indolines in high yield. A mechanistic analysis of the C-N coupling reactions involving Pd(IV) intermediates was carried out using means of kinetics and quantum mechanical (DFT) calculations.

Formation of carbazoles and indolines via oxidative intramolecular C-N coupling of amido aryl and amido alkyl Pd(II) complexes with H2O2 as oxidant: A mechanistic analysis

254th National Meeting (2017)

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