Oxidatively Resistant Ligands for Palladium-Catalyzed Aerobic Alcohol Oxidation

The complex [(neocuproine)Pd(OAc)](2)[OTf](2) (1) catalyzes the aerobic oxidation of 2-heptanol at room temperature, but Competitive ligand oxidation leads to low catalyst lifetimes. In an effort to mitigate the oxidative degradation of the ligand, a variety of Pd complexes ligated by fluorinated phenanthrolines (bis-2,9-(trifluoromethyl)-1,10-phenanthroline (btfm-phen), 4-methyl-2-(trifluoromethyl)-1,10-phenanthroline (tfmm-phen), and 2-(o-difluoropheny1)-1,10-phenanthroline (odfp-phen)) were prepared and tested. Active catalyst precursors were generated by in situ conproportionation of (N- N)Pd(OAc)(2) and [(N-N)Pd(NCCH3)(2)[OTf](2). Pd complexes derived from tfmm-phen catalyzed the aerobic oxidation of 2-heptanol at room temperature with up to 22 turnovers, nearly double that of 1.