Catalytic conversions in water. Part 23: Steric effects and increased substrate scope in the palladium-neocuproine catalyzed aerobic oxidation of alcohols in aqueous solvents

The steric influence of substituents on the 2- and 9-positions of phenanthroline in the (2,9-R-2-1,10-phenanthroline)palladium(II)-catalyzed aerobic oxidation of 2-hexanol was investigated by means of high throughput experimentation. (Neocuproine)Pd-(OAc)(2) (R=CH3) was found to be a highly active catalyst for alcohol oxidation in 1:1 water/DMSO mixtures. The catalyst is unique in that it tolerates water, polar co-solvents and a wide variety of functional groups in the alcohol. Turn-over frequencies of > 1500 h(-1) were achieved and a series of alcohols was oxidised with 0.1 to 0.5 mol % of catalyst.