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-R2-1,10-phenanthroline)palladium(II)-catalyzed aerobic oxidation of 2-hexanol was investigated by means of high throughput experimentation. (Neocuproine)Pd(OAc)2 (R[DOUBLE BOND]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.