Ligands for fine chemicals catalysis : design, synthesis and application of novel bisoxazoline catalysts

Abstract

Organometallic catalysts are used to achieve highly efficient syntheses of simple as well as complex organic compounds, both in industry as well as in the laboratory. Our aim in this project is to design novel Rh and Ir metal complexes as catalysts for alcoholysis of silanes as well as for the addition of alcohols, amines to alkynes to give medicinally importance heterocyclic compounds. During this investigation, we found a very convenient route to obtain substituted hydroxybenzaldehydes. A major accomplishment is that 2,4,6-Trimethylphenol was selectively activated and oxidized to 3,5-dimethyl-4- hydroxybenzaldehyde (scheme 1) in very good yields using catalytic or equivalent amounts of CuCl2 in the presence of K2CO3 and H2O2 in i-PrOH at 65 C with and without the use of ligands. The effect of the molar ratios of CuCl2, K2CO3 and H2O2 on the yields and product distribution was examined (see table). The oxidation reaction was found to proceed smoothly without the use of additives or ligands which were reported to be necessary. In another development, the use of ligands was found to decrease the yields and even selectivities. Currently, we are studying the use of a series of ligands in the above reaction. Moderate yields and high selectivities were obtained. More work is being conducted to increase the yield of the products.