8(9)-对-(艹孟)烯二醇-1,2的选择性催化氧化

Selective Catalytic Oxidation of 8(9)-p-Menthendiol-l ,2

用钼酸铵催化剂在温和条件下(20—50℃)以稀过氧化氢进行8-(9)-对孟烯二醇-1,2的选择性催化氧化,得到孟烯醇酮的选择性达90%以上.考察了影响氧化反应的各种因素,提出了可能的反应机理.

Selective catalytic oxidation of 8 (9)-p-menthendiol- 1, 2 to 8 (9)-p-menthenolone-2 has been investigated in detail. Based on the work of catalytic oxidation by dilute hydrogen peroxide with various catalysts, it was discovered that better reaction conversion and higher selectivity could be obtained with hydrogen peroxide (H2O2) as the oxygen donor and ammonium molybdate ((NH4)6 Mo7O24 ?4H2O)as the reaction catalyst. In this work the effects of various operating conditions such as solvents, amounts of catalyst, reaction temperature and phase transfer reagents on both selectivity and conversion of the reaction have been considered and experimented carefully.If the molar ratio of substrate to catalyst was more than 20, the oxidation conversion decreased with the decreasing of catalyst amounts used, but it showed no pronounced effect on the selectivity. In this study reaction temperature was shown to have little effect on the reaction products, if it was selected and controlled in the range between 20-50℃. The effects of various phase transfer reagents on reaction have also been determined, in this case best results in terms of reaction conversion and selectivity were obtained by addping n-Bu4NCl in the reaction system.The optimum reaction conditions selected were as follows: The molar ratio of substrate to catalyst was 20, the reaction temperature was controlled at 30℃ , using acetone as the solvent and 30% H2O2 as the oxidizer. In the presence of both NaOAc and n-Bu4NCl the 85% conversion and 96% selectivity were obtained.The possible reaction mechanism has also been discussed in this paper. It was confirmed by FT-IR Oanalysis the Moactive complex might be formed during the reaction. Probably it may be thisOcomplex that oxidizes the sec-alcohol into its related keto compounds.