Catalytic Oxidation Of α-isophorone To 4-ketoisophorone

Free radical reactions in organic synthesis are widely used, with irreplaceable advantages over ion reactions. The research and development of free radicals catalyst gradually comes up as a hot research subject in developing new organic synthesis reaction. Since the catalytic performance of N-hydroxyphthalimide was found, the nitroxyl radical organocatalysts, such as N-hydroxyphthalimide,has shown excellent performance, and it is gradually attracting and will attract more and more attentions.Ketoisophorone(KIP) is the important intermediate in the process of synthesizing carotinoid, vitamin E and other compounds. Generally, KIP is prepared through the oxidation of isophorone (IP). At present there are two major synthetic methods:one is direct oxidation, another is indirect oxidation. The method of indirect oxidation includes a step of isomerization of a-IP to (3-IP under high temperature, so the direct oxidation of a-IP becomes more attractive for preparing KIP.In this thesis, homogeneous and heterogeneous catalytic systems for the aerobic oxidation of a-isophorone to KIP have been investigated.In heterogeneous system, a detailed study has been conducted on the influence of several parameters, namely, solvents, various metal oxides, and alkali on the convertion and selectivity for the desired reaction. A maximum isophorone conversion of 27.2% with 70.8% selectivity to KIP was obtained, the reaction was carried out in ethylbenzene at 100℃for 20 h with copper-manganese oxide loading on zeolite as catalyst, molecular oxygen as an oxidant. Herein, ethylbenzene is not only as a solvent but also as an oxidant precursors and the process is not a complete free radical mechanism. Adding free radical initiator (NHPI) in the system, the conversion and selectivity were increased up to 31.6% and 72.1% respectively.In homogeneous system, NHPI was employed as catalyst in the oxidation of a-isophorone. Using 1 mol% NHPI and 0.5 mol% CoCl2 as catalyst, molecular oxygen as an oxidant, an excellent isophorone conversion of 51.0% with 53.8% selectivity to KIP was observed under solvent-free condition at 100℃for 10 h. Otherwise, the metal and solvent-free direct oxidation of a-IP to KIP using 3,4,5,6-Tetrachloro-N-hydroxyphthalimide (TCNHPI) as the catalyst and molecular oxygen as the oxidant was studied, and the effect of temperature, reaction time and the amount of TCNHPI was investigated. Besides, an innovative design of consecutive air-flowing device was used to study the effect of the flowing rate of air. The result indicated that consecutive air-flowing could improve the catalytic property, but the catalytic property nearly stayed stable when the flowing rate was increased over 0.2L/min. The difference between the presence and absence of co-catalyst, other conditions the same, was also studied. A conclusion is that under metal-and solvent-free condition, co-catalyst almost made no difference.