| The Michael addition is a very important reaction in the process of constructing the carbon-carbon bond, carbon-heteroatom bond, and occupies a significant status in the synthesis of both natural products and organic compounds. Tandem reaction means that reactant conducts two or more steps of reaction under the same condition continuously. There exist many kinds of tandem reactions that based on the Michael addition, in which the Michael addition-amine/ketone condensation tandem reaction has many significance in synthetizing all kinds of N-heterocyclic compounds. Although there are many kinds of catalysts of Michael addition and Michael addition--amine/ketone condensation tandem reaction, these can only apply to simple-structured reactants with low resistance and fail to completely catalyze high resistanceα, β-unsaturated compounds. Therefore it is of great significance in studying and discovering the new-type efficient catalyst.Ce Cl3·7H2O-Na I is an excellent Lewis acid catalyst which is capable of catalyzing many kinds of organic chemical reactions. In order to improve its catalyzing effect, Ce Cl3·7H2O-Na I is often loaded on chromatographic Si O2 to synthesize supported catalyst. However, problems like catalyst asymmetry loading, unstable performance of catalyst and so on showed up frequently since the range scope of the size of chromatographic Si O2 is too broad and the appearances of particles is over-diversified.The major work of this thesis is studying and preparing the supported catalyst Ce Cl3?7H2O-Na I/Si O2 based on the exact size and appearance of the microsphere Si O2. Besides,a systematic research was conducted on the catalyzing effect of the Michael addition-tandem reaction of high resistance α, β-unsaturated ketones to thiophenols of this catalyst.This thesis composed of three parts.The first part of the thesis determine the 5μm-microsphere Si O2 as the supporter, the alcohol as the solvent by filtrating a range of supporters, loading solvent, times of loading and so on, to prepare the supported catalyst Ce Cl3·7H2O-Na I/Si O2. Its structure was also characterized through SEM, EDS and XRD.In the second part of the thesis, the Michael addition and the Michael addition —amine/ketone condensation tandem reaction of this catalyst toward aminothiophenols and highresistance α, β-unsaturated ketones were systematically studied. The detailed contents were as follows:1、The reaction conditions of the usage of catalyst, the reaction time and solvent have been optimized systematically. The optimal reaction condition was determined as taking Ce Cl3?7H2O-Na I/Si O2 as the catalyst with molar ratio of catalyst to substrate chalcone as 1:1; the reaction time as 2h; the chloroform as the solvent.2、The universality of catalyst has been investigated. Under the optimal condition, we can get the product of Michael addition-tandem reaction with high resistance α, β-unsaturated ketones(5a~5n) and 2-amino/2-amino-4-chloro-benzenethiol as the reactant and a better yield(87% the top). Compared to the catalyst of Ce Cl3·7H2O-Na I/Si O2 supported by column chromatography silica gel, the author discovered that the catalyzing efficiency of the catalyst used in this thesis has been improved about 25%.3、The reusability of catalyst and the catalyzing mode toward tandem reaction have been studied. The study showed that this catalyst, to some extent, possesses reusability that the appearance of the catalyst keep the same after been used five times, while the metal cerium lost a little and the catalyzing activity declined accordingly. Besides, this catalyst has catalyzing effect toward both the two steps of Michael addition-amine/ketone condensation tandem reaction.The third part of this thesis studied the catalyzing effect of this catalyst of the Michael addition reaction toward the thiophenol, except for the substitutive aminothiophenol, to the high resistance α, β-unsaturated ketone. The reaction conditions of the usage of catalyst, the reaction time and solvent have been optimized systematically. The optimal reaction condition was determined as taking Ce Cl3?7H2O-Na I/Si O2 as the catalyst with molar ratio of catalyst to substrate chalcone as 1:2; the reaction time as 6h; the chloroform as the solvent. Under the optimal condition, we obtained the product of Michael addition, with 8 thiophenol derivants(6c~6j) and high resistance α, β-unsaturated ketone(5i) as the reactant, the middle degree of catalyzing effect. Furthermore, since the degree of nucleophilicity varies with different nucleophile, the stronger the nucleophilicity, the higher the product ratio of reaction. |
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