Study On Green Oxidation Reactions Using Hydrogen Peroxide As An Oxidant

Oxidation reaction is the most important synthetic transformation in organic chemistry, which occupy one third of the areas. Commonly, traditional oxidation reaction employs the stoichiometric oxidizing agents, which are expensive, hazardous or toxic. Meanwhile toxic solvent is usually used to dissolve oxidizing agent and a large amount of inorganic waste is produced after workup. Hence, in terms of economical and environment concern, catalytic oxidation process with inexpensive and environmental-friendly oxidant is extremely valuable. Hydrogen peroxide is an oxidant of ideal choice. It is cheap, readily available and gives water as the only byproduct. Among various oxidizing agents, hydrogen peroxide as benign oxidant has attracted organic chemists’attention for a long time. Organosulfur compounds, carbonyl compounds and epoxy compounds are important raw materials and intermediates in organic synthesis. Although many different catalytic oxidation systems are developed to overcome the limitations of conventional methods, most of them still have some drawbacks, such as low catalytic activity, difficult recovery of catalyst, long reaction time, incapable of a broad range of some substrates and so on. Therefore, the development of a simple, economic, efficient and environmental process for these compounds synthesis is of great significance in both practice and theory.The main objective of this dissertation is to perform the oxidations of sulfides to sulfoxides or sulfones, thiols to disulfides, alcohols to carbonyl compounds, benzylic halides to aromatic aldehydes or ketones, olefins to epoxides using hydrogen peroxide as an oxidant with a view to develop new environment-friendly methods and the specific research contents include the following aspects.A selective and efficient procedure for the oxidation of various sulfides with30%hydrogen peroxide catalyzed with sodium tungstate dihydrate in the presence of trioctylmethylammonium dihydrogen phosphate as PTC, respectively, to the corresponding sulfoxides or sulfones is developed. The oxidation reaction is carried out at-5℃to0℃in the presence of hydroxypropyl-β-cyclodextrins for sulfoxides or at50℃to60℃for sulfones. The mild reaction conditions, easy workup, and good yields of the products are the major advantages of this method.A green, straightforward and novel method for the oxidation of thiols to the corresponding disulfides is developed using hydrogen peroxide catalyzed by tetrabutylammonium iodide (TBAI) in water at room temperature. Compared with the former catalytic oxidation system, this method had some merits such as easy-operation, short reaction time and excellent yields.A new triple site phosphotungstate is used as isolated catalyst in the oxidation of alcohols, and the effect of reaction conditions on the catalytic reaction is investigated. It is found that a new oxidation reaction system using hydrogen peroxide in combination with TBAP has been developed, which is capable of converting alcohols into the corresponding carbonyl compounds in good to excellent isolated yields. Moreover this catalyst could be easily recovered by simple workup and reused up without any appreciable loss of its activity. Mild reaction conditions, good to high yields, stability, easy isolation of the compounds, good thermoregulated biphasic behavior and excellent recyclability of the catalyst are the attractive features of this methodology.A novel procedure for the oxidation of benzyl halides to the corresponding carbonyl compounds with hydrogen peroxide catalyzed by2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO) in water is developed. The oxidation mechanism and the effects of reaction factors are examined. This procedure includes many advantages such as mild reaction conditions, simplicity of operation, good to high yields. The results demonstrate that NaBr as co-catalyst is crucial to realize the oxidation of benzylic halides to aldehydes or ketones. It can shorten reaction time greatly. Benzyl bromide and their derivative show higher reactivity than benzyl chloride and their derivative without the addition of NaBr.A new schiff based complex of iron ion (TPTTTI) is synthesized, and found that the catalyst could epoxidize olefins efficiently. The effects of reaction conditions such as the amount of catalyst and various oxidants, temperature and solvents on the catalytic reaction are investigated. The results show that TPTTTI demonstrate the good performance and a wide range of aromatic and aliphatic olefines are found to be applicable to the catalytic system. Addition of bipydine can efficiently diminish the over-oxidation of epoxidation product. Advantages of our procedure include simplicity of operation, mild condition, and good to better yields. A possible reaction pathway is proposed to explain the formation of epoxidize.