Investigation On Phosphotungstic Acid-Catalyzed C-C And C-N Bond Formation

As a part of the sustainable development strategy,environmental protection has been paid more and more attentions in modern society.Environmentally safe solvents and catalysts are preferred to the traditional ones which are usually toxic and precious organic solvents and heavy metal catalysts.As a result,the conception "green chemistry" came into being.In a green organic synthesis,procedures involving direct thermal heating or utilizing water as solvent are always welcomed to minimize the use of organic solvents.Some small organic molecules and catalysts that can be recovered and reused are employed extensively in various organic transformations.In this thesis, investigations focused on heteropoly acids-catalyzed C-C and C-N bond formation reactions and the synthesis of xanthenediones and acridinediones under thermal conditions are described.1.12-Phosphotungstic acid(PWA) has been used as an efficient,eco-friendly,and air- and moisture-stable catalyst to promote the direct dehydrative substitution of the hydroxy group of benzylic and allylic alcohols with variousβ-dicarbonyl compounds.When 1-phenyl-ethanol was employed as alkylating agent,the reaction was performed in nitromethane at room temperature to afford high yield. The loading of catalyst was extremely low.2.Direct hydroalkylation of styrene and norborene with 1,3-dicarbonyl compounds has been developed by using PWA as the catalyst.Reactions proceeded without any solvent,providing a clean and eco-friendly access to alkylated pentanediones.3.Under the catalysis of PWA,various amino compounds including sulfonamides, benzamides,and anilines could react with alcohols to afford alkylated amino derivatives in high yields.Various alcohols are tolerable under the present conditions including benzylic alcohols,allylic alcohols as well as simple aliphatic alcohols(methanol and ethanol).The potential reusable property of heteropoly acid makes this protocol more attractive.4.The aminohydrogenation of simple alkenes including styrene,norborene and cyclohexene with sulfonamide,benzamides or electron-deficient anilines were also catalyzed by PWA to afford Markovnikov adducts in high yields.5.In the absence of any solvent,the reactions of various aromatic aldehydes with 5,5-dimethyl-1,3-cyclohexanedione catalyzed by methanesulfonic acid under thermal heating conditions smoothly afforded xanthenediones in nearly quantitative yields.Under the same melt conditions,rapid and highly efficient synthesis of acridinediones could also be achieved using ammonium acetate and p-toluidine as the nitrogen source.