Synthesis And Immolization Of Pyridinium Salts And Their Catalytic Activities Researches

Catalysis is a useful technology in organic synthesis. Phase-transfer catalyst (PTC) has the considerable advantages, such as permitting reaction carry out under moderate condition, improving reaction rates and yields. In order to dissolve shortcomings existing in homogeneous, immobilization of PTC is one of the current interest to chemist. In this dissertation, traditional phase-transfer fluorination and solid-solid-liquid triphase-transfer esterification were studied, respectively.The first section:Fluorine-containing aromatic compounds are of current interest because of their special chemical and biological properties in agricultural and pharmaceutical research areas. Although a number of methods for the introducing fluorine into the organic molecules have been developed and successfully utilized for synthesis of fluoro aromatic compounds, halogen-exchange by potassium fluoride (KF) seems to be one of the most practical and useful methods. This kind of reaction must be carried out under elevated temperature.4-(N', N'-dialkylamino) pyridinium salts are the new phase-transfer catalysts. They have higher thermal stabilities than normal pyridinum salts because of the resonance of dialkylamino and pyridine ring, which make the positive charge delocalized in multiple atoms. In this paper, a series of thermal stable PTC based on dimethylamino pyridinium salts were synthesized and characterized by ~1HNMR, mp, IR, and MS. The activities of the catalysts were evaluated in the typical aromatic nucleophilic substitution reaction (fluorination) and the excellent results were obtained.The effects of various reaction conditions such as molar ratio of KF, structure of N-alkyl and anions, the type of substituents in substrates, reaction solvent, and temperature on the activities of catalysts were investigated in detail. Among the catalysts prepared, 4-(N', N'-dimethylamino)-N-ethylhexyl pyridinium salt (Cat2) exhibited the highest catalytic activity. It gave p-nitrofluorobenzene in yield up to...