Research On The New Reactions Of Pyridinium Salts

Pyridinium salt has been widely used in organic synthesis. The aromaticity, the alkaline and the electron-withdrawing effect of pyridine makes pyridinium salt has a wealth of chemical reactivities. It can undertake nucleophilic addition reaction, Michael addition,1,3-dipolar addition, nucleophilic substitution reactions and a-migration, and it is widely used in organic synthesis.This thesis consists of three chapters. The first chapter is a literature review for the reactions and applications of pyridinium salt in organic synthesis. Finally we put forward the research ideas of this paper, to study the new reactions of pyridinium salt.In the second chapter of this paper, the reaction of acetophenone pyridinium salt with aziridines was discussed. It was found that the ring opening of N-tosylcyclohexeneimine resulted from the attack of carbon of acetophenone pyridinium salt did not occurr under anhydrous and basic conditions, but in the presence of a small amount of water the above reactants led to p-amino alcohol esters. Further studies revealed that it was resulted from the ring opening reaction of water with aziridine, followed by the reaction of the generated alcohol with pyridinium salt. Then we optimized the reaction conditions by studying the different solvents, reaction temperature, and the ratio of reaction materials in the presence of water. At last we found CH3CN was a proper solvent; the proper molar ratio of N-tosylcyclohexeneimine, pyridinium salt la, triethylamine was1:3:3. When they reacted under reflux, the highest yield of the target product (52%) was obtained. Then we tested different types of pyridinium salts (la-le) to react with aziridine under above conditions, and found that pyridinium salt gave moderate to high yields (46-80%). The reactions of H2O/pyridinium salts (la or le) with different aziridines under above conditions were studied, and corresponding β-amino alcohol esters were abtained in the yields of46-98%.In the third chapter, the reactions of pyridinium salts and alcohol were studied. Firstly we used benzyl alcohol as the substrate, and it reacted with pyridinium salt to generate benzyl benzoate in the presence of a base. Optimizing the reaction conditions, we found toluene was a good solvent; the proper molar ratio of pyridinium salt, benzyl alcohol and Na2CO3was 1:1:3.5; and higher yields for target product can be obtained under reflux. Finally, we used different alcohols as reaction substrates to test the reaction, and varoius derivatives of benzoate can be obtained in the yields of85-98%. Because a carbon was removed with piridinyl in the reaction, it provided a new method for shortening carbon chain in organic synthesis.