Study On The Synthesis Of Polysubstituted Pyrroles

Polysubstituted Pyrroles and their derivatives are important fine chemical intermediates.They are widely used in many fields,such as pharmaceutical,pesticides,daily used home chemicals,dope,textile, printing and dyeing.Especially,along with the research and applications of porphyrins in many areas are continuously enhanced in the recent years,the research on the synthesis of polysubstituted pyrroles which were used as precursor for the preparation of porphyrin complexes has been attracted more and more interests.Many methods can be used to synthesize polysubstituted pyrroles,the main methods are of the condensation, cycloisomerisation and widening of the ring.However,more studies and applications are focused on the first one among these mothods.In this paper,seven polysubstituted pyrroles were synthesized from ethyl acetoacetate,diethyl malonate or methyl 3-oxopentanoate which undergo nitrosation,reduction and cyclization condensation reactions.The final target compounds are:2-methoxycarbonyl-3-ethyl-4-acetyl-5-methylpyrrole (a),2,4-methoxycarbonyl-3,5-diethylpyrrole(b),2-ethoxy-carbonyl -3-methyl-4-methoxycarbonyl-5-ethylpyrrole(c),2,4-diethoxy-carbonyl -3,5-dimethyl-pyrrole(d),2-ethoxycarbonyl-3,5-dimethyl-4-acetylpyrrole (e),2-ethoxy-carbonyl-3,4-dimethylpyrrole(f),2-ethoxy-carbonyl -3,5-dimethylpyrrole(g).Among these,the first three polysubstituted pyrroles(a-c) haven't been reported.The results indicate that reaction conditions of reduction and cyclization condensation have important influence on the yield of the polysubstituted pyrroles,so that the yields in different reaction conditions have been studied in detail through changing reaction conditions.The optimum reaction conditions were then determined as follows.The mole ratio of zinc powder and main starting reactants is 2.7-2.8:1,the pH is controlled at 4-4.5 and the temperature under 95-100℃.The yield of six target products is up to 56-67%under the given optimum reaction conditions. The synthesized pyrroles were characterized by melting point measurement, UV-vis,FTIR and 1~HNMR spectroscopies as well as the electrochemical methods.This thesis contains six chapters.The first chapter briefly introduced the applications of polysubstituted pyrroles in the fields of medicine, pesticides,biology,polymers and the functional materials.The second chapter summarized the primary classical methods and the novel methods used in recent years for synthesis of the polysubstituted pyrroles.The third chapter described and discussed the synthesis procedures of the polysubstituted pyrroles.The forth chapter exmined the effect factors on the synthesis yields of pyrroles and the optimum reaction conditions were then determined.The fifth chapter described and discussed the characteristic methods of the synthesized compounds and the sixth chapter is the summarization and the expectation to the future research works.