| 2-Pyridylaldehydes is an important pharmaceutical intermediate and fine chemical raw material.Studying the synthesis of 2-pyridylaldehydes has practical application value.In this paper,after analyzing the relevant literature,it was planned to synthesize2-methyl pyridine N-oxide by using 2-methyl pyridine as raw material and hydrogen peroxide as oxidant through catalytic oxidation.After acylation and hydrolysis of 2-methyl pyridine N-oxide to obtain 2-pyridine methanol,the target product 2-pyridylaldehydes was synthesized by air oxidation.The thesis first investigated the effects of different catalysts and solvents on the preparation of 2-methyl pyridine nitrogen oxides by oxidation of 2-methyl pyridine with hydrogen peroxide.Phosphotungstic acid/H2O2 catalytic oxidation system catalyzed the reaction of 2-methyl pyridine to form 2-methyl pyridine N-oxide,the yield of 2-methyl pyridine N-oxide was 64.8%,which was relatively low.The preparation of 2-methyl pyridine N-oxide by HAc/H2O2 was a conventional method,2-methyl pyridine N-oxide yield was 84.9%,the reaction time was long,and needed to use HAc as a solvent.The TS-1/H2O2catalytic oxidation system had the characteristics of green and high efficiency,and the other product of the reaction was H2O,which did not produce environmental pollution,the reaction selectivity was high,and catalyzed the reaction time of 2-methyl pyridine to produce 2-methyl pyridine N-oxideis short.Under the reaction conditions of 0.050 mol 2-methyl pyridine,n（2-methyl pyridine）:n（H2O2）=1.0:4.0,2.0 g TS-1,20 m L deionized water,70℃for 2 h,the conversion rate of 2-methyl pyridine was 90.9%,the reaction selectivity was 98.9%,the yield of 2-methyl pyridine N-oxide was 89.9%,and it had a better industrial prospect.Secondly,using 2-methyl pyridine N-oxide as raw material,the thesis carried out an experimental study on the preparation of 2-pyridine methanol through the acylation and hydrolysis of 2-methyl pyridine N-oxide.While n（2-picoline N-oxide）:n（acetic anhydride）=1.0:3.0,condensation and reflux reaction at 90℃for 4 h,2-pyridine methyl acetate yield is 99.7%.n（trifluoroacetic anhydride）:n（2-methyl pyridine N-oxide）=1.0:1.0,the reaction at 90℃for 8 h,the yield of trifluoroacetic acid-2-pyridine methyl ester reaches 75.3%.While the reaction time was extended,the amount of 2-methyl pyridine produced gradually increased,leading to a decrease in the selectivity of the reaction.The reaction of mixed acid anhydride composed of acetic acid and trifluoroacetic anhydride and 2-methyl pyridine N-oxide to form trifluoroacetic acid-2-pyridyl methyl ester was relatively difficult.The yield of 2-pyridine methyl acetate hydrolyzed to 2-pyridine methanol was calculated with reference to the literature value of 91.3%,and the total yield of 2-pyridine methanol was 91.0%.Finally,the thesis studied 2-pyridine methanol as raw material,TEMPO and TEMPO-IL-PF6 as catalyst,TBN,Cu Cl2 as auxiliary agent,and air as oxidant to study the catalytic effect of the reaction to form 2-pyridylaldehydes.At the same time,in order to reduce costs and facilitate industrialization,the oxidation effect of Na NO3 as a nitrogen source to replace TBN was also studied.TEMPO catalyzes the oxidation of 2-pyridine methanol,at 60℃air oxidation,the conversion of 2-pyridine methanol was higher.The TEMPO-IL-PF6 catalyst prepared by ionic liquidization had a better catalytic effect on 2-pyridine methanol to form 2-pyridylaldehydes than TEMPO.Three catalyst systems as TEMPO/TBN,TEMPO/Cu Cl2,TEMPO/TBN/Cu Cl2 could catalyze reactions,but TEMPO/TBN/Cu Cl2 catalyst system had the best catalytic performance among the three systems.In the TEMPO/TBN/Cu Cl2 catalytic system,Na NO3 was used instead of TBN as the nitrogen source,and the catalytic oxidation of 2-pyridine methanol in the air could also generate 2-pyridylaldehydes.The TEMPO/TBN/Cu Cl2catalytic system catalyzed the reaction of air to oxidize 2-pyridine methanol to produce2-pyridylaldehydes was the optimal catalytic system in this paper.The reaction conditions were 0.050 mol 2-pyridine methanol,5 mol%TEMPO,20 m L CH3CN,40mol%TBN,5 mol%Cu Cl2,2 m L water,condensed and refluxed at 60℃for 10 h,and the conversion rate of 2-pyridylaldehydes reached 30.5%,reaction selectivity was99.1%,2-pyridylaldehydes yield was 30.1%.Since the conversion rate of 2-pyridine methanol was only 30.5%,there were many unreacted 2-pyridine methanol.After recovering the unreacted 2-pyridine methanol,the yield of 2-pyridylaldehydes was adjusted to 98.6%.From 2-methyl pyridine as raw material,the oxidation of 2-methyl pyridine by H2O2 and catalyzed by TS-1 to synthesize 2-methyl pyridine N-oxide,the yield of 2-methyl pyridine N-oxide was 89.9%;2-methyl pyridine N-oxide and acetic anhydride were acylated to synthesize 2-pyridyl methyl acetate.2-Pyridine methyl acetate was hydrolyzed to obtain 2-pyridine methanol.The yield of 2-pyridine methanol was 91.0%;using TEMPO/TBN/Cu Cl2 catalytic system to catalyze the air oxidation of 2-pyridine methanol to synthesize 2-pyridylaldehydes,the yield of 2-pyridylaldehydes was 98.6%.The total yield of 2-pyridylaldehydes synthesized from 2-methyl pyridine was 80.6%. |
