Study On Green Preparation Technology Of 3-pyrroline

In recent years,the application of pyrroline compounds in pesticides and medicine has attracted wide attention from researchers at home and abroad.3-pyrroline is an important nitrogen-containing core of many natural products and biologically active molecules,and substances containing 3-pyrroline structure exhibit a variety of biological activities.At present,most of the process routes for the synthesis of 3-pyrroline are complicated,energy-consuming,no economic benefit,and low yield.Therefore,this article used pyrrole as the raw material to carry out the research on the green synthesis process of 3-pyrroline.Meanwhile,this article used a microchannel reactor to further study the green synthesis process of 3-pyrroline derivative 3-ethyl-4-methyl-3-pyrroline-2-one.1.Pyrrole was used as a raw material,and active zinc reacted with hydrochloric acid to generate active hydrogen,which was used for selective hydrogenation of pyrrole to generate3-pyrroline.Firstly,control experiments were set up,and the optimal conditions for activating zinc powder were obtained.The solvent was dimethyl sulfoxide,the activation temperature was 30℃,the activation time was 1.5 hours,the molar ratio of zinc powder to acetic acid was1:2,and the concentration of acetic acid was 60 wt%.The results showed that the reactivity of zinc powder was improved and the yield was increased from 0.02%to 29.67%.Then in the stage of synthesizing 3-pyrroline,the single variable control method was used to screen and optimize the reaction conditions.The best conditions were obtained.The molar ratio of pyrrole,hydrochloric acid,and zinc powder was 1:10:4,and the concentration of hydrochloric acid was 30 wt%.The molar ratio of sodium hydroxide to hydrochloric acid was 1:1,the reaction temperature was 10°C,and the reaction time was 6 hours.According to the reaction results,the reaction selectivity was high,and the by-product was only pyrrole polymer that is not easily soluble in water.Finally,by introducing the extraction separation method,the separation effect of various extractants was investigated,and it was found that when ether was used as the extractant,the separation effect was good,and the yield was increased from 0 to29.67%.This scheme had simple synthesis route,low cost,low energy consumption,and meets the requirements of environmental protection.Through gas chromatography（GC）,infrared spectroscopy（FTIR）,nuclear magnetic resonance（NMR）,and high-resolution mass spectrometry（MS）characterization methods,it was proved that 3-pyrroline was obtained.At the same time explore the reaction mechanism of the entire reaction process.2.Diallylamine that was used as a raw material reacted with 4-toluenesulfonyl chloride to generate N,N-diallyl-4-methylbenzenesulfonamide to protect the amino group.Zinc reduced niobium chloride to produce low-valent niobium.The organozinc compound produced by the reaction of Ph CH₂Cl₂ and Zn was activated by trimethylchlorosilane（TMSC1）,The Nb-based active material was formed by the reaction of low-priced Nb with organozinc compounds formed stilbene through the dimerization of organozinc compounds.Stilbene catalyzed the cyclization reaction of N,N-diallyl-4-methylbenzenesulfonamide,then the benzenesulfonyl group was removed by hydrogen bromide in acetic acid to obtain3-pyrroline.By setting up a control experiment to optimize the reaction conditions,the results were as follows.At the stage of protecting the amino group,the molar ratio of N,N-diallylamine and 4-toluenesulfonyl chloride was 1.1:1,and the reaction time was 16 h;In the process of ring-forming reaction to synthesize N-（p-toluenesulfonyl）-3-pyrroline,the molar ratio of Zn to N,N-diallyl-4-methylbenzenesulfonamide was 1.5:1,and the reaction solvent was Tetrahydrofuran,Nb Cl5 was 10 mol%;In the process of removing benzenesulfonyl to synthesize 3 pyrroline,50 wt%HBr glacial acetic acid solution was better,and the reaction mechanism of the entire reaction process was explored.3.This article focused on the green synthesis process of3-ethyl-4-methyl-3-pyrroline-2-one that is a derivative of 3 pyrroline.Firstly,a microchannel reactor was used to carry out the alkylation reaction using the"ethanol+water"double solvent to form a liquid-liquid homogeneous reaction system.In comparison with the tank reactor,the reaction time was shortened from 2 hours to 3.33 minutes,and the reaction conversion rate was increased from 45.80%to 57.21%.By using orthogonal experiment method and single control variable method,the optimal reaction conditions of the microchannel reactor were obtained.The molar ratio of sodium ethoxide,ethyl acetoacetate and ethyl iodide was 1:1:1,the reaction temperature was 80℃,the flow rate was 6 m L/min,the feed concentration was 1 mol/L,the residence time was 3.33 minutes,and the highest yield was 57.21%.Then the tank reaction was used to discuss the influencing factors of nucleophilic substitution reaction,catalytic hydrogenation reaction.By setting up control experiments,the optimal reaction conditions for nucleophilic substitution reaction were obtained.The molar ratio of sodium cyanide to ethyl acetoacetate was 2:1,the reaction temperature was 25℃,and the reaction time was 3 hours;the optimal reaction conditions for the catalytic hydrogenation reaction were following:reaction pressure was 3.5 MPa,reaction temperature was 35℃,the reaction time was 6 hours,Raney nickel was 3.3 wt%.The highest yield was 53.12%（based on ethyl 2-ethylacetoacetate）.Through characterization methods,it was proved that this route could obtain 3-ethyl-4-methyl-3-pyrrolidin-2-one.