Synthesis And Thermal Behavior Analysis Of N-Substituted Pyrrole Flavor Precursor Derivatives

This study explored the reaction of synthesis of 19 new N-substituted pyrrole flavor precursors based on alkylation and paal-Knorr reaction.The main results obtained are as follows:1.In alkaline condition,glucosamine hydrochloride as raw material,after oxidation and cyclization,four 2-methyl-5-pyrrolidine compounds were synthesized(3a-3d),and then 3b and bromo n-butane 4f were used as templates to screen and determine the route.The optimal route was to synthesize 16 kinds of 2-methyl-5-formyl-N-substituted pyrrole derivative(5a-5p)under the condition that K2CO3 as the base catalyst,MeCN as the solvent,TBAB as the phase transfer catalyst and the temperature is 65℃.2.2,5-dimethyl-N-pyrroleacetic acid(compound 6)was esterified with isobutanol 7a,isobutenol 7b and prenol 7c to synthesize three 2,5-dimethyl-N-substituted pyrrole compounds(8a-8c).3.The compounds 5b,5c,5f,5h,and 5k were selected and the preliminary thermal behavior analysis of the product was carried out by thermogravimetry(TG-DTG-DSC).The results showed that the main weight loss interval of compound 5b was 205.5 ℃-320.0℃,the fastest weight loss rate of 5b was 310.0℃,and the whole weight loss of 5b was 99.91%;The main weight loss of compound 5c ranged from 146.3℃ to 270℃,and the weight loss rate of 5c was at 257.50℃,the maximum weight loss of 5c was 99.12%;the main weight loss of compound 5f was 117.7℃-285℃.At 267℃,the weight loss rate of 5f was the largest,the whole weight loss of 5f was 99.26%;The main weight loss interval of compound 5h was 128.6℃-280.1℃,the fastest weight loss rate of 5h was 275.0℃,the whole weight loss of 5h was 82.38%;the main weight loss interval of compound 5k is 108.9-297℃,the fastest weight loss rate of 5k was 280.0℃,and the whole weight loss of 5k was 100.00%;therefore,thermogravimetric analysis can explain compound 5b,5c,5f,5h and 5k had good thermal stability at room temperature,which provides an effective theoretical basis for the study of pyrolysis behavior.4.Select compounds 5a,5b,5c,5d,5e,5f,5g,5h,5j,5k,51,5m,5n,5o,5p,8a as representatives,using pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS)analyze its pyrolysis behavior.From the analysis of the cleavage products,the main pyrolysis components were mostly aroma components such as pyrrole derivatives,pyrazine derivatives,pyridine derivatives and anthracene derivatives.Many of these pyrolysis products have unique flavor characteristics and have been proven to be used as tobacco flavors or food flavors in the tobacco and food industries.