Synthesis Of Compounds Of Vanillin Series Catalyzed By Copper-complexes

Vanillin is an important synthetic perfume, which plays a very important role inpeople’s daily lives, is widely used in food, plating, agriculture and pharmaceuticalindustry.According to statistics, the global annual demand for vanillin is about17,000tons, and presents a trend of increasing. China is a major vanillin exporter, whereascompared with foreign countries, there are some differences in production scales andcost savings, in addition, there are still some problems about product quality andenvironmental pollution. Therefore, the ultimate solution is to exploit cheap materialsand outstanding synthetic route.In this article, an intermediate3-bromo-4-hydroxybenzaldehyde was selectivelysynthesized by using p-hydroxybenzaldehyde as raw material, and then, the targetcompound vanillin was synthesized from the intermediate. The emphasis of thisarticle is the synthesis of compounds including the intermediate and compounds ofvanillin series and process optimization of reaction conditions. The innovation of thisarticle is adding active ligand to reaction system, which can change the activity of thecatalyst by forming coordinated complexe, to improve yields. The results wereconcluded as follows.The optimal synthetic condition of3-bromo-4-hydroxybenzaldehyde was foundas follows: n（bromine）: n（p-hydroxybenzaldehyde）=0.8:1.0; the mixture of methanoland chloroform as reaction solvent; reaction temperature0℃, reaction time1hour.Under the conditions, the yield of desired product reached93.5%（based on bromine）,with98.0%purity（determined by HPLC）. The structure of product were characterizedby¹H NMR、¹³C NMR.The optimal synthetic conditions of vanillin were found as follows: compared tothe blank group, the author selected19kinds of ligands and synthesized3plants ofligands, to do parallel experiments to screen the excellent ligand L-proline. Thereaction condition was n（3-bromo-4-hydroxybenzaldehyde）: n（sodium methoxide）:n（anhydrous copper chloride）: n（L-proline）=1.0:3.0:0.1:0.2; reaction temperaturewas120℃, reaction time was8hours. Under these conditions, the yield of desiredproduct reached92.3%（based on3-bromo-4-hydroxybenzaldehyde）, with99.0%purity（determined by HPLC）. The structure of product was characterized by1HNMR、¹³C NMR. We have totally synthesized7kinds of compounds of vanillin series underoptimal conditions mentioned above. Although the yields slightly decreased comparedto itself, all these experiments would be beneficial to the development and applicationof related derivatives, with a certain market prospect.