Study On The Synthesis Of P-methylsulfone Benzaldehyde

4-methylsulfonyl benzaldehyde is an important medical intermediate of florfenicol,etc.It is a broad-spectrum chloramphenicol for veterinary use.For examples,it was used for bacterial diseases of pigs,chickens and fish caused by bacteria,especially for respiratory and intestinal infections.The preparation of thiamphenicol usually use p-methylsulfone toluene as raw material,through substitution reaction by bromine and hydrolysis.This production process has obvious drawbacks,such as low atom utilization rate,difficult separation,low conversion and selectivity.Now using oxygen or hydrogen peroxide as direct oxidant is becoming more and more popular in the research of oxidation reaction.Therefore,oxygen and hydrogen peroxide were selected as oxidants to prepare 4-methylsulfonyl benzaldehyde in this paper so as to be suitable for industrial production.Based on three different substrates(p-methylsulfonyltoluene,p-methylsulfonylbenzyl alcohol,and p-methylthio benzaldehyde),various synthesis methods of p-methylsulfone benzaldehyde were studied.In the experiment with p-methylsulfone toluene as raw material,the Co/Mn/Br catalytic system was optimized,including the types of cobalt salts,manganese salts,bromide species,the concentration,temperature,time,catalyst dosage and catalyst proportion,etc.The experimental results show that under the same conditions,when the proportion of manganese in cobalt-manganese increases,the oxidation rate decreases,the conversion rate decreases and the selectivity increases,but the yield decreases.Increasing the concentration of the reaction solution is also beneficial to increase the conversion and selectivity of the reaction,and selecting an appropriate reaction time is advantageous for obtaining the optimum reaction yield.In the synthesis method of 4-methylsulfonyl benzaldehyde using p-methylsulfonylbenzyl alcohol as raw material,the main oxidant was nitric acid.High selectivity was obtained.It comes down to nitrous acid which is broken down in the reaction,attacking the hydroxyl carbon to form an intermediate.High efficiency and selectivity of the process make almost no by-products.The highest conversion rate was 98%and the selectivity was almost 100%.In addition,it is found that the factors hindering the reaction conversion rate and catalyst cycle are very simple.The decomposition product of nitric acid is mainly NO,which will be gradually lost as oxygen is poured in.Moreover,the product is solid at the reaction temperature,and the raw material is liquid under this condition.In the process of product generation,the raw material will be wrapped,which hinders the reaction.In the synthesis method using p-methylthio benzaldehyde as raw material,the thioether was oxidized by hydrogen peroxide.V2O5 with high activity was used as catalyst to promote the reaction.After optimization experiments on temperature,concentration,catalyst amount,etc.,it was found that the reaction conversion rate was close to 100%and the selectivity was up to 85.5%with 4 ml of water as the solvent.The similar reaction result was obtained with the insoluble solvent.It indicated that the higher the concentration of hydrogen peroxide in the reaction,the more favorable the reaction.Besides,the soluble solvent disperses the hydrogen peroxide to cause the conversion rate to decrease.In this paper,a variety of attempts have been made to prepare 4-Methylsulfonyl benzaldehyde,in order to find the most suitable solution for industrial production and replace the current production method with heavy pollution problem,low selectivity and high environmental protection cost.At the same time,the low selectivity scheme found in the experiment provides a new idea for the preparation of benzoic acid.