Synthesis Of 2-chloro-4-methyl Sulfonyl Benzoic Acid

2-chloro-4-(methylsulfonyl)benzoic acid(CMSBA)is the key intermediate of novel herbicide 3-[2-chloro-4-(methylsulfonyl)benzoyl]bicyclo[3.2.1]octane-2,4-dione(Benzobicyclon),with large domestic and external demand.Reported mainly synthetic routes are using 4-methyl-thiophenol as a raw material.After 4 steps reaction and recrystallization,pure products are obtained in 57%overall yield.The starting material 4-methyl-thiophenol(negative bivalent sulfur)is expensive and reducted by 4-methyl-benzene-sulfonyl-chloride(hexavalent sulfur),then is oxidized to sulfonyl(hexavalent sulfur).The process involves expensive redox reagents,not clean redox process and large sulfur valence change so the main problems of reported process are the poor redox and atom economy,producing many oxidation by-products,low yield and generating large amount of waste water.Hence,exploring an economic,suitable industrial production process of CMSBA is very important.In this paper,we use the available 4-methyl-benzene-sulfonyl-chloride as starting materials.Through reduction,methylation,chlorination and oxidation reaction and,ultimately,the total yield of CMSBA is 68.8%.Explore the process of one-pot synthesis of 4-methyl-sulfonyl-toluene.Using 4-methyl-benzene-sulfonyl-chloride as raw materials solves the problems of expensive raw material and poor redox economy.4-methyl-benzene-sulfonyl-chloride via melt into,reduction of sulfinate,methylation process,a pot method lets sulfonyl chloride into sulfonyl,which simplifies the production process,reduces the losses caused by the transfer of material for reaction process and improves product yield.Using methyl chloride instead of chloroacetic acid(or dimethyl sulfate)solves the problems of poor atom economy and low efficiency of reaction.Adding an appropriate amount of ice into the filtrate of post-processing realizes the recycle of water,which reduces production cost and water emissions.Under optimized process conditions,the yield of 4-methly-sulfonyl-toluene is up to 85.3%,higher than 60?70%reported in literatures.Improve sulfuric acid catalytic chlorination process of 4-methyl-sulfonyl-toluene,especially study the suitable concentration of sulfuric acid.Using 80wt%sulfuric acid insteat of 98wt%sulfuric acid and using 65wt%fuming sulfuric acid configuration with 65wt%post-process sulfuric acid gets 80wt%for recycling use.The usage of fuming sulfuric acid is 48%and the amount of waste acid is only 29.2%of traditional process.Under the optimized condition,product yield is 96%.Develope nitric acid catalytic oxidation process of 2-chloro-4-methyl-sulfonyl-toluene(CMSBA).In closed condition and HNO3/CuI catalytic system,realize the nitric acid and NOx recycling use,which reduces the dasage of nitric acid and emissions of NOx.The nitric acid dosage of the nitric acid catalytic oxidation method is 12.5%and NOx emissions is 5%of traditional process.Under the optimized condition,CMSBA yield is 84.2%and product purity is 99.7%.Apply nitric acid catalytic oxidation process to aromatic methyl's oxidation.The result shows that the more strong of substituent's electronic absorption ability is,the lower product yield isThis paper provides an economic,environmental,high yield and suitable for industrial process for the production of CMSBA.The products of the reactions are confirmed by 1H NMR and 13C NMR.In this paper,the process of one pot synthesis of 4-methyl-sulfonyl-toluene and nitric acid catalytic oxidation of 2-chloro-4-methylsulfonyl-toluene are novative processes;The circulation of sulfuric acid and nitric acid catalytic oxidation technology have a guiding significance for clean production;Nitric acid catalysis oxygen transfer process of aromatic methyl has popularization and application value.