Improved Process For The Synthesis Of Metribuzin

As a typical triazine herbicide,metribuzin is widely used in China because of its high efficiency,low toxicity and high selectivity.Metribuzin is one of the major herbicides in China,it's also an important herbicide on the market in our country.So research on synthesis of metribuzin has an important practical value.On the basis of consulting and summarizing the relevant literature at home and abroad,the synthesis process of metribuzin was studied with 1,1-dichloro-3,3-dimethyl-2-butanone as raw material,through hydrolysis,oxidation,cyclization and other reactions to obtain intermediate 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5-(4H)-one.First of all,methan-ol,dimethyl carbonate and dimethyl sulfate were explored.Finally,metribuzin was prepared from 4-amino-6-tert-butyl-3-mercapto-1,2,4-triazine-5(4H)-one and dimethyl sulfate by me-thylation,great progress has been made in the experiment.The mechanism of each reaction was discussed in detail.Based on this,by improving the feed mode and explore the appropriate oxidation reagents,the effects of reaction temperature,reaction time,material ratio and pH value on the reaction yield are investigated by single factor and orthogonal experiments.The yield of hydrolysis,oxidation,cyclization reaction reaching up to 90%.Synthesis of metribuzin with dimethyl sulfate as methylating reagent has the advantages of low cost,mild reaction condition and less waste water discharge.The yield of the experiment is 84.1%.At last,the qualitative and quantitative analysis methods of metribuzin and its intermediates were established(HPLC).At the same time,the chemical structures of the products are confirmed by 1H-NMR and MS.By means of optimizing the technology conditions,the reaction operation has been simplified,the cost of production has been greatly cutted down.Above all,the industrial process of metribuzin has been found.