Study On The New Synthetic Process Of Penoxsulam

Research on the new process of Penoxsulam is of great significance for agricultural production.In recent years,research on the important synthetic blocks of Penoxsulam has been continuously reported,but there will be a series of problems in its synthesis process,such as expensive raw materials,long routes,use of toxic and harmful reagents.How to develop an efficient and convenient synthesis process is still a challenging subject.1.This paper describes the convenient and efficient synthesis of Penoxsulam in4 steps.The main features of the synthesis include a regioselective lithiation and subsequent electrophilic substitution from commercial available 3-Bromobenzotrifluoride to provide the 2-bromo-6-(trifluoromethyl)phenyl)(propyl)sulfane,then a Cu-catalyzed C-O coupling to introduce the difluoroethoxy moiety,and a chloro-oxidation condition to give the desired Sulfonyl chloride.Coupling reaction between the obtained sulfonyl chloride fragment and the heterocyclic ammonia fragment yielded Penoxsulam in a higher yield.The entire synthesis process has the characteristics of cheap raw materials,short routes and environmental friendly.2.A mild and efficient method for the preparation of difluoroethyl aryl ethers was developed by the Ullmann coupling reaction of aryl bromides or iodides with2,2-difluoroethanol.This reaction proceeds smoothly in the presence of Cu I and8-hydroxyquinoline/t-Bu OK,and has a broad substrate scope.ESI-MS analysis supported the existence of LCu(III)Ar(OR)species during this catalytic reaction.Further DFT calculations suggest a mechanism involving oxidative addition,followed by nucleophile substitution and reductive elimination would be rational.In short,we have developed a new process for the synthesis of Penoxsulam,and developed a carbon-oxygen coupling reaction method and performed DFT calculations on its mechanism.