Study On The Synthesis Of Aryl Sulfinates

Sulfinic acid and its salts can be widely applied in the fields of medicine,printing and dyeing,pesticide.They are important intermediates for the synthesis of chemical compounds with the functional group of sulfonyl such as sulfoxides,sulfonamides,sulfuryl chloride by the creation of many chemical bonds such as C-C bond,S-hybrid bond,C-hybrid bond under different reaction conditions.There are some shortages for the synthesis of chemical compound in the class of sulfinic acid.For example,the reaction requires an environment of high pressure and low temperature with severe condition.The synthesis consumes a large amount of organic solvent with fugacity.The reaction system is complicated with long duration and high cost.Therefore,it is of great significance to develop a method for the preparation of sulfinic acid with gentle condition,efficiency and convenience,cheap and accessible raw materials.According to the chemical reaction equation,the most direct method for the preparation of aromatic sulfinic acid is the Friedel-Crafts reaction of sulfonamide for aromatic compound and sulfur dioxide.Due to the toxicity and hard manipulation of SO₂ gas,it is not widely applied in commercial organic synthesis.Therefore,a substitute of Sulphur dioxide was introduced in this work for the reaction with the corresponding aromatic compound.Also,ionic liquid was used as catalyst as well as solvents for this reaction and their catalytic performance was investigated.The research of this paper mainly includes the following aspects.1.With acetanilide as an example,the substitute of SO₂was used to prepare sulfinic acid.The different kind of Lewis acids were used as the catalyst.The optimum reaction conditions and the suitable catalyst system were obtained.2.The method was applied to other aromatic compounds and the optimum reaction conditions were obtained,then the differences of experimental results were analyzed and compared.3.A variety of ionic liquids were synthesized and applied to the reaction of SO₂ and acetanilide for preparation of the corresponding Sulfinic acid.The ionic liquids were used as catalyst as well as solvents to avoid consumption for large amount of volatile organic solvents,enhance the reaction speed and restrain the side reaction.The result shows that the catalytic reaction only works when there is a certain Lewis acid strength for the catalyst.The best catalytic performance was realized with 0.55triethylamine hydrochloride/AlCl₃（the mole ratio of triethylamine hydrochloride/AlCl₃ is 0.55 which is recorded as 0.55Et₃NHCl/AlCl₃）.The complete comsumption of acetanilide is achieved within 4h under the temperature of 90℃with the yield of solfinic acid reaching 87.76%.We proved that it is[Al₂Cl₇]^-instead of AlCl₃ that functions as the catalytic agent in the system.