Preparation Of Symmetrical Diselenides With Se/Co/H₂O Under Atmospheric Pressure

Diselenides are important organic reagents and intermediates in synthetic chemistry,because Se-Se bond can be easily converted into different reactive species and stabilize the charge of organic molecules.Generally,only dibenzyl diselenides can be synthesized in Se/CO/H₂O system,but the synthesis of diphenyl diselenides has not been reported.In this paper,an efficient method for the synthesis of symmetrical diphenyl diselenides was introduced,which concerns selenation of nitro aromatic compounds with Se/CO/H₂O in DMF to afford diselenides under atmospheric pressure in the presence of bases.We used 2,4-dinitroanisole and stoichiometric selenium as starting materials to prepare symmetric diselenides.We investigated the effects of the reaction time,the type and amount of solvent,the type and amount of co-catalyst,the reaction temperature and the amount of water on the reaction.The optimal reaction conditions were obtained:2,4-dinitroanisole:5 mmol;Se:5 mmol;H₂O:2 mL;Na₂CO₃:5mmol;T:95?;t:2 h.The yield of diselenides under optimum conditions was up to91%.Under the optimal reaction conditions,a series of symmetrical nitrobenzene diselenides were obtained by changing the substrate for preparing diselenides,such as the type of leaving group and the number of electron-withdrawing group.On the base of experiments,we speculated the mechanism of selenization reaction.Hydrogen selenide is generated in situ with selenium,carbon monoxide and water,and then forms hydrogen diselenide with selenium.Hydrogen diselenide forms sodium diselenide with sodium carbonate.Sodium diselenide as a nucleophile attacks the carbon on the benzene ring attached to the methoxy group,and then nucleophilic substitution takes place.