Ionic liquid [omim][NO3], a green medium for room-temperature synthesis of benzothiazinone derivatives in one pot

An efficient one-pot procedure is developed at room temperature for the reaction of 2-aminothiophenols with 2-bromoalkanoates in ionic liquid (IL) [omim][NO3], providing the corresponding benzothiazin-3-one derivatives in high yields without using any other base or additive. Products are easily obtained by simple extraction of the reaction mixtures with Et2O. In most cases, evaporation of the volatile contents leads to precipitation of the products and therefore the use of chromatographic separations is avoided. The IL is then recovered and reused in next reactions without loosing its activity. The procedure is successfully extended to the synthesis of the respective 2-carboxylate derivatives via the reaction of 2-aminothiophenols with 2-bromomalonates.