Ionic liquid [bmim][NO3], an efficient medium for green and one-pot synthesis of benzothiazinones at room-temperature

A one-pot room-temperature procedure is developed for an efficient reaction of 2- aminothiophenols with 2-bromoalkanoates in ionic liquid [bmim][NO3] to obtain high yields of different benzothiazin-3-ones under base- and additive-free conditions. Products are easily separated from the reaction mixtures by Et2O extraction. Notably, condensation of the extract under reduced pressure results in precipitation of the products and, consequently, no chromatographic separation is needed. The ionic liquid can be recovered and successfully recycled into subsequent reactions without significant loss of activity.