[Omim][NO3], a Green and Base-Free Medium for One-Pot Synthesis of Benzothiazinones at Room Temperature

A general and efficient room-temperature procedure is developed for high-yield synthesis of 2H-benzo[b][1,4]thiazin-3(4H)-one derivatives in one pot from the reaction of 2-aminothiophenols with 2-bromoalkanoates in ionic liquid [bmim]NO₃ without the use of any catalyst, base, or additive. Products were obtained in good yields by simple extraction with Et₂O followed by evaporation of the volatile contents and recrystallization from Et₂O. The ionic liquid was recycled and reused in the next reaction without the loss of its activity.