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The oxidation of 1,3,5-trisubstituted pyrazolines to pyrazoles is a very important reaction. Pyrazoles are widely used as analgesic, anti-inflammatory, antipyretic, antiarrhythmic, tranquilizing, muscle relaxant, psychoanaleptic, anticonvulsant, monoamineoxidase inhibitor, antidiabetic and antibacterial activities. 1,3,5-Trisubstituted pyrazolines can be easily prepared from phenylhydrazine and chalcone derivatives. Oxidative aromatization of pyrazolines, with oxidizing reagents provides an efficient method for the preparation of pyrazole derivatives. Several reagents such as Zr(NO3)4, Pd/C, Co(II) and oxygen, iodobenzene diacetate, lead tetraacetate, MnO2, potassium permanganate and NBS, have been reported for the preparation of pyrazoles. It is note worthy to say that most of the procedures have been developed for this purpose suffer from some disadvantages including need to use excess reagent, long reaction times, high temperatures, formation of side products and difficulty to remove the reagent from the sensitive pyrazoles. Herein, we report on a simple and efficient procedure for oxidative aromatization of 1,3,5-substituted pyrazolines to pyrazoles using N,N'-dibromo-N,N'-1,2-ethanediylbis(ptoluenesulphonamide) [BNBTS] (Fig. 1). The advantages of BNBTS are as follows: 1. It can be prepared easily. 2. It is stable in atmospheric conditions for two months. 3. After completing the reaction and evaporation of solvent, the sulphonamide can be recovered and reused many times without decreasing the yield. The reaction of 1,3,5-trisubstituted pyrazolines with BNBTS in carbon tetrachloride at room temperature afforded pyrazoles without side products (Scheme 1). The results of the conversion of various 1,3,5-trisubstituted pyrazolines to their corresponding pyrazoles are presented in Table 1. Since BNBTS contains two bromine atoms which are attached to nitrogen atoms it is very probable that this reagent releases Br in situ which can conduct as an electrophilic species. Therefore the following mechanism

N,N'-Dibromo-N,N'-1,2-ethanediylbis(p-toluenesulphonamide) as a Useful Reagent for Oxidation of 1,3,5-Trisubstituted Pyrazolines