synthesis of fully substituted pyrazoles via regioselective 1,3-dipolar cycloaddition reaction

A regioselective and convenient method for the synthesis of fully substituted pyrazole derivatives was developed from the 1,3-dipolar cycloaddition reaction of nitrile imine generated in situ from hydrazonoyl chloride and et3n with 1,4-benzothiazin-3(4h)-one. the structure of the target molecule 3d was confirmed by x-ray diffraction. an efficient synthesis of a series of 1h-pyrazole-4-carboxylate is reported. a multicomponent reaction was designed using 2-aminothiophenol, dialkyl acetylenedicarboxylate, and hydrazonoyl chloride in the presence of et3n in etoh at room temperature. the structure of the target molecules was confirmed by x-ray diffraction.