1,3-Dipolar Cycloaddition Reaction of Nitrile Oxides to Isatin Imines

  A simple and efficient one-pot route for the synthesis of novel spiro [indolin– oxadiazol] derivativesby 1,3-dipolar cycloaddition reaction of nitrile oxides and isatin imine under classical or microwave irradiation conditions is described.4-amino-5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-thione was synthesized by cyclization of thiocarbohydrazide and acetic acid. 3-((3-methyl-5-thioxo-1,5-dihydro-4H-1,2,4-triazol-4-yl)imino)indolin-2-one was prepared by condensation of primary amine of 4-amino-5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-thione with isatin through a single step and 4'-(3-methyl-5-thioxo-1H-1,2,4-triazol-4(5H)-yl)- 3'-(substituted phenyl)-4'-hydro spiro[indolin-3,5'[1,2,4]oxadiazol]-2-one were afforded by the reaction of corresponding Schiff base with hydroximinoyl chloride and their derivatives under basic conditions at room temperature. The products were obtained in good yields. Elemental analysis, IR, 1H NMR, 13C NMR, and Mass spectral data confirmed the structure of newly synthesized compounds.