Iodine-Catalyzed One-Pot Four-Component Synthesis of Spiro[indoline-3,4′-pyrano-pyrazole] Derivatives

An efficient, facile, and useful synthetic method was developed for the production of spiro[indoline-3,4 '-pyrano-pyrazole] carbonitrile derivatives through a one-pot, four-component reaction involving hydrazine hydrate, diketene, substituted isatins, and malononitrile or ethyl cyanoacetate in the presence of iodine as the efficient catalyst in ethanol at room temperature. Significantly, this remarkable method provides novel spiropyranopyrazole derivatives in good to high yields. The significant aspects of this protocol are facile work-up approach and a greener process because the use of toxic and hazardous solvents are avoided.