Multi-Component Syntheses of Spiro[furan-2,3'-indoline]-3-carboxylate Derivatives Using Ionic Liquid Catalysts

Two previously described Brønsted acidic ionic liquids, 3,3'-(1,6-hexanediyl)bis(1-methyl)-1 -imidazolium hydrogen sulfate ( ) and 1,1'-(1,6-hexanediyl)bis(pyridinium) hydrogen sulfate ( ), were used as catalysts for the preparation of spiro[furan-2,3'-indoline]-3-carboxylate derivatives via a three-component reaction of anilines, isatins ( -alkyl-indoline-2,3-diones), and diethyl acetylenedicarboxylate, in high yields. The use of ultrasonic (US) irradiation led to the targeted products ( - ) in high yields ranging from 80% to 98%. Under the same conditions, the use of sulfuric acid and acetic acid as a Brønstedt catalyst did not yield the desired benchmark product .