Multi-Component Syntheses of Spiro[furan-2,3′-indoline]-3-carboxylate Derivatives Using Ionic Liquid Catalysts
Mehdi Khalaj,
Maryam Zarandi,
Malihe Samadi Kazemi,
Seyed Mahmoud Musavi,
Johannes Hohnsen,
Axel Klein
Affiliations
Mehdi Khalaj
Department of Chemistry, Buinzahra Branch, Islamic Azad University, Buinzahra 1477893855, Iran
Maryam Zarandi
Department of Chemistry, Buinzahra Branch, Islamic Azad University, Buinzahra 1477893855, Iran
Malihe Samadi Kazemi
Department of Chemistry, Faculty of Science, Bojnourd Branch, Islamic Azad University, Bojnourd 9417697796, Iran
Seyed Mahmoud Musavi
Department of Chemistry, Buinzahra Branch, Islamic Azad University, Buinzahra 1477893855, Iran
Johannes Hohnsen
Faculty of Mathematics and Natural Sciences, Department of Chemistry and Biochemistry, Institute for Inorganic Chemistry, University of Cologne, Greinstrasse 6, D-50939 Köln, Germany
Axel Klein
Faculty of Mathematics and Natural Sciences, Department of Chemistry and Biochemistry, Institute for Inorganic Chemistry, University of Cologne, Greinstrasse 6, D-50939 Köln, Germany
Two previously described Brønsted acidic ionic liquids, 3,3′-(1,6-hexanediyl)bis(1-methyl)-1H-imidazolium hydrogen sulfate (Cat1) and 1,1′-(1,6-hexanediyl)bis(pyridinium) hydrogen sulfate (Cat2), were used as catalysts for the preparation of spiro[furan-2,3′-indoline]-3-carboxylate derivatives via a three-component reaction of anilines, isatins (N-alkyl-indoline-2,3-diones), and diethyl acetylenedicarboxylate, in high yields. The use of ultrasonic (US) irradiation led to the targeted products (1a–15a) 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 1a.
