Background: Spiro compounds are one of the most important organic molecules. Spiro rings
such as spiroketals are present in numerous natural products; simple spiroketals are known insect
pheromones. A small number of spiro containing drugs has been investigated during the last several
decades. New attempts resulted in the incorporation of new synthetic building blocks for Spiro scaffold
to facilitate more active drug molecules. Thus, we have redesigned the chemical process for the synthesis
of active pharmacological Spiro derivatives in avoiding harmful organic solvent and toxic catalyst
under ambient reaction conditions.
Methods: Spiro[furan-2,11'-indeno[1,2-b]quinoxaline]s were prepared through domino one-pot and
multicomponent condensation reactions of 2,2-dihydroxy-1,3-indanedione, 1,2-diaminobenzenes, dialkyl
acetylenedicarboxylates and alkyl isocyanides in the presence of 1-butyl-3-methylimidazolium tetrafluoroborate
([bmim] BF4) at ambient temperature. The whole of the products constructions were detected
by elemental analyses and IR, 1H NMR, 13C NMR, mass spectra.
Results: A range of spiro[furan-2,11'-indeno[1,2-b]quinoxaline] derivatives were synthesized from a variety
of substrates under the optimized reaction condition. Different types of dialkyl acetylenedicarboxylate
and isocyanide derivatives were examined. All of them gave excellent yields of the desired
products under the optimized reaction conditions. Also, we planned to perform the model reaction in the
presence of neutral ionic liquids as reusable reaction medium. These results indicated that, in comparison
with catalyst free conditions, ionic liquids resulted in a faster reaction with a higher yield. Also, hydrophilic
[bmim] BF4 showed better results than hydrophobic [bmim] PF6.
Conclusion: It is noteworthy to mention that a very quick, efficient and eco-compatible process for the
synthesis of spiro[furan-2,11'-indeno[1,2-b]quinoxaline]s is explained. These compounds were prepared
through domino one-pot and multicomponent condensation reactions of 2,2-dihydroxy-1,3-indanedione,
1,2-diaminobenzene, dialkyl acetylenedicarboxylates and alkyl isocyanides in the presence of 1-butyl-3-
methylimidazolium tetrafluoroborate ([bmim] BF4) at ambient temperature. Among the most important
advantages of this method is simple work up procedure, excellent yields and high purity with short reaction
times using ILs as green recoverable solvents.