BRØNSTED ACIDIC IONIC LIQUID-CATALYZED SYNTHESIS
507
activity makes the proposed catalyst convenient for
CONFLICT OF INTEREST
No conflict of interest is declared by the authors.
REFERENCES
large-scale syntheses. Thus, the attractive features of
this protocol are simple and green procedure, short
reaction time, high yield, and reusability of the catalyst.
EXPERIMENTAL
1. Cole, A.C., Jensen, J.L., Ntai, I., Tran, K.L.T.,
Weaver, K.J., Forbes, D.C., and Davis, J.H., J. Am.
Chem. Soc., 2002, vol. 124, no. 21, p. 5962.
All chemicals were purchased from Merck and
Sigma-Aldrich and were used without further purifica-
tion. Melting points were recorded on a Büchi B-545
apparatus in open capillary tubes. The H and 13C
1
2. Wang, Y.-M., Ulrich, V., Donnelly, G.F., Lorenzini, F.,
Marr, A.C., and Marr, P.C., ACS Sustainable Chem.
Eng., 2015, vol. 3, no. 5, p. 792.
NMR spectra were recorded on a Bruker Avance-500
spectrometer using CDCl3 as solvent and solvent peaks
or TMS as internal standards. The high-resolution mass
spectra (electrospray ionization) were recorded on
a Bruker micrOTOF-QII MS instrument. Microwave
irradiation was performed on a CEM Discover
BenchMate apparatus, which offers microwave syn-
thesis with safe pressure regulation using a 10-mL
pressurized glass tube with Teflon-coated septum and
vertically focused IR temperature sensor controlling
the reaction temperature. Flash column chromatog-
raphy (length 60 cm, internal diameter 1.5 cm) was
performed on silica gel.
3. Kefayati, H., Bazargard, S.J., Vejdansefat, P.,
Shariati, S., and Kohankar, A.M., Dyes Pigm., 2016,
vol. 125, p. 309.
4. Xing, H., Wang, T., Zhou, Z., and Dai, Y., Ind. Eng.
Chem. Res., 2005, vol. 44, no. 11, p. 4147.
5. Greaves, T.L. and Drummond, C.J., Chem. Rev., 2015,
vol. 115, no. 20, p. 11379.
1-Methyl-3-sulfo-1H-imidazol-3-ium chloride
[Msim]Cl. A microwave tube was charged with
1-methyl-1H-imidazole (0.082 g, 1 mmol) and chloro-
sulfonic acid (0.116 g, 1 mmol). The mixture was
heated at 60°C for 20 min in a monomode microwave
oven. After cooling, the mixture was then washed with
diethyl ether and dried in a Christ Alpha 1-2 LD Plus
freeze-dryer to afford [Msim]Cl as a colorless viscous
oil in 94% yield.
6. Sibrian-Vazquez, M., Escobedo, J.O., Lowry, M.,
Fronczek, F.R., and Strongin, R.M., J. Am. Chem. Soc.,
2012, vol. 134, no. 25, p. 10502.
7. Di Micco, S., Mazue, F., Daquino, C., Spatafora, C.,
Delmas, D., Latruffe, N., Tringali, C., Riccio, R., and
Bifulco, G., Org. Biomol. Chem., 2011, vol. 9, no. 3,
p. 701.
https://doi.org/10.1039/C0OB00480D
8. Jardosh, H.H. and Patel, M.P., Med. Chem. Res., 2012,
vol. 22, no. 6, p. 2954.
General procedure for the preparation of
14-aryl-14H-dibenzo[a,j]xanthenes 3a–3n. A micro-
wave tube containing a mixture of β-naphthol
(2 mmol), aromatic aldehyde 2a–2n (1 mmol), and
[Msim]Cl (0.15 mmol) was heated under microwave
irradiation at 120°C for 30 min. After cooling to room
temperature, the mixture was washed with water to
remove the catalyst. The crude product was purified by
recrystallization from an appropriate solvent. The
products were identified by comparing their melting
points and spectral characteristics (1H and 13C NMR
and mass spectra) with those of samples reported
previously (Table 2).
9. Khurana, J.M., Chaudhary, A., Lumb, A., and Nand, B.,
Can. J. Chem., 2012, vol. 90, no. 9, p. 739.
10. Fernandez, A., Alvarez, E., Alvarez-Manzaneda, R.,
Chahboun, R., and Alvarez-Manzaneda, E., Chem.
Commun., 2014, vol. 50, no. 86, p. 13100.
https://doi.org/10.1039/C4CC05116E
11. Lukeman, M., Simon, H., Wan, P., and Wang, Y.H.,
J. Org. Chem., 2015, vol. 80, no. 22, p. 11281.
Recycling of [Msim]Cl. The water layer containing
the ionic liquid catalyst was collected and washed with
ethyl acetate (3×10 mL) to remove organic impurities.
Water was then evaporated at 80°C under reduced
pressure, and the catalyst was dried at 60°C for 4 h
and reused.
12. Saha, S. and Schneider, C., Org. Lett., 2015, vol. 17,
no. 3, p. 648.
13. Jha, A. and Beal, J., Tetrahedron Lett., 2004, vol. 45,
no. 49, p. 8999.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 56 No. 3 2020