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was monitored by TLC (petroleum ether–ethyl acetate 3 : 2).
Aer completion, the reaction mixture was dissolved in hot
ethanol (5 ml) and the catalyst was removed with an external
magnet. The solvent was evaporated under reduced pressure
to yield the crude product, which was then puried by
recrystallization from hot ethanol and water to afford the pure
1,4-DHP.
Acknowledgements
We gratefully acknowledge the nancial support from the
Research Council of the University of Kashan for supporting
this work with Grant no. (256722/VI).
Fig. 7 Reuse of IL–Ni(II)–MNPs in the synthesis of 1,4-dihydropyridines in the
model reaction.
References
FT-IR (KBr, cmꢁ1): 1656, 1612, 1584. 1H NMR (400 MHz,
CDCl3): dH (ppm): 10.22 (broad, 1H, Ar-H), 7.59 (1H, dd, J ¼ 7.89
and 2.86 Hz, Ar-H), 7.26 (1H, dd, J ¼ 7.89 and 2.79 Hz, Ar-H),
4.06 (2H, t, J ¼ 7.25 Hz, –NCH2), 3.86 (3H, s, –NCH3), 3.30 (9H, s,
OCH3), 1.74 (2H, tt, J ¼ 7.14 Hz, –CH2), 0.37 (2H, t, J ¼ 7.09 Hz,
SiCH2). 13C NMR (100 MHz, CDCl3, TMS): dC ¼ 138.13, 123.34,
121.58, 58.53, 51.66, 36.51, 24.32, 18.2, 7.03. Anal. calcd: C,
48.45; H, 8.39; N, 8.69. Found: C, 48.35; H, 8.32; N, 8.79%.
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4.4. Synthesis of IL-containing Ni2+
The IL-containing Ni2+ was synthesized according to a method
reported by other authors.24 In the experiment, anhydrous NiCl2
(0.65 g, 0.05 mol), IL (3.23 g, 0.10 mol) and anhydrous aceto-
nitrile (100 ml) were added into a 250 ml round bottom ask
and the mixture was reuxed at 363 K for 24 h under a N2
atmosphere until a transparent blue solution was obtained.
Aer cooling, acetonitrile was evaporated under vacuum. A blue
viscous liquid was obtained aer washing with toluene, and was
dried under vacuum for 24 h and the IL–Ni(II) was obtained.
4.5. Modication of magnetic nanoparticles with IL–Ni2+
(IL–Ni(II)–MNPs)
The detailed procedure for preparing the IL–Ni(II)–MNPs cata-
lyst is described in the literature.16 In brief, freshly prepared
Fe3O4 nanoparticles (2 g) were suspended in methanol (250 ml),
and sonicated for 30 min. The resultant suspension was
mechanically stirred, followed by the addition of a solution of
methanol (100 ml) containing IL–Ni(II) (6 g) and concentrated
ammonia (28%, 1 ml). Stirring under N2 was continued for 36 h.
The modied magnetite nanoparticles were magnetically
separated and washed three times with ethanol (95%, 50 ml)
and dried under a vacuum for 24 h.
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4.6. Synthesis of 1,4-DHPs
To a mixture of the aromatic aldehyde (1 mmol), ethyl ace-
toacetate (2 mmol), and ammonium acetate (1.5 mmol) in a 10
ml round bottom ask, Fe3O4–MNPs modied with IL–Ni2+
(the IL–Ni(II)–MNPs catalyst) (0.012 g) was added. The mixture
was homogenized and stirred at 70 ꢀC for the appropriate time
until the reaction was complete. The progress of the reaction
26100 | RSC Adv., 2013, 3, 26094–26101
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