JOHARI et al., Orient. J. Chem., Vol. 30(3), 1191-1196 (2014)
1193
stirred at room temperature for 72 h under an inert
atmosphere.The resulting ionic liquid was extracted
from the aqueous phase using dichloromethane and
the layers separated. The dichloromethane layer
was washed using distilled water to the excess
unreacted acid and chloride salt. The aqueous
layer was tested with litmus paper and silver nitrate
whilst the dichloromethane layer was concentrated
to give a yellow liquid.The yellow liquid was directly
treated with activated charcoal and filtered through
basic alumina to give 1-butyl-3-methylimidazolium
tetrafluoroborate (28 %) as a colorless liquid 28. IR
(KBr) 3565.66 (OH), 1635.22 (C=C), 1064.73 (CN)
DMSO-d6) ´ 136.9 (NCN), 124.0 (C-4), 122.6 (C-
5), 49.1 (NCH2CH2CH2CH3), 36.1 (NCH3), 31.8
(NCH2CH2CH2CH3), 19.2 (NCH2CH2CH2CH3),
13.5 (NCH2CH2CH2CH3); MS (ESI+) m/z 423.21
[2(C4C1im) + PF6] and 139.12, [C4C1im], MS (ESI-)
m/z 429.05 [2(PF6) + (C4C1im)] and 144.96 [PF6].
Procedure for the preparation of cycloadducts
1 and 2
Reaction between 1-p-tolyl-2,5-dione and
anthracene in [Bmim][BF4] at rt
In a two-neck round bottom flask,
anthracene and 1-p-tolyl-2,5-dione were added
directly into [Bmim][BF4] and the resulting reaction
mixture was stirred at room temperature for 72 h
under an inert atmosphere. The desired product
was removed from the ionic liquid by extracting the
solution with diethyl ether. The diethyl ether was
removed under vacuum and the residual powder
obtained was purified by column chromatography
using a mixture of hexane: ethyl acetate (9:1) as the
eluent to give the cycloadduct 1 (86%) as a colorless
powder. IR (KBr) 3422.16 (OH), 2928.43 (sp3
1
cm–1; H NMR (400 MHz, DMSO-d6) δ 9.01 (1H,
s, CH-2), 7.70 (1H, s, CH-4), 7.63 (1H, s, CH-5),
4.15 (2H, t, J= 7.32 Hz, NCH2CH2CH2CH3), 3.88
(3H, s, NCH3), 1.76 (2H, m, NCH2CH2CH2CH3),
1.25 (2H, m, NCH2CH2CH2CH3), 0.88 (3H, t, J=
7.32 Hz, NCH2CH2CH2CH3); 13C NMR (100 MHz,
DMSO-d6) ´ 136.9 (NCN), 124.0 (C-4), 122.7 (C-
5), 49.0 (NCH2CH2CH2CH3), 36.1 (NCH3), 31.8
(NCH2CH2CH2CH3), 19.1 (NCH2CH2CH2CH3),
13.6 (NCH2CH2CH2CH3); MS (ESI+) m/z 365.25
[2(C4C1im) + BF4] and 139.12 [C4C1im]; MS (ESI-)
m/z 313.12 [2(BF4) + C4C1im].
1
CH),1650.51 (C=O), 1045.41 (C-N)cm–1; H NMR
(400 MHz, CDCl3) δ 7.41 (2H, d, J= 8.40 Hz, ArCH),
7.33 (2H, d, J= 8.80 Hz, ArCH), 7.19 (4H, m, ArCH),
7.08 (2H, d, J= 8.04 Hz, ArCH), 6.36 (2H, d, J= 8.08
Hz, ArCH), 4.87 (2H, s, sp CH), 3.36 (2H, s, sp CH),
2.27 (3H, s, CH3); 13C NMR (100 MHz, CDCl3) ´
176.3 (C=O), 141.3 (aromatic C=C), 138.8 (aromatic
C=C), 136.9 (aromatic C=C), 129.8 (aromatic
C=C), 128.8 (aromatic C=C), 127.2 (aromatic
C=C), 126.9 (aromatic C=C), 126.2 (aromatic
C=C), 125.2 (aromatic C=C), 124.4 (aromatic
C=C), 123.4 (aromatic C=C), 121.8 (aromatic
C=C), 50.0 (quaternary C), 47.1 (quaternary C),
45.9 (quaternary C), 36.5 (quaternary C), 31.9
(quaternary C), 29.7 (quaternary C), 28.9 (HC=C),
19.4 (HC=C), 13.4 (CH3); mp 270.0- 270.2°C; MS
(EI+) m/z 365.4 (M+, 100%).
1-Butyl-3-methylimidazolium hexafluoro
phosphate [Bmim][PF6]
Lithium hexafluorophosphate was mixed
with 1-butyl-3-methylimidazolium chloride, [Bmim]
[Cl] in a two-neck round bottom flask. The reaction
mixture was stirred in dry dichloromethane at room
temperature for 72 h under an inert atmosphere.
The reaction mixture was filtered and the excess
lithium chloride was washed with dichloromethane.
The combined organic extraction was washed with
distilled water until the aqueous layer was free
from halide, determined using the silver nitrate test.
The dichloromethane layer was concentrated to
give a yellow liquid. The yellow liquid was treated
with activated charcoal and filtered through acidic
alumina to give 1-butyl-3-methylimidazolium
hexafluorophosphate (27%) as a colorless liquid
28. IR (KBr) 3392.27 (OH), 1649.54 (C=C), 1008.56
Reaction between 1-p-tolyl-2,5-dione and
anthracene in [Bmim][BF4] at reflux (90 °C)
Inatwo-neckroundbottomflask,anthracene
and 1-p-tolyl-2,5-dione were added directly into
[Bmim][BF4] and the resulting reaction mixture was
heated at refluxed (90 °C) for 2 h under an inert
atmosphere.The desired product was removed from
the ionic liquid by extracting the solution with diethyl
ether.The diethyl ether was removed under vacuum
1
(CN) cm–1; H NMR (400 MHz, DMSO-d6) δ 9.00
(1H, s, CH-2), 7.67 (1H, s, CH-4), 7.61 (1H, s, CH-
5), 4.14 (2H, t, J= 7.32 Hz, NCH2CH2CH2CH3), 3.83
(3H, s, NCH3), 1.76 (2H, m, NCH2CH2CH2CH3),
1.26 (2H, m, NCH2CH2CH2CH3), 0.89 (3H, t, J=
7.32 Hz, NCH2CH2CH2CH3); 13C NMR (100 MHz,