1694
C. Betti et al. / Tetrahedron 64 (2008) 1689e1695
4.2.7. 1-Octyl-3-methylimidazolium 4-nitrophenoxide
[omim][4NO2PhO] (4f)
until the 1,2-dimethyl imidazole disappeared (the progress of
the reaction was monitored by GC and/or NMR). The crude
was rinsed several times with n-hexane to remove the un-
reacted octyl halide. Residual solvent was removed from the
imidazolium salts 40bed under vacuum (90 ꢀC at
ꢃ0.01 mmHg) for 6 h. Reaction time, yield, and physical,
spectroscopic and analytical data of ILs 40bed are as follows.
Waxy oil; 94%; 1H NMR (300 MHz, CDCl3) d (ppm) 9.94 (s,
1H), 7.91 (d, 2H, J¼9.4 Hz), 7.25e7.22 (m, 2H), 6.28 (d, 2H,
J¼9.4 Hz), 4.10 (t, 2H, J¼7.5 Hz), 3.91 (s, 3H), 1.82e1.75
(m, 2H), 1.24e1.20 (m, 10H), 0.84 (t, 3H, J¼6.8 Hz); MS
(FABþ): m/z 195 ([omim]þ, 100), 528 ([(omim)2(4NO2PhO)]þ,
18); Elemental analysis calcd (%) for C18H27N3O3: C 64.84, H
8.16, N 12.60; found: C 64.5, H 8.2, N 12.5.
4.3.1. 1-Octyl-2,3-dimethylimidazolium chloride [om2im]-
[Cl] (40b)
IL 3l was commercially available material, used after dehy-
dration under vacuum (60e70 ꢀC at <0.01 mmHg for 6 h).
1
A very hygroscopic wax; 84 h; 98%; H NMR (300 MHz,
CDCl3) d (ppm) 7.78 (A part of an AB system, d, 1H,
J¼2.08 Hz), 7.40 (B part of an AB system, d, 1H,
J¼2.08 Hz), 4.17 (t, 2H, J¼7.5 Hz), 4.05 (s, 3H), 2.81
(s, 3H), 1.84e1.76 (m, 2H), 1.32e1.25 (m, 10H), 0.86 (t, 3H,
J¼6.7 Hz); MS (ESþ): m/z 209.2 ([om2im]þ, 100), 453.1
([(om2im)2Cl]þ, 52); Elemental analysis calcd (%) for
C13H25ClN2: C 63.78, H 10.29, N 11.44; found: C 63.5, H
10.5, N 11.5.
4.2.8. 1-Hexyl-2,3-dimethylimidazolium methanesulfonate
[hm2im][MeSO3] (30j)
n-Hexyl methanesulfonate23 (18.03 g, 0.1 mol) and 1,2-di-
methyl imidazole (9.90 g, 0.103 mol) were placed in
a 100 mL round-bottomed flask, fitted with a reflux condenser,
and a CaCl2 drying tube. The mixture was then heated at 90 ꢀC
under stirring for 3 h until the methanesulfonate disappeared
(the progress of the reaction was monitored by NMR), dis-
solved in CH2Cl2 (80 mL), washed with a solution of saturated
Na2SO4 containing 5% methanesulfonic acid (2ꢄ5 mL), and
then with saturated Na2SO4 (3ꢄ5 mL) until neutrality. The or-
ganic phase was dried over anhydrous Na2SO4, concentrated
by using a rotary evaporator, and dried under vacuum (60e
70 ꢀC at <0.01 mmHg) for 6 h, obtaining 26.26 g (95% yield)
of a very hygroscopic solid; mp¼127e128 ꢀC; 1H NMR
(200 MHz, CDCl3) d (ppm) 7.50 (A part of an AB system, d,
1H, J¼2.1 Hz), 7.27 (B part of an AB system, d, 1H,
J¼2.1 Hz), 4.13 (t, 2H, J¼7.5 Hz), 3.94 (s, 3H), 2.73 (s, 3H),
2.72 (s, 3H), 1.85e1.73 (m, 2H), 1.38e1.27 (m, 6H), 0.88
(t, 3H, J¼6.8 Hz); MS (ESþ): m/z 181.3 ([hm2im]þ, 100), 457.4
([(hm2im)2(MeSO3)]þ, 38); MS (ESꢁ): m/z 95.0 ([MeSO3]ꢁ,
100), 650.0 ([((hm2im)(MeSO3))2(MeSO3)]ꢁ, 60); Elemental
analysis calcd (%) for C12H24N2O3S: C 52.15, H 8.75, N
10.14; found: C 52.4, H 8.6, N 10.2.
4.3.2. 1-Octyl-2,3-dimethylimidazolium bromide [om2im]-
[Br] (40c)
Wax; 48 h; 88%; 1H NMR (300 MHz, CDCl3) d (ppm) 7.72
(A part of an AB system, d, 1H, J¼2.0 Hz), 7.43 (B part of an
AB system, d, 1H, J¼2.0 Hz), 4.16 (t, 2H, J¼7.5 Hz), 4.01
(s, 3H), 2.78 (s, 3H), 1.82e1.75 (m, 2H), 1.29e1.22 (m, 10H),
0.84 (t, 3H, J¼6.6 Hz); MS (ESþ): m/z 209.2 ([om2im]þ,
100), 497.0 ([(om2im)729Br]þ, 10), 499.0 ([(om2im)821Br]þ,
10); Elemental analysis calcd (%) for C13H25BrN2: C 53.98,
H 8.71, N 9.68; found: C 53.6, H 8.9, N 9.7.
4.3.3. 1-Octyl-2,3-dimethylimidazolium iodide [om2im]-
[I] (40d)
1
Pale yellow solid; mp¼86e87 ꢀC; 24 h; 89%; H NMR
(300 MHz, CDCl3) d (ppm) 7.56 (A part of an AB system,
d, 1H, J¼2.0 Hz), 7.36 (B part of an AB system, d, 1H,
J¼2.0 Hz), 4.15 (t, 2H, J¼7.5 Hz), 3.98 (s, 3H), 2.81 (s,
3H), 1.88e1.78 (m, 2H), 1.33e1.24 (m, 10H), 0.86 (t, 3H,
J¼6.6 Hz); MS (ESþ): m/z 209.2 ([om2im]þ, 100), 544.9
([(om2im)2I]þ, 34); Elemental analysis calcd (%) for
C13H25IN2: C 46.43, H 7.49, N 8.33; found: C 46.6, H 7.6,
N 8.4.
4.2.9. 1-Hexyl-2,3-dimethylimidazolium perchlorate
[hm2im][ClO4] (30i)
Obtained from 30j by anion metathesis, according to a previ-
ously described procedure;24,28 99.7% yield; oil; n2D0 1.4732;
1
r25¼1.172 g mLꢁ1; r60¼1.141; H NMR (300 MHz, CDCl3)
d (ppm) 7.30 (A part of an AB system, d, 1H, J¼2.2 Hz), 7.23
(B part of an AB system, d, 1H, J¼2.1 Hz), 4.04 (t, 2H,
J¼7.5 Hz), 3.81 (s, 3H), 2.62 (s, 3H), 1.82e1.72 (m, 2H),
1.36e1.27 (m, 6H), 0.85 (t, 3H, J¼6.8 Hz); MS (ESþ): m/z
181.3 ([hm2im]þ, 100), 461.8 ([(hm2im)2(ClO4)]þ, 68); Ele-
mental analysis calcd (%) for C11H21ClN2O4: C 47.06, H
7.54, Cl 12.63, N 9.98; found: C 46.8, H 7.7, N 10.0.
4.3.4. 1-Octyl-2,3-dimethylimidazolium 4-nitrophenoxide
[om2im][4NO2PhO] (40f)
Obtained from 40b by anion metathesis, according to a pre-
viously described procedure;24,28 93% yield; hygroscopic
1
solid; mp¼85e86 ꢀC; H NMR (300 MHz, CDCl3) d (ppm)
7.81 (d, 2H, J¼9.3 Hz), 7.18 (A part of an AB system, d,
1H, J¼2.1 Hz), 7.10 (B part of an AB system, d, 1H,
J¼2.1 Hz), 6.20 (d, 2H, J¼9.3 Hz), 3.95 (t, 2H, J¼7.5 Hz),
3.75 (s, 3H), 2.53 (s, 3H), 1.78e1.72 (m, 2H), 1.29e1.24
(m, 10H), 0.86 (t, 3H, J¼6.7 Hz); MS (ESþ): m/z 209.2
([om2im]þ, 100), 555.7 ([(om2im)2(4NO2PhO)]þ, 12); Ele-
mental analysis calcd (%) for C19H29N3O3: C 65.68, H 8.41,
N 12.09; found: C 65.9, H 8.3, N 12.0.
4.3. General procedure for the synthesis of 1-octyl-2,3-
dimethylimidazolinium halides [om2im][Hal] (40bed)
1,2-Dimethyl imidazole (1.0 mol) and an excess of an n-octyl
halide (6bed) (1.1 mol) were placed in a 100 mL round-
bottomed flask, fitted with a reflux condenser and a CaCl2 dry-
ing tube. The mixture was then heated at 90 ꢀC under stirring