[HSO3-bPydin][HSO4]. 1H NMR (500 MHz, D2O, d ppm):
1.62-1.68 (m, 2H), 1.99-2.05 (m, 2H), 2.80-2.83 (t, 2H, J =
7.5 Hz), 4.49-4.52 (t, 2H, J = 7.5 Hz), 7.91-7.94 (d, 2H, J =
7 Hz), 8.38-8.41 (t, 1H, J = 8 Hz), 8.71-8.72 (d, 1H, J = 5.5 Hz).
Under vigorous stirring, 1,3-propane or 1,4-butane sultone
(0.2 mol ) was added slowly to trimethylsilylimidazole (0.1 mol),
while the flask was cooled in an ice bath. After the reaction
had finished, the reaction mixture was stirred for half an hour
and then water was added dropwise. The reaction mixture was
then dried under vacuum to remove water and the byproduct
trimethylsilanol, giving the requisite precursor zwitterions. Next,
a stoichiometric amount of acid H2SO4 (or HCl or H3PO4) was
added slowly to the aqueous solution of the zwitterions and the
mixture stirred for six hours at reflux. The mixture was then
dried under vacuum to afford the final products of the desired
novel SO3H-functionalized ILs bearing two alkyl sulfonic acid
groups. The products were obtained with 92–95% yields and in
high purities, as assessed by NMR and HRMS spectroscopy.
Notes and References
1 D. A. Horton, G. T. Bourne and M. L. Smythe, Chem. Rev., 2003,
103, 893–930.
2 For reviews, see: (a) R. B. Van Order and H. G. Lindwall, Chem. Rev.,
1942, 30, 69–96; (b) G. W. Gribble, J. Chem. Soc., Perkin Trans. 1,
2000, 1045–1075; (c) S. Cacchi and G. Fabrizi, Chem. Rev., 2005, 105,
2873–2920; (d) G. R. Humphrey and J. T. Kuethe, Chem. Rev., 2006,
106, 2875–2911; (e) K. Kru¨ger (ne´e Alex), A. Tillack and M. Beller,
Adv. Synth. Catal., 2008, 350, 2153–2167; (f) For selected recent
examples of indole synthesis, see: L. Ackermann, Org. Lett., 2005, 7,
439-442; (g) N. Asao and H. Aikawa, J. Org. Chem., 2006, 71, 5249–
5253; (h) M. Nakamura, L. llies, S. Otsubo and E. Nakamura, Org.
Lett., 2006, 8, 2803–2805; (i) Y. Du, R. Liu, G. Linn and K. Zhao,
Org. Lett., 2006, 8, 5919–5922; (j) K. Cariou, B. Ronan, S. Mignani,
L. Fensterbank and M. Malacria, Angew. Chem., Int. Ed., 2007, 46,
1881–1884; (k) S. Wu¨rtz, S. Rakshit, J. J. Neumann, T. Droge and
F. Glorius, Angew. Chem., Int. Ed., 2008, 47, 7230–7233; (l) D. R.
Stuart, M. Bertrand-Laperle, K. M. N. Burgess and K. Fagnou,
J. Am. Chem. Soc., 2008, 130, 16474–16475; (m) Y. Miyazaki and S.
Kobayashi, J. Comb. Chem., 2008, 10, 355–357; (n) Y. Ohta, H. Chiba,
S. Oishi, N. Fujii and H. Ohno, Org. Lett., 2008, 10, 3535–3538.
3 For reviews, see: (a) B. Robinson, Chem. Rev., 1963, 63, 373–401;
(b) B. Robinson, Chem. Rev., 1969, 69, 227–250; (c) For selected
recent examples of Fischer indole synthesis, see: H.-S. Mun, W.-H.
Ham and J.-H. Jeong, J. Comb. Chem., 2005, 7, 130–135; (d) A. M.
Schmidt and P. Eilbracht, J. Org. Chem., 2005, 70, 5528–5535; (e) P.
Linnepe (ne´e Ko¨hling), A. M. Schmidt and P. Eilbracht, Org. Biomol.
Chem., 2006, 4, 302–313; (f) B. P. Bondzic, A. Farwick, J. Liebich and
P. Eilbracht, Org. Biomol. Chem., 2008, 6, 3723–3731; (g) H. Chen,
L. S. Eberlin, M. Nefliu, R. Augusti and R. G. Cooks, Angew. Chem.,
Int. Ed., 2008, 47, 3422–3425.
[(HSO3-p)2im][HSO4]. 1H NMR (500 MHz, D2O, d ppm):
2.12–2.18 (m, 4H), 2.75–2.78 (t, 4H, J = 7.5 Hz), 4.18–4.21 (t,
4H, J = 7.5 Hz), 7.39–7.40 (d, 2H, J = 1.5 Hz), 8.70 (s, 1H). 13
C
NMR (125 MHz, D2O, d ppm): 27.6, 49.8, 50.4, 125.1, 138.3.
HRMS: calcd for C9H17N2O6S2: 313.0528 [M-HSO4]+, found:
313.0527 [M-HSO4]+.
4 (a) V. Hegde, P. Madhukar, J. D. Madura and R. P. Thummel, J. Am.
Chem. Soc., 1990, 112, 4549–4550; (b) Y. K. Lim and C. G. Cho,
Tetrahedron Lett., 2004, 45, 1857–1859; (c) E. Yasui, M. Wada and
N. Takamura, Tetrahedron Lett., 2006, 47, 743–746; (d) K. G. Liu,
A. J. Robichaud, J. R. Lo, J. F. Mattes and Y. Cai, Org. Lett., 2006,
8, 5769–5771.
5 (a) J. L. Rutherford, M. P. Rainka and S. L. Buchwald, J. Am.
Chem. Soc., 2002, 124, 15168–15169; (b) L. Ackermann and R. Born,
Tetrahedron Lett., 2004, 45, 9541–9544; (c) T. M. Lipin´ska and S. J.
Czarnocki, Org. Lett., 2006, 8, 367–370; (d) K. Alex, A. Tillack, N.
Schwarz and M. Beller, Angew. Chem., Int. Ed., 2008, 47, 2304–2307.
6 (a) D. Bhattacharya, D. W. Gammon and E. van Steen, Catal. Lett.,
1999, 61, 93–97; (b) S. B. Mhaske and N. P. Argade, Tetrahedron,
2004, 60, 3417–3420; (c) A. Dhakshinamoorthy and K. Pitchumani,
Appl. Catal., A, 2005, 292, 305–311.
7 (a) For selected reviews on task-specific ionic liquids, see: K.
Binnemans, Chem. Rev., 2005, 105, 4148–4204; (b) C. Baudequin,
D. Bre´geon, J. Levillain, F. Guillen, J.-C. Plaquevent and A.-C.
Gaumont, Tetrahedron: Asymmetry, 2005, 16, 3921–3945; (c) Z. Fei,
T. J. Geldbach, D. Zhao and P. J. Dyson, Chem.–Eur. J., 2006, 12,
2122–2130; (d) H. Ohno and K. Fukumoto, Acc. Chem. Res., 2007,
40, 1122–1129; (e) For selected recent examples of acidic ionic liquids,
seeZ. Fei, D. Zhao, T. J. Geldbach, R. Scopelliti and P. J. Dyson,
Chem.–Eur. J., 2004, 10, 4886–4893; (f) S. Li, Y. Lin, H. Xie, S.
Zhang and J. Xu, Org. Lett., 2006, 8, 391–394; (g) H. Zhang, F. Xu,
X. Zhou, G. Zhang and C. Wang, Green Chem., 2007, 9, 1208–1211;
(h) D. Zhao, J. Wang and E. Zhou, Green Chem., 2007, 9, 1219–1222;
(i) A. Fernicola, S. Panero, B. Scrosati, M. Tamada and H. Ohno,
ChemPhysChem, 2007, 8, 1103–1107.
8 (a) G. L. Rebeiro and B. M. Khadikar, Synthesis, 2001, 0370–372;
(b) R. Calderon Morales, V. Tambyrajah, P. R. Jenkins, D. L. Davies
and A. P. Abbott, Chem. Commun., 2004, 158–159; (c) D.-Q. Xu,
W.-L. Yang, S.-P. Luo, B.-T. Wang, J. Wu and Z.-Y. Xu, Eur. J. Org.
Chem., 2007, 1007–1012.
9 (a) A. C. Cole, J. L. Jensen, I. Ntai, K. L. T. Tran, K. J. Weaver, D. C.
Forbes and J. H. Davis, Jr., J. Am. Chem. Soc., 2002, 124, 5962–5963;
(b) S. Kitaoka, K. Nobuoka and Y. Ishikawa, Chem. Commun., 2004,
1902–1903; (c) D. Li, F. Shi, J. Peng, S. Guo and Y. Deng, J. Org.
Chem., 2004, 69, 3582–3585; (d) J. Gui, H. Ban, X. Cong, X. Zhang,
Z. Hu and Z. Sun, J. Mol. Catal. A: Chem., 2005, 225, 27–31; (e) S.
Sahoo, T. Joseph and S. B. Halligudi, J. Mol. Catal. A: Chem., 2006,
244, 179–182; (f) J. Shen, H. Wang, H. Liu, Y. Sun and Z. Liu, J. Mol.
Catal. A: Chem., 2008, 280, 24–28; (g) Q. Yang, Z. Wei, H. Xing and
[(HSO3-b)2im][HSO4]. 1H NMR (500 MHz, D2O, d ppm):
1.48–1.54 (m, 4H), 1.76–1.82 (m, 4H), 2.69–2.72 (m, 4H), 3.99–
4.02 (t, 4H, J = 7.5 Hz), 7.29 (d, 2H, J = 2 Hz), 8.59 (s, 1H).
13C NMR (125 MHz, D2O, d ppm): 20.9, 28.0, 48.9, 50.0, 122.4,
135.2. HRMS: calcd for C11H21N2O6S2: 341.0841 [M-HSO4]+,
found: 341.0844 [M-HSO4]+.
UV-VIS acidity evaluation
Tested ethanol solutions were prepared from dried ethanol,
3-nitroanline and ILs, or 98% H2SO4, 85% H3PO4 and 37%
HCl. All the spectra were recorded on a SHIMADZU UV-2550
spectrophotometer at room temperature.
Representative procedure for the one-pot Fischer indole synthesis
Cyclohexanone (0.49 g, 5.0 mmol) was mixed with [(HSO3-
p)2im][HSO4] (2.5 mmol) in water (15 mL), and phenylhydrazine
(0.54 g, 5.0 mmol) was added. The mixture was then stirred at
80 ◦C for about 0.5 h. Reaction progress was monitored by
GC-MS. After completion, the reaction mixture was cooled
to room temperature, and 1,2,3,4-tetrahydrocarbazole was ob-
tained by filtration and drying without further purification. The
remaining mixture of [(HSO3-p)2im][HSO4]/H2O was treated
by a strongly acidic cation exchange resin (Dowex-50) at
room temperature and was then reused for the subsequent
catalytic cycle after filtering off the cation exchanged resin.
The cation exchanged resin was then regenerated by treatment
1
with 3 mol L-1 hydrochloric acid aqueous solution. H NMR
(500 MHz, CDCl3, d ppm): 1.86–1.93 (m, 4H), 2.70–2.74 (m,
4H), 7.05–7.12 (m, 2H), 7.27-7.29 (d, 1H, J = 7.5 Hz), 7.45-7.47
(d, 1H, J = 7.5 Hz), 7.67 (s, 1H). MS (EI): m/z 171 [M]+.
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