Table 2 Removal of small molecules using PDMS for Soxhlet
extraction
cheap, commercially available starting materials and the extrac-
tions were not labor intensive. Although we did not explore it,
after extraction the RTIL could be recycled for further reactions.
We would like to thank the American Cancer Society, the
American Chemical Society–Petroleum Research Funds, the
Research Corporation, and the University of Iowa for financial
support.
Entry
Small molecule
Yield
1
2
3
5
7
98%
86%
79%
a
Notes and references
4
5
6
66%
98%
0%
{
Olefin ring-closing metathesis with Schrock’s catalyst in RTIL. In a glove
box, Schrock’s catalyst (25 mg, 0.033 mmol) and BMIM (1 mL) were
added to a Schlenk flask. The flask was sealed and removed from the glove
box and attached to a Schlenk manifold. The Schlenk flask was placed in a
7
5 uC oil bath for 10 minutes. Diethyl diallylmalonate, 5, (151 mL,
0.63 mmol) was added to the Schlenk flask under N and stirred for 1 h.
2
The reaction was cooled to room temperature and the ionic liquid was
subsequently removed by Soxhlet extraction. The product was cleaned by
subsequent column chromatography (10% ethyl acetate–90% hexane) to
yield a clear liquid 6 (111 mg, 84% yield). The H and C NMR data
correlate with those reported in the literature.
1
13
11
a
Isolated as a mixture of acetal–aldehyde (9 : 1 molar ratio).
1
(a) R. D. Rogers and K. R. Seddon, Science, 2003, 302, 792–793; (b)
L. Xu, W. Chen and J. Xiao, Organometallics, 2000, 19, 1123–1127; (c)
S. V. Dzyuba and R. A. Bartsch, Angew. Chem., Int. Ed., 2003, 42,
148–150.
1–5 in Table 2 were successfully extracted from BMIM using this
method; these molecules are also mostly insoluble in water. Their
solubility in water is important because PDMS is hydrophobic and
polar molecules diffuse through it at slower rates than apolar
2 (a) P. Wasserscheid and W. Keim, Angew. Chem., Int. Ed., 2000, 39,
772–3789; (b) T. Welton, Chem. Rev., 1999, 99, 2071–2083.
(a) W.-H. Lo, H.-Y. Yang and G.-T. Wei, Green Chem., 2003, 5,
39–642; (b) C. M. Gordon and A. McCluskey, Chem. Commun., 1999,
1431–1432.
4 (a) R. H. Grubbs, S. J. Miller and G. C. Fu, Acc. Chem. Res., 1995, 28,
46–452; (b) D. Astruc, New J. Chem., 2005, 29, 42–56; (c) R. H. Grubbs,
Handbook of Metathesis Catalysts, Wiley-VCH, Weinheim, Germany,
003.
5 (a) P. Bonh oˆ te, A.-P. Dias, N. Papageorgiou, K. Kalyanasundaram and
M. Gr a¨ tzel, Inorg. Chem., 1996, 35, 1168–1178; (b) A. Kamal and
G. Chouhan, Adv. Synth. Catal., 2004, 346, 579–582; (c) P. Nockemann,
K. Binnemans and K. Driesen, Chem. Phys. Lett., 2005, 415, 131–136;
3
3
6
9–11
molecules.
extract the water soluble diacid, 20, using a PDMS thimble. After
days, methanol outside the thimble was evaporated to dryness
To test the limit of this method, we attempted to
4
6
1
and only a trace amount of 20 was observed by H NMR
spectroscopy. Thus, one limitation of this method is that the most
polar substrates will not readily diffuse through PDMS under
these conditions. Because of this limitation, this method could
potentially be used to separate apolar and polar molecules.
Soxhlet extractions were also performed following the metath-
esis reactions of all substrates listed in Table 1 in order to obtain
isolated yields on smaller scale reactions (approximately 100 mg
for each reaction in Table 1). The extractions were successful for
separating the ionic liquid from the products. Small contaminants
due to decomposed Schrock’s catalyst also escaped the PDMS
membrane in each case, so the products were purified by
subsequent column chromatography to obtain the isolated yields
as shown in Table 1.
2
(d) S. Carda-Broch, A. Berthod and D. W. Armstrong, Anal. Bioanal.
Chem., 2003, 375, 191–199; (e) A. Paul, P. K. Mandal and A. Samanta,
Chem. Phys. Lett., 2005, 402, 375–379; (f) P. A. Z. Suarez, J. E. L.
Dullius, S. Einloft, R. F. De Souza and J. Dupont, Polyhedron, 1996,
15, 1217–1219.
6
(a) G. C. Fu and R. H. Grubbs, J. Am. Chem. Soc., 1993, 115,
3800–3801; (b) G. C. Fu and R. H. Grubbs, J. Am. Chem. Soc., 1992,
1
1
8
14, 5426–5427; (c) G. C. Fu and R. H. Grubbs, J. Am. Chem. Soc.,
992, 114, 7324–7325; (d) R. R. Schrock, Tetrahedron, 1999, 55,
141–8153.
7 (a) A. K. Chatterjee, T.-L. Choi, D. P. Sanders and R. H. Grubbs,
J. Am. Chem. Soc., 2003, 125, 11360–11370; (b) W. E. Crowe and
Z. J. Zhang, J. Am. Chem. Soc., 1993, 115, 10998–10999; (c)
O. Br u¨ mmer, A. R u¨ ckert and S. Blechert, Chem.–Eur. J., 1997, 3,
In summary, BMIM is an attractive new solvent for both olefin
ring-closing and cross metathesis reactions using Schrock’s
catalyst. These reactions were comparable to the same reactions
in methylene chloride, and proceeded to y100% conversion at
441–446; (d) W. E. Crowe, D. R. Goldberg and Z. J. Zhang,
Tetrahedron Lett., 1996, 37, 2117–2120.
(a) K. Nomura, S. Takahashi and Y. Imanishi, Macromolecules, 2001,
8
3
(
2
4, 4712–4723; (b) R. R. Schrock, Acc. Chem. Res., 1990, 23, 158–165;
c) C. Cazalis, V. H e´ roguez and M. Fontanille, Macromol. Chem. Phys.,
000, 201, 869–876.
75 uC for molecules containing a variety of functional groups. In a
second important extension, we developed a new method to
extract small amounts of organic products from BMIM by
carrying out a Soxhlet extraction using PDMS thimbles. This
method is general and should work well for all but the most polar
of substrates and, importantly, can be carried out on small
amounts of materials. The thimbles were easy to fabricate from
9 T. Sch a¨ fer, R. E. Di Paulo, R. Franco and J. G. Crespo, Chem.
Commun., 2005, 2594.
1
0 J. N. Lee, C. Park and G. M. Whitesides, Anal. Chem., 2003, 75,
544–6554.
1 M. T. Mwangi, M. B. Runge and N. B. Bowden, J. Am. Chem. Soc.,
2006, 128, 14434–14435.
6
1
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