Table 1 Conversion and selectivity %
Entry
Conditionsa
Conversionb (%)
Selectivityb E/Z (%)
1
2
3
Toluene–NEt3–Pd(OAc)2–2PPh3
Toluene–NEt3–[BMI][Br]–Pd(OAc)2–2PPh3
Toluene–NEt3–ionocats
25
20
20
95/5
97/3
98/2
a
b
Ratio of palladium to substrate: 1%. Measured by H NMR.
1
coated with the liquid catalyst film. On the other hand, in
ionogels, reactants diffuse in the 3D continuous liquid phase
which fills all the pores. Similarly products diffuse back out of
the material according to the two different routes. Thus,
diffusion should be by far easier in SILF. However, in the
liquid phase SILF are subjected to the risk of extensive
leaching, in relation to the minute amount of ionic liquid on
the support. Even in the case of complete immiscibility in the
feedstock–product mixture, the ionic liquid film may be
mechanically removed from the support by the liquid flow.
As a consequence, SILF look like the most convenient process
for continuous gas-phase reactions, whereas it is demonstrated
here that ionogels offer an interesting alternative for liquid-
phase reactions.
7 V. I. Parvulescu and C. Hardacre, Chem. Rev., 2007, 107,
2615–2665.
8 M. H. Valkenberg, C. de Castro and W. F. Hoelderich, Green
Chem., 2002, 4, 88–93.
9 A. Riisager, R. Fehrmanna, M. Haumannb and P. Wasserscheid,
Top. Catal., 2006, 40, 91–102.
10 A. Riisager, R. Fehrmann, M. Haumann and P. Wasserscheid,
Eur. J. Inorg. Chem., 2006, 695–706.
11 M. R. Castillo, L. Fousse, J. M. Fraile, J. I. Garcia and
J. A. Mayoral, Chem.–Eur. J., 2007, 13, 287–291.
12 J. Le Bideau, P. Gaveau, S. Bellayer, M. A. Neouze and A. Vioux,
Phys. Chem. Chem. Phys., 2007, 9, 5419–5422.
13 M.-A. Neouze, J. Le Bideau, P. Gaveau, S. Bellayer and A. Vioux,
Chem. Mater., 2006, 18, 3931–3936.
14 H. Hagiwara, Y. Sugawara, T. Hoshi and T. Suzuki, Chem.
Commun., 2005, 2942–2944.
15 H. Hagiwara, Y. Sugawara, K. Isobe, T. Hoshi and T. Suzuki,
Org. Lett., 2004, 6, 2325–2328.
16 C. P. Mehnert, R. A. Cook, N. C. Dispenziere and M. Afeworki,
J. Am. Chem. Soc., 2002, 124, 12932–12933.
17 S. Dai, Y. H. Ju, H. J. Gao, J. S. Lin, S. J. Pennycook and
C. E. Barnes, Chem. Commun., 2000, 243–244.
18 C. P. Mehnert, E. J. Mozeleski and R. A. Cook, Chem. Commun.,
2002, 3010–3011.
19 H. Hagiwara, K. H. Ko, T. Hoshi and T. Suzuki, Chem. Commun.,
2007, 2838–2840.
20 S. Breitenlechner, M. Fleck, T. E. Muller and A. Suppan, J. Mol.
Catal. A: Chem., 2004, 214, 175–179.
21 O. Jimenez, T. E. Mueller, C. Sievers, A. Spirkl and J. A. Lercher,
Chem. Commun., 2006, 2974–2976.
22 C. Sievers, O. Jimenez, R. Knapp, X. Lin, T. E. Mueller,
A. Tuerler, B. Wierczinski and J. A. Lercher, J. Mol. Catal. A:
Chem., 2008, 279, 187–199.
23 F. Shi, Q. Zhang, Y. Gu and Y. Deng, Adv. Synth. Catal., 2005,
347, 225–230.
24 F. Shi, Q. Zhang, D. Li and Y. Deng, Chem.–Eur. J., 2005, 11,
5279–5288.
Conclusion
In conclusion, Pd containing ionogels prepared by the
incorporation of a Pd complex into the ionic liquid solution
before gelation were shown to be active in the Heck–Mizoroki
coupling reaction. These ionogels could be cast as small
cones containing identical Pd contents, thus providing
convenient ready-to-use catalyst doses for organic synthesis.
No significant difference was noticeable by comparison
with corresponding homogeneous catalysis. No leaching of
catalytic species took place during the reaction. Moreover,
ammonium salts were shown to be trapped in the ionogels.
This provides an efficient method for isolating the products,
free of metal and salt residues, and offers some advantages
over SILF when operating in the presence of an organic
solvent.
25 A. J. Carmichael, M. J. Earle, J. D. Holbrey, P. B. McCormac and
K. R. Seddon, Org. Lett., 1999, 1, 997–1000.
26 J. Howarth and A. Dallas, Molecules, 2000, 5, 851–855.
27 D. Nair, J. T. Scarpello, I. F. J. Vankelecom, L. M. Freitas Dos
Santos, L. S. White, R. J. Kloetzing, T. Welton and
A. G. Livingston, Green Chem., 2002, 4, 319–324.
28 S. T. Handy and M. Okello, Tetrahedron Lett., 2003, 44,
8395–8397.
29 Y. Liu, M. Li, Y. Lu, G.-H. Gao, Q. Yang and M.-Y. He, Catal.
Commun., 2006, 7, 985–989.
30 L. Zhou and L. Wang, Synthesis, 2006, 2653–2658.
31 N. A. Hamill, C. Hardacre and S. E. J. McMath, Green Chem.,
2002, 4, 139–142.
Acknowledgements
This study was performed with the supports of the
Regional Councils of Languedoc-Roussillon (grant SV)
and of Britanny (grant MG) and was carried out with
instruments (Syncore Buchi) of the CITRennes platform
(Rennes 1 University).
32 L. S. Ott, M. L. Cline, M. Deetlefs, K. R. Seddon and R. G. Finke,
J. Am. Chem. Soc., 2005, 127, 5758–5759.
33 C. C. Cassol, A. P. Umpierre, G. Machado, S. I. Wolke and
J. Dupont, J. Am. Chem. Soc., 2005, 127, 3298–3299.
34 J.-C. Xiao and J. n. M. Shreeve, J. Org. Chem., 2005, 70,
3072–3078.
References
1 S. Polarz and A. Kuschel, Chem.–Eur. J., 2008, 14, 9816–9829.
2 F. Goettmann and C. Sanchez, J. Mater. Chem., 2007, 17,
24–30.
3 S. R. Jagtap, M. J. Bhanushali, A. G. Panda and B. M. Bhanage,
Catal. Lett., 2006, 112, 51–55.
35 V. Calo, A. Nacci, A. Monopoli, A. Detomaso and P. Iliade,
Organometallics, 2003, 22, 4193–4197.
4 J. P. Arhancet, M. E. Davis, J. S. Merola and B. E. Hanson,
Nature, 1989, 339, 454–455.
36 V. Calo, A. Nacci, A. Monopoli, S. Laera and N. Cioffi, J. Org.
Chem., 2003, 68, 2929–2933.
5 C. P. Mehnert, Chem.–Eur. J., 2005, 11, 50–56.
6 H. Olivier-Bourbigou and F. Favre, in Ionic Liquids in Synthesis,
ed. P. Wasserscheid and T. Welton, Wiley-VCH, Weinheim, 2008,
vol. 2, pp. 464–468.
37 L. J. Xu, W. P. Chen and J. L. Xiao, Organometallics, 2000, 19,
1123–1127.
38 Q.-X. Wan, Y. Liu, Y. Lu, M. Li and H.-H. Wu, Catal. Lett., 2008,
121, 331–336.
ꢀc
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2009
2020 | New J. Chem., 2009, 33, 2015–2021