620
M. Shokouhimehr et al.
LETTER
Table 4 Effect of Tetrabutylammonium Salts on the Polymer-
and the product obtained with high yield in a shortened
reaction time, due to the high efficiency of the NHC–Pd
complex located solely on the surface of the polymer-
supported resin.
Supported NHC–Pd-Catalyzed Heck Reactiona
NHC–Pd complex
(1 mol%)
I
+
TBA (1.5 equiv)
DMA
Acknowledgment
additive (1.3 equiv)
120 °C, 3 h
This work was supported by the Nano Systems Institute National
Core Research Center (NSI-NCRC) program of KOSEF, Korea,
and the Brain Korea 21 Program supported by the Ministry of
Education and Human Resources Development.
Entry
Additives
Yield (%)b
1
2
3
4
–
70
85
80
77
n-Bu4NAc
n-Bu4NBr
n-Bu4NI
References and Notes
(1) (a) Tsuji, J. Palladium Reagents and Catalyst; Wiley: New
York, 1996. (b) Bräse, S.; de Meijere, A. Metal Catalyzed
Cross-Coupling Reactions; Diederich, F.; Stang, P. J., Eds.;
Wiley-VCH: Weinheim, 1998.
(2) (a) Beletskaya, I. P.; Cheprakov, A. V. Chem. Rev. 2000,
100, 3009. (b) Dounay, A. B.; Overman, L. E. Chem. Rev.
2003, 103, 2945. (c) de Meijere, A.; Meyer, F. E. Angew.
Chem., Int. Ed. Engl. 1994, 33, 2379.
(3) de Vries, J. G. Can. J. Chem. 2001, 79, 1086.
(4) Dell’Anna, M. M.; Mastrorilli, P.; Muscio, F.; Nobile, C. F.;
Suranna, G. P. Eur. J. Inorg. Chem. 2002, 5, 1094.
(5) (a) Blaser, H.-U.; Indolese, A.; Schnyder, A.; Steiner, H.;
Studer, M. J. Mol. Catal. A: Chem. 2001, 173, 3; and
references therein. (b) Biffis, A.; Zecca, M.; Basato, M. J.
Mol. Catal. A: Chem. 2001, 173, 249. (c) Herrmann, W. A.;
Köcher, C. Angew. Chem., Int. Ed. Engl. 1997, 36, 2162.
(d) Herrmann, W. A. Angew. Chem. Int. Ed. 2002, 41, 1290.
(e) Schwarz, J.; Böhm, P. W. V.; Gardiner, G. M.; Grosche,
M.; Herrmann, A. W.; Hieringer, W.; Raudaschl-Sieber, G.
Chem. Eur. J. 2000, 6, 1773.
(6) (a) Cho, J. K.; Park, B. D.; Lee, Y. S. Tetrahedron Lett.
2000, 41, 7481. (b) Cho, J. K.; Kim, D. W.; Namgung, J. Y.;
Lee, Y. S. Tetrahedron Lett. 2001, 42, 7443. (c) Cho, J. K.;
Park, B. D.; Park, K. B.; Lee, Y. S. Macromol. Chem. Phys.
2002, 203, 2211. (d) Kim, H. Y.; Cho, J. K.; Chung, W. J.;
Lee, Y. S. Org. Lett. 2004, 6, 3273.
a Reaction conditions: 1.0 mmol 4-iodotoluene, 1.3 equiv styrene, 10
mL DMA.
b Isolated yield.
regeneration or further addition of the catalyst. The NHC–
Pd catalyst remained highly active after six consecutive
cycles of the Heck reaction, and the product butyl-
cinnamate was obtainted in high yield in each recycled
reaction (Table 5).
Meanwhile, the last two filtrates (entries 5 and 6) were an-
alyzed by ICP-AES, which proved there was no palladium
leaching during these processes.12
In summary, we demonstrated the use of a stable and
reusable polymer supported N-heterocyclic carbene–pal-
ladium complex for the Heck reaction. The major advan-
tages of our system are that the catalyst can be recycled
Table 5 Recycling of Catalyst Systema
O
O
I
NHC–Pd complex
OnBu
(7) (a) Kim, J.-H.; Kim, J.-W.; Shokouhimehr, M.; Lee, Y.-S. J.
Org. Chem. 2005, 70, 6714. (b) Kim, J. H.; Jun, B. H.;
Byun, J. W.; Lee, Y. S. Tetrahedron Lett. 2004, 45, 5827.
(8) Heck, R. F. J. Am. Chem. Soc. 1968, 90, 5518.
(9) (a) Yang, C.; Nolan, P. S. Synlett 2001, 1539. (b) Ludwig,
M.; Strömberg, S.; Svensson, M.; Åkermark, B.
+
OnBu
TBA (1.5 equiv)
DMA
120 °C, 3 h
Entry
Recycle
Yield (%)b
Organometallics 1999, 18, 970. (c) Fu, G. C.; Littke, A. F.
J. Org. Chem. 1999, 64, 10.
1
2
3
4
5
6
1
95
95
95
94
95
94
2
3
4
5
6
(10) (a) Li, Z.; Li, F.; Wang, Q.; Tao, F. Tetrahedron Lett. 2005,
46, 6159. (b) Anson, M. S.; Leese, M. P.; Tonks, L.;
Williams, J. M. J. J. Chem. Soc., Dalton Trans. 1998, 3529.
(c) Leese, M. P.; Williams, J. M. Synthesis 1999, 1645.
(11) (a) Galland, J.; Jeffery, T. Tetrahedron Lett. 1994, 35, 4103.
(b) Jeffery, T. Tetrahedron Lett. 1994, 35, 3051.
(c) Fagnou, K.; Lautens, M. Angew. Chem. Int. Ed. 2002, 41,
26.
(12) The filtrate was treated with a mixture (2 mL) of concd HCl
and HNO3 (3:1, v/v) at 50 °C for 1 h. Following this, the
resulting solution was filtered, and diluted with H2O to 20
mL, then analyzed by ICP-AES.
a Reaction conditions: 1.0 mmol 4-iodobenzene, 1.3 equiv n-butyl-
acrylate, 10 mL DMA.
b Isolated yield.
Synlett 2006, No. 4, 618–620 © Thieme Stuttgart · New York