Weight loss during catalyst recycling is probably responsible
for the observed effect. Using heterocyclic 2-chloropyridine
(5a) and 4-benzoxazole (5b) in the reaction with 1 afforded the
cross-coupling products 6a and 6b in 79 and 62% yields,
respectively (Scheme 2).
2 A. Stolle, T. Szuppa, S. E. S. Leonhardt and B. Ondruschka,
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3 K. Tanaka and F. Toda, Chem. Rev., 2000, 100, 1025.
4 K. Tanaka, Solvent-free Organic Synthesis, Wiley-VCH, Weinheim,
2nd edn, 2008.
5 G. Kaupp, J. Phys. Org. Chem., 2008, 21, 630.
6 M. O0Brien, R. Denton and S. V. Ley, Synthesis, 2011, 1157.
7 S. L. James, C. J. Adams, C. Bolm, D. Braga, P. Collier, T. Friscic,
F. Grepioni, K. D. M. Harris, G. Hyett, W. Jones, A. Krebs,
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J. W. Steed and D. C. Waddell, Chem. Soc. Rev., 2012, 41,
413–447.
The side reaction of aryl–aryl coupling can be slightly
reduced when working under argon atmosphere. This, how-
ever, is a task that cannot easily be when using a planetary ball
mill. In comparison to results previously published for the
cross-coupling of bromo-N-heteroarenes in a similar ball mill,8
the yields obtained with the present catalyst are considerably
higher, although the reaction times are longer.
8 S. Feldbæk Nielsen, D. Peters and O. Axelsson, Synth. Commun.,
2000, 30, 3501.
9 L. M. Klingensmith and N. E. Leadbeater, Tetrahedron Lett.,
2003, 44, 765.
10 F. Schneider and B. Ondruschka, ChemSusChem, 2008, 1, 622.
11 E. Tullberg, D. Peters and T. Frejd, J. Organomet. Chem., 2004,
689, 3778.
Conclusions
12 D. A. Fulmer, W. C. Shearhouse, S. T. Mendonza and J. Mack,
Green Chem., 2009, 11, 1821.
13 R. Thorwirth, A. Stolle and B. Ondruschka, Green Chem., 2010,
12, 985.
14 R. Thorwirth, A. Stolle, B. Ondruschka, A. Wild and
U. S. Schubert, Chem. Commun., 2011, 47, 4370.
15 R. Schmidt, R. Thorwirth, T. Szuppa, A. Stolle, B. Ondruschka
and H. Hopf, Chem.–Eur. J., 2011, 17, 8129.
16 F. Bernhardt, R. Trotzki, T. Szuppa, A. Stolle and B. Ondruschka,
Beilstein J. Org. Chem., 2010, 6, No.7.
17 K. Martina, S. E. S. Leonhardt, B. Ondruschka, M. Curini,
A. Binello and G. Cravotto, J. Mol. Catal. A: Chem., 2011, 334,
60.
In summary, we have reported an interesting protocol for
Suzuki cross-couplings under ball milling conditions using a
HMDI cross-linked CS/Pd-derivative as catalyst. The catalyst
was prepared in water via sonochemical cross-linking with
HMDI in the presence of the metal salt. This catalyst can be
reused three times and shows low metal leaching during its
application in the Suzuki cross-coupling of aryl chlorides. The
average to high yields that were obtained with several aryl
chlorides, compared with the poor results reported in the
literature, may open the door to reactions with poorly reactive
substrates in the ball mill and possibility to catalyst recycling.
18 G. Cravotto, S. Tagliapietra, M. Trotta and B. Robaldo, Ultrason.
Sonochem., 2005, 12, 95.
19 S. E. S. Leonhardt, A. Stolle, B. Ondruschka, G. Cravotto,
C. De Leo, K. D. Jandt and T. F. Keller, Appl. Catal., A, 2010,
379, 30.
20 H.-F. Zhang, L. Zhang and Y.-C. Cui, React. Funct. Polym., 2007,
67, 322.
Acknowledgements
Financial support from MIUR (PRIN 2008 ‘‘A Green
Approach to Process Intensification in Organic Synthesis’’)
is gratefully acknowledged.
21 X. Xu, P. Liu, S. Li, P. Zhang and X. Wang, React. Kinet. Catal.
Lett., 2006, 88, 217.
22 L. Saikia, J. M. Baruah and A. J. Thakur, Org. Med. Chem. Lett.,
2011, 1, 12.
23 G. Cravotto, M. Beggiato, A. Penoni, G. Palmisano,
S. Tollari, J.-M. Leveque and W. Bonrath, Tetrahedron Lett.,
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Notes and references
1 B. Rodrıguez, A. Bruckmann, T. Rantanen and C. Bolm, Adv.
Synth. Catal., 2007, 349, 2213.
c
New J. Chem.
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012