LETTER
Cooperative Heterogeneous Catalysis
1527
amide, which mimics the surface-bound amine in 13, in
combination with amine-free particles 8 was conducted
under otherwise identical conditions. However, biphenyl
was not formed in that case (Table 2, entry 5) which gives
strong evidence for the necessity of the covalent attach-
ment of the amine entity at the surface of the particle.
References and Notes
(1) (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
(b) Miyaura, N.; Yamada, K.; Suzuki, A. Tetrahedron Lett.
1979, 3437. (c) Suzuki, A. J. Organomet. Chem. 1999, 576,
147. (d) Barder, T. E.; Walker, S. D.; Martinelli, J. R.;
Buchwald, S. L. J. Am. Chem. Soc. 2005, 127, 4685.
(2) For the immobilization of Pd catalysts, see: (a) Kim, J. W.;
Kim, J. H.; Lee, D. H.; Lee, Y. S. Tetrahedron Lett. 2006,
47, 4745. (b) Alacid, E.; Nájera, C. J. Organomet. Chem.
2009, 694, 1658. (c) Ogasawara, S.; Shinji, K. J. Am. Chem.
Soc. 2010, 132, 4608. (d) Soomro, S. S.; Röhlich, C.;
Köhler, K. Adv. Synth. Catal. 2011, 353, 767. (e) Kitamura,
Y.; Sakurai, A.; Udzu, T.; Maegawa, T.; Monguchi, Y.;
Sajiki, H. Tetrahedron 2007, 63, 10596. (f) Zhang, P.-P.;
Zhang, X.-X.; Sun, H.-X.; Liu, R.-H.; Wang, B.; Hui, Lin. Y.
Tetrahedron Lett. 2009, 50, 4455.
(3) For recent developments on the immobilization of palladium
into MSNs, see: (a) Gürbüz, N.; Vural, S.; Yaşar, S.;
Özdemir, I.; Seşkin, T. J. Inorg. Organomet. Polym. 2010,
20, 19. (b) Zhaoa, H.; Dingb, G.; Xua, L.; Caib, M. Appl.
Organomet. Chem. 2011, 25, 871. (c) Zheng, G.; Wang, P.;
Cai, M. Chin. J. Chem. 2009, 27, 1420. (d) Fan, G.; Cheng,
S.; Zhu, M.; Gao, X. Appl. Organomet. Chem. 2007, 21, 670.
(e) Deme, J.; Park, S.; Čejka, J.; Štěpnička, P. Catal. Today
2008, 132, 63. (f) Bhunia, S.; Sen, R.; Koner, S. Inorg.
Chim. Acta 2010, 363, 3993. (g) Glasspoole, B. W.; Webb,
J. D.; Crudden, C. M. J. Mol. Catal. A: Chem. 2011, 337, 56.
(h) Glasspoole, B. W.; Webb, J. D.; Crudden, C. M. J. Catal.
2009, 265, 148. (i) Sharma, K. K.; Birandar, A. V.; Das, S.;
Asefa, T. Eur. J. Inorg. Chem. 2011, 3174. (j) Komura, K.;
Nakamura, H.; Sugi, Y. J. Mol. Catal. A: Chem. 2008, 293,
72. (k) Lv, G.; Mai, W.; Jin, R.; Gao, L. Synlett 2008, 1418.
(l) Chen, W.; Li, P.; Wang, L. Tetrahedron 2011, 67, 318.
(m) Fukaya, N.; Ueda, M.; Onozawa, S.; Bandoa, K. K.;
Miyaji, T.; Takagi, Y.; Sakakura, T.; Yasuda, H. J. Mol.
Catal. A: Chem. 2011, 342–343, 58. (n) Gruber-Woelfler,
H.; Radaschitz, P. F.; Feenstra, P. W.; Haas, W.; Khinast, J.
G. J. Catal. 2012, 286, 30. (o) Dhara, K.; Sarkar, K.;
Srimani, D.; Kumar Saha, S.; Chattopadhyay, P.; Bhaumik,
A. Dalton Trans. 2010, 39, 6395. (p) Modak, A.; Mondal, J.;
Sasidharan, M.; Bhaumik, A. Green Chem. 2011, 13, 1317.
(4) Dickschat, A. T.; Behrends, F.; Bühner, M.; Ren, J.; Weiß,
M.; Eckert, H.; Studer, A. Chem. Eur. J. 2012, 18, 16689.
(5) Dickschat, A. T.; Behrends, F.; Surmiak, S.; Weiß, M.;
Eckert, H.; Studer, A. Chem. Commun. 2013, 49, 2195.
(6) (a) Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Angew. Chem.
Int. Ed. 2001, 40, 2004. (b) Kowollik et al. recently
Table 2 Suzuki–Miyaura Coupling of Chlorobenzene with Phenyl-
boronic Acid Using Catalysts 13–16
Entry
Catalyst
Yield of biphenyl (%)a
1
13
14
15
16
8
99
2
not detected
not detected
not detected
not detected
3
4
5b
a GC conversion.
b 2-(Dimethylamino)-N-isopropylacetamide was added.
In order to rule out that the reactions are catalyzed by Pd
complexes which leached out of the solid support we ran
a reaction to around 66% conversion and carefully filtered
off the particles. The filtrate was then kept for additional
two hours at 80 °C and no further conversion was noted
proving that the successful reaction occurred with the
surface-ligated Pd catalyst.9
In conclusion, we have successfully prepared mono- and
bifunctional mesoporous silica nanoparticles by co-con-
densation of TEOS and triethoxysilanes bearing azides
and alkoxyamines at their termini.10 Chemical surface
functionalization by orthogonal click chemistry and sub-
sequent palladation provided various catalysts which
were successfully used in the Suzuki–Miyaura cross-cou-
pling reaction. The triazole–pyridyl-based Pd complexes
showed high activity and the catalyst could be recycled by
simple filtration ten times without losing activity. We
showed that additional amine functionalities at the surface
influence the reactivity of the particles. The structure of
the amine is important to observe cooperative effects ex-
erted by the basic functionality. Subtle variation of the
amine structure and the linker unit led to inactive material.
Although, the mechanism for the increased activity is cur-
rently not understood, this paper shows that the late-stage
functionalization is an efficient tool for the preparation of
a small catalyst library.
redefined the ‘click’-reaction at surface; nonetheless, for the
readers convenience we would still like to call it ‘click’
reaction: Barner-Kowollik, C.; Du Prez, F. E.; Espeel, P.;
Hawker, C. J.; Junkers, T.; Schlaad, H.; Van Camp, W.
Angew. Chem. Int. Ed. 2011, 50, 60. (c) For ‘click to chelate’
approach, see: Struthers, H.; Mindt, T. L.; Schibli, R.
Dalton. Trans. 2010, 39, 675.
(7) For the use of the triazole–pyridyl moiety and related
structure motives, see: (a) Zhang, G.; Wang, Y.; Wen, X.;
Ding, C.; Li, Y. Chem. Commun. 2012, 48, 2979. (b) Chan,
T. R.; Hilgraf, R.; Sharpless, K. B.; Fokin, V. V. Org. Lett.
2004, 6, 2853. (c) Wang, D.; Denux, D.; Ruiz, J.; Astruc, D.
Adv. Synth. Catal. 2013, 355, 129. (d) Barz, M.; Herdtweck,
E.; Thiel, W. R. Angew. Chem. 1998, 110, 2380.
Acknowledgment
We thank the SFB 858 for funding our work and Prof. Hellmut
Eckert and Frederik Behrends (WWU Münster) for conducting the
solid-state NMR studies.
(8) (a) Wagner, H.; Brinks, M. K.; Hirtz, M.; Schäfer, A.; Chi,
L.; Studer, A. Chem. Eur. J. 2011, 17, 9107. (b) Schulte, B.;
Tsotsalas, M.; Becker, M.; Studer, A.; De Cola, L. Angew.
Chem. Int. Ed. 2010, 49, 6881. (c) Becker, M.; De Cola, L.;
Studer, A. Chem. Commun. 2011, 47, 3392.
Supporting Information for this article is available online at
m
iotSrat
ungIifoop
r
t
© Georg Thieme Verlag Stuttgart · New York
Synlett 2013, 24, 1523–1528