Communications
that of the recycled Pd-mont (Figure 1c). The above results
[4] a) T. Kawabata, T. Mizugaki, K. Ebitani, K. Kaneda, J. Am.
Chem. Soc. 2003, 125, 10486; b) T. Kawabata, M. Kato, T.
Mizugaki, K. Ebitani, K. Kaneda, Chem. Eur. J. 2005, 11, 288.
strongly support allylation taking place on coordinately
unsaturated Pd atoms in the sub-nanoordered Pd clusters.
The use of the Pd-mont in the allylation of cis-3-acetoxy-
[
5] Heterogeneous allylic substitution reactions by polymer-bound
Pd catalysts: a) B. M. Trost, E. Keinan, J. Am. Chem. Soc. 1978,
5
-carbomethoxycyclohex-1-ene with 2a was found to provide
100, 7779; b) D. E. Bergbreiter, B. Chen, J. Chem. Soc. Chem.
superior selectivity towards the corresponding cis product
Commun. 1983, 1238; c) Y. Uozumi, K. Shibatomi, J. Am. Chem.
Soc. 2001, 123, 2919; d) R. Akiyama, S. Kobayashi, J. Am. Chem.
Soc. 2003, 125, 3412.
[
5a]
compared with [Pd(PPh ) ] (Scheme 1). The steric steering
3
4
occurred during the nucleophilic attack of 2a on the surface
p-allyl intermediate, which is strongly shielded from endo
attack.
In conclusion, sub-nanoordered Pd clusters were synthe-
sized within the interlayer of the montmorillonite. The Pd-
mont acted as a highly efficient heterogeneous catalyst for
allylic substitution reactions under organic-ligands-free con-
ditions. Moreover, this Pd-mont has the advantage of being:
[
6] Reviews of organic synthesis using Pd catalysts: a) I. I. Moiseev,
M. N. Vargaftik, New J. Chem. 1998, 22, 1217; b) Handbook of
Organopalladium Chemistry for Organic Synthesis: (Ed.: E.
Negishi), Wiley, Chichester, 2002; c) A. Roucoux, J. Schulz, H.
Patin, Chem. Rev. 2002, 102, 3757; d) J. Tsuji, Palladium
Reagents and Catalysts, Wiley, Chichester, 2004.
[7] Polymer micelle-encapsulated Pd sub-nanoclusters: a) K. Oka-
moto, R. Akiyama, H. Yoshida, T. Yoshida, S. Kobayashi, J. Am.
Chem. Soc. 2005, 127, 2125; zeolite-supported Pd sub-nano-
clusters: b) K. Okumura, K. Nota, K. Toshida, M. Niwa, J. Catal.
1
) stable in air, 2) highly active even under aqueous con-
ditions, and 3) reusable without any loss of activity or
selectivity. The sterically hindered interlayer space of the
mont plays an important role in stabilizing the highly
coordinatively unsaturated Pd clusters, which suppresses
agglomeration into large inactive Pd particles.
2005, 231, 245.
[
8] For reviews of allylic substitution reactions: a) J. Tsuji, Tetrahe-
dron 1986, 42, 4361; b) J. Tsuji, I. Minani, Acc. Chem. Res. 1987,
20, 140; c) G. Consiglio, R. M. Waymouth, Chem. Rev. 1989, 89,
257; d) S. A. Godleski in Comprehensive Organic Synthesis,
Vol. 4 (Eds.: B. M. Trost, I. Fleming), Pergamon, New York,
1
991, chap. 3.3; e) Handbook of Organopalladium Chemistry for
Organic Synthesis, Vol. II (Ed.: E. Negishi), Wiley, New York,
002, chap. V.
9] It is reported that [Pd(dba) ] is oxidized by O in DMF: Y. C.
Received: November 15, 2006
Revised: January 29, 2007
Published online: March 22, 2007
2
[
2
2
Jung, R. K. Mishra, C. H. Yoon, K. W. Jung, Org. Lett. 2003, 5,
2231.
10] See the Supporting Information for details.
11] The interlayer space of the Pd-mont expanded from 5.3 to 9.6
Keywords: allylation · clays · cluster compounds ·
heterogeneous catalysis · palladium
.
[
[
when soaked in H O.
2
[
1] a) C. N. R. Rao, G. U. Kulkarni, P. J. Thomas, P. P. Edwards,
Chem. Soc. Rev. 2000, 29, 27; b) H. Bönnemann, R. M. Richards,
Eur. J. Inorg. Chem. 2001, 2455; c) R. G. Finke in Metal
Nanoparticles. Synthesis, Characterization and Applications
[
[
12] C. Groux, M. Massacret, P. Lhoste, D. Sinou, Organometallics
1
995, 14, 4585.
II
0
13] Treatment of the Pd -mont with KBH did not give Pd species
4
quantitatively, and some parts of the monomeric divalent species
remained (Figure 1b). After the first use of the Pd-mont in the
(
Eds.: D. L. Feldheim, C. A. Foss, Jr.), Mercel Dekker, New
II
York, 2002, chap. 2, p. 17; d) Nanoparticles (Ed.: G. Schmid),
Wiley-VCH, Weinheim, 2004; e) Encyclopedia of Nanoscience
and Nanotechnology (Ed.: H. S. Nalwa), American Scientific
Publishers, California, 2004; f) X. Wang, J. Zhuang, Q. Peng, Y.
Li, Nature 2005, 437, 121.
allylation, the residual Pd species could be converted into the
0
Pd species and the estimated size of the Pd clusters grew from
II
0
.57 to 0.82 nm. Allylation did not occur when the Pd -mont was
used without treatment by KBH (Figure 1a), and Pd clusters
4
could not be obtained.
[
2] D. Astruc, F. Lu, J. R. Aranzaes, Angew. Chem. 2005, 117, 8062;
Angew. Chem. Int. Ed. 2005, 44, 7852.
[
14] The decreased Pd-Pd shell intensity is attributable to an increase
in the disordered phase difference of the XAFSwave as a result
of the formation of the p-allyl complex.
[
3] a) T. J. Pinnavaia, Science 1983, 220, 365; b) P. Laszlo, Acc.
Chem. Res. 1986, 19, 121; c) Y. Izumi, M. Onaka, Adv. Catal.
1992, 38, 245.
3
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2007, 46, 3288 –3290