C O MMU N I C A T I O N S
complex.10 In a competitive reaction of olefins between 2a and
n-butylacrylate (2b) with iodobenzene, the PdHAP-1 gave a high
product ratio of 9.6 for n-butylcinnamate to stilbene, which
3 4
significantly exceeded 4.1 observed with Pd(PPh ) . The above
phenomena support that this Heck reaction does not proceed via
0
II
II
IV
10,11
the traditional Pd /Pd cycle but via the Pd /Pd mechanism.
These unusual performances of Pd are attributed to the extremely
II
robust monomeric Pd structure surrounded by phosphate ligands
on the hydroxyapatite surface, which effectively serves as a
powerful alternative to organic ligands.
3
We have demonstrated a novel approach to catalyst design using
hydroxyapatites and realized excellent catalytic performances. No
Pd leaching was observed, and then the catalysts were recyclable.
The PdHAP catalytic systems are therefore suitable for large-scale
operations, meeting the increasing demands for environmentally
friendly chemical processes. We expect that our immobilizing
protocol based on hydroxyapatites as a macroligand will offer an
attractive route for the design of functional catalysts at the atomic
and molecular level.
Figure 1. (a) Fourier transforms of k -weighted Pd K-edge EXAFS
experimental data for (A) PdHAP-0, (B) PdHAP-1, (C) recovered
PdHAP-0, and (D) recovered PdHAP-1 for the oxidation of 1-phenylethanol.
Phase shift was not corrected. Reactions were conducted with 1-phenyl-
ethanol (1 mmol), PdHAP (0.1 g, Pd: 2 µmol), and trifluorotoluene (5 mL)
at 90 °C for 1 h under O2 atmosphere. (b) Proposed surface structures around
II
Pd of PdHAP-0 (E) and PdHAP-1 (F).
Table 1. Aerobic Oxidation of Alcohols Catalyzed by PdHAP-0a
entry
alcohol
Pd (mol %)
t/h
yield (%)b
1
2
3
4
5
benzyl alcohol
0.2
0.2
0.2
0.2
0.6
0.2
0.2
0.2
0.6
0.6
0.6
0.6
1
3
99
99
99
98
94
87
80
80
91
84
84
99
Acknowledgment. We thank Dr. T. Yamamoto (Kyoto Uni-
versity) and Dr. T. Uruga (JASRI) for XAFS measurements.
4-methylbenzyl alcohol
4-isopropylbenzyl alcohol
1-phenylethanol
cyclopropylphenylmethanol
cinnamyl alcohol
3-octen-2-ol
3
1
24
6
24
24
24
24
24
24
Supporting Information Available: Experimental procedure, curve
fitting analysis, and TEM images (PDF). This material is available free
of charge via the Internet at http://pubs.acs.org.
c
6
c
7
8
c
carveol
2-octanol
cyclobutanol
cyclopentanol
9
References
1
1
1
0
1
2
(
1) (a) Heck, R. F. Palladium Reagents in Organic Syntheses; Academic
Press: London, 1985. (b) Tsuji, J. Palladium Reagents and Catalysts;
Wiley: Chichester, 1995. (c) Trost, B. M. Angew. Chem., Int. Ed. Engl.
1995, 34, 259. (d) Applied Homogeneous Catalysis with Organometallic
Compounds; Cornils, B., Herrmann, W. A., Eds.; VCH: Weinheim, 1996.
2-thiophenemethanol
a
Reaction conditions: alcohol (1 mmol), trifluorotoluene (5 mL),
b
PdHAP-0 (0.1-0.3 g, Pd: 2-6 µmol), 90 °C, O2 atmosphere. Yields were
determined by GC analysis based on alcohol using an internal standard
technique. Toluene (5 mL) was used as the solvent.
(e) Jia, C.; Kitamura, T.; Fujiwara, Y. Acc. Chem. Res. 2001, 34, 633.
c
(2) (a) Gates, B. C. Chem. ReV. 1995, 95, 511. (b) Basset, J.-M.; Lefebre, F.;
Santini, C. Coord. Chem. ReV. 1998, 178-180, 1703. (c) Iwasawa, Y.
Prepr. Solid Catal. 1999, 427. (d) Bergbreiter, D. E. Med. Res. ReV. 1999,
Table 2. Heck and Suzuki Reactions Catalyzed by PdHAP-1a
19, 439.
(
3) (a) Yamaguchi, K.; Mori, K.; Mizugaki, T.; Ebitani, K.; Kaneda, K. J.
Am. Chem. Soc. 2000, 122, 7144. (b) Mori, K.; Yamaguchi, K.; Mizugaki,
T.; Ebitani, K.; Kaneda, K. Chem. Commun. 2001, 461.
(
4) Sugiyama, S.; Minami, T.; Hayashi, H.; Tanaka, M.; Shigemoto, N.;
Moffat, J. B. J. Chem Soc., Faraday Trans. 1996, 92, 293.
(
5) For recent reports of aerobic alcohol oxidation, see: (a) Mark o´ , I. E.;
Giles, P. R.; Tsukazaki, M.; Chell e´ -Regnaut, I.; Urch, C. J.; Brown, S.
M. J. Am. Chem. Soc. 1997, 119, 12661. (b) Peterson, K. P.; Larock, R.
C. J. Org. Chem. 1998, 63, 3185. (c) Hanyu, A.; Takezawa, E.; Sakaguchi,
S.; Ishii, Y. Tetrahedron Lett. 1998, 39, 5557. (d) Nishimura, T.; Onoue,
T.; Ohe, K.; Uemura, S. J. Org. Chem. 1999, 64, 6750. (e) ten Brink,
G.-J.; Arends, I. W. C. E.; Sheldon, R. A. Science 2000, 287, 1636. (f)
Dijksman, A.; Marino-Gonzalez, A.; Payeras, A. M. I.; Arends, I. W. C.
E.; Sheldon, R. A. J. Am. Chem. Soc. 2001, 123, 6826. (g) Son, Y.-C.;
Makwana, V. D.; Howell, A. R.; Suib, S. L. Angew. Chem., Int. Ed. 2001,
yield (%)b
entry
aryl bromide
acceptor
t/h
TON (−)
1
2
3
4
5
6
1a
1b
1c
1a
1b
1c
1a
1b
1c
2a
2a
2a
2b
2b
2b
3
24
24
20
20
24
20
4
94
90
96
91
94
98
80
91
94
47 000
45 000
48 000
45 500
47 000
49 000
40 000
45 500
47 000
40, 4280. (h) Liotta, L. F.; Venezia, A. M.; Deganello, G.; Longo, A.;
c
7
Martorana, A.; Schay, Z.; Guczi, L. Catal. Today 2001, 66, 271. (i) D o¨ bler,
C.; Mehtretter, G. M.; Sundermeier, U.; Eckert, M.; Militzer, H.-C.; Beller,
M. Tetrahedron Lett. 2001, 42, 8447. (j) Steinhoff, B. A.; Fix, S. R.;
Stahl, S. S. J. Am. Chem. Soc. 2002, 124, 766.
c
8
9
3
6
c
3
4
a
Reaction conditions: aryl halide (37.5 mmol), acceptor (45 mmol),
(6) See Supporting Information for experimental details.
-
3
PdHAP-1 (0.05 g, 2-10 mol % of Pd based on aryl bromide), K2CO3
45 mmol), NMP (50 mL), 130 °C, Ar atmosphere. Yields were determined
by GC analysis based on aryl halid using an internal standard technique.
o-Xylene (50 mL) was used as solvent; 120 °C.
(7) For recent reports of heterogeneous Pd-catalyzed Heck and Suzuki
reactions, see: (a) Christian, P. M.; David, W. W.; Jackie, Y. Y. J. Am.
Chem. Soc. 1998, 120, 12289. (b) Jayasree, S.; Seayad, A.; Laurent, R.
D.; Henrike, H.; Klaus, K. J. Am. Chem. Soc. 2001, 123, 5990. (c) Mubofu,
E. B.; Clark, J. H.; Macquarrie, D. J. Green Chem. 2001, 3, 23. (d) K o¨ hler,
K.; Heidenreich, R. G.; Krauter, J.-G. E.; Pietsch, J. Chem.-Eur. J. 2002,
8, 622.
8) There is controversy whether the Heck reaction using solid Pd catalysts
occurred on their surface or not, see: (a) Zhao, F.; Murakami, K.; Shirai,
M.; Arai, M. J. Catal. 2000, 194, 479. (b) Davies, I. W.; Matty, L.; Hughes,
D. L.; Reider, P. J. J. Am. Chem. Soc. 2001, 123, 10139.
b
(
c
of coupling products. Pd leaching in the filtrate was not detected
by ICP. Therefore, it can be said that this Heck reaction proceeds
on the PdHAP-1 surface, but not with dissolved palladium species.8
In contrast, the PdHAP-0 catalyst was less effective in the Heck
reaction of 1a with 2a (TON ) 1060 for 24 h), where the formation
(
(
9) Fauvarque, J.-F.; Pfl u¨ ger, F. J. Organomet. Chem. 1981, 208, 419.
(
10) Ohff, M.; Ohff, A.; van der Boom, M. E.; Milstein, D. J. Am. Chem. Soc.
0
of Pd particles with a diameter of ca. 50 Å was observed by TEM.
1997, 119, 11687.
In the present PdHAP-1 catalyst system, the competitive Heck
reactions in an equimolar mixture of p-substituted iodobenzenes
using 2a gave a Hammett F value of 1.09, which differs from 2.00
(11) (a) Herrmann, W. A.; Brossmer, C.; O¨ fele, K.; Reisinger, C.-P.; Priermeier,
T.; Beller, M.; Fischer, H. Angew. Chem., Int. Ed. Engl. 1995, 34, 1844.
(
b) Shaw, B. L.; Perera, S. D.; Staley, E. A. Chem. Commun. 1998, 1361.
JA020444Q
J. AM. CHEM. SOC.
9
II
3 4
with Pd(PPh ) , but is similar to 1.39 with the Pd PCP-type
9
VOL. 124, NO. 39, 2002 11573