Angewandte
Chemie
mixture had cooled to room temperature, the organic product was
Table 3: Phenol
formation
from
aryl
halides.
extracted with diethyl ether (3 75 mL). The organic fractions were
washed with deionized water and then dried with MgSO4. After
filtration, volatile substances were removed under reduced pressure
to yield the final product.
General procedure for synthesis of phenols from aryl halides:[38]
A mixture of PANI/Pd (1 mol% Pd), KOH (5.0 equiv), and aryl
halide (1.0 equiv) was stirred at 1008C for the indicated time. The
reaction mixture was cooled to room temperature, carefully acidified
with dilute aqueous HCl until the pH reached ca. 1, and extracted
with diethyl ether. The separated organic layer was dried over
anhydrous MgSO4, filtered, and concentrated under reduced pres-
sure. The crude material was purified by crystallization. Yields
depended on scale and the precision of workup.
Entry
1
X
Substrate, Ar
Yield [%]
81
Cl
2
3
Br
Br
80
90
Experimental details, NMR spectra of products, and details of
catalyst-loading results and recycling experiments are available as
Supporting Information.
4
Br
89
Received: March 30, 2007
Published online: July 26, 2007
À
Keywords: C C coupling · nanostructures · palladium ·
polymers · supported catalysts
.
À
C Cl bonds of 1,2-dichlorobenzene, followed by phenol
formation on increasing the temperature and reaction time.
[1] D. Astruc, F. Lu, J. R. Aranzaes, Angew. Chem. 2005, 117, 8062;
Angew. Chem. Int. Ed. 2005, 44, 7852.
[2] B. M. Choudary, M. Roy, S. Roy, M. L. Kantam, B. Sreedhar,
K. V. Kumar, Adv. Synth. Catal. 2006, 348, 1734.
[3] A. Houdayer, R. Schneider, D. Billaud, J. Ghanbaja, J. Lambert,
Appl. Organomet. Chem. 2005, 19, 1239.
[4] a) J. X. Huang, R. B. Kaner, J. Am. Chem. Soc. 2004, 126, 851;
b) J. X. Huang, S. Virji, B. H. Weiller, R. B. Kaner, J. Am. Chem.
Soc. 2003, 125, 314.
[5] a) J. X. Huang, R. B. Kaner, Chem. Commun. 2006, 367; b) J. X.
Huang, S. Virji, B. H. Weiller, R. B. Kaner, Chem. Eur. J. 2004,
10, 1314.
[6] H. L. Wang, W. G. Li, Q. X. Jia, E. Akhadov, Chem. Mater. 2007,
19, 520.
[7] M. Kralik, A. Biffis, J. Mol. Catal. A 2001, 177, 113.
[8] S. K. Pillalamarri, F. D. Blum, A. T. Tokuhiro, M. F. Bertino,
Chem. Mater. 2005, 17, 5941.
In conclusion, we have shown that palladium nanoparti-
cles supported on polyaniline nanofibers are active catalysts
for Suzuki coupling between aryl chlorides and phenylboronic
acid and for phenol formation from aryl halides and
potassium hydroxide in water and air. Applications of this
catalyst system, with an emphasis on the scope of tandem
reactions, are in development.
[9] K. Mallick, M. J. Witcomb, A. Dinsmore, M. S. Scurrell,
Langmuir 2005, 21, 7964.
Experimental Section
All manipulations were carried out in air unless otherwise stated.
Synthesis of Pd nanoparticles supported by polyaniline nano-
fibers: Polyaniline/Pd composite was prepared by first synthesizing
polyaniline nanofibers in a rapidly mixed reaction.[40] An aqueous
solution of camphorsulfonic acid was used as reaction medium and
ammonium peroxodisulfate as oxidant. Aniline was distilled imme-
diately before use. The crude fibers were purified by centrifugation
and washing with deionized water, NaOH, and then three more times
with water. Palladium nanoparticles were grown by combining a
2 gLÀ1 aqueous nanofiber dispersion with a 10 mm solution of
palladium(II) nitrate (4:1) and incubation for one day. The resulting
solution was then dialyzed to remove any remaining palladium salt in
fresh deionized water every 4 h for 2 d. ICP analysis of the filtrates
after dialysis showed no palladium. Elemental analysis (wt%) found
for dried samples of Pd/PANI: C 65.70, H 4.39, N 12.72, Pd 10.9;
calcd: C 65.15, H 3.79, N 12.66, Pd 10.3. Most Pd/PANI suspensions
have 2 mm Pd.
[10] Metal-Catalyzed Cross-Coupling Reactions, Vol. 2 (Eds.: A.
de Meijere, F. Diederich), Wiley-VCH, Weinheim, 2004.
[11] A. Suzuki, J. Organomet. Chem. 1999, 576, 147.
[12] K. Tamao, N. Miyaura, Top. Curr. Chem. 2002, 219, 1.
[13] Aqueous-Phase Organometallic Catalysis (Eds.: B. Cornils,
W. A. Herrmann), Wiley-VCH, Weinheim, 2004.
[14] K. H. Shaughnessy, R. B. DeVasher, Curr. Org. Chem. 2005, 9,
585.
[15] N. E. Leadbeater, Chem. Commun. 2005, 2881.
[16] Organic Synthesis in Water (Ed.: P. A. Grieco), Academic Press,
Dordrecht, 1998.
[17] J. C. Galland, M. Savignac, J. P. Genet, Tetrahedron Lett. 1999,
40, 2323.
[18] L. Botella, C. Najera, Angew. Chem. 2002, 114, 187; Angew.
Chem. Int. Ed. 2002, 41, 179.
[19] L. Botella, C. Najera, J. Organomet. Chem. 2002, 663, 46.
[20] C. Najera, J. Gil-Molto, S. Karlstrom, L. R. Falvello, Org. Lett.
2003, 5, 1451.
[21] I. Ozdemir, Y. Gok, N. Gurbuz, E. Cetinkaya, B. Cetinkaya,
Heterocycl. Chem. 2004, 15, 419.
[22] I. Ozdemir, S. Demir, S. Yasar, B. Cetinkaya, Appl. Organomet.
Chem. 2005, 19, 55.
General protocol for Suzuki coupling: Aryl halide (1 equiv),
phenylboronic acid (1.5 equiv), and base (4 equiv) were added to
20 mL of deionized water. The solution was stirred at 80–1008C. Pd/
PANI (0.05 mol%) was added to the stirred solution, and the reaction
mixture stirred for 2–4 h or for the time indicated. After the reaction
Angew. Chem. Int. Ed. 2007, 46, 7251 –7254
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