A. R. Hajipour and G. Azizi
were activated by heating with aqueous 5 M HCl with vigorous stir-
ring overnight. The activated silica was separated by centrifugation
(6000 rpm, 10 min), washed thoroughly with distilled water and
dried at 150°C overnight before undergoing chemical surface mod-
ification. The above solution containing 4 mmol of 1 was added to a
suspension of nanosilica (10 g) in dry CHCl3 (60 ml) under argon at-
mosphere. The resulting mixture was refluxed for 5 h. After cooling,
the solid materials were filtered off and the residue was subjected
to Soxhlet extraction with CHCl3 overnight and then dried in an
oven at 80°C to afford palladium complex/PTC matrix immobilized
on silica nanoparticles as a purple solid (Fig. 1S). The final material
had a palladium loading of 0.024 mmol gÀ1 as determined using
atomic absorption spectroscopy.
Figure 5. Powder XRD diffraction patterns of original catalyst (top) and
reused catalyst (bottom).
General procedure for coupling reactions
In a 5 ml round-bottom flask equipped with magnetic stirrer bar,
the aryl halide (1 mmol) was mixed with sodium tetraphenylborate
(1.12 mmol), base (2 mmol), water (1.5 ml) and catalyst (5 mg). The
mixture was then stirred at room temperature for the specified
time. After completion of the reaction, the catalyst was removed
by centrifugation and the reaction mixture was extracted with
EtOAc (3 × 5 ml). The filtrates were combined together and dried
over anhydrous CaCl2. The solvent was evaporated under reduced
pressure to give the corresponding products. In most cases, the
purity of the products was found, using GC, to be more than 95%
without any chromatographic purification. Other products were
purified using column chromatography (80:20, hexane–EtOAc). In
the case of aryl bromides and activated aryl chlorides, reactions
were performed at reflux temperature. A 3 ml stainless steel reactor
was used at 130°C for less reactive aryl chlorides.
Palladium chloride (99%, reagent plus) was purchased from Sigma-
Aldrich. Triphenylphosphine, NaHCO3 and aryl halides were purchased
from Merck.
NMR spectra were recorded with a Bruker Avance DPX spectrom-
eter (1H NMR 400 or 300 MHz) in CDCl3 with tetramethylsilane as
the internal standard. UV–visible spectra were recorded with a
Jasco V-570 UV-vis-NIR spectrometer and a Jasco ARN-475 acces-
sory for diffuse reflectance. Transmission electron microscopy im-
ages were obtained with a Philips CM10. Palladium content of the
catalyst was measured using a PerkinElmer 2380 atomic absorption
spectrophotometer.
Preparation of catalyst
The catalyst was prepared according to our previous work,[33] as de-
scribed in the following.
Conclusions
Preparation of compound 1
A new supported matrix containing palladium and PTC and its
application in the cross-coupling reactions of aryl halides and
water-soluble sodium tetraphenylborate have been developed
based on simple simultaneous anchoring of palladium and PTC
on silica nanoparticles. These reactions take place in water as sol-
vent without the need for addition of any organic co-solvent, thus
rendering this process economically and ecologically acceptable.
In a well-dried 100 ml round-bottom flask, a solution of
triphenylphosphine (1.311 g, 5 mmol) in dry toluene (30 ml) and
(3-iodopropyl)trimethoxysilane (1.450 g, 5 mmol) were added. The
system was then filled with argon three times and refluxed for 24
h under an argon atmosphere. The progress of the reaction was
monitored using TLC (80:20, hexane–EtOAc). After completion of
the reaction, the resulting two-phase reaction mixture was then
allowed to cool to room temperature and the organic layer was
separated from the phosphonium salt layer. The resulting glassy
pale yellow material was then thoroughly washed with dry toluene
under gentle heating (1 × 10 ml) and Et2O (3 × 5 ml) and finally
dried under vacuum (640 mmHg) for 1 h at 40°C (80%, 2.2 g,
4 mmol).
Acknowledgments
We gratefully acknowledge the funding support received for this
project from the Isfahan University of Technology, IR Iran. Further fi-
nancial support from the Center of Excellence in Sensor and Green
Chemistry Research, Isfahan University of Technology, is gratefully
acknowledged.
Preparation of phosphonium salt–Pd complex 2
In a well-dried 100 ml round-bottom flask equipped with magnetic
stirrer bar and containing a CHCl3 (40 ml) solution of 1 (2.2 g, 4
mmol) was added PdCl2 (44.5 mg, 0.25 mmol). The system was then
evacuated and refilled with argon. The mixture was then allowed to
react with stirring at reflux temperature for 1 h under an argon
atmosphere. The system was then allowed to cool to room
temperature to afford a dark red–purple complex solution (Fig. 1S).
References
[1] A. Markham, K. Goa, Drugs 1997, 54, 299.
[2] R. Capdeville, E. Buchdunger, J. Zimmermann, A. Matter, Nature Rev.
Drug Discov. 2002, 1, 493.
[3] D. Schönfelder, O. Nuyken, R. Weberskirch, J. Organometal. Chem.
2005, 690, 4648.
[4] H. Tomori, J. M. Fox, S. L. Buchwald, J. Org. Chem. 2000, 65, 5334.
[5] F. Liron, C. Fosse, A. Pernolet, E. Roulland, J. Org. Chem. 2007, 72, 2220.
[6] A. S. Guram, X. Wang, E. E. Bunel, M. M. Faul, R. D. Larsen, M. J. Martinelli,
J. Org. Chem. 2007, 72, 5104.
[7] E. A. B. Kantchev, C. J. O’Brien, M. G. Organ, Angew. Chem. Int. Ed. 2007,
46, 2768.
Preparation of phosphonium–Pd complex/PTC matrix immobilized on silica
nanoparticles
Silica nanoparticles with a size of about 12 nm were synthesized ac-
cording to a previously reported procedure.[37] Silica nanoparticles
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Appl. Organometal. Chem. 2015, 29, 712–717