1
205
Synlett
A. Ohtaka et al.
Cluster
Acknowledgment
Si(OMe)3
PS-PdONPs (25 mol%)
The authors are grateful to the Nanomaterials and Microdevices Re-
search Center (NMRC) of OIT for financial and instrumental supports.
NaOH (3 equiv)
TBAC (1 equiv)
H2O, 80 °C, 20 h
0%
1.0 mmol
References and Notes
Br
(1) (a) Nanoparticles and Catalysis; Astruc, D., Ed.; Wiley-VCH:
Weinheim, 2008. (b) Yasukawa, T.; Miyamura, H.; Kobayashi, S.
Chem. Soc. Rev. 2014, 43, 1450. (c) Yan, N.; Xiao, C.; Kou, Y.
Coord. Chem. Rev. 2010, 254, 1179.
PS-PdNPs (1.5 mol%)
NaOH (3 equiv)
TBAC (1 equiv)
MeOH (4.5 equiv)
H2O, 80 °C, 3 h
0.5 mmol
86%
(2) Jeffery, T. Tetrahedron Lett. 1994, 35, 3051.
(
3) (a) Deraedt, C.; Astruc, D. Acc. Chem. Res. 2014, 47, 494. (b) Fihri,
A.; Bouhrara, M.; Nekoueishahraki, B.; Basset, J.-M.;
Polshettiwar, V. Chem. Soc. Rev. 2011, 40, 511.
Scheme 1 Side reactions
(
4) (a) Nasrollahzadeh, M.; Sajadi, S. M.; Honarmand, E.; Maham,
M. New J. Chem. 2015, 39, 4745. (b) Wu, L.; Zhang, X.; Tao, Z.
Catal. Sci. Tech. 2012, 2, 707. (c) Bernechea, M.; de Jesus, E.;
Lopez-Mardomingo, C.; Terreros, P. Inorg. Chem. 2009, 48, 4491.
The Hiyama coupling reaction using PS-PdONPs as a
catalyst seems to proceed through the mechanistic pathway
as presented in Scheme 2. First, leaching of palladium takes
place by base. Leached palladium species are re-stabilized
onto polystyrene after the reaction with aryltrimethoxysi-
lane. Subsequently, aryl bromide reacts to generate the
product. When the Hiyama coupling reaction of 4-bromo-
toluene with phenyltrimethoxysilane was interrupted at
(5) (a) Srimani, D.; Sawoo, S.; Sarkar, A. Org. Lett. 2007, 9, 3639.
(b) Sreedhar, B.; Kumar, S.; Yada, D. Synlett 2011, 1081. (c) Ranu,
B. C.; Dey, R.; Chattopadhyay, K. Tetrahedron Lett. 2008, 49,
3
430. (d) Nasrollahzadeh, M.; Sajadi, S. M.; Honarmand, E.;
Maham, M. New J. Chem. 2015, 39, 4745. (e) Shah, D.; Kaur, H.
Curr. Catal. 2014, 3, 39. (f) Alacid, E.; Nájera, C. Adv. Synth. Catal.
20% conversion and continued after removal of the catalyst
2006, 348, 945. (g) Paul, A.; Chatterjee, ; Rajkamal, D.; Banerjee,
(hot filtration test), no increase in the yield of coupling
S.; Yadav, S. RSC Adv. 2015, 5, 71253. (h) Kong, F.; Zhou, C.;
Wang, J.; Yu, Z.; Wang, R. ChemPlusChem 2013, 78, 536.
product was observed. Furthermore, no palladium species
was observed in the filtrate by ICP-AES analysis. These re-
sults are consistent with the hypothesis that the reaction
with bromobenzene takes place in a heterogeneous system.
In addition, Pd(II) nanoparticles are reduced by MeOH to
Pd(0) nanoparticles that have little catalytic activity for the
Hiyama coupling reaction in water.
(
i) Ohtaka, A.; Sansano, J. M.; Nájera, C.; Miguel-García, I.;
Berenguer-Murcia, Á.; Cazorla-Amorós, D. ChemCatChem 2015,
, 1841.
7
(
6) (a) Liao, W.-T.; Yang, X.-J.; Tseng, Y.-Y.; Wu, C.-C.; Liu, L.-J.; Tsai,
F.-Y. Asian J. Org. Chem. 2015, 4, 1112. (b) Liu, X.; Zhao, X.; Lu, M.
Catal. Lett. 2015, 145, 1549. (c) Nasrollahzadeh, M.; Banaei, A.
Tetrahedron Lett. 2015, 56, 500.
(7) (a) Chinchilla, R.; Nájera, C. Chem. Soc. Rev. 2011, 40, 5084.
(
1
b) Gholinejad, M.; Hamed, F.; Biji, P. Dalton Trans. 2015, 44,
4293. (c) Shunmughanathan, M.; Puthiaraj, P.; Pitchumani, K.
supported Pd(II) NPs
soluble species
ChemCatChem 2015, 7, 666. (d) Nasrollahzadeh, M.; Mohammad
Sajadi, S.; Maham, M.; Ehsani, A. RSC Adv. 2015, 5, 2562.
leaching
[
Pd-OH]
NaOH
Ar1 Si(OMe)3
HO Si(OMe)3
(8) General Procedure for Hiyama Coupling Reaction (Table 1):
To a screw-capped vial with a stirring bar were added 4-bromo-
toluene (86.4 mg, 0.5 mmol), phenyltrimethoxysilane (152 mg,
0.75 mmol), PS-PdONPs (2.9 mg, 1.5 mol% of Pd), TBAC (142 mg,
0.5 mmol), and aq NaOH solution (1.5 M, 1 mL). After stirring at
80 °C for 3 h, the reaction mixture was cooled to r.t. by immedi-
Ar1 Ar2
Ar2 Br
Ar1 Pd
redeposition
[
Pd-Ar1]
ately immersing the vial in H O (ca. 20 °C) for about 10 min.
2
After separating the catalyst and the aqueous phase by centrifu-
gation, the aqueous phase was decanted. The recovered catalyst
was washed with H O (5 × 3.0 mL) and Et O (5 × 3.0 mL), which
Scheme 2 A plausible reaction mechanism
2
2
were then added to the aqueous phase. The aqueous phase was
extracted eight times with Et O. The combined organic extracts
PS-PdONPs have high catalytic activity for the Hiyama
coupling reaction in water, but PS-PdNPs showed no activi-
ty. The difference in catalytic activity for the Hiyama cou-
pling reaction in water between PS-PdONPs and PS-PdNPs
has been demonstrated to be caused by the difference in
mechanisms. The determination of the structure of the
leaching species is now in progress.
2
were dried over MgSO4 and concentrated under reduced pres-
1
sure. The product was analyzed by H NMR. The recovered cata-
lyst was dried in vacuo and reused. Furthermore, the amount of
Pd metal in the aqueous phase determined by ICP-AES analysis
was <0.1 ppm.
1
4-Methylbiphenyl: H NMR (CDCl ): δ = 7.55–7.60 (m, 2 H),
3
7.47–7.50 (m, 2 H), 7.39–7.43 (m, 2 H), 7.29–7.33 (m, 1 H),
13
7
.20–7.25 (m, 2 H), 2.38 (s, 3 H). C NMR (CDCl ): δ = 141.1,
3
138.3, 136.9, 129.4, 128.7, 128.7, 126.9, 21.1. CAS registry
number: 644-08-6.
©
Georg Thieme Verlag Stuttgart · New York — Synlett 2016, 27, 1202–1206