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ChemComm
DOI: 10.1039/C5CC04554A
COMMUNICATION
Journal Name
after reuse, although the nanoparticles agglomerate into large could be achieved even after recycle for 7 times. Hence, this
ones to some extent. The heterogeneous nature of [Co]@Ag composite might be an ideal heterogeneous support for the
composite was verified by HPLC and ICP-AES. No trace (below immobilization of homogeneous catalyst. On account of its
the detection limit) of chiral cobalt complex was detected in large surface area, remarkable stability, entrapment of flexible
the supernatant solution. Furthermore, the molar ratio of [Co] dopant and high conductivity, organically doped metals could
to Ag remained 1:140 before and after reusing for 7 times also be a perfect choice for chiral modified electrode.
analysed by ICP-AES, indicating that dopant would not leach
from the composite during the catalysis procedure, although
Notes and references
the weight of composite slightly reduced. According to EDAX
patterns, chiral cobalt complex could also remain its
Financial support from National Natural Science Foundation of
homogenous dispersion in the composite (Fig. S8). All the
China (21173085, 21203066, 21373090, 21473060) is
experiments demonstrated that [Co]@Ag composite we
gratefully acknowledged.
prepared is highly stable and reusable. This could be attributed
to metallic silver cage forming around the dopant, which
effectively prevented the entrapped chiral cobalt complex
1
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3
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from leaching during the reaction.
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1
1
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Fig. 5 Reuse of [Co]@Ag cathode. Reaction conditions as Table 1, entry 3.
5
1
1
4 G. Bergonzini, L. Gramigna, A. Mazzanti, M. Fochi, L. Bernardi,
A. Ricci, Chem. Commun., 2010, 46, 327-329.
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Encouraged by excellent results obtained with 1-phenylethyl
bromide (1a), the preparative scope of substrates was further
1
33, 14804-14813.
studied of this catalytic system. Using reaction conditions of 16 B. L. Chen, H. W. Zhu, Y. Xiao, Q. L. Sun, H. Wang, J. X. Lu,
Table 1, entry 3, wide range of substituted benzyl bromides
including both electron-withdrawing and electron-donating
Electrochem. Commun., 2014, 42, 55–59.
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8 H. Behar-Levy, D. Avnir, Adv. Funct. Mater., 2005, 15, 1141-
1
1
groups could be asymmetric electrolyzed with CO
2
to
1
146.
phenylpropionic acids in moderate to good yields and ee
1
9 I. Yosef, D. Avnir, Chem. Mater., 2006, 18, 5890-5896.
values. As is obvious from the results summarized in Table S1, 20 G. Nesher, G. Marom, D. Avnir, Chem. Mater., 2008, 20
Co]@Ag composite could be applicable to the asymmetric
4425–4432.
carboxylation with wide range of substrates. In addition,
Co]@Ag composite was also effective for the asymmetric
carboxylation of 1-phenylethyl chloride. 70% yield and 20% ee
,
[
2
2
1 H. Behar-Levy, O. Neumann, R. Naaman, D. Avnir, Adv.
Mater., 2009, 19, 1207–1211.
2 R. Ben-Knaz, R. Pedahzur, D. Avnir, Adv. Funct. Mater., 2010,
[
2
0, 2324–2329.
value (Table S1 entry 8) could be obtained using the same 23 S. Krackl, A. Company, Y. Aksu, D. Avnir, M. Driess,
reaction condition as 1-phenylethyl bromide.
ChemCatChem, 2011, 3, 227-232.
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Chem. Commun., 2014, 50, 8868-8870.
2
2
In conclusion, [Co]@Ag composite was synthesized for the
first time. It was successfully introduced to asymmetric
carboxylation of benzyl bromides with CO
2
, which could realize
2
heterogeneous catalysis, CO fixation and asymmetric
2
synthesis on one catalyst. Both the preparation of composite 27 I. Yosef, R. Abu-Reziq, D. Avnir, J. Am. Chem. Soc., 2008, 130
,
1
1880-11882.
8 L. D. Pachon, I. Yosef, T. Z. Markus, R. Naaman, D. Avnir, G.
Rothenberg, Nat. Chem., 2009,
, 160−164.
and catalysis procedure were performed under mild conditions,
without the utilization of high temperature, pressure or
additive catalyst in reaction solution. Moreover, [Co]@Ag
shown remarkable stability and reusability, similar results
2
2
1
9 H. P. Yang, H. Wang, J. X. Lu, Electrochem. Commun., 2015,
55, 18-21.
4
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