Notes and references
z Preparation of Pd@SBA-15r: 10 mmol H2PdCl4 aqueous solution
(4 ml) was mixed with SBA-15r (100 mg) under agitation for 1 h. The
as-synthesized sample was dried at 80 1C for 8 h under vacuum. The
dried sample was placed in a tube furnace under a hydrogen/argon
(10/90) atmosphere and heated at 400 1C for 3 h to yield Pd@SBA-15r
.
The Pd loading on the sample was 3.5 wt% (ICP-AES).
Typical procedure for Suzuki–Miyaura reaction: Bromobenzene
(0.8 mmol), phenylboronic acid (1.0 mmol) and tetrabutyl ammonium
bromide (TBAB, 0.5 mmol) were added to a suspension of the Pd
catalyst (0.08 mol%) in aqueous K2CO3 solution (2.4 mmol, 5 ml).
The reaction mixture was stirred at 80 1C under N2 atmosphere for 1 h
and then filtered and washed with brine and diethyl ether. The organic
phase was subsequently extracted with diethyl ether (3 ꢁ 20 ml), and
dried over anhydrous MgSO4. After filtration, the solvent was
removed under vacuum and the residue was purified by silica gel
chromatography with petroleum ether/ethyl acetate (20/1) as the
eluent to yield the pure product.
Fig. 3 Kinetic profiles for coupling reactions between bromobenzene
and phenylboronic acid catalyzed by Pd@SBA-15r with addition of
different compounds (reaction condition similar to Table 1, entry 9).
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coordinate with the graphene layer of a carbonous surface
through p–p interactions.2 To confirm the graphene environ-
ment inside the channels of Pd@SBA-15r, naphthalene and
anthracene were employed as small molecular probes, as these
arenes can be preferentially adsorbed onto the internal surface
of SBA-15r and block the channels of these nanoreactors.
These two compounds and a non-aromatic compound decalin
(0.5 equiv. to bromobenzene) were thus separately added into
the flasks before the coupling reactions. A kinetic study (Fig. 3)
showed that with addition of naphthalene and anthracene, the
coupling reactions were decelerated significantly, while decalin
only slightly slow down the reaction probably due to a diluent
effect. This series of experiments unambiguously confirmed the
presence of carbon thin film lining in Pd@SBA-15r nano-
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film-lined SBA-15 nanoreactor was assembled for highly
efficient heterogeneous Suzuki–Miyaura cross coupling reactions
in aqueous media. The Pd@SBA-15r catalyst could be easily
separated and recovered from reaction mixture. Its catalytic
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designed nanoreactor in other reactions is currently under way
in our lab.
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The support of National Natural Science Foundation of
China (91023008), Ph. D. Programs Foundation of Ministry
of Education of China (20100074110002), the Fundamental
Research Funds for the Central Universities, and Shanghai
Leading Academic Discipline Project (B502) is gratefully
acknowledged. AH thanks Prof. Zheng Jiao for his kindly
help in TEM.
c
This journal is The Royal Society of Chemistry 2011
Chem. Commun., 2011, 47, 10707–10709 10709