Green catalysts derived from agricultural and industrial waste products: The preparation of phenols from CsOH and Aryl iodides using CuO on mesoporous silica

Article abstract of DOI:10.1002/ejoc.201101206

The synthesis of CuO catalysts supported on mesoporous silica derived from rice husks and semiconductor copper from chemical mechanical planarization (Cu-CMP) wastewater is described. These catalysts are active for the coupling reaction of CsOH with aryl iodides. Low catalyst loading (1 mol-%) without the need for ancillary ligands make these very attractive "green" catalysts. The synthesis of CuO catalysts supported on mesoporous silica derived from rice husks and semiconductor copper from chemical mechanical planarization (Cu-CMP) wastewater is described. These catalysts are active for the coupling reaction of CsOH with aryl iodides. Low catalyst loading (1 mol-%) without the need for ancillary ligands make these very attractive "green" catalysts. Copyright

Full text of DOI:10.1002/ejoc.201101206

FULL PAPER
DOI: 10.1002/ejoc.201101206
Green Catalysts Derived from Agricultural and Industrial Waste Products:
The Preparation of Phenols from CsOH and Aryl Iodides using CuO on
Mesoporous Silica
Chien-Ching Chan,[a] Yan-Wun Chen,[b] Chi-Shen Su,[b] Hong-Ping Lin,*[b] and
Chin-Fa Lee*[a]
Keywords: Supported catalysis / Mesoporous materials / Waste prevention / Sustainable chemistry / Copper /
Cross-coupling
The synthesis of CuO catalysts supported on mesoporous sil-
ica derived from rice husks and semiconductor copper from
chemical mechanical planarization (Cu-CMP) wastewater is
described. These catalysts are active for the coupling reac-
tion of CsOH with aryl iodides. Low catalyst loading (1 mol-
%) without the need for ancillary ligands make these very
attractive “green” catalysts.
hulls are a byproduct of human food processing. Owing to
the high silica content (around 15 wt.-% in dried rice husk),
Introduction
Phenolic motifs are important building blocks in organic the rice husks are also a readily available source of silica.[14]
synthesis and materials chemistry.[1] The traditional meth-
Table 1. Optimization of CuO on mesoporous silica catalyzed cou-
ods for preparing these molecules rely on harsh reaction
conditions[2] that often prevent functional group tolerance
and limit their practical application. Transition-metal-cata-
lyzed coupling reactions of metal hydroxides with aryl ha-
lides provides an alternative route to overcome these diffi-
culties.[3–12] Palladium-catalyzed hydroxylation of aryl ha-
lides has been reported by Buchwald,[5] Beller,[6] Diacone-
scu,[7] and Kwong.[8] The use of a combination of copper
salts with appropriate ligands has also been reported for the
same purpose.[9–12] Ancillary ligands are, however, a neces-
sity in all the above protocols.[5–12] Herein, we report that
CuO on mesoporous silica can be used as a catalyst for
the coupling of CsOH with aryl iodides under ligand-free
conditions.
Recently, we communicated that CuO on mesoporous sil-
ica A (see Table 1), templated by gelatin, is a very effective
catalyst for C–S coupling reactions.[13] Distinct from our
previous report, we were determined to find a greener cata-
lytic system that could be used to prepare phenols. In fact,
we demonstrate here that these greener catalysts show bet-
ter catalytic performance than the catalyst that was used
previously in the C–S coupling reaction.[13] Rice husks or
pling of 1-iodo-4-methoxybenzene with CsOH.[a]
Entry
Catalyst (silica source, CuO/silica)
Yield [%][b]
1
2
3
4
5
6
7
A (gelatin-silicate, 1:20)
B (gelatin-silicate, 1:5)
C (rice husk, 1:20)
D (rice husk, 1:5)
CuO
CuO/SiO2 (CuO/SiO2 = 1:5)
D (rice husk, 1:5)
87
76
85
94
16
23
47[c]
[a] Reaction conditions: CuO on mesoporous silica (0.01 mmol,
1 mol-%), 1-iodo-4-methoxybenzene (1.0 mmol), CsOH-H2O
(3.0 mmol) in DMSO (0.5 mL)/H2O (0.5 mL). [b] Isolated yield. [c]
KOH (3.0 mmol) was used instead of CsOH-H2O.
Results and Discussion
Mesoporous silicates of high surface area can be ob-
tained from simple hydothermal (100 °C) treatment of an
acidic solution (pH 2.0–3.0 and rice husk/acidic solution
weight ratio ca. 1:10) and calcination (600 °C) in air (see
the Supporting Information, Figure S1 for TEM image and
N2 adsorption–desorption isotherm of the mesoporous sil-
icates). Consequently, the mesoporous silica from rice husks
was thought to be a reasonable substitute for the gelatin-
[a] Department of Chemistry, National Chung Hsing University,
Taichung, Taiwan 402, R.O.C
Fax: +886-4-2286-2547
E-mail: cfalee@dragon.nchu.edu.tw
[b] Department of Chemistry, National Cheng Kung University,
Tainan, Taiwan 701, R.O.C.
E-mail: hplin@mail.ncku.edu.tw
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201101206.
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Green Catalysts from Industrial Waste Products
templated mesoporous silicas (e.g., MCM-41 or SBA- tribution profiles of Si, and Cu elements and diffuse ring-
15).[15] Although the CuO supported on silica from rice diffraction patterns indicate an even distribution of CuO
husks ash and commercial copper salt is known,[16] the di- active sites on the mesoporous silica. In accordance with
rect synthesis of CuO on mesoporous silica from rice husks the TEM data, the existence of two broad X-ray diffraction
and copper-containing wastewater has not yet been re- (XRD) peaks at high-angle of 35.8° and 38.2° (i.e., CuO
ported. Here, we report the synthesis of CuO supported on diffraction peaks) reveal that the CuO is well-dispersed
mesoporous silica derived from rice husks and Cu-CMP onto the surface of the mesoporous silica, where the meso-
wastewater from copper chemical mechanical planarization porous silica from rice husks may prevent the formation
(Cu-CMP) processes through a hydroxide-precipitation and of CuO nanoparticles from self-condensation (Figure 1, e).
100 °C-hydrothermal treatment.[17] Finally, the CuO on Furthermore, the calcined CuO on mesoporous silica sam-
mesoporous silica catalyst was obtained from high-tempera- ple presented is uniformly green, rather than black, which
ture calcination of the Cu(OH)2-containing mesoporous sil- is observed for mesoporous silica containing CuO nanopar-
ica.
ticles prepared by impregnation methods (Figure 2). When
The transmission-electron microscopy (TEM) images of the N2 adsorption–desorption isotherm was analyzed (Fig-
CuO on mesoporous silica (Figure 1, a) show a wormhole- ure 1, f), the BET surface area was found to be about
like mesostructure; CuO nanoparticles of high electron- 285 m2 g–1; the pore size, calculated by the Barrett–Joyner–
density were not observed. At higher magnification, the Halenda (BJH) method, was centered at 6.5 nm (inset in
amorphous structure was observed without any significant Figure 1, f). Similar surface area and porosity between
CuO lattice infringement. To further demonstrate the even mesoporous silica and CuO on mesoporous silica indicate
distribution of CuO, TEM EDX-mapping and selected area that the CuO is well-dispersed on the pore wall of the meso-
electron diffraction were used (Figure 1, b–d). Similar dis- porous silica rather than blocking the pores. Accordingly,
the CuO active sites are well-dispersed on the mesoporous
silica, and highly accessible to the environment, which
should give rise to high activity for coupling reactions, with
the added feature of recyclability.
Figure 2. Optical micrographs of the CuO-containing mesoporous
silica samples at the same chemical composition (Cu/Si molar ratio
ca. 5) synthesized by using different synthetic methods. (a) CuO
on mesoporous silica prepared by using rice husks and Cu-CMP
wastewater as silica and CuO precursors through the synthetic pro-
cess developed here. (b) CuO on mesoporous silica obtained from
the typical impregnation method.
Initially, 1-iodo-4-methoxybenzene was screened in the
coupling with CsOH to determine the optimal reaction con-
ditions; the results are summarized in Table 1. The product
was obtained in good to excellent yields by using this cata-
lyst system. Interestingly, catalyst A (Cu/silica = 1:20) was
not only reactive for C–S coupling reactions;[13] but was
also suitable for C–O coupling reactions, affording the tar-
get in 87% yield (Table 1, entry 1). It is important to note
that catalyst D (Cu/silica = 1:5) gave the best result, yielding
the product in 94% isolated yield (Table 1, entry 4). The
Figure 1. Scanning transmission-electron microscopy images
(STEM), in conjunction with EDX elemental mapping of the re-
effect of the Cu/silica ratio is not yet clear; when the reac-
tion was carried out using CuO as the catalyst, the product
was obtained in only 16% yield (Table 1, entry 5). A control
experiment was performed using CuO and SiO2 as the cata-
lyst, but this resulted in only 23% yield of the product
(Table 1, entry 6). These low yields indicate that leached
sulting CuO on mesoporous silica prepared by using Cu-CMP
wastewater and rice husks as precursors. (a) TEM image. (b) Si
element distribution image. (c) Cu element distribution image. (d)
The selected area electron diffraction pattern of the CuO on meso-
porous silica sample. (e) High-angle XRD pattern, and (f) N2
adsorption–desorption isotherm, with (insert) the pore-size distri-
bution of the CuO on mesoporous silica.
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Table 2. CuO on mesoporous silica catalyzed coupling reaction of species do not have high activities. When KOH was used
aryl iodides with CsOH.[a]
instead of CsOH, the product was afforded in 47% yield
(Table 1, entry 7). Lower yields were observed when 1-iodo-
4-methoxybenzene was replaced by bromobenzene (10%
GC yield) or chlorobenzene (trace amount) under the same
conditions.
Based on the optimized conditions, we examined the
scope of this catalytic system. As listed in Table 2, a variety
of electron-donating and -withdrawing aryl iodides were
studied as CsOH coupling partners, and the corresponding
phenols were obtained in good to excellent yields. Func-
tional groups including nitro (Table 2, entry 2), chloro (en-
try 4), alcohol (entry 10), enolizable ketones (entries 11 and
12), and carboxylic acids (entries 13, 14, and 15) were all
tolerated under the conditions employed. The application
of more sterically demanding substrates resulted in slightly
lower yields (Table 2, entries 3, 5, 13, and 16).
To study the potential recyclability of the catalyst, 4-
iodo-4-methoxybenzene was treated with CsOH. As sum-
marized in Table 3, the catalyst could be reused for several
runs without significant loss of activity. TEM images (see
the Supporting Information, Figure S2) of the CuO on
mesoporous silica after the fourth reaction reveal that the
pore structure was retained without any significant forma-
tion of CuO nanoparticles (from aggregation). By compar-
ing the energy-dispersive spectroscopy (EDS) data of the
CuO on mesoporous silica catalysts before and after the
fourth run, we found the Cu/Si atomic ratio of the fourth-
run sample had decreased from 2.0:10 to 1.6:10. The 20%
decrease in the CuO content indicates that the CuO active
sites remain highly stabilized on the mesoporous silica dur-
ing multiple catalytic cycles. The copper species from leach-
–
ing will form the soluble species such as Cu(OH)3 and
2–
Cu(OH)4 under strong base conditions,[18] such as those
employed here {[CsOH] ≈ 3.0 m}. It is therefore under-
standable that the observed Cu/Si atomic ratio of the
fourth-run sample decreased. As mentioned earlier, if the
activity mainly came about as a result of leached (homogen-
eous) components,[2] the CuO and the CuO/SiO2 should
both give good yields of the product, however, only CuO
on mesoporous silica was observed to be active, giving the
product in 94% isolated yield (Table 1, entry 4). The 20%
decrease in the Cu content of the CuO on mesoporous sili-
cate after the fourth reaction cycle indicates that the CuO
active sites bond strongly with the mesoporous silica, and
this heterogeneous catalyst system shows good activity for
the coupling reaction of aryl iodides with CsOH.
Table 3. Reuse of CuO on mesoporous silica D for the preparation
of 2a.[a]
Run
1
2
3
4
Yield [%] 94
92
92
88
[a] Reaction conditions unless otherwise stated: CuO on mesopo-
rous silica (0.01 mmol, 1 mol-%), CsOH/H2O (3.0 mmol) in DMSO
(0.5 mL)/H2O (0.5 mL). [b] Isolated yield. [c] CsOH/H2O
(4.0 mmol) was used. [d] Catalyst (3 mol-%) was used.
[a] Reaction conditions: 3.0 mmol scale reaction was performed;
after 24 h, the reaction mixture was treated with HCl and diluted
with H2O and EtOAc, the catalyst was recovered by centrifugation
then dried in an oven overnight.
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Eur. J. Org. Chem. 2011, 7288–7293

Green Catalysts from Industrial Waste Products
General Procedure for the Reaction Described in Table 1: A sealable
tube equipped with a magnetic stir bar was charged with CsOH/
H2O (504 mg, 3.0 mmol) in a dry-box under a nitrogen atmosphere.
The tube was then covered with a rubber septum and removed from
the dry-box. Under a nitrogen atmosphere, catalyst (1.0 mol-%),
1-iodo-4-methoxybenzene (234.0 mg, 1.0 mmol), DMSO (0.5 mL),
and H2O (0.5 mL) were added by using a syringe. The septum was
then replaced by a Teflon®-coated screw cap and the reaction vessel
was heated at 120 °C in an oil bath. After stirring at this tempera-
ture for 24 h, the heterogeneous mixture was cooled to room tem-
perature; HCl (10%, 1.0 mL) was added and the mixture was di-
luted with EtOAc (20 mL). The resulting solution was filtered
through a pad of silica gel then washed with EtOAc (20 mL) and
concentrated to give the crude material, which was purified by col-
umn chromatography (SiO2; hexane/EtOAc, 4:1) to give 2a.
Conclusions
We have reported that CuO on mesoporous silica based
catalysts can be prepared conveniently from rice husks and
wastewater from semiconductor Cu-CMP processing.
Furthermore, this system has been shown to be catalytically
active for the coupling of CsOH with a variety of aryl iod-
ides. More applications of these novel catalysts in organic
synthesis are being developed in our laboratory.
Experimental Section
General Information: All chemicals were purchased from commer-
cial suppliers and used without further purification. Toluene was
dried with sodium; dioxane, DME, and DMF were dried with
CaH2 and stored in the presence of activated molecular sieves. All
reactions were carried out under an inert atmosphere. Flash
chromatography was performed on Merck silica gel 60 (230–
400 mesh). NMR spectra were recorded with a Varian Unity Inova-
600 or a Varian Mercury-400 instrument using CDCl3 as solvent.
Chemical shifts are reported in parts per million (ppm) and refer-
enced to the residual solvent resonance. Coupling constants (J) are
reported in Hertz [Hz]. Standard abbreviations indicating multi-
plicity are as follows: s = singlet, d = doublet, t = triplet, dd =
double doublet, q = quartet, m = multiplet, br. = broad. Melting
points (m.p.) were determined with a Büchi 535 apparatus. GC–
MS analyses were performed with a HP 5890 GC connected to a
HP 5972 MS. High-resolution mass spectra were carried out with
a Jeol JMS-HX 110 spectrometer by the services at the National
Chung Hsing University.
4-Methoxyphenol (2a):[9] Obtained by following the above general
procedure using D as the catalyst (3.8 mg, 0.01 mmol) and 1-iodo-
4-methoxybenzene (234.0 mg, 1.0 mmol). Purification (SiO2,
CH2Cl2) provided 2a as a white solid (116 mg, 94% yield); m.p.
1
49–51 °C (ref.[9] 55–57 °C). H NMR (400 MHz, CDCl3): δ = 3.75
(s, 3 H), 5.87 (br. s, 1 H), 6.77 (s, 4 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 55.8, 114.9, 116.1, 149.5, 153.5 ppm.
General Procedure for the Reaction Described in Table 2: A sealable
tube equipped with a magnetic stir bar was charged with CsOH/
H2O (504 mg, 3.0 mmol) in a dry-box under a nitrogen atmosphere.
The tube was then covered with a rubber septum and removed from
the dry-box. Under a nitrogen atmosphere, catalyst D (1.0 mol-%),
aryl iodide (1.0 mmol), DMSO (0.5 mL), and H2O (0.5 mL) were
added by using a syringe. The septum was then replaced by a Tef-
lon®-coated screw cap and the reaction vessel was heated at 120 °C
in an oil bath. After stirring at this temperature for 24 h, the hetero-
geneous mixture was cooled to room temperature; HCl (10%,
1.0 mL) was added and the mixture was diluted with EtOAc
(20 mL). The resulting solution was filtered through a pad of silica
gel then washed with EtOAc (20 mL) and concentrated to give the
crude material, which was purified by column chromatography
(SiO2; hexane/EtOAc or CH2Cl2/methanol) to give 2.
Preparation of Mesoporous Silica from Rice Husks: To directly ob-
tain mesoporous silica from rice husk having a high surface area
(ca. 250 m2 g–1) and large porosity, dry rice husks (3.0–5.0 g) were
suspended in 50.0 mL of a sulfuric acid solution (pH ≈ 3.0) and
then hydrothermally treated at 100 °C for 6 h. Filtration, drying,
and calcination at 600 °C in air gave the mesoporous silica with
a Brunauer–Emmett–Teller (BET) surface area of approximately
235 m2 g–1 and pore size of approximately 6.0 nm (Figure S1).
4-Methylphenol (2b):[9] Obtained by following the general pro-
cedure for Table 2 using 1-iodo-4-methylbenzene (0.218 mg,
1.0 mmol). The crude mixture was purified by column chromatog-
raphy (SiO2; CH2Cl2) to give 2b as a yellow oil (95.9 mg, 89%
Cu2+ Removal from Wastewater and the Synthesis of CuO on Meso-
porous Silica Catalysts Using Rice Husks: The mesoporous silica
can be used directly as an absorbent to remove the Cu2+ ions from
the waste water from Cu-CMP slurry processing. To remove the
Cu2+ ions and prepare a well-dispersed CuO-silica catalyst, 1.0 g
of mesoporous silica from rice husk was added to 220 mL of
0.015 m Cu2+ aqueous solution diluted from the Cu-CMP waste
water ([Cu2+] ≈ 0.50 m). Using the dilute Cu2+ solution can prevent
the formation of large copper hydroxide aggregation from self-con-
densation during precipitation. The pH of the gel solution was ad-
justed to 6.0–7.0 by dropwise addition of 0.15 m NaOH solution,
and then the gel solution was hydrothermally treated for 24 h at
100 °C. Filtration, and drying gave the Cu(OH)2-silica. The CuO
on mesoporous silica catalyst (Cu/Si ≈ 2:10) was obtained from
calcination at 500 °C in air on the Cu(OH)2-silica. Concerning the
safety of the reaction effluent, the residual [Cu2+] concentration in
the waste solution was measured, and the [Cu2+] concentration was
found to be less than 3.0 ppm (this corresponds to the effluent stan-
dard for Cu2+ ions in Taiwan). Accordingly, this is an environmen-
tally-friendly synthetic strategy for the preparation of the CuO on
mesoporous catalyst and this synthetic process is capable of remov-
ing toxic Cu2+ ions from Cu-CMP waste water. In addition, the
Cu2+ ion from Cu-CMP waste water was almost completely incor-
porated into the CuO on silica catalyst.
1
yield). H NMR (400 MHz, CDCl3): δ = 2.25 (s, 3 H), 5.29 (br. s,
1 H), 6.73 (d, J = 8.8 Hz, 2 H), 7.01 (d, J = 8.8 Hz, 2 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 20.4, 115.1, 130.0, 130.0, 152.9 ppm.
4-Nitrophenol (2c):[9] Obtained by following the general procedure
for Table 2 using 1-iodo-4-nitrobenzene (249.0 mg, 1.0 mmol), then
purified by column chromatography (SiO2; hexane/EtOAc, 2:1) to
give 2c as a yellow solid (130 mg, 94% yield); m.p. 110–112 °C
(ref.[9] 110–115 °C). 1H NMR (400 MHz, [D6]DMSO): δ = 3.38 (br.
s, 1 H), 6.92 (d, J = 8.0 Hz, 2 H), 8.11 (d, J = 8.0 Hz, 2 H) ppm. 13
C
NMR (100 MHz, [D6]DMSO): δ = 115.8, 126.1, 139.7, 164.0 ppm.
2-Methoxyphenol (2d):[10] Obtained by following the general pro-
cedure for Table 2 using 1-iodo-2-methoxybenzene (0.234 mg,
1.0 mmol), then purified by column chromatography (SiO2;
CH2Cl2) to afford 2d as a colorless oil (95.4 mg, 77% yield). 1H
NMR (400 MHz, CDCl3): δ = 3.85 (s, 3 H), 6.83–6.89 (m, 3 H),
6.91–6.94 (m, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 55.7,
110.7, 114.5, 120.1, 121.3, 145.5, 146.5 ppm.
4-Chlorophenol (2e):[9] Obtained by following the general procedure
for Table 2 using 1-chloro-4-iodobenzene (238.5 mg, 1.00 mmol),
then purified by column chromatography (SiO2; hexane/EtOAc,
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H.-P. Lin, C.-F. Lee et al.
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4:1) to afford 2e as a yellow oil (109 mg, 85% yield). 1H NMR
(400 MHz, CDCl3): δ = 5.14 (br. s, 1 H), 6.76 (d, J = 8.0 Hz, 2 H),
EtOAc, 2:1) to afford 2m as a pink solid (92.4 mg, 68% yield); m.p.
90–91 °C (ref.[21] 90–95 °C). 1H NMR (400 MHz, CDCl3): δ = 2.61
7.18 (d, J = 8.0 Hz, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = (s, 3 H), 7.09–7.13 (m, 1 H), 7.34 (t, J = 8.0 Hz, 1 H), 7.50–7.55
116.6, 125.7, 129.5, 153.8 ppm.
(m, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 26.7, 114.7,
120.8, 121.0, 129.9, 138.4, 155.7, 156.4 ppm.
2,4,6-Trimethylphenol (2f):[6a] Obtained by following the general
procedure for Table 2 using 2-iodo-1,3,5-trimethylbenzene (246 mg,
1.0 mmol), then purified by column chromatography (SiO2; hexane/
EtOAc, 4:1) to afford 2f as a yellow solid (74.9 mg, 55% yield);
2-Hydroxybenzoic Acid (2n):[22] Obtained by following the general
procedure for Table 2 using CsOH/H2O (672 mg, 4.0 mmol) and
2-iodobenzoic acid (248 mg, 1.00 mmol), then purified by column
chromatography (SiO2; CH2Cl2/MeOH, 9:1) to obtain 2n as a col-
orless solid (106 mg, 77% yield); m.p. 149–152 °C (ref.[22] 158–
161 °C). 1H NMR (400 MHz, [D6]DMSO): δ = 6.88–6.95 (m, 2 H),
7.49 (t, J = 8.0 Hz, 1 H), 7.78 (d, J = 8.0 Hz, 1 H) ppm. 13C NMR
(100 MHz, [D6]DMSO): δ = 113.0, 117.2, 119.2, 130.4, 135.7,
161.3, 172.1 ppm.
3-Hydroxybenzoic Acid (2o):[23] Obtained by following the general
procedure for Table 2 using CsOH/H2O (672 mg, 4.0 mmol) and 3-
iodobenzoic acid (248.0 mg, 1.0 mmol), then purified by column
chromatography (SiO2; CH2Cl2/MeOH = 9:1) to give 2o as a yellow
solid (121 mg, 88% yield); m.p. 193–195 °C (ref.[23] 200–203 °C).
1H NMR (400 MHz, [D6]DMSO): δ = 6.97–7.00 (m, 1 H), 7.25 (t,
J = 8.0 Hz, 1 H), 7.36–7.40 (m, 2 H), 9.85 (br. s, 1 H) ppm. 13C
NMR (100 MHz, [D6]DMSO): δ = 116.1, 120.1, 120.3, 129.8,
132.3, 157.6, 167.6 ppm.
4-Hydroxybenzoic Acid (2p):[10] Obtained by following the general
procedure for Table 2 using CsOH/H2O (672 mg, 4.0 mmol) and 4-
iodobenzoic acid (248.0 mg, 1.0 mmol), then purified by column
chromatography (SiO2; CH2Cl2/MeOH, 9:1) to obtain 2p as a yel-
low solid (128 mg, 93% yield); m.p. 201–203 °C (ref.[10] 213-
217 °C). 1H NMR (400 MHz, [D6]DMSO): δ = 6.83 (d, J = 8.4 Hz,
2 H), 7.81 (d, J = 8.4 Hz, 2 H), 11.57 (br. s, 1 H) ppm. 13C NMR
(100 MHz, [D6]DMSO): δ = 115.4, 121.7, 131.9, 161.9, 167.6 ppm.
1
m.p. 67–69 °C (ref.[6a]: 70–72 °C). H NMR (400 MHz, CDCl3): δ
= 2.21 (s, 9 H), 4.10 (br. s, 1 H), 6.78 (s, 2 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 15.8, 20.3, 122.8, 129.1, 129.3, 149.8 ppm.
4-tert-Butylphenol (2g):[19] Obtained by following the general pro-
cedure for Table 2 using 1-tert-butyl-4-iodobenzene (0.18 mL,
1.0 mmol), then purified by column chromatography (SiO2;
CH2Cl2) to afford 2g as a white solid (100 mg, 67% yield); m.p. 96–
98 °C (ref.[19] 96–100 °C). 1H NMR (400 MHz, CDCl3): δ = 1.28 (s,
9 H), 5.75 (br. s, 1 H), 6.77 (d, J = 8.0 Hz, 2 H), 7.23 (d, J = 8.0 Hz,
2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 31.5, 34.0, 114.8,
126.4, 143.6, 152.8 ppm.
3-Methylphenol (2h):[9] Obtained by following the general pro-
cedure for Table 2 using 3-iodotoluene (0.128 mL, 1.0 mmol), then
purified by column chromatography (SiO2; CH2Cl2) to give 2h as
1
a yellow oil (77.3 mg, 72% yield). H NMR (400 MHz, CDCl3): δ
= 2.28 (s, 3 H), 5.07 (br. s, 1 H), 6.62–6.65 (m, 2 H), 6.74 (d, J =
7.2 Hz, 1 H), 7.10 (t, J = 7.2 Hz, 1 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 21.3, 112.3, 116.0, 121.6, 129.4, 139.8, 155.2 ppm.
2-Methylphenol (2i):[9] Obtained by following the general procedure
for Table 2 using 2-iodotoluene (0.10 mL, 1.0 mmol), then purified
by column chromatography (SiO2; CH2Cl2) to give 2i as a yellow
oil (89.5 mg, 83% yield). 1H NMR (400 MHz, CDCl3): δ = 2.23 (s,
3 H), 4.70 (br. s, 1 H), 6.74 (d, J = 7.6 Hz, 1 H), 6.83 (t, J = 7.6 Hz,
1 H), 7.03–7.12 (m, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
15.7, 114.9, 120.7, 123.8, 127.0, 131.0, 153.6 ppm.
2-Ethyl-6-methylphenol (2q):[24] Obtained by following the general
procedure for Table 2 using 2-ethyl-6-methyl iodobenzene
(246.0 mg, 1.00 mmol), then purified by column chromatography
(SiO2; hexane/EtOAc, 9:1) to give 2q as a yellow oil (97.8 mg, 72%
Phenol (2j):[9] Obtained by following the general procedure for
Table 2 using iodobenzene (0.11 mL, 1.00 mmol), then purified by
column chromatography (SiO2; CH2Cl2) to give 2j as a colorless
solid (86.3 mg, 92% yield); m.p. 36–38 °C (ref.[9] 40–42 °C). 1H
NMR (400 MHz, CDCl3): δ = 5.74–5.78 (br. s, 1 H), 6.83 (d, J =
7.6 Hz, 2 H), 6.91 (t, J = 7.6 Hz, 1 H), 7.20 (t, J = 7.6 Hz, 2
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 115.3, 120.9, 129.7,
155.0 ppm.
1
yield). H NMR (400 MHz, CDCl3): δ = 1.22 (t, J = 7.6 Hz, 3 H),
2.23 (s, 3 H), 2.61 (q, J = 7.6 Hz, 2 H), 4.37 (br. s, 1 H), 6.78 (t, J
= 7.6 Hz, 1 H), 6.98 (d, J = 7.6 Hz, 1 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 13.9, 15.8, 23.0, 120.3, 123.0, 126.8, 128.4,
129.2, 151.6 ppm.
Supporting Information (see footnote on the first page of this arti-
cle): TEM image and N2/adsorption desorption isotherm of the
mesoporous silica and the TEM images of the CuO on mesoporous
silica after the fourth reaction cycle.
1,3-Benzenediol (2k):[20] Obtained by following the general pro-
cedure for Table 2 using CsOH/H2O (672 mg, 4.0 mmol) and 3-
iodophenol (220.0 mg, 1.0 mmol), then purified by column
chromatography (SiO2; hexane/EtOAc, 2:1) to give 2k as a white
solid (96.8 mg, 88% yield); m.p. 104–106 °C (ref.[20] 109–112 °C).
1H NMR (400 MHz, [D6]DMSO): δ = 3.41 (s, 1 H), 6.15–6.18 (m,
3 H), 6.90 (t, J = 8.0 Hz, 1 H), 9.16 (s, 1 H) ppm. 13C NMR
(100 MHz, [D6]DMSO): δ = 102.7, 106.4, 129.9, 158.6 ppm.
Acknowledgments
The National Science Council, Taiwan (NSC, 99-2113-M-005-004-
MY2 and NSC95-2113-M-006-011-MY3); the National Chung
Hsing University and Landmark Project of the National Cheng
Kung University are gratefully acknowledged for financial support.
We thank Prof. Fung-E. Hong for sharing his GC–MS instruments.
4Ј-Hydroxyacetophenone (2l):[9] Obained by following the general
procedure for Table 2 using 4Ј-iodoacetophenone (246.0 mg,
1.00 mmol), then purified by column chromatography (SiO2; hex-
ane/EtOAc, 2:1) to give 2l as a white solid (112 mg, 83% yield);
m.p. 102–103 °C (ref.[9] 109–111 °C). 1H NMR (400 MHz, CDCl3):
δ = 2.60 (s, 3 H), 6.97 (d, J = 8.8 Hz, 2 H), 7.92 (d, J = 8.8 Hz, 2
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 26.2, 115.6, 129.4,
131.3, 161.6, 198.9 ppm.
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7292
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Green Catalysts from Industrial Waste Products
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Published Online: October 27, 2011
Eur. J. Org. Chem. 2011, 7288–7293
© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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