Preparation and characterization of multi-walled carbon nanotubes (MWCNTs), functionalized with phosphonic acid (MWCNTs-C-PO3H2) and its application as a novel, efficient, heterogeneous, highly selective and reusable catalyst for acetylation of alcohols, phenols, aromatic amines, and thiols

Article abstract of DOI:10.1007/s13738-013-0339-9

A novel, efficient, heterogeneous, and reusable multi-walled carbon nanotubes (MWCNTs), functionalized with phosphonic acid (MWCNTs-C-PO ₃H₂) has been synthesized. The synthesized CNTs were characterized using some electron microscopic techniques such as scanning electron microscopy (SEM), atomic force microscopy (AFM), Energy dispersive X-ray spectroscopy (EDAX), and also some thermal and spectroscopic methods such as thermogravimetry (TG). The nitrogen adsorption behavior of the MWCNTs-C-PO₃H₂ catalyst was evaluated using the TG instrumentation system at 25°C. The catalyst was applied successfully for highly efficient and selective acetylation of alcohols, phenols, thiols and aromatic amines with acetic anhydride at room temperature under solvent-free conditions. The reusability of the catalyst was checked and the recovered catalyst was reused for five runs without significant loss in activity.

Full text of DOI:10.1007/s13738-013-0339-9

J IRAN CHEM SOC
DOI 10.1007/s13738-013-0339-9
ORIGINAL PAPER
Preparation and characterization of multi-walled carbon
nanotubes (MWCNTs), functionalized with phosphonic acid
(MWCNTs–C–PO H ) and its application as a novel, efficient,
heterogeneous, highly selective and reusable catalyst
3 2
for acetylation of alcohols, phenols, aromatic amines, and thiols
Farzaneh Dehghani
Mohammad Mehdi Doroodmand
•
Ali Reza Sardarian
•
Received: 7 May 2013 / Accepted: 1 September 2013
Ó Iranian Chemical Society 2013
Abstract A novel, efficient, heterogeneous, and reusable
multi-walled carbon nanotubes (MWCNTs), functionalized
with phosphonic acid (MWCNTs–C–PO H ) has been
functionalized CNTs have been applied as a catalyst in
organic synthesis, for example, ([Ni ((OH) -salen)]
2
MWCNTs) was used as a catalyst in oxidation of phenol with
H O [10], oxidation of cyclohexene was catalyzed by ([Mn
3
2
synthesized. The synthesized CNTs were characterized
using some electron microscopic techniques such as scan-
ning electron microscopy (SEM), atomic force microscopy
2
2
((OH) -salen)]MWCNTs) [11], and synthesis of 1,4-Disub-
2
0
stituted 1,2,3-Triazoles via copper(II) complex of 4 -phenyl-
0
0
00
(
AFM), Energy dispersive X-ray spectroscopy (EDAX),
2,2 :6 ,2 -terpyridine on activated multiwall carbon nano-
II
tubes [AMWCNTs–O–Cu –PhTPY] as a catalyst [12].
and also some thermal and spectroscopic methods such as
thermogravimetry (TG). The nitrogen adsorption behavior
of the MWCNTs–C–PO H catalyst was evaluated using
Phosphoric acid and phosphonic acid have recently
attracted much attention because of their high charge carrier
concentration, thermal stability, and oxidation resistance.
More importantly, amphoteric phosphoric/phosphonic
acids, which are advantageous over sulfonic acid, can make
possible proton conduction in the dry state by forming
dynamic hydrogen bond networks [13, 14]. So far, the
functionalization with phosphoric acid has been widely
studied [15–17], but acid leaching by water is problematic
for their applications due to the hydrolytically unstable
linkage O–P of phosphoric acid with silicate or polymer
backbones. To avoid the problem, the use of phosphonic acid
derivatives has been reported [18, 19]. Phosphonic acids are
considered to be a promising proton carrier at intermediate
temperatures (100–150 °C) because of their good proton
donor and acceptor properties. Furthermore, phosphonic
acids have a better thermal stability than sulfonic acid [20,
21]. In this regard, the phosphonic acid functionalization via
hydrolytically stable C–P bond is more attractive.
3
2
the TG instrumentation system at 25 °C. The catalyst was
applied successfully for highly efficient and selective
acetylation of alcohols, phenols, thiols and aromatic
amines with acetic anhydride at room temperature under
solvent-free conditions. The reusability of the catalyst was
checked and the recovered catalyst was reused for five runs
without significant loss in activity.
Keywords MWCNTs–C–PO H ꢀ Heterogeneous
3
2
catalyst ꢀ Reusable catalyst ꢀ Acetylation
Introduction
Functionalization of carbon nanotubes (CNTs) is an effec-
tive way to improve the physical properties and develop the
solubility of CNTs. Some of the functionalization approa-
ches, reported before, have involved the formation of cova-
lent bonds and non-covalent interactions [1–9]. Some
Recently, a few number of phosphonic functionalized
CNTs have been prepared via covalent bond formation, for
example, by reacting fluorinated carbon nanotubes (F-
CNTs) with 3-aminopropylphosphonic acid [22] or p–p
stacking interactions [23, 24]. But there is not any report
about functionalization of CNTs with phosphonic acid
functional group via formation of C–P covalent bond
F. Dehghani ꢀ A. R. Sardarian (&) ꢀ M. M. Doroodmand
Chemistry Department, College of Sciences, Shiraz University,
71454 Shiraz, Iran
e-mail: sardarian@susc.ac.ir
123

J IRAN CHEM SOC
between carbon atoms of CNTs with phosphor atom of
phosphonic acid group. Therefore, because of the inter-
esting features of phosphonic acid functional group [20,
MWCNT–OH [26–28], Then phosphoryl chloride (2.0 mL)
was added to *0.05 g of hydroxy-functionlized MWCNTs
in 25 mL round-bottom flask under nitrogen atmosphere
and the reaction mixture was stirred at room temperature
for 2 h. Water (10 mL) was poured to the resultant mixture
and whole mixture was stirred at room temperature for 1 h
to produce MWCNTs–O–PO H . After centrifuging the
2
1], we decided to synthesize multi-walled carbon nano-
tubes (MWCNTs) functionalized with phosphonic acid via
direct C–P covalent bond (MWCNTs–PO H ) and then
3
2
study its efficiency as a novel heterogeneous Brønsted acid
catalyst in acetylation of hydroxyl groups of alcohols,
phenols, aromatic amines, and thiols, which is the most
commonly transformations used in organic synthesis as an
efficient and inexpensive way for protection of thiol,
amino, alcoholic, and phenolic hydroxyl groups in a mul-
tistep synthetic process [25].
3
2
suspension solution and several washing of solid with
acetone, the synthesized MWCNT–O–PO H was dried in
3
2
vacuum oven at 60 °C for 4 h.
General procedure for acetylation reactions
Alcohol, aniline, phenol or thiol (2.0 mmol) was added to a
solution of acetic anhydride (2.0 mmol) and catalyst
(MWCNTs–C–PO H ) (0.1 mol %, 0.052 g) in a 5 mL
Experimental
3
2
round-bottom flask, which was equipped with a magnetic
stirrer. The reaction mixture was stirred at room tempera-
ture. After completion of the reaction, which was deter-
mined by TLC monitoring (petroleum ether and ethyl
acetate, 70:30), ethanol (5 mL) was added to the residue
and the resultant mixture was stirred at room temperature
for 10 min. Then, the catalyst was separated by centrifuge
and ethanol was evaporated under reduced pressure. The
crud product was purified by column chromatography on
silica gel with petroleum ether and ethyl acetate (70:30) to
give the pure product.
All products were known and their physical and spectro-
scopic data were compared to those of authentic samples.
Chemicals were either prepared in our laboratories or were
purchased from Fluka or Merck. The purity of the products
was determined by TLC on silica gel polygram SIL G/UV
2
54 plates. IR spectra were obtained using a Shimadzu FT-
IR 8300 spectrophotometer. NMR spectra were recorded
on a Bruker Avance DPX-250 (1H-NMR 250 MHz and
1
3C NMR 62.9 MHz) spectrometer in pure deuterated
solvents with tetramethylsilane as an internal standard.
The synthesized CNTs were characterized using some
electron microscopic techniques such as scanning electron
microscopy (SEM, XL-30 FEG SEM, Philips, 20 kV),
atomic force microscopy (AFM, DME-SPM, version
Results and discussion
2
.0.0.9), and also using some thermal and spectroscopic
The CVD techniques were used for the synthesis of
MWCNTs–C–PO H (Fig. 1A). For this purpose, acety-
methods such as thermogravimetry.
3
2
lene with 99 % purity and ferrocene were used as CNT
precurser and catalyst. Iron nanoparticles were librated
in situ from ferrocene and catalyzed MWCNTs formation
in the presence of thiophene as as sulfur precursor for
increasing the length of CNT [29].
Preparation of MWCNTs–C–PO H
3
2
-
1
Acetylene gas with a flow rate of *50 mL min was
bubbled into a sloution containing ferrocene (0.30 g), tri-
phenylphosphine (3.0 g), and thiophene (0.7 mL) in ben-
zene (25 mL). This was mixed with hydrogen and argon
Then phoshorous atom was doped on carbon nano-
structures by the reaction of MWCNTs with triphenyl-
phosphine at 1,300 °C under the atomsphere of hydrogen
and argon in a quartiz tube. Then hydrogen peroxide oxi-
dized the produced phoshore-doped carbon nanostructures
to obtain MWCNs–C–PO H and also simultaneously
-
1
with flow rates to 0.5 and 800 mL min , respectively,
followed by introduction into a quartiz tube passed through
a 80-cm tubing furnace set at 1,300 °C. The produced
phosphore-doped carbon nanostructures were then directly
purified from any amorphous carbon via purging oxygen
and aerosols of hydrogen peroxide into the production line,
followed by on-line activation using ultraviolet (UV) and
microwave irradiators.
3
2
purified it from any amorphous carbon as graphically
shown in Fig. 1B.
Normal distribution of CNTs was evaluated based on
scanning electron microscopy (SEM) and atomic forced
microscopy (AFM) as shown in Fig. 2A, B. Based on the
SEM image (Fig. 2A), the external diameter of the CVD-
synthesized MWCNTs was estimated to 3–8 nm. In addi-
tion, according to the AFM image (Fig. 2B); the width of
the band at half-height of the voltage profile peak (Fig. 2C)
Preparation of MWCNTs–O–PO H
3
2
To synthesize MWCNT–O–PO H2, the CVD-synthesized
3
MWCNTs were initially activated via O treatment to form
3
1
23

J IRAN CHEM SOC
3 2 3 2
Fig. 1 Schematic of CVD-synthesized MWCNTs–C–PO H catalyst (A), and schematic representing the CVD-synthesis of MWCNT–C–PO H
(
B)
3 2
Fig. 3 Residual EDAX spectrum of MWCNTs–C–PO H
This result revealed that there was an acceptable relation
between the weight percentage of phosphor, which was
functionalized on MWCNTs (*4 %), and the result
obtained from the EDAX spectrum (Fig. 3). Also, as it was
shown (Fig. 4A), MWCNTs were completely decomposed
at *750 °C.
3 2
Fig. 2 Characterization of MWCNTs–C–PO H including: SEM
image (A), AFM image (B), and voltage profile image (C)
The nitrogen adsorption behavior of the MWCNTs–C–
PO H catalyst was also evaluated using the TG instru-
3
2
revealed the size of the MWCNTs. This value was in good
agreement with the results obtained from SEM image.
The residual EDAX spectrum indicated that, large
amounts of phosporesous atoms (*4.1 % w/w) were
positioned in the MWCNTs matrix (Fig. 3).
mentation system at 25 °C. According to the nitrogen
adsorption isotherms (Fig. 4B), significant increasing was
2
-1
observed *830 m g in the active surface area of the
MWCNTs when functionalized with –PO group.
H
3 2
Back-titration method was also utilized as an effective
technique for evaluation of the percentage of acidic func-
tional group doped on MWCNTs and characterizing the
structure of MWCNT functionalized by phosphonic acid. For
The thermogram of the MWCNTs–C–PO H samples,
3
2
taken using a home-made thermogravimetric (TG) ana-
lyzer, was also shown in Fig. 4A.
In accordance with the thermogram (Fig. 4A), the sig-
nificant decrease observed in the weight percentage of the
MWCNTs–C–PO H sample (*11.65 %) at 270 °C, was
this propose, initially MWCNTs–O–PO H was synthesized
3 2
by oxidation of MWCNT according to the known procedure
[26–28], phosphorylation of MWCNTs–OH and hydrolysis
3
2
related to the decomposition of –PO H functional group.
of MWCNTs–O–POCl , respectively (Scheme 1).
2
3
2
123

J IRAN CHEM SOC
Fig. 4 Thermogram of MWCNT–PO
H
3 2
(A), and nitrogen adsorption isotherms of MWCNTs and MWCNTs–C–PO
H
3 2
at 25 °C (B)
O3
CH3
OAc
CH3
MWCNTs
OH
MWCNTs
MWCNTs-C-PO H
3
2
OH
Ac O / Solvent/ Temperature
Cl P=O / RT
2
3
2
hr
Scheme2 Acetylation of 1-phenylethanol with acetic anhydride
H O / RT
2
MWCNTs
OPO(OH)2
MWCNTs
OPOCl2
1
hr
Table 1 Acetylation of 1-phenylethanol with acetic anhydride in the
presence of MWCNTs–C–PO
temperature
H
3 2
in different conditions at room
Scheme 1 Schematic representing the CVD-synthesis of MWCNT–
O–PO
3 2
H
a
Catalyst (mol %) Time (min) Yield (%)
Entry Solvent
1
2
3
4
5
6
7
8
9
1
1
a
Solvent-free None
60
20
13
10
10
60
60
20
90
20
60
25
75
87
95
95
50
53
96
90
92
–
Solvent-free 0.05
Solvent-free 0.07
Solvent-free 0.1
Solvent-free 0.15
EtOH
0.1
0.1
0.1
0.1
0.1
0.1
EtOAc
CH
CH
2
Cl
2
3
CN
0
1
CHCl
3
2
H O
Isolated yield
around 3.95 % and a significant change in pH to 5.8 and
.02 was observed for MWCNTs–C–PO H and
MWCNTs–O–PO H compared with the pure MWCNTs,
6
3
2
Fig. 5 FT-IR spectra of MWCNTs–O–PO
C–PO (B)
3 2
H (A), and MWCNTs–
3
2
3 2
H
respectively. Although the phosphorous oxidation number
is five for both compounds, these results revealed stronger
acidity of MWCNTs–C–PO H compared with MWCNTs–
3 2
Then 0.01 g of each pure carbon nanomaterial
MWCNT, MWCNTs–PO H and MWCNTs–O–PO H )
O–PO H . Stronger acidic strength of MWCNTs–C–
3 2
(
3
2
3 2
PO H might be as a direct consequence of the inductive
3 2
was suspended in excess amount of NaOH (0.01 M,
effect of carbon atom [30] and resonance effect of the
oxygen atom attached to phosphorous atom in MWCNTs–
10 mL) and sonicated at a frequency of *500 kHz for
30 min. The carbon nanomaterial was separated by cen-
O–PO H .
3 2
trifugation and the solution was titrated with HCl (0.05 M).
According to the data obtained from this method, the
weight percentage of the acidic group was evaluated to be
For more evidence about the C–P bond formation, the
FT-IR spectra of both MWCNTs–O–PO H and
3
2
1
23

J IRAN CHEM SOC
Table 2 Acetylation of alcohols and phenols to the corresponding esters in the presence of MWCNTs–C–PO
at room temperature
H
3 2
under solvent-free conditions
a
b
Entry
1
Substrate
Product
Time [min]
5
Yield [%]
OAc
OH
97
OH
OAc
OAc
2
3
10
10
92
94
O N
2
O N
2
OH
Cl
Cl
OH
OAc
4
5
95
95
95
95
80
MeO
MeO
OH
OAc
5
6
10
CH3
OH
CH3
OAC
1
0
7
8
10
60
OH
OH
OAc
Cl
O
P
OCHCH3
Cl
O
OCHCH
OCH CH
3
OCH CH
P
2
3
2
3
OAc
H C
H C
3
3
OH
OAc
9
H C
H C
3
3
2
0
80
H C
H C
3
3
123

J IRAN CHEM SOC
Table 2 continued
a
b
Entry
Substrate
Product
Time [min]
90
Yield [%]
OAc
OH
1
1
0
1
85
O N
2
O N
2
OH
OAc
60
90
84
OH
OAc
7
0
1
1
2
3
OAc
OH
c
55
87
83
AcO
HO
OH
OH
OAc
8
5
0
0
c
1
1
1
4
5
6
OAc
OH
OAc
90
87
OH
OAc
65
CH3
CH3
OH
OAc
1
7
60
80
90
85
H C
H C
3
3
OH
OAc
CH3
1
8
CH3
1
23

J IRAN CHEM SOC
Table 2 continued
a
b
Entry
Substrate
Product
Time [min]
60
Yield [%]
OH
OAc
1
9
90
Br
Br
OH
OAc
SAc
6
4
0
0
82
93
2
2
0
1
Cl
Cl
SH
SH
SAc
5
95
95
2
2
2
3
NH2
NHAc
15
NH2
NHAc
2
2
4
5
2
0
90
HO
HO
NC
COOH
COOH
NC
25
95
93
NHAc
NH2
CN
NHAc
CN
NH2
3
0
2
6
123

J IRAN CHEM SOC
Table 2 continued
a
b
Entry
Substrate
Product
Time [min]
Yield [%]
Cl
Cl
2
2
7
8
1
3
5
5
95
NH2
NHAc
O N
O N
2
2
95
NH2
NHAc
Br
Br
2
3
9
0
1
7
5
0
96
75
NH2
NHAc
N
N
H
Ac
a
b
c
1 13
All products were fully characterized by H NMR, C NMR spectra and compared to those of authentic samples
Isolated yield
2
Two equivalent of Ac O were used
MWCNTs–C–PO H2 was studied as shown in Fig. 5.
3
amount of the catalyst. According to the results, shown in
Table 1 (entries 1–5), the model reaction gave only 25 %
yield of the desired product in the absence of the catalyst
after 1 h at room temperature and the highest yield of the
corresponding acetate was produced after 10 min when 0.1
or 0.15 mol % of the catalyst was used (Table 1, entry 4
and 5). Examination of the model reaction in the presence
of 0.1 mol % of the catalyst in different solvents at room
temperature showed that 1-phenylethyl acetate was
obtained more efficiently in dichloromethane compare with
the other solvents (Table 1, entries 6–10) and it did not
proceed at all in water (Table 1, entry 11). According to the
represented results in Table 1, the best efficiency was
observed under solvent-free condition in the presence of
0.1 mol % of the catalyst and at room temperature.
Significant differences were observed in accordance with
the spectra shown in Fig. 5. As clearly revealed in the FT-
IR spectrum of MWCNTs–C–O–PO H2 (Fig. 5A), the
3
-
sharp and strong peak positioned at 1,061 cm is related
1
to the formation of P–O–CH [31]. Also the shoulder situ-
-
1
ated at 1,233.9 cm is related to the P=O bond formation
32]. Whereas, in accordance with the FT-IR spectrum of
MWCNT–C–PO H (Fig. 5B), no absorbance peak is
[
3
2
-
1
observed at absorption regions at around 1,061 cm
,
however, the sharp absorbance peak representing the for-
mation of P=O bond still existed.
After characterization of the catalyst, we decided to
utilize it for acetylation of alcohols and phenols with acetic
anhydride to their corresponding acetate esters.
For optimization of the reaction parameters, we inves-
tigated the ability of MWCNTs–C–PO H for the acety-
Therefore, with the optimized condition in hand, the
scope of method and its versatility on the different type of
alcohols was explored. According to the results, shown in
Table 2, primary alcohols such as benzylic alcohols were
easily acetylated and gave the corresponding acetates in
excellent yields and the data obtained in this way revealed
3
2
lation of 1-phenylethanol with equimolar of acylating
reagent, acetic anhydride, as a model reaction (Scheme 2).
Initially, the reaction was performed under solvent free
condition at room temperature in the presence of different
1
23

J IRAN CHEM SOC
Table 3 Selective acetylation of alcohols, phenols, thiols and aromatic amines by competitive method with MWCNTs–C–PO
free conditions at room temperature
H
3 2
under solvent-
a
b
Entry
Substrate
Product
Time [min]
Yield [%]
10
CH3
OH
CH3
OAc
1
5
OH
OAc
9
0
OH
OAc
9
5
2
5
H C
3
0
H C
3
OAc
H C
OH
3
H C
H C
3
3
H C
3
OAc
OH
0
CH3
OAc
CH3
10
3
OH
9
5
OH
OAc
0
4
5
9
5
OH
OAc
OH
OAc
10
75
5
H C
H C
20
3
3
OH
OAc
H C
H C
3
3
H C
H C
3
3
123

J IRAN CHEM SOC
Table 3 continued
a
b
Entry
Substrate
Product
Time [min]
Yield [%]
1
8
0
7
N
H
N
Ac
6
15
Br
Br
NH2
NHAc
NHAc
NH2
HO
100
0
HO
COOH
COOH
7
25
40
15
NH2
AcO
CO H
2
OH
OAc
SAc
2
7
0
8
8
SH
OH
OAc
SAc
0
SH
9
10
NH2
NHAc
8
8
a
The substrates were treated with Ac
Isolated yield
2
O (1.0 eq)
b
the substituents had no remarkable effect on the acetyla-
tion yield (Table 2, entries 1–4). Also secondary alcohols
smoothly transformed to the desired acetate in excellent
yields (Table 2, entries 6–8), in the presence of the cat-
alyst under solvent-free conditions at room temperature,
except the a-hydroxyphosphonate that was converted to
the related product in longer reaction time and lower yield
According to the summarized data in Table 2, the related
phenyl acetates were obtained in excellent yields from
phenols with both electron-donating and electron-with-
drawing substituents (Table 2, entries 10–20). No com-
petitive Fries rearrangement was observed for phenolic
substrates and in general, acetylation of phenols pro-
ceeded in longer reaction times in comparison with
alcohols.
(
Table 2, entry 8). As a tertiary alcohol, t-butanol was
also carried out the acetylation reaction in excellent yield
after 20 min (Table 2, entry 9). Then, the ability of this
catalyst was investigated in acetylation of phenols.
The ability of this catalyst was also checked in acety-
lation of thiols and the related products were obtained in
excellent yields (Table 2, entries 21and 22).
1
23

J IRAN CHEM SOC
3 2
Table 4 Comparison between different acid catalysts with MWCNTs–C–PO H for acetylation of benzyl alcohol with acetic anhydride
Entry
Catalyst (Mol %)
Reaction conditions
Time [min]
Yield [%]
Ref.
1
2
3
4
5
6
7
8
9
MWCNTs–C–PO
3
H
2
(0.1 mol %)
RT/Solvent-free, 1 eq Ac
2
O
5
97
97
–
Mn (haacac) Cl)] (5 mol %)
TiCl (OTf) (1 mol %)
Sn (IV) (tpp) (BF (1 mol %)
MoO /Al (5 mol %)
Ce (OTf) (1.0 mol %)
Mg(ClO (1 mol %)
14[NaP 110] (o.1 mol %)
tin porphyrin–hexamolybdate (1 mol %)
30 °C/Solvent-free, 1.5 eq Ac
2
O
300
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[41]
a
3
RT/Solvent-free, 1 eq Ac
RT/CH CN, 2 eq Ac
RT/Solvent-free, 2 eq Ac
RT/CH CN, 1.5 eq Ac
RT/Solvent-free, 1 eq Ac
2
O
O
O
Im.
96
4
)
2
3
2
O
1
99
3
2
O
3
2
20
15
15
75
4
99
3
2
O
98
4
)
2
2
100
98
H
5 30
W O
2
RT/Solvent-free, 1.5 eq Ac O
(
IV)
RT/CH
RT/CH
3
CN, 2 eq Ac
CN, 3 eq Ac
2
O
O
100
90
IV
[V (TPP)(OTf)
1
0
2
] (0.5 mol %)
3
2
0.5
a
Immediately
(Table 3, entries 3–50. The results were shown –SH group
in thiophenol can be highly selective acetylated in the
presence of –OH group in phenols (Table 3, entry 8). Also
primary amino group can be highly selective acetylated in
the presence of –OH group in phenols and –SH group in
thiophenol (Table 3, entries 7 and 9) and secondary amines
(Table 3, entry 6).
Comparing efficiency of MWCNTs–C–PO H with
2
3
some of the reported catalysts in the literature showed
superiority of this free metal and heterogeneous catalyst, at
least concerning the amount of catalyst and acetic anhy-
dride used in the acetylation of benzyl alcohol (Table 4).
For checking the reusability of the catalyst, the reaction
of 1-phenylethanol with acetic anhydride was carried out
using 0.1 mol % MWCNTs–C–PO H in a 10 mmol scale.
3 2
Fig. 6 Reuse of MWCNTs–C–PO H for acetylation of 1-phenyl-
ethanol with acetic anhydride
3
2
After completion of the reaction, the catalyst was recov-
ered by centrifuge and dried under air. Then the dried
catalyst was reused for five successive reactions without
further purification and considerable loss in catalyst
activity, Fig. 6.
Also we examined the ability of this catalyst in acety-
lation of aromatic amines such as aniline and substituted
anilines with different electron-withdrawing groups such as
CN, NO , Cl, Br, and COOH (Table 2, entries 23–30).
2
According to the summarized data in Table 2, the related
amides were obtained in excellent yields. Also diphenyl-
amine, as a secondary amine, was transformed to the
desired amide in good yield in the presence of the catalyst
under solvent-free conditions at room temperature
Conclusions
(
Table 2, entry 30).
In this study, efficient, free metal, heterogeneous, and
reusable multi-walled carbon nanotubes (MWCNTs),
functionalized with phosphonic acid (MWCNTs–C–
PO H ) have been synthesized and applied successfully
Selective acetylation of alcohols, phenols, thiols, and
aromatic amines was also examined by competitive method
Table 3). Therefore, one equivalent of each substrate was
(
3
2
mixed and then the acetylation reaction was run in the
presence of 0.1 mol % of MWCNTs–C–PO H and one
for highly efficient and selective acetylation of phenolic
hydroxyl groups, and different classes of alcohols, aro-
matic amines and thiols with acetic anhydride under
solvent-free conditions and at room temperature with easy
work up.
3
2
equivalent of acetic anhydride at room temperature under
solvent-free conditions. The data obtained in this way
revealed primary alcohols can be highly selective acety-
lated against secondary and tertiary alcohols (Table 3,
entries 1 and 2). Also, it was possible to do selective
acylation of all types of alcohols in the presence of phenols
Acknowledgments We are grateful to research council of Shiraz
University for the financial support of this work.
123

J IRAN CHEM SOC
References
20. E. Parcero, R. Herrera, S.P. Nunes, J. Membr. Sci. 285, 206
(
2006)
1. M. Schuster, T. Rager, A. Noda, K.D. Kreuer, J. Maier, Fuel Cells
, 355 (2005)
2. A. Oki, L. Adams, V. Khabashesku, Y. Edigin, P. Biney, Zh Luo,
Materials Lett. 62, 918 (2008)
3. P. Li, H. Liu, Y. Ding, Y. Wang, Y. Chen, Y. Zhou, Y. Tang, H.
Wei, Ch. Cai, T. Lu, J. Mater. Chem. 22, 15370 (2012)
4. M. Zheng, P. Li, G. Fu, Y. Chen, Y. Zhou, Y. Tang, T. Lu, Appl.
Catal. B 129, 394 (2013)
5. T.W. Greene, P.G.M. Wutz, Protective Groups in Organic Syn-
thesis, 2nd edn. (Wiley, New York, 1991), p. 50
2
2
2
2
2
2
2
2
2
1
. J.L. Bahr, J. Yang, D.M. Kosynkin, M.J. Bronikowski, R.E.
Smalley, J.M. Tour, J. Am. Chem. Soc. 123, 6536 (2001)
. F. Pompeo, D. Reasaco, Nano Lett. 2, 369 (2002)
. C.A. Dyke, J.M. Tour, Nano Lett. 3, 1215 (2003)
. M.S. Strano, C.A. Dyke, M.L. Usrey, P.W. Barone, M.J. Allen,
H. Shan, C. Kittrell, R.H. Hauge, J.M. Tour, R.E. Smalley, Sci-
ence 301, 1519 (2003)
5
2
3
4
5
. J. Chen, A.M. Rao, S. Lyuksyutov, M.E. Itkis, M.A. Hamon, H.
Hu, R.W. Cohn, P.C. Eklund, D.T. Colbert, R.E. Smalley, R.C.
Haddon, J. Phys. Chem. 105, 2525 (2001)
6. D.B. Mawhinney, V. Naumenko, A. Kuznetsova, J.T. Yates, J.
Liu, R.E. Smalley, J. Am. Chem. Soc. 122, 2383 (2000)
7. L.T. Cai, J.L. Bahr, Y.X. Yao, J.M. Tour, Chem. Mater. 14, 4235
6
. M.C. O’Connell, P. Boul, L.M. Ericson, C. Huffman, Y. Wang,
E. Haroz, C. Kuper, J. Tour, K.D. Ausman, R.E. Smalley, Chem.
Phys. Lett. 342, 265 (2001)
(
2002)
7
8
9
. D. Chattopadhyay, S. Lastella, S. Kim, F. Papadimitrikapoulos, J.
Am. Chem. Soc. 124, 728 (2002)
. D. Chattopadhyay, I. Galeska, F. Papadimitrikapoulos, J. Am.
Chem. Soc. 125, 3370 (2003)
. N. Karousis, N. Tagmatarchis, D. Tasis, Chem. Rev. 110, 5366
8. H. Kuzmany, A. Kukovecz, F. Simon, M. Holzwebe, Ch.
Kramberger, T. Pichler, Synth. Met. 141, 113 (2004)
9. Zhu Hongwei, Ci Lijie, Xu Cailu, Ji Liang, Wu Dehai, Diam.
Relat. Mater. 11, 1349 (2002)
30. L.D. Freeman, G.O. Doak, Chem. Rev. 57, 479 (1959)
31. X. Lu, J. Zhu, J. Huang, X. Tao, J. Mol. Catal. 41, 235 (1987)
32. J. Zhu, X. Lu, J. Chem. Soc. Commun. 17, 1318 (1987)
33. M. Salavati-Niasari, S. Hydrazadeh, A. Amiri, S. Salavati, J. Mol.
Catal. A: Chem. 231, 191 (2005)
(
2010)
0. M. Salavati-Niasari, M. Bazarganipour, Appl. Surf. Sci. 255,
963 (2008)
1. M. Salavati-Niasari, S.N. Mirsattari, M. Bazarganipour, Polyhe-
dron 27, 3653 (2008)
1
1
1
1
2
3
3
4. H. Firouzabadi, N. Iranpoor, S. Farahi, J. Mol. Catal. A: Chem.
2
5. M. Moghadam, Sh Tangestaninejad, V. Mirkhani, I. Moham-
madpoor-Baltork, S. Abdolmanaf Taghavi, J. Mol. Catal. A:
Chem. 274, 217 (2007)
2. H. Sharghi, S. Ebrahimpourmoghaddam, M.M. Doroodmand, A.
Purkhosrow, Asian J. Org. Chem. 1, 377 (2012)
89, 61 (2008)
3. H. Steininger, M. Schuster, K.D. Kreuer, A. Kaltbeitzel, B.
Bingol, W.H. Meyer, S. Schauff, G. Brunklaus, J. Maier, H.W.
Spiess, Phys. Chem. Chem. Phys. 9, 1764 (2007)
4. B. Lafitte, P. Jannasch, in Advances in Fuel Cells, ed. by T.S.
Zhao, K.D. Kreuer, T.V. Nguyen (Elsevier, Amsterdam, 2007),
p. 120
3
3
6. A.K. Chakraborti, R. Gulhane, Tetrahedron Lett. 44l, 3521 (2003)
7. R. Dalpozzo, A. De Nino, L. Maiuolo, A. Procopio, M. Nardi, G.
Bartoli, R. Romeo, Tetrahedron Lett. 44, 5621 (2003)
8. K. Chakraborti, L. Sharma, R. Gulhane, Shivani, Tetrahedron 59,
1
3
3
4
4
1
1
1
1
5. M. Nogami, R. Nagao, G. Wong, T. Kasuga, T. Hayakawa, J.
Phys. Chem. B. 103, 9468 (1999)
6. Y. Nishiyama, K. Ochi, N. Nishiyama, Y. Egashira, K. Ueyama,
Electrochem. Solid-State Lett. 11, 86 (2008)
7. M. Yoshizawa-Fujita, K. Fujita, M. Forsyth, D.R. MacFarlane,
Electrochem. Commun. 9, 1202 (2007)
8. H. Steininger, M. Schuster, K.D. Kreuer, A. Kaltbeitzel, B.
Bingol, W.H. Meyer, S. Schauff, G. Brunklaus, J. Maier, H.W.
Spiess, Phys. Chem. Chem. Phys. 9, 1764 (2007)
9. M. Schuster, K.D. Kreuer, H. Steininger, J. Maier, Solid State
Ionics 179, 523 (2008)
7
661 (2003)
9. M.M. Heravi, F.K. Behbahani, F.F. Bamoharram, J. Mol. Catal.
A: Chem. 253, 16 (2006)
0. M. Araghi, V. Mirkhani, M. Moghadam, Sh Tangestaninejad, I.
Mohammdpoor-Baltork, Dalton Trans. 41, 11745 (2012)
1. S.A. Taghavi, M. Moghadam, I. Mohammadpoor-Baltork, Sh
Tangestaninejad, V. Mirkhani, A.R. Khosropour, Inorg. Chim.
Acta 377, 159 (2011)
1
1
23