Direct synthesis of nitriles from aldehydes and hydroxylamine hydrochloride catalyzed by a HAP@AEPH2-SO3H Nanocatalyst

Article abstract of DOI:10.1071/CH16126

We describe an efficient method for the direct preparation of nitriles from aldehydes and hydroxylamine hydrochloride catalyzed by sulfonated nanohydroxyapatite functionalized by 2-aminoethyl dihydrogen phosphate (HAP@AEPH2-SO3H) as an eco-friendly and recyclable solid acid nanocatalyst. In this protocol the use of a solid acid nanocatalyst provides a green, useful, and rapid method for the preparation of nitriles in excellent yields. In addition, the notable feature of this methodolgy is that the synthesized nanocatalyst can be recovered and reused five times without any noticeable loss of efficiency.

Full text of DOI:10.1071/CH16126

CSIRO PUBLISHING
Aust. J. Chem.
Full Paper
http://dx.doi.org/10.1071/CH16126
Direct Synthesis of Nitriles from Aldehydes
and Hydroxylamine Hydrochloride Catalyzed
by a HAP@AEPH -SO H Nanocatalyst
2
3
A
A
,
B
A
Samane Memar Masjed, Batool Akhlaghinia,
and Nasrin Razavi
Monireh Zarghani,
A
A
Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad,
Mashhad 9177948974, Iran.
B
Corresponding author. Email: akhlaghinia@um.ac.ir
We describe an efficient method for the direct preparation of nitriles from aldehydes and hydroxylamine hydrochloride
catalyzed by sulfonated nanohydroxyapatite functionalized by 2-aminoethyl dihydrogen phosphate (HAP@AEPH2-
SO H) as an eco-friendly and recyclable solid acid nanocatalyst. In this protocol the use of a solid acid nanocatalyst
3
provides a green, useful, and rapid method for the preparation of nitriles in excellent yields. In addition, the notable feature
of this methodolgy is that the synthesized nanocatalyst can be recovered and reused five times without any noticeable loss
of efficiency.
Manuscript received: 2 March 2016.
Manuscript accepted: 15 May 2016.
Published online: 14 June 2016.
Introduction
the development of a simple, highly efficient, and catalytic
process is still in great demand.
Nitriles, as a key constituent in various natural products, are
important starting materials in chemical and pharmaceutical
industries, and have been widely used in the production
of valuable compounds such as polymers, agrochemicals,
In recent years, solid acid catalysts, which play a significant
role in the development of clean technologies, have attracted
increasing interest and been successfully used in a variety of
[
1]
[25]
pharmaceuticals, and dyes. In addition, they serve as useful
precursors in the synthesis of many magnificent functional
catalytic reactions.
As compared with traditional liquid
acids, solid acid catalysts have many advantages such
as efficiency, operational simplicity, easy recyclability, non-
corrosive nature, and environmental friendliness. To the best of
our knowledge, the employment of solid acids in the synthesis of
[
2]
[3]
compounds such as amides, carboxylic acids, amines,
[4]
[
5]
[6]
[7]
ketones, esters, and heterocycles. Up to now, a large
number of synthetic protocols for the preparation of nitriles have
[8]
[26]
been developed, including the hydrocyanation of alkenes,
[
the Sandmeyer reaction of diazonium salts, the Rosenmund–
nitriles has been poorly exploited in the past. So it is of great
practical importance to develop a more efficient and environ-
mentally benign method for this synthesis.
9]
[
10]
von Braun reaction of aryl halides,
synthesis.
and the Kolbe nitrile
Other alternative methods for the synthesis of
[11]
Previously, we successfully synthesized sulfonated nano-
hydroxyapatite functionalized by 2-aminoethyl dihydrogen
phosphate (HAP@AEPH -SO H) as a new, green hetero-
these compounds involve the one-step conversion of aldehydes
into nitriles, which is one of the most efficient and cleanest
routes for this transformation.
studies on the preparation of nitriles from aldehydes have
received much attention and several methods are reported in
the literature, which include using trichloroisocyanuric acid
2
3
[
12]
During the past decades,
geneous nanocatalyst by modification of nanohydroxyapatite
with 2-aminoethyl dihydrogen phosphate (AEPH ) (as a new
2
bifunctional organic molecule) and then sulfonating with
[
27]
chlorosulfonic acid.
sized nanocatalyst was initially used for the synthesis of
The catalytic activity of the synthe-
[
13]
[14]
[15]
[16]
(
(
(
TCCA),
[
dry alumina,
Ag nanoparticles (NPs),
FeCl3,
graphite, zinc oxide
[BMIM(SO H)][OTf]
17]
[18]
0
ZnO),
4,4 -(aryl methylene)bis(1H-pyrazol-5-ol) derivatives with
good to excellent yields. After that, the catalytic use of the
HAP@AEPH -SO H nanocatalyst was extended to the direct
3
[
19]
BMIM ¼ 1-butyl-3-methyl-imidazolium),
acetohydroxamic
[22]
[20]
[21]
acid/Bi(OTf) , CuO NPs, CeCl ꢀ7H O/KI/H O , triflic
3
3
2
2
2
2
3
[23]
[24]
[28]
acid, and electrochemical methods. However, earlier syn-
thetic methods suffered from one or more of the following
drawbacks: the use of strong acids or bases or oxidants, prolonged
reaction time, low yield, requirement of excess reagents/catalysts,
laboriouswork-up procedures, orharsh reaction conditions. Thus,
esterification of carboxylic acids with alcohols.
As
expected, the desired products (esters) were obtained in high
yields. So, prompted by these findings and in continuation of
our studies on the development of novel and efficient hetero-
[
29]
geneous catalysts in the synthesis of organic compounds,
Journal compilation � CSIRO 2016
www.publish.csiro.au/journals/ajc

B
S. M. Masjed et al.
O
HAP@AEPH -SO H
2
3
NH OH·HCl
R
CN
ꢀ
H
2
Dry DMF, 120ꢁC
R
R ꢂ C H , 4-(OH)C H , 2-(OH)C H , 4-(OMe)C H , 3-(OMe)C H , 4-(OEt)C H ,
6
4
6
4
6
4
6
4
6
4
6 4
i
4
-(Me)C H , 2-MeC H , 4-(Pr)C H , 4-(Me N)C H , 4-(Cl)C H , 2,6-(Cl) C H ,
6 4 6 4 6 4 2 6 4 6 4 2 6 3
4
-(Br)C H , 4-(NO )C H , 4-(CN)C H , 2-pyridyl, 3-pyridyl, 2-Thiophene, 1-naphtyl,
6
4
2
6
4
6 4
CH (CH ) CH , CH (CH ) CH , (CH ) CH-CH .
3
2 3
2
3
2 6
2
3 2
2
O
O
O
P
NHSO H
3
O
O
Cat:
O
P
NHSO H
3
O
O
O
O
n a n o H A P
P
NHSO H
3
O
O
HAP@AEPH -SO H
2
3
Scheme 1. Direct preparation of nitriles from aldehydes and hydroxylamine hydrochloride catalyzed
by HAP@AEPH -SO
2
3
H nanocatalyst.
(a)
(b)
3800
3300
2800
2300
1800
1300
800
300
Wavenumbers [cmꢃ1
]
Fig. 1. FT-IR spectrum of (a) HAP@AEPH and (b) HAP@AEPH -SO H.
2 3
2
herein, we report the application of HAP@AEPH -SO H as a
3
The FT-IR spectra of HAP@AEPH and HAP@AEPH -
2 2
2
reusable solid acid nanocatalyst to the efficient synthesis of
nitriles from aldehydes and hydroxylamine hydrochloride
SO H are shown in Fig. 1. As can be seen from Fig. 1a, the
3
ꢁ
stretching and bending vibrations of the OH ion in hydroxy-
ꢁ1
(
Scheme 1).
apatite were detected around 3572 and 630 cm respectively.
ꢁ1
Also, the broad band at 3450–3050 cm (due to stretching
vibration) and the weak band at 1637–1630 cm
ꢁ1
(due to
bending vibration) were attributed to the crystal water and
surface adsorbed water. Additional vibrational modes at 1098,
Results and Discussion
Characterization of the Nanocatalyst
The HAP@AEPH -SO H nanocatalyst was synthesized
ꢁ1
1031, 962, 601, 571, and 471 cm could be ascribed to the
asymmetric, symmetric stretching, and bending vibrations of
2
3
[
27]
according to the procedure reported in our previous study.
3
the PO4 ions respectively.
ꢁ
[30]
The structure and morphology of the prepared nanocatalyst was
characterized by the following techniques: FT-IR spectroscopy,
X-ray powder diffraction (XRD), scanning electron microscopy
Successful functionalization
of the nanoHAP with AEPH was evidenced by the absorption
2
ꢁ
1
bands at 2917 and 2851cm
due to the asymmetric and
[31]
(SEM), transmission electron microscopy (TEM), thermogravi-
symmetric vibrational frequencies of –CH (Fig. 1a). In the
FT-IR spectrum of HAP@AEPH -SO H (Fig. 1b), the intensity
of the absorption bandat 3450–3050cm was increased because
of the presence of more OH groups which appeared after
sulfonation. In addition, two new absorption bands appeared
2
metric analysis (TGA), differential thermal analysis (DTA),
elemental analysis (CHN), and Brunauer–Emmett–Teller (BET)
surface area analysis which confirmed the successful preparation
2
3
ꢁ
1
[27,28]
of the new nanocatalyst.

Direct Synthesis of Nitriles from Aldehydes
C
(211)
(201) (002)
(300)
(213)
(202) (310) (222)
(004)
(
b)
a)
(
10
20
30
40
50
60
70
80
2q [deg.]
Fig. 2. The XRD patterns of (a) HAP@AEPH
2
2 3
and (b) HAP@AEPH -SO H.
ꢁ
1
[38]
embedded via AEPH on the surface of nanoHAP. From
the change of weight percentage in the TGA thermogram, it can
at 1325 and 1155 cm , which were ascribed to the asymmetric
32]
2
[
and symmetric stretching frequencies of S¼O. These results
revealed that the modified nanoHAP were functionalized by
–
be estimated that the amount of AEPH and sulfonic acid
2
SO H groups successfully.
3
functionalized into the surface of the catalyst are ,5.60 and
8.00 % respectively.
In addition to structural confirmation and TGA, quantitative
XRD measurements were used to identify the crystalline
structure of HAP@AEPH and HAP@AEPH -SO H. As shown
in Fig. 2, characteristic peaks ((002), (211), (300), (202), (310),
2
2
3
determination of AEPH and sulfonic acid onto the surface of
2
(222), (213) and (004)) were observed for both samples. These
peaks are consistent with the JCPDS file (PDF No. 74-0565)
nanoHAP were performed by elemental analysis (Table 1).The
elemental analysis of the catalyst showed that 1.008 mmol of
AEPH and 1.040 mmol of sulfonic acid are incorporated into
[
33]
and reveal that the resultant nanoparticles were nanoHAP with a
hexagonal phase. It is also observed that the modification of the
nanoHAP with AEPH and chlorosulfuric acid did not result in a
2
1.000 g of HAP@AEPH -SO H. Notably, the obtained results
2
3
from elemental analysis of the nanocatalyst are in good agree-
ment with the results obtained from TGA.
The amount of acidic sites in HAP@AEPH -SO H was also
2
phase change of the nanoHAP.
Although XRD analysis of the HAP@AEPH -SO H showed
2
3
2
3
no considerable broadening or shifting of peaks when compared
with the XRD of HAP@AEPH (Fig. 2), an additional peak
determined by back-titration analysis of the catalyst: 100 mg of
catalyst was added to a solution of NaOH (15 mL, 0.1 N). The
resulting suspension was maintained at room temperature over-
night under stirring. After that, the suspension was filtered. The
filtrate was neutralized by a standard solution of HCl (0.1 M).
The consumed volume of HCl (14.1 mL) determined the amount
of loaded NHSO H per 1.000 g of HAP@AEPH -SO H
2
observed in the HAP@AEPH -SO H pattern at 2y ¼ 25.48 could
2
3
be attributed to a small impurity of CaSO due to sulfonation
4
[
34]
(
JCPDS: 37-1496) (Fig. 2b).
SEM and TEM were used to obtain direct information about
the structure and morphology of the HAP@AEPH -SO H NPs.
2
3
3
2
3
From the SEM images shown in Fig. 3a, b, HAP@AEPH -SO H
2
(0.900 mmol of NHSO H per 1.000 g of nanocatalyst). This
3
3
NPs have a uniform nanorod morphology which is similar to
result is in good agreement with those of the results obtained
from TGA and elemental analysis.
[35]
the particle morphology reported elsewhere.
Fig. 3c, d show the TEM images of the HAP@AEPH -SO H
In addition,
The nitrogen adsorption–desorption isotherm of the
HAP@AEPH -SO H demonstrates the average surface area,
pore volume, and pore size of the HAP@AEPH -SO H.
2
3
NPs. It was found that the synthesized NPs are rod in shape with
a mean size range of 10–100 nm. Obviously, there was no
essential change in the nanoHAP morphology after being
2
3
2
3
In comparison with the literature, the surface area of
HAP@AEPH -SO H is a little smaller than the pure HAP
[
36]
functionalized with AEPH and sulfonic acid.
2
2
3
[
39]
TGA of the nanoparticles was also used to determine the
content of organic functional groups of the sample (Fig. 4).
For HAP@AEPH , weight loss at temperatures below 2008C
NPs (Table 2).
Catalytic Synthesis of Nitriles
2
(4.00 %) is attributed to the physically adsorbed water on the
catalyst surface. Also, the weight loss of the nanocatalyst in the
In continuation of our recent studies on the application of the
HAP@AEPH -SO H nanocatalyst in the development of
2
3
[
27,28]
range of 200 to 5008C is related to the thermal decomposition of
AEPH anchored on the surface of nanoHAP (Fig. 4a).
useful synthetic methodologies,
that uses HAP@AEPH -SO H as a green and efficient solid
we now show a protocol
[
37]
The
TGA thermogram of HAP@AEPH -SO H (Fig. 4b) shows three
2
2
3
acid nanocatalyst for direct preparation of nitriles from alde-
hydes and hydroxylamine hydrochloride (Scheme 1). In an
endeavour to start our present investigation, the reaction of
4-methoxybenzaldehyde and hydroxylamine hydrochloride
2
3
weight loss steps. The initial weight loss up to 2008C is due to
absorbed water, the second step involves the decomposition of
AEPH which started after 2008C and continued up to 5008C.
2
The last step can be observed between 500 and 8508C, corre-
sponding to the thermal decomposition of SO H groups
(NH OHꢀHCl) was chosen as a model reaction for optimizing
2
the reaction conditions (Table 3).
3

D
S. M. Masjed et al.
(a)
(b)
40 nm
(c)
(d)
100 nm
2 3 2 3
Fig. 3. (a, b) SEM images of HAP@AEPH -SO H. (c, d) TEM images of HAP@AEPH -SO H.
DrTGA
TGA
[
mg minꢃ1]
[
%]
100.0
0.05
(
a)
b)
90.0
80.0
70.0
60.0
50.0
(
0
337.15ꢁC
762.25ꢁC
1
12.07ꢁC 316.24ꢁC
5
2.67ꢁC
TGA HAP@AEPH2
DTA HAP@AEPH2
TGA HAP@AEPH -SO H
ꢃ0.05
2
3
DTA HAP@AEPH -SO H
2
3
0
200.0
400.0
600.0
800.0
1000.0
Temperature [ꢁC]
Fig. 4. The TGA/DTA thermograms of (a) HAP@AEPH
2
2 3
and (b) HAP@AEPH -SO H.
In the absence of any catalyst at 1208C, no reaction occurred
HAP@AEPH -SO H as a solid acid nanocatalyst has been
2 3
after 24 h (Table 3, entry 1), while 4-methoxybenzonitrile can
be obtained in 98 % yield when 8 mol-% of HAP@AEPH2-
SO H was used as catalyst (Table 3, entry 2).The role of
further confirmed when a similar reaction was carried out in
the presence of HAP NPs and HAP@AEPH NPs (Table 3,
entries 3 and 4). It was observed that the desired product was
2
3

Direct Synthesis of Nitriles from Aldehydes
E
2 2 3
Table 1. TGA and elemental analysis data of HAP@AEPH and HAP@AEPH -SO H
ꢁ
1
ꢁ1
Elemental analysis [w/w % (mmol g )]
Samples
TGA [% (mmol g )]
AEPH
H
2
O
2
SO
3
H
C
N
S
HAP@AEPH
HAP@AEPH
2
4.000 (2.200)
4.000 (2.200)
5.600 (1.010)
5.600 (1.010)
–
2.409 (1.004)
2.419 (1.008)
1.397 (1.000)
1.409 (1.007)
–
2
3
-SO H
8.000 (1.065)
3.32 (1.040)
2 3
Table 2. BET surface area, pore volume and pore size of HAP@AEPH -SO H
2
ꢁ1
3
Pore volume [cm g
ꢁ1
Sample
Morphology
Nanoparticle
S
BET [m g
]
]
Pore size [nm]
12.011
HAP@AEPH
2
3
-SO H
130.2
0.391
2
Table 3. Direct conversion of 4-methoxybenzaldehyde into 4-methoxybenzonitrile in the presence of HAP@AEPH -
3
SO H nanocatalyst under different reaction conditions
Entry
Catalyst
Solvent
Molar ratio
Temperature
Time
[min]
Isolated
[
mol-%]
(4-methoxybenzaldehyde/
[8C]
yield [%]
NH
2
OHꢀHCl)
1
2
–
8
8
8
10
6
8
8
8
8
8
8
8
8
8
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMSO
1 : 5
1 : 5
1 : 5
1 : 5
1 : 5
1 : 5
1 : 5
1 : 4
1 : 3
1 : 2
1 : 3
1 : 3
1 : 3
1 : 3
1 : 3
120
120
24 h
45
20
98
40
40
98
70
80
98
98
80
20
70
75
50
30
A
3
120
24
B
4
120
24
5
6
7
8
9
120
40
120
45
110
45
120
45
120
45
10
11
12
13
14
15
120
45
120
2 h
8 h
4 h
2 h
9 h
H
2
O
Reflux
Reflux
Reflux
Reflux
THF
CH
CH
3
CN
Cl
2
2
A
B
The reaction was performed in the presence of HAP NPs.
2
The reaction was performed in the presence of HAP@AEPH NPs.
scarcely obtained (40 %). In order to optimize the reaction
conditions, different amounts of catalyst were first examined
on the model reaction. As shown in Table 3, a further increase in
the amount of catalyst has no significant effect on the yield or
reaction time (Table 3, entry 5), whereas decreasing the amount
of HAP@AEPH -SO H nanocatalyst led to a lower yield of the
desired product (Table 3, entry 6). An attempt was also made to
catalyse the reaction at lower temperature but the outcome was
not promising (Table 3, entry 7). The effect of different molar
Consequently, the optimal reaction conditions have been iden-
tified: applying a 1 : 3 molar ratio of 4-methoxybenzaldehyde/
NH OHꢀHCl at 1208C, inthepresence of8 mol-% HAP@AEPH -
2
2
SO H nanocatalyst.
3
Encouraged by our initial studies, we next explored the
generality and scope of the protocol using a series of structurally
different aldehydes under the optimized reaction conditions
(Table 3, entry 9). The results are displayed in Table 4. From
this table, it is clear that all reactions afforded the corresponding
products in moderate to high yields irrespective of the electronic
nature of the aldehydes (Table 4, entries 1–22). Aromatic
aldehydes bearing an electron-donating group afford the corres-
ponding products rapidly in high yields (Table 4, entries 2–10).
In contrast, the reaction of aromatic aldehydes with electron
2
3
ratios of 4-methoxybenzaldehyde/NH OHꢀHCl on the reaction
2
rate was also investigated. It can be seen that a decrease in molar
ratio from 1 : 5 to 1 : 3 has no effect on the reaction yield (95 %)
(
1
(
Table 3, entries 8, 9). However, reducing the molar ratio from
: 3 to 1 : 2 was accompanied by a considerable drop of yield
Table 3, entry 10). In addition, the reaction was carried out in
withdrawing substituents such as –Cl, –Br, –NO , and –CN,
2
different solvents. Among the various solvents tested, DMF was
found to be the best solvent giving a maximum yield of the
desired product in a short reaction time. As shown in Table 3,
in the reactions employing DMSO, H O, THF, CH CN, and
require longer reaction times to proceed properly (Table 4,
entries 11–15). Moreover, it should be noted that the ortho-
substituted aldehydes render lower yields (Table 4, entry 3, 8, 12)
due to the steric hindrance. In our study, to expand the scope
of this methodology, a series of hetero-arylaldehydes were
employed to react with hydroxylamine hydrochloride under the
optimized conditions. The desired products were obtained in
2
3
CH Cl as solvents, the reactions did not progress efficiently and
2
2
low yields of the corresponding product were obtained
even after a long reaction time (Table 3, entries 11–15).

F
S. M. Masjed et al.
Table 4. Direct conversion of various aldehydes into nitriles in the presence of HAP@AEPH
under optimized reaction conditions
2 3
-SO H nanocatalyst
O
HAP@AEPH -SO H
2
3
NH OH·HCl
R
CN
ꢀ
H
2
R
Dry DMF, 120ꢁC
Entry
1
Aldehyde
O
Product
Time [min]
120
Isolated yield [%]
75
CN
H
2
3
4
5
45
90
45
90
96
92
98
92
O
CN
H
HO
HO
O
CN
OH
H
OH
O
CN
H
MeO
MeO
O
CN
H
OMe
OMe
6
7
8
45
60
98
95
85
O
O
CN
H
H
EtO
Me
EtO
Me
CN
120
O
CN
Me
H
Me
O
9
100
90
CN
H
1
0
1
60
97
88
O
CN
H
Me N
2
Me N
2
1
120
O
CN
H
Cl
Cl
(Continued)

Direct Synthesis of Nitriles from Aldehydes
G
Table 4. (Continued)
Entry
Aldehyde
Product
Time [min]
180
Isolated yield [%]
80
12
Cl
O
Cl
CN
H
O
Cl
Cl
1
1
3
4
120
180
88
70
CN
H
Br
Br
O
O
CN
H
O N
2
O N
2
1
5
120
72
CN
H
NC
NC
1
1
6
7
180
120
75
90
O
CN
N
H
N
O
H
N
CN
N
1
1
8
9
120
120
85
85
O
H
H
CN
S
S
O
CN
20
100
95
O
CN
H
2
2
1
2
120
180
80
75
O
CN
H
O
CN
H
admirable yields but in longer reaction times due to the electron
withdrawing effect of the heteroatom on the aromatic ring
an efficient solid acid nanocatalyst for direct synthesis of nitriles
from aldehydes with hydroxylamine hydrochloride.
(
Table 4, entries 16–18).
The catalyst was also efficient in the conversion of
-naphthylaldehyde to the corresponding product (Table 4,
All reactions were monitored by TLC, and there is substantial
evidence to confirm the structures of the synthesized nitriles. For
this purpose, all purified products were characterized by com-
parison of their melting points, and FT-IR and mass spectra with
those of authentic samples. In the FT-IR spectrum, a strong
1
entry 19). In addition, when the aliphatic aldehydes such as
hexanal, octanal, and 3-methylbutanal were examined, the
reactions proceeded smoothly and produced the corresponding
nitriles in good yields (Table 4, entries 20–22). These results
demonstrated the superior properties of HAP@AEPH -SO H as
ꢁ
1
sharp absorption band at 2260–2200 cm was assigned to the
þ
CN group of nitriles. The molecular ion peaks (M ) observed in
the mass spectra were in agreement with the excepted molecular
2
3

H
S. M. Masjed et al.
O
Dry DMF
OH
R1
R1
H ꢀNH2OH·HCl
N
120ꢁC
I
ꢀ
OH2
O
O
O
O
O
O
O
ꢃ
nanoHAP
O SHN
P
nanoHAP
P
NHSO3H
R1
N
3
O
II
1
R -CN ꢀ H O
2
Scheme 2. Proposed mechanism for direct preparation of nitriles from aldehydes and hydroxylamine hydrochloride in the
presence of HAP@AEPH -SO H nanocatalyst.
2
3
weights. The melting points of the synthesized products also
agree with the literature values. Likewise, the selected com-
Table 5. Conversion of 4-methoxybenzaldehyde into
4-methoxybenzonitrile in the presence of reused
1
pounds were further identified by H and C NMR spectroscopy.
13
A
nanocatalyst
1
3
In the C NMR spectrum, a signal at around 118 ppm is assigned
to the quaternary carbon of nitrile.
On the basis of the above results, and also in accordance with
Entry
Run
Time [min]
Isolated
yield [%]
[
28,29b]
previous literature reports,
a plausible mechanism is
1
2
3
4
5
1
2
3
4
5
45
45
45
45
45
98
98
98
95
95
proposed as shown in Scheme 2. It is seen that the reaction
proceeds via the aldoxime (I), which is formed by carrying out
the reaction of aldehyde and hydroxylamine hydrochloride in
[29]
dry DMF at 1208C. This idea is supported by performing the
reaction in the absence of catalyst (Table 3, entry 1). Afterwards
in acidic media, dehydration of the aldoxime leads to formation
of a nitrile, which is promoted by the protonation of the hydroxy
group using a solid acid catalyst converting this moiety to a
better leaving group. The solid acid nanocatalyst then re-enters
the catalytic cycle by providing the active sites for further
turnovers.
A
Reaction conditions: 4-methoxybenzaldehyde (1 mmol),
hydroxylamine hydrochloride (3 mmol), HAP@AEPH
2
-
SO H nanocatalyst (8 mol-%), dry DMF (5 mL).
3
Conclusion
We attempted to expand the application of a HAP@AEPH2-
SO H nanocatalyst in organic reactions. In this sense, a new and
efficient procedure for direct preparation of nitriles from alde-
hydes and hydroxylamine hydrochloride by the HAP@AEPH2-
SO H nanocatalyst is reported. This new approach has several
Recycling of the acid catalyst is an important process from
different aspects such as environmental concerns, costs of the
catalyst, and its toxicity. In respect of this, the possibility of
recycling the HAP@AEPH -SO H nanocatalyst was examined
3
2
3
3
using the reaction of 4-methoxybenzaldehyde and NH OHꢀHCl
2
superiorities versus previous reports, such as short reaction
times, simple procedure, high atom economy, excellent yields,
generality, and recyclability of the catalyst. In addition, this new
acidic nanocatalyst can be considered as an attractive alternative
to harmful corrosive acids. For instance, its reusability with
consistent activity for at least five cycles is also established,
which indicates that, liquid acids or other solid acid catalysts can
be substituted by HAP@AEPH -SO H as a green solid acid
under the optimized conditions (Table 5). In order to regenerate
the nanocatalyst, after each cycle, it was separated by centrifuge,
and washed several times with EtOAc. It was then dried in an
oven at 508C and used in the next run. The results show that this
catalyst can be reused five times without any significant loss in
activity.
Moreover, the efficiency of this method is demonstrated by
comparison of our results on direct preparation of nitriles from
aldehydes and hydroxylamine hydrochloride with the results
reported in the literature (Table 6). As it is evident from Table 6,
HAP@AEPH -SO H is one of the most effective nanocatalysts
2
3
nanocatalyst.
Experimental
2
3
General
for this purpose, leading to the rapid formation of 4-methoxy-
benzonitrilein high yield. Incomparison, severalof the previously
reported methods suffer from long reaction times to achieve
appropriate yields as well as use of strong Lewis acids, expensive
The purity determinations of the products were accomplished
using TLC on silica gel polygram STL G/UV 254 plates. The
melting points of products were determined with an Electro-
thermal type 9100 melting point apparatus. FT-IR spectra were
[15,16,22,29,40]
and toxic metals, and tedious work-up procedures.

Direct Synthesis of Nitriles from Aldehydes
I
Table 6. Comparison efficiency of various catalysts in the direct conversion of 4-methoxybenzaldehyde into
4
-methoxybenzonitrile
Entry
Catalyst
Amount of
catalyst [g]
Solvent
Temperature [8C]
Time [h]
Yield [%]
Ref.
1
2
3
4
5
6
FeCl
Graphite/MeSO
Bi(OTf)
CeCl
ꢀ7H
KF/Al
HAP@AEPH
3
0.081
0.1
DMF
–
154
100
4
98
98
95
82
91
98
[15]
[16]
2
Cl
120 min
17
3
0.11
CH
–
3
CN
Reflux
R.T
[29]
3
2
O/KI/H
2
O
3 mmol
7.25
120 min
7
[22]
2
O
3
DMF
DMF
100
[40]
2
-SO
3
H
0.08
120
45 min
Present study
recorded on pressed KBr pellets using an AVATAR 370 FT-IR
spectrometer (Therma Nicolet spectrometer, USA) at room
tube, and dropping funnel, a solution of (NH ) HPO (50 mL,
4 2 4
0.65 M at pH adjusted to 10 with NH OH) was added at 908C
4
with stirring. AEPH (0.8 g, 5 mmol) was added to the resulting
2
ꢁ1
temperature in the range between 4000 and 400 cm with a
ꢁ1
resolution of 4 cm . NMR spectra were obtained with Bruker
AMX 100, 300, and 400 MHz instruments in CDCl . Elemental
suspension. The precipitate was maintained in contact with the
reaction solution for 5 h at 908C under stirring. Then suspen-
sion was centrifuged at 250000 g for 10 min and repeatedly
3
analyses were performed using a Thermo Finnegan Flash EA
1
112 series instrument. Mass spectra were recorded with a
washed with CO -free distilled water (3 ꢂ 20 mL). The product
2
CH7A Varianmat Bremem instrument at 70 eV electron impact
ionization, in m/z (rel.-%). TGA and DTA analysis were per-
formed using a Shimadzu Thermogavimetric Analyzer (TG-50)
in the temperature range of 25–9008C at a heating rate of
(nanoHAP functionalized with AEPH ) was dried at 508C
2
[
27,28]
overnight.
Preparation of HAP@AEPH -SO H
2
3
ꢁ
1
1
08C min under air atmosphere. SEM images were recorded
To a magnetically stirred mixture of HAP@AEPH (1 g) in
2
using Leo 1450 VP scanning electron microscope operating at
an acceleration voltage 20 kV, resolution of ,2 nm, image with
a magnification of 20 to 300 000 times (LEO, Germany). TEM
was performed with a Leo 912 AB microscope (Zeiss, Germany)
with an accelerating voltage of 120 kV, image with a magnifi-
cation of 80 to 500 000 times, equipped with a high resolution
CCD Camera. The crystal structure of the catalyst was analyzed
by XRD using a D8 ADVANCE Bruker diffractometer operated
2
0 mL of dry dichloromethane, 0.5 mL (0.75 mmol) of chloro-
sulfuric acid was added drop by drop at room temperature. After
0 min the suspension was filtered and washed with 20 mL of
2
dichloromethane and dried at room temperature to afford
[27,28]
HAP@AEPH -SO H as a white powder.
2
3
Catalyst Product Characterization
[
41]
Benzonitrile (Table 4, Entry 1). Oil (Lit.
1
oil). nmax (neat)/
˚
at 40 kV and 30 mA utilising Cu Ka radiation (l 0.154 A), at a
step size of 0.0408 and step time of 1.5 s. The diffraction angles
ꢁ
cm 3066, 2228 (CN) 1599, 1489, 1447, 1287, 1177, 1070,
025, 927, 759, 687, 547. dH (CDCl , 400 MHz) 7.66–7.59
1
3
(
2y) were scanned from 108 to 808. BET surface area and pore
size distribution were measured on a Belsorp mini II system at
1968C using N as adsorbate. All of the products were known
(m, 3H, Ar), 7.50–7.46 (m, 2H, Ar). dC (CDCl , 100 MHz)
3
þ
1
32.7, 132.0, 129.0, 118.7, 112.4. m/z (ESI) 103 (5 %, M ).
4
ꢁ
2
-Hydroxybenzonitrile (Table 4, Entry 2). Mp 108–1108C
compounds and characterized using FT-IR spectroscopy, mass
spectrometry, and comparison of their melting points with
known compounds. The structure of selected products was
[
20]
ꢁ1
(
Lit.
111–1128C). nmax (KBr)/cm 3310, 2233 (CN), 1907,
785, 1612, 1586, 1510, 1443, 1377, 1284, 1222, 1164, 1103,
1
967, 839, 701, 669, 547. m/z (ESI) 119 (91 %, M ).
þ
1
13
further confirmed using H and C NMR spectroscopy.
2
[
-Hydroxybenzonitrile (Table 4, Entry 3). Mp 92–948C
948C). nmax (KBr)/cm
42]
ꢁ1
(Lit.
3231, 3068, 2966, 2864,
Typical Procedure for Preparation of 4-Methoxybenzonitrile
2
1
6
729, 2602, 2508, 2467, 2345, 2239 (CN), 1604, 1505, 1458,
369, 1306, 1269, 1239, 1102, 1037, 947, 848, 769, 754, 731,
87, 567, 496, 465. m/z (ESI) 119 (95 %, M ).
4-Methoxybenzonitrile (Table 4, Entry 4). Mp 56–588C
To a solution of4-methoxybenzaldehyde (1mmol, 0.136 g) in dry
DMF (5mL), hydroxylamine hydrochloride (3mmol, 0.208 g)
þ
was added with stirring for 15 min at 1208C. HAP@AEPH2-
SO H nanocatalyst (8 mol-%, 0.08 g) was then added to the
3
[43]
ꢁ1
(Lit.
(
58–598C). nmax (KBr)/cm 3050, 2931, 2847, 2213
CN), 1604, 1506, 1454, 1303, 1256, 1170, 1020, 828, 678, 546,
resultant solution. After completion of the reaction (which was
monitoredbyTLC), cooling, andseparationofthe nanocatalyst by
centrifugation, the reaction mixture was poured into water
þ
4
06. m/z (ESI) 148 (23 %, M ).
3
[44]
-Methoxybenzonitrile (Table 4, Entry 5). Oil (Lit.
ꢁ1
oil).
nmax (neat)/cm 3076, 2970, 2944, 2835, 2230 (CN), 1764,
(
(
10 mL). The resulting mixture was extracted with ethyl acetate
3ꢂ 10 mL) and dried over sodium sulfate. After evaporation of
1
1
737, 1595, 1580, 1486, 1465, 1428, 1373, 1327, 1289, 1246,
164, 1145, 1045, 912, 873, 855, 788, 682, 596, 534, 475. m/z
the solvent, the crude product was purified by thin-layer chro-
matography using n-hexane/ethyl acetate (4 : 1) as eluent to afford
þ
(
(
ESI) 148 (31 %, M ).
4
Lit.
4-methoxybenzonitrile (0.130 g, 98 %).
-Ethoxybenzonitrile (Table 4, Entry 6). Mp 51–538C
51–538C). nmax (KBr)/cm 3071, 2995, 2980, 2939,
[
45]
ꢁ1
Preparation of NanoHAP Functionalized with AEPH2
HAP@AEPH2)
2896, 2219 (CN), 1604, 1573, 1506, 1475, 1392, 1301, 1259,
1172, 1109, 1039, 918, 845, 809, 707, 547. m/z (ESI) 147
(10 %, M ).
(
þ
To a solution of Ca(NO ) ꢀ4H O (50 mL, 1.08 M, at pH
3
2
2
[46]
4-Methylbenzonitrile (Table 4, Entry 7). Mp 26–278C (Lit.
adjusted to 10 with NH OH) in a three-necked 500 mL round-
4
ꢁ
1
bottomed flask equipped with a condenser, argon gas inlet
26–288C). nmax (neat)/cm 3041, 2926, 2861, 2227 (CN),

J
S. M. Masjed et al.
1
1
7
918, 1739, 1608, 1507, 1452, 1379, 1245, 1177, 1113,
047, 957, 819, 703, 547, 438 cm . dH (CDCl , 400 MHz)
3
.53 (d, J 8.2, 2H, Ar), 7.27 (d, J 8.2, 2H, Ar), 2.42 (s, 3H, CH3).
100 MHz) 133.2, 132.8, 132.5, 132.3, 128.6, 128.5, 127.5,
þ
53]
ꢁ1
125.0, 124.8, 117.7, 110.1. m/z (ESI) 153 (100 %, M ).
[
Hexanenitrile (Table 4, Entry 20). Oil (Lit.
oil). dH
(CDCl , 300 MHz) 2.34 (t, J 12.0, 2H, CH ), 1.72–1.62
d (CDCl , 100 MHz) 143.6, 131.9, 129.7, 119.1, 109.2, 21.7.
C
3
3
2
þ
m/z (ESI) 117 (19 %, M ).
-Methylbenzonitrile (Table 4, Entry 8). Oil (Lit.
(m, 2H, CH ), 1.49–1.32 (m, 4H, CH ), 0.93 (t, J 12.0, 3H,
2 2
[47]
2
oil).
nmax (neat)/cm 3064, 3038, 2962, 2925, 2865, 2227 (CN),
CH ). d (CDCl , 75 MHz) 119.7, 30.6, 24.9, 21.7, 16.9, 13.5.
3 C 3
ꢁ
1
[54]
Octanenitrile (Table 4, Entry 21). Oil (Lit.
ꢁ
oil). nmax
(neat)/cm 2962, 2930, 2859, 2246 (CN), 1462, 1427, 1377,
1
1
6
608, 1508, 1450, 1412, 1382, 1177, 1120, 1041, 955, 817, 710,
þ
þ
69, 546, 439. m/z (ESI) 117 (10 %, M ).
4
1119, 723. m/z (ESI) 125 (2 %, M ).
3-Methylbutanenitrile (Table 4, Entry 22). Oil (Lit.
nmax (neat)/cm 3648, 2966, 2933, 2876, 2246, 1467, 1425,
1391, 1342, 1282, 1171, 1114, 935, 891, 820. m/z (ESI) 83
[
20]
[55]
-Isopropylbenzonitrile (Table 4, Entry 9). Oil (Lit.
ꢁ
oil).
oil).
1
ꢁ1
nmax (neat)/cm 3078, 2965, 2929, 2872, 2228 (CN), 1737,
1
8
684, 1606, 1503, 1460, 1366, 1244, 1197, 1100, 1053, 1018,
þ
þ
38, 761, 695, 566. m/z (ESI) 145 (17 %, M ).
(3 %, M ).
4
28C (Lit.
-(Dimethylamino)benzonitrile (Table 4, Entry 10). Mp 70–
[
48]
ꢁ1
7
2
9
72–758C). nmax (KBr)/cm 2917, 2864, 2814,
207 (CN), 1606, 1524, 1446, 1368, 1227, 1171, 1125, 1066,
Supplementary Material
þ
38, 817, 645, 544. m/z (ESI) 146 (95 %, M ).
4
Details of analysis of nitrile derivatives are available on the
Journal’s website.
-Chlorobenzonitrile (Table 4, Entry 11). Mp 89–918C
[
43]
ꢁ1
3086, 3043, 2974, 2218
CN), 1909, 1783, 1662, 1584, 1481, 1393, 1267, 1180, 1083,
(
(
Lit.
928C). nmax (KBr)/cm
Acknowledgements
1
2
1
009, 826, 703, 580, 539. d (CDCl , 400 MHz) 7.61 (d, J 8.6,
H 3
H, Ar), 7.47 (d, J 8.6, 2H, Ar). d (CDCl , 100 MHz) 139.5,
C
The authors gratefully acknowledge the partial support of this study by
Ferdowsi University of Mashhad Research Council (grant no. p/3/38854).
3
þ
33.3, 129.6, 117.9, 110.7. m/z (ESI) 137 (85 %, M ).
,6-Dichlorobenzonitrile (Table 4, Entry 12). Mp 140–1438C
2
[
49]
ꢁ1
References
(
Lit.
142–1458C). nmax (KBr)/cm 3145, 3090, 2230 (CN),
748, 1706, 1571, 1509, 1430, 1228, 1196, 1102, 782, 714, 547.
[
1] (a) R. C. Larock, Comprehensive Organic Transformations 1989
1
m/z (ESI) 172 (92 %, M ).
þ
(VCH: New York, NY).
(
b) C. Grundmann, in Houben-Weyl: Methodender Organischen
4
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[
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ꢁ1
(
Lit. 113–1158C). nmax (KBr)/cm 3106, 3060, 2991, 2933,
[
2
1
857, 2227 (CN), 1603, 1527, 1437, 1346, 1288, 1190, 1103,
þ
010, 858, 749, 679, 540. m/z (ESI) 182 (100 %, M ).
4
(
b) P. C. Ducept, S. P. Marsden, Synlett 2000, 692.
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ꢁ1
(
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1498C). nmax (KBr)/cm 3059, 2963, 2926, 2855,
224 (CN), 1733, 1687, 1584, 1503, 1380, 1343, 1240, 1157,
2
1
8
1
(b) M. Chihiro, H. Nagamoto, I. Takemura, K. Kitano, H. Komatsu,
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H
3
.37 (d, J 8.8, 2H, Ar), 7.91 (d, J 8.8, 2H, Ar). dC (CDCl3,
00 MHz) 150.0, 133.4, 124.2, 118.3, 116.8. m/z (ESI) 148
[
4] (a) S. J. Wittenberger, B. G. Donner, J. Org. Chem. 1993, 58, 4139.
þ
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(
45 %, M ).
Terephthalonitrile (Table 4, Entry 15). Mp 218–2208C
Lit.
2
1
(
b) T. R. Bailey, G. D. Diana, P. J. Kowalczyk, V. Akullian, M. A.
Eissenstat, D. Cutcliffe, J. P. Mallamo, P. M. Carabateas, D. C. Pevear,
[
17]
ꢁ1
(
219–2208C). nmax (KBr)/cm 3096, 3050, 2962,
924, 2854, 2230 (CN), 1941, 1809, 1692, 1500, 1402, 1276,
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(
c) P. K. Kadaba, Synthesis 1973, 71.
198, 1025, 844, 641, 561. d (CDCl , 400 MHz) 7.81 (s, 4H,
3
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T. Ravindranathan, A. V. Bedekar, Tetrahedron Lett. 1998, 39, 459.
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H
Ar). d (CDCl , 100 MHz) 132.8, 117.0, 116.7. m/z (ESI) 128
C
3
þ
(
(
5 %, M ).
-Cyanopyridine (Table 4, Entry 16). Oil (Lit.
[
41]
[
6] R. F. Smith, J. A. Albright, A. M. Waring, J. Org. Chem. 1966, 31,
4100. doi:10.1021/JO01350A053
2
oil). nmax
neat)/cm 2917, 2864, 2814, 2207 (CN), 1606, 1524, 1446,
368, 1227, 1171, 1125, 1066, 938, 817, 645, 544. d (400 MHz,
ꢁ
1
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7] M. E. Fabiani, Drug News Perspect. 1999, 12, 207.
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1
H
[
CDCl ) 7.35 (s, 1H, Py), 7.74 (s, 1H, Py), 7.844 (d, J 6.4,
3
H, Py), 8.51 (s, 1H, Py). m/z (ESI) 104 (12 %, M ).
þ
1
[
[
51]
3
8–518C). nmax (KBr)/cm 3141, 3083, 3026, 2990 (CN), 2239,
-Cyanopyridine (Table 4, Entry 17). Mp 46–508C (Lit.
(
b) T. Sandmeyer, Ber. Dtsch. Chem. Ges. 1885, 18, 1492.
ꢁ1
4
1
1
doi:10.1002/CBER.188501801322
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973, 1718, 1591, 1543, 1493, 1414, 1331, 1236, 1206, 1111,
þ
081, 987, 827, 775, 559. m/z (ESI) 104 (12 %, M ).
Thiophen-2-carbonitrile (Table 4, Entry 18). Oil (Lit. oil).
[
52]
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ꢁ
1
1
nmax (neat)/cm 3109, 3098, 2221 (CN), 1413, 1349, 1232,
(
1
157, 1077, 1040, 856, 719, 567, 524, 486. m/z (ESI) 109
þ
4020(01)91791-0
(
30 %, M ).
1
[
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JO01076A001
ꢁ1
3
1
5
8
7
48C). nmax (neat)/cm 3058, 2926, 2847, 2222 (CN), 1625,
586, 1508, 1375, 1342, 1242, 1162, 1047, 863, 803, 772, 689,
72, 453. d (CDCl , 400 MHz) 8.21 (d, J 8.0, 1H, Ar), 8.05 (d, J
H
.0, 1H, Ar), 7.92–7.88 (m, 2H, Ar), 7.69–7.66 (m, 1H, Ar),
.62–7.7.58 (m, 1H, Ar), 7.52–7.48 (m, 1H, Ar). d (CDCl ,
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3

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