Oxidative amidation of benzyl alcohol, benzaldhyde, benzoic acid styrene and phenyl acetylene catalyzed by ordered mesoporous HKUST-1-Cu: Effect of surface area on oxidative amidation reaction

Article abstract of DOI:10.1002/aoc.4822

HKUST-1-Cu synthesized in the presence and absence of P-123 trough solvotermal method. After characterization using some different microscopic and spectroscopic techniques such as XRD, FT-IR, SEM, ICP, BET and TEM its catalytic activity was investigated in the oxidative coupling of benzyl alcohol, benzaldhyde, benzoic acid, styrene and phenyl acetylene with N,N-dialkylformamides for the preparation of N,N-dimethylformamides. Different derivatives of tertiary amides were synthesized in moderate to good yields in the presence of just ~0.28?mol% of this catalytic system. Reusability of the synthesized catalysts was examined and catalysts were reusable for 8 times without significant decrease in optimized conditions.

Full text of DOI:10.1002/aoc.4822

Received: 10 September 2018
DOI: 10.1002/aoc.4822
Revised: 5 January 2019
Accepted: 7 January 2019
F U L L P A P E R
Oxidative amidation of benzyl alcohol, benzaldhyde, benzoic
acid styrene and phenyl acetylene catalyzed by ordered
mesoporous HKUST‐1‐Cu: Effect of surface area on
oxidative amidation reaction
Haleh Mohebali | Ali Reza Mahjoub | Meghdad Karimi
| Akbar Heydari
Chemistry Department, Tarbiat Modare
HKUST‐1‐Cu synthesized in the presence and absence of P‐123 trough
solvotermal method. After characterization using some different microscopic
and spectroscopic techniques such as XRD, FT‐IR, SEM, ICP, BET and TEM its
catalytic activity was investigated in the oxidative coupling of benzyl alcohol,
benzaldhyde, benzoic acid, styrene and phenyl acetylene with N,N‐
dialkylformamides for the preparation of N,N‐dimethylformamides. Different
derivatives of tertiary amides were synthesized in moderate to good yields in
the presence of just ~0.28 mol% of this catalytic system. Reusability of the
synthesized catalysts was examined and catalysts were reusable for 8 times
without significant decrease in optimized conditions.
University, Tehran, Iran, P. O. Box, 14155‐
4383 Tehran, Iran
Correspondence
Ali Reza Mahjoub and Meghdad Karimi,
Chemistry Department, Tarbiat Modare
University, Tehran, Iran, P. O. Box 14155‐
4383, Tehran, Iran.
Email: mahjouba@modares.ac.ir;
meghdadkarimi1365@gmail.com
KEYWORDS
heterogeneous catalysis, HKUST‐1, ordered mesoporous HKUST‐1, oxidative amidation
1 | INTRODUCTION
the best solution for synthesizing amides through
oxidative coupling via various precursors. Utilization
In recent best studies, Amide functional groups in medic-
inal compounds are one of the most significant functional
groups in chemistry world, because it has key role for
instance as a linker for amino acid conversion to
protein.[1] Generally amides have synthesized in two
steps; at the first step carboxylic group transform to more
reactive functional group likewise acyl chloride and
second step contain reaction between these product and
amine compounds.[2] The creation of stoichiometric
values of waste, low atom economy and the use of toxic
reagents are the results of these processes. For solving
these problems, new methods have been replaced with
them such as metal‐free methods (like organo‐catalysts)
and boron reagents. Nevertheless, it faces with low
atomic efficiency and difficult products separation.[3]
Amide synthesis methods catalyzed with metals have
been drawn attention. In addition, direct amidation are
simple and low cost reagent has included both aspect of
eco‐friendly and step economically of reactions that cause
to convert to efficient methods for amidation. Since,
direct amidation of aldehydes and alcohol with amines,[4]
carboxylic acids, azoles and alcohol with formamides[5]
and methyl arens with different source of amines[6] have
been reported. There are most attractive due to the
achieving best efficiency from homogenous catalysts than
heterogeneous ones.4h, 7 But using homogenous catalyst
have accompanied with increasing toxicity and the cost
of metals. Hence, these methods have been applied for
researching more than industrial. For achieving more
efficiency, usage of heterogeneous or homo‐heterogonous
catalysts (fixing them on organic or inorganic supports in
liquid phase) has been developed.[8,9] According to the
green chemistry, new development synthesis methods
for making new linkers are very important in organic
Appl Organometal Chem. 2019;e4822.
wileyonlinelibrary.com/journal/aoc
© 2019 John Wiley & Sons, Ltd.
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https://doi.org/10.1002/aoc.4822

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MOHEBALI ET AL.
chemistry and also all of them have been done with
heterogeneous catalysts. Accordingly, amplification of
methods based on heterogonous catalysts is more
attractive in industrial applications.[9]
2.2 | Preparation of the HKUST‐1
Porous HKUST‐1 MOF was prepared using a hydrother-
mal method based on the reported procedures.[16] In a
typical experiment, 6 mmmol (1.4 g) of copper nitrate
trihydrate and 3.36 mmol (0.71 g) of trimisic acid
(benzene‐1,3,5‐tricarboxylic acid or H3BTC) were
dissolved in 40 ml of DMF at room temperature. The
mixture was stirred magnetically completely for 2 h.
The reaction mixture was kept at 80 °C overnight without
stirring. The solid was filtered off and washed thoroughly
with hot EtOH/DMF. The resultant blue solid (denoted as
HK) was dried in air at 110 °C overnight.
Metal organic frameworks (MOFs) are classes of
mesoporous compounds which have been shown good
abilities as heterogonous catalysts. As we can know
MOFs have been illustrated essentially catalytic proper-
ties because of their organic‐ inorganic and polymeric
structures. Therefore, Catalysts based on MOFs can
synthesis by post‐synthesis and assembling. In contrast,
the number of Catalysts based on MOFs are less than
number of MOFs have made.[10,11] Among of them, the
most significant things are open metal sites. Notably,
the most important applications of these structures are
catalysts,[12] adsorption/separation,[13] storage[14] and
sensing.[15] Following our last works about oxidative
amidation methods, we addresses synthesis of N, N‐
dimethyle amides via oxidative coupling of benzyl
alcohol, benzaldhyde, benzoic acid styrene and phenyl
acetylene catalyzed and N, N‐ dialkyl foramides under
moderate conditions and using ordered mesoporous
HKUST‐1 as a catalysts.
2.3 | Preparation of the ordered
mesoporous HKUST‐1
In a typical experiment, 2.0 g of Pluronic P123 (Aldrich,
average Mw ≅ 5800), was dissolved in 40 ml of DMF at
room temperature. The mixture was stirred magnetically
dissolving the surfactant completely and subsequently
sonicated for 15 mins. Then, 6 mmmol (1.4 g) of copper
nitrate trihydrate and 3.36 mmol (0.71 g) of trimisic acid
(benzene‐1,3,5‐tricarboxylic acid or H3BTC) were added
frequently and the mixture was stirred at 35 °C for
10 hr. Then, for aging process, the reaction mixture
was kept at 80 °C overnight without stirring. The solid
was filtered off and washed thoroughly with hot
EtOH/DMF using a soxhelet apparatus for 36 hr to
remove the surfactant molecules. The resultant blue
solid (denoted as OMHK) was dried in air at 110 °C
overnight.[17]
2 | EXPERIMENTAL SECTION
2.1 | General
All materials were purchased from Merck Company and
used with no more purification. The reaction was
precisely monitored by analytical thin layer chromatogra-
phy (TLC) using ethyl acetate and n‐hexane as eluents.
Due to needs to achieving final pure and isolated target
molecules, a scaled‐up thin layer chromatography was
Merck 0.2 mm of silica gel 60F‐254 Al‐plates. Spectral
analysis performed with aid of Infrared spectra (IR) on a
Shimadzu FT‐IR‐8400S spectrometer and in following
for definite characterization of all first‐made products
with 1H NMR (500 MHz) and 13C NMR (125 MHz) spectra
recorded on Bruker DRX‐500 Avance spectrometers with
CHCl3 and DMSO as solvent at ambient temperature
(relative to TMS as internal standard). Primary results
for reaction progress were obtained by Gas Chromatogra-
phy(GC) (Yonglin 6100;BP‐5;30 m×0.25×mm ×0.25 μm)
with toluene as general solvent for injection and nitrogen
as inert carrier gas. All yields referred to the isolated
products. The mentioned catalyst EDX spectra were
recorded on an Oxford Instrumental® and also SEM
images were obtained on Zeiss‐Sigma VP 500. Transmis-
sion electron microscopy (TEM) measurements were
carried out at 120 kV (Philips, model CM120).
2.4 | General procedure for the oxidative
amidation of benzyl alcohol, benzaldhyde,
benzoic acid styrene and phenyl acetylene
with N,N‐dialkylformamide
The oxidative amidation reaction was carried out in a two
necked round bottom flask with a condenser at air
atmosphere. In a typical experiment, a mixture of
substrate (1 mmol and 0.5 mL about toluene) and catalyst
(20 mg, ~0.28 mol%) in N,N‐dialkylformamide (2.0 ml)
was placed in reactor at room temperature. Then, TBHP
(70 wt % in H2O, 1.5 equiv.) was slowly added to the
reaction mixture over a 5 min period, and the mixturewas
placed in an oil bath with magnetic stirring at 80 °C in an
open atmosphere. After completion as judged by TLC, the
reaction mixture was cooled to room temperature,
extracted with ethyl acetate, and washed with saturated
NaHCO3 solution, water, and brine solution, respectively.
The organic layer was collected and dried over Na2SO4.

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The solvent was removed under reduced pressure and the
residue was purified by column chromatography on silica
gel (petroleum ether/ethyl acetate) to afford the pure
product. The products were characterized by IR, NMR
analysis, and mass spectrum. The spectral data of known
compounds were compared with those reported in the
literature.
3.1 | Characterization of HKUST‐1 and
ordered mesoporous HKUST‐1
After Preparation, some different microscopic and
spectroscopic techniques such as XRD, FT‐IR, SEM,
ICP, BET and TEM were used to confirm the structure
of the catalyst.
3 | RESULTS AND DISCUSSIONS
3.1.1 | FT‐IR spectroscopy
As shown in Scheme 1, HKUST‐1 was prepared in three
steps. At first, a solution of Cu (NO3)2.3H2O and trimisic
acid (benzene‐1,3,5‐tricarboxylic acid or H3BTC) in DMF
was prepared by the mixing precursors for 2 hr. On the
other hand, the reaction mixture was kept at solvotermal
conditions without stirring. (Scheme 1). The blue solid
filtered off and washed using a soxhelet apparatus to
remove the unreacted molecules (or surfactant molecules
about OMHK). The final structure of the catalyst was
obtained via the drying of B. (for details see experimental
section).
The formation of HKUST‐1 was further confirmed by
the FT‐IR spectroscopy (Figure 1). The broad band
observed at 2500–3300 cm−1 region in benzene tricar-
boxylic acid is due to O–H stretching in carboxylic
group, which is shifted to 3100–3600 cm−1 region in
the complex indicating the presence of loosely bound
water molecules in [Cu3(BTC)2]. The presence of located
EtOH was confirmed by the stretching vibrations that
appeared at about 2923 cm−1 (C–H stretching
vibrations) in the FT‐IR spectrum. In particular, the IR
absorption bands in the 1700–1500 cm−1 and 1500–
SCHEME 1 Schematic synthesis of
HKUST‐1 (HK) and ordered mesoporous
HKUST‐1 (OMHK)
FIGURE 1 FT‐IR spectra of HK
(Black), OMHK (red)

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MOHEBALI ET AL.
1300 cm−1 range are due to υasym(C–O2) and υsym(C–O2)
stretching mode, respectively; The band observed
around 1715 cm−1 can be significantly assigned to acidic
C=O stretching vibration present in the ligand BTC,
which after complexation with Cu2+ is shifted to
1643 cm−1 suggesting that deprotonation has happened.
This clearly indicates that the carboxylate ion
participates in the complex formation. Moreover, the
characteristic vibration at 725 cm−1 may be attributed
to Cu–O stretching vibration, in which the oxygen atom
is coordinated with Cu. Moreover, the absence of DMF
absorption bands for the HKUST‐1 synthesized in
DMF showed that [Cu3(BTC)2] DMF is exchanged with
EtOH trough soxhelet apparatus so no observed; IR
bands around 1450 cm−1 are due to a combination of
benzene ring stretching and deformation modes;
whereas, IR absorption bands around 700 cm−1 are
due to υ (C– H) bending mode.
of water or guest molecules. OMHK MOF molecular
formula was assumed as Cu3(BTC)2(H2O)3.xH2O and
number of crystal water (x) was about 3.0. After that the
sample was not shown any significant weight change up
to 250 °C and then gradually started to lose the weight. This
result confirmed the stability of the framework at higher
temperature and there were almost no impurities on the
structure. Complete decomposition started at about 320
to 400 °C to A sudden weight change (around 45 wt.%)
was observed at 295 °C due to a complete transformation
into CO2 and Cu2O or metal Cu.[18]
3.1.3 | Scanning Electron microscopy
(SEM) analysis
As illustrated in Figure 3, the particle morphology was
studied by scanning electron microscopy (SEM) and the
identification of HK (a) and OMHK (b) before and after
(d) reaction was based on the analysis of SEM images
(Figure 3). It has been confirmed from the FE‐SEM that
there are no other phases present except the blocks of
the produced MOF. Thus, we may conclude that our
synthesized samples were almost free from the unreacted
chemicals. It also shows that the HK‐1 AND OMHK
particles have octahedral shape with average diameters
of approximately 15–20 μm and after 5 cycle this
morphology is stable.
3.1.2 | Thermogravimetric/differential
thermal analyses (TGA/DTA)
As shown in Figure 2, the thermogravimetric profile of
synthesized OMHK is consistent with prominent weight‐
loss steps. It followed that a fully hydrated molecular sieve
contains up to 12 wt. % water and other guest molecules. At
the initial period the weight loss is due to the evaporation
FIGURE 2 Thermogravimetric and differential thermogravimetric analysis of the catalyst

MOHEBALI ET AL.
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FIGURE 3 SEM Analysis of the HK before (a) and after (b) and OMHK before (c) and after reaction (d)
pattern from the single X‐Ray data (CCDC number
2300380 or 112954). The diffraction peaks of HK and
OMHK solvotermal synthesized samples are well consis-
tent with available literature and the simulated pattern
published by Chui et al,13 calculated using single crystal
data are comparable (with three main peaks, 2θ = 11.01,
13.53 and 15.59). Difrractogram of the [Cu3(BTC)2]
resulted at presence of surfactant (OMHK, red diagram)
lower crystallinity indicated from the peaks that not really
sharp (Figure 5). Moreover, the sharper peaks in the range
area of 2θ from 18 to 26° assumed represent the peak of the
coordinated and or uncoordinated solvent in the com-
pound. However, these kinds of peaks do not imply the
3.1.4 | Transmission electron microscopy
(TEM)
Transmission electron microscopy (TEM) confirmed the
ordered mesochannels in the OMHK, with octahedral
morphology and a pore size range of ~15 nm (Figure 4).
3.1.5 | X‐ray powder diffraction (XRD)
patterns
The phase purity of bulk products were confirmed by pow-
der X‐Ray analysis (Figure 3) and fitted with the simulated
FIGURE 4 TEM micrographs of OMHK

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MOHEBALI ET AL.
FIGURE 5 XRD pattern of HK (Black)
and OMHK (red)
significant impurities and found also in some referred liter-
atures. Therefore synthesized [Cu3(BTC)2] under this
experimental condition exhibits the crystalline structure
of [Cu3(BTC)2] in which twelve carboxylate oxygen atom
from two BTC molecules and each of the three Cu2+ ions
forms [Cu3(BTC)2] like structure with paddle‐wheel units
of fcc lattice.[19]
3.1.6 | Brunauer–Emmett–teller (BET)
analysis
The specific surface area was measured using the BET
method and the pore size distribution was calculated
using the classical Barrett–Joyner–Halenda model. As
shown in Figure 6, the adsorption desorption curves for
FIGURE 6 N2 adsorption–desorption isotherms of HK (black) and OMHK (red)

MOHEBALI ET AL.
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the composites displayed the type IV adsorption–
desorption isotherms, which is the typical characteristics
of mesoporous materials. And the BET specific surface
area is calculated 582 and 1271m2/g for HK and OMHK
respectively. The composites also showed the narrow
pore size distribution, and the pore size is 1.63 and
2.52 nm for HK and OMHK respectively (Figure 7).
reactions between substrates and N,N‐dimethyl formam-
ide were performed as the model reactions to find the
optimum conditions (Scheme 2).
3.2 | Application of HK and OMHK for
the oxidative amidation reaction
3.2.1 | General survey to investigate the
best primary condition of reactions
After characterization of the catalyst structure, its cata-
lytic activity was studied in coupling reaction between
different substrates (benzyl alcohol, benzaldhyde, styrene
and phenyl acetylene) and N,N‐dialkyl formamides. The
SCHEME 2 Model reactions for oxidative amidation of different
substrates (reaction A, B,C, D, E for benzyl alcohol, benzaldhyde,
styrene and phenyl acetylene respectively)
FIGURE 7 BJH desorption dV/dD Pore Volume plot

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MOHEBALI ET AL.
The first reaction was implemented under the follow-
ing conditions: substrates (benzyl alcohol, benzaldhyde,
styrene and phenyl acetylene, mmol), N,N‐
dimethylformamide (2 ml), aqueous tert‐butyl hydroper-
oxide (TBHP) as the oxidant (1.5 equiv), catalyst (10 mg,
~0.28 mol% of Cu), under Ar atmosphere at room temper-
ature for 4 hr. Under these conditions, the corresponding
product was achieved with 9(7), 5(5), 10(6), 8(5), 5(3) %
yield respectively (Yields in parentheses are corresponded
to reactions in the presence of HK) (Figure 8).
Apart from TBHP, oxidative effect of other various
oxidants such as mCPBA, H2O2, UHP and NaOCl in dif-
ferent equivalents was probed but none was as effective
as TBHP (Figure 10). In the absence of the catalyst and
oxidant, no product was formed (Figure 11).
By increasing the temperature to 80 °C, the product
yield significantly rose and higher temperature had little
impact on the reaction efficiency (Figure 12).
1
About reaction D and E increasing the temperature
had negative effect (Figure 12).
Owing to the improved efficacy, the effect of parame-
ters such as amount of the catalyst, different oxidants, time
of the reactions and different temperatures were investi-
gated and the results are as follows: The amount of catalyst
was initially optimized and it was found that 40 mg of HK
and OMHK (for all of the reactions of A, B, C, D, E) were
sufficient to promote these reactions and OMHK was
better than HK (Figure 9).
To evaluate the catalytic activity in the synthesis of
other amides by this method, various substrates used
and reacted with dialkylformamides (Table 1). Under
the standard reaction conditions, at the first time different
derivatives (include of EDG and EWG functional groups)
of benzyl alcohol, benzaldhyde, benzoic acid, styrene and
phenyl acetylene were converted to the corresponding
amides in acceptable yields (Table 2).
FIGURE 8 Yields of model reactions
(reactions was run with 10 mg catalyst,
substrates (benzyl alcohol, benzaldhyde,
benzoic acid, styrene and phenyl
acetylene, 1 mmol), DMF (2 ml), TBHP
(1.5 equiv.), 8 hr at room temperature
under Ar atmosphere. Yield determined
by GC‐FID spectroscopy with an internal
standard)
FIGURE 9 Checking the effect of catalysts amount on reaction yield (reactions was run with different mass of catalyst, substrates (benzyl
alcohol, benzaldhyde, benzoic acid, styrene and phenyl acetylene, 1 mmol), DMF (2 ml), TBHP (1.5 equiv.), 8 hr at room temperature under
Ar atmosphere. Yield determined by GC‐FID spectroscopy with an internal standard)

MOHEBALI ET AL.
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FIGURE 10 Checking the effect of
oxidant on reaction yield (reactions was
run with different 40 mg of catalysts,
substrates (benzyl alcohol, benzaldhyde,
benzoic acid, styrene and phenyl
acetylene, 1 mmol), DMF (2 ml), oxidant
(1.5 equiv.), 8 hr at room temperature
under Ar atmosphere. Yield determined
by GC‐FID spectroscopy with an internal
standard)
FIGURE 11 Checking the effect of
amount of oxidant on reaction yield
(reactions were run with 40 mg of
catalysts, substrates (benzyl alcohol,
benzaldhyde, benzoic acid, styrene and
phenyl acetylene, 1 mmol), DMF (2 ml),
different equivalents (1.5, 3, 4.5, 6, 7.5, 9)
of TBHP as oxidant (1.5 equiv.), 8 hr at
room temperature under Ar atmosphere.
Yield determined by GC‐FID spectroscopy
with an internal standard)
FIGURE 12 Checking the effect of
temperature on reaction yield (reaction
was run with 40 mg catalyst, substrates
(benzyl alcohol, benzaldhyde, benzoic
acid, styrene and phenyl acetylene,
1 mmol), DMF (2 ml), TBHP (8 equiv.),
8 hr at different temperatures under Ar
atmosphere. Yield determined by GC‐FID
spectroscopy with an internal standard)
In this study, two methods for the synthesis of
HKUST‐1 have been used. According to the characteriza-
tions of the prepared structures, one of the methods is
HKUST‐1 and in another method, ordered mesoporous
HKUST‐1. These two structures are different in surface
area and interaction between substrates and catalysts. In
ordered mesoporous structures, the type of interaction
of the substrates with the structure increases due to the
presence of regular honeycomb structure that results
from the use of surfactants and the formation of
structures around surfactants. These pores actually act
like nano‐reactors and the reactions inside these nano‐
reactors are performed with high efficiency. In this
reaction, the copper ions in the catalyst with electron
transfer (based on the mechanisms proposed in related
reports[20]) to the oxidant (which is herein to be known
TBHP) causes the formation of radical active species
and eventually, by binding radical species together, the
product, the final one is created. These electron transfer
reactions between copper and oxidizing species as well
as substrates are carried out at the catalyst surface.
Therefore, the higher the contact surface of the catalyst
with the species, the efficiency increases. By changing
the structure from HKUST‐1 to ordered mesoporous

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MOHEBALI ET AL.
TABLE 1 Preparation of various amides in the presence of HKa
TABLE 2 Preparation of various amides in the presence of HK
and OMHKa
Y
FG
Yield (%)b
H (1a)
74
46
59
65
p‐OMe (2a)
p‐Cl (3a)
p‐NO2 (4a)
11a
11b
11c
11d
(33%)
(35%)
11e
(30%)
(30%)
(62%)b
(61%)c
(45%) (65%)
(44%) (65%)
H (1a)
63
40
55
63
12a
12b
12c
12d
12e
p‐OMe (2a)
p‐Cl (3a)
p‐NO2 (4a)
(61%)
(60%)
(45%) (61%)
(44%) (63%)
(33%)
(35%)
(30%)
(31%)
13a
(20%)
(28%)
13b
13c
13d
13e
H (1a)
80
50
65
70
(15%) (23%)
(19%) (35%)
(N.D.)d (N.D.)
p‐OMe (2a)
p‐Cl (3a)
p‐NO2 (4a)
(10%)
(10%)
14a
14b
14c
14d
14e
(31%)
(40%)
(21%) (40%)
(30%) (51%)
(10%)
(22%)
(10%)
(19%)
H (1a)
54
37
47
55
p‐OMe (2a)
p‐Cl (3a)
p‐NO2 (4a)
15a
(20%)
(38%)
15b
15c
15d
(N.D.)
(12%)
15e
(N.D.)
(10%)
(15%) (61%)
(28%) (46%)
H (1a)
52
30
40
51
p‐OMe (2a)
p‐Cl (3a)
p‐NO2 (4a)
aReaction conditions: Substrate (1 mmol), DMF (2 ml), TBHP (8 equiv.), Cat-
alyst (40 mg, ~0.28 mol%), at 80 °C under Ar. atmosphere.
bThe yields refer to the isolated pure products.
aReaction conditions: Substrate (1 mmol), DMF (2 ml), TBHP (8 equiv.), Cat-
alyst (40 mg, ~0.28 mol%), at 80 °C under Ar. atmosphere.
bThe yields refer to the isolated pure products.
cThe yields refer to the isolated pure products by HK and OMHK
respectively.
dNot detected.
HKUST‐1, due to the presence of honeycomb cavities
resulting from the use of surfactants (as seen clearly in
TEM images), the available catalyst surface, and more
specifically, the copper ion, is increased to produce
radical active species. As shown in Table 1, the
derivatives of benzyl alcohol, benzaldhyde, benzoic acid
styrene and phenyl acetylene, which differ only electron-
ically and have different functional groups, have been
investigated and compared with each other. From the
yield of the reactions, the existence of EWGs (electron
withdrawing groups) on substrates causes the reaction
to be carried out with higher efficiency. Given the
mechanism of these reactions, it is evident that the EWGs
(electron withdrawing groups) cause radical stability, and
thus the field will be conducive to the reaction. Instead,
the presence of EWGs (electron withdrawing groups)
has made the conditions unfavorable for the formation
of radical species, and this clearly manifests itself in the
efficiency of the reactions.
the effects of size of molecules and the effect of
synthesized catalysts using surfactant (honeycomb
structure), different derivatives of dimethylformamide
TABLE 3 Preparation of various amides in the presence of HK
and OMHKa
Cat.
Yield (%)b
1
2
3
4
5
80
81
84
85
88
aReaction conditions: benzoic acid (1 mmol), DMF (2 ml), TBHP (8 equiv.),
Catalyst (40 mg, ~0.28 mol%), at 80 °C under Ar. atmosphere.
bThe yields refer to the isolated pure products.
On the other hand, as mentioned above, these honey-
comb cavities act like a nano‐reactors, which increases
the catalytic efficiency. Additionally, in the HKUST‐1
structure, the pores have a spatial extent and there is no
possibility of reacting to some substrates. To investigate
Catalysts 1, 2, 3, 4, 5 are OMHK‐H2O, OMHK‐CH3CN‐72 (72 hr immersion
in CH3CN, without heating and vacuum), OMHK‐24 (24 h immersion in
CH3CN, after heating and vacuum), OMHK‐48 (48 hr immersion in CH3CN,
after heating and vacuum), OMHK‐72 (72 h immersion in CH3CN, after
heating and vacuum) respectively.

MOHEBALI ET AL.
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were investigated. To compare these derivatives, benzyl
alcohol, benzaldehyde, benzoic acid, and phenyl acety-
lene has been used without functional groups to prevent
electron effects.
As the results of the reactions show (Table 2), when
small derivatives are used, there is no significant
difference in the structure of HKUST‐1 and ordered
mesoporous HKUST‐1, while in the case of larger
derivatives, difference is clearly visible.
associated with better efficiency for both catalysts due to
the less probability of producing different products. Due
to the fact that other substrates were first converted to
benzoic acid during the process (reported according to
the proposed mechanisms) and then reacted with DMF,
there was a likelihood of the production of side products
in this direction, thus reducing the reaction efficiency.
To investigate the effects of the metal center of the
synthesized structure, the structure with the coordinated
water molecules (host solvent) was first immersed in the
acetonitrile (guest solvent) for 24, 48 and 72 hrs, and then
Regarding the mechanisms reported in the references,
the reaction of oxidative amidation on benzoic acid is
FIGURE 13 Catalyst reusability
(reaction was run Substrate (1 mmol),
DMF (2 ml), TBHP (8 equiv.), Catalyst
(40 mg, ~0.28 mol%), 8 h at 80 °C under Ar
atmosphere. Yield determined by GC‐FID
spectroscopy with an internal standard)
FIGURE 14 Leaching test for catalytic oxidation based on OMHK

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MOHEBALI ET AL.
SCHEME 3 Plausible mechanism for the oxidative amidation of benzyl alcohol, benzaldhyde, benzoic acid styrene and phenyl acetylene
in the presence of Cu (II)‐TBHP
the structure was immersed in a temperature of 80 °C for
24 hrs, until the acetonitrile molecule coordinate to the
metal (guest solvent) removed. Then, for comparison,
the oxidation reaction was studied using two structures.
As can be seen, using two structures, there is no signifi-
cant difference in the efficiency of the reaction. Of course,
the slight increase in reaction efficiency by using an open
metal site structure could be due to its ability to coordina-
tion using substrate and increase its electron transfer
capability (Table 3). The results of the reactions using
the structures show that, with increasing time for immer-
sion of the catalyst in acetonitrile, the amount of solvent
that has been replaced is increased and the size of the
open metal sites is increasing, thereby increasing the
efficiency of the reactions.
240 min. This finding indicates that no leaching of the
catalytically active sites occurs and that HK and OMHK
exhibit a typical heterogeneous catalyst nature.
Although there is no precise mechanism for this
transformation, according to previous reports,[20] the
proposed mechanism is shown in Scheme 3. First, the
substrates (benzyl alcohol, benzaldehyde and phenyl
acetylene) are oxidized to benzoic acid by Cu (II)/TBHP.
Then in the presence of copper (II), TBHP produces
radical 1 which immediately reacts with DMF and radical
2 is formed. The copper (I) generated at this step of the
reaction converts TBHP to radical 3 and the copper (II)
is again formed and recycled. Then radical 4 is achieved
via abstraction of H from acid by radical 3. Coupling
radical 2 with radical 3 followed by the extrusion of
CO2 will form the final product.
All the products were characterized by recording
their melting points (in some cases), and from their
1
IR, H‐NMR and 13C‐NMR spectra.
Reusability of the catalysts was evaluated in the
synthesis of N,N‐dimethylbenzamide (Figure 13). After
completing the reaction; the catalyst was removed by
centrifuging, washed with ethanol and dried for reuse.
HK and OMHK were recycled 8 times in the oxidative
amidation reaction without significant loss of its activity.
In order to gain insight into the heterogeneous nature
of catalyst, a leaching test was carried out. As indicated in
Figure 14, no further reaction took place without catalyst
after initiation of the oxidative amidation reaction at
4 | CONCLUSIONS
In summary, we have developed a novel protocol for the
one‐pot oxidative amidation of benzyl alcohol,
benzaldhyde, benzoic acid styrene and phenyl acetylene
with N,N‐dialkylformamides. ~0.28 mol% of catalyst was
used for the preparation of different derivatives of amides
in moderate to good yields. Porosity of this catalyst has
crucial important effect on selectivity and yield of reac-
tion. The ordered mesoporous nanocatalyst was stable

MOHEBALI ET AL.
13 of 13
[8] P. Barbaro, F. Liguori, Heterogenized Homogeneous Catalysts for
Fine Chemicals Production: Catalysis by Metal Complexes, Vol.
33, Springer, Dordrecht 2010.
and could be reused in 8 successive runs with no signifi-
cant loss of activity.
[9] J. M. Thomas, W. J. Thomas, Platinum Met. Rev. 1996, 40, 8.
ACKNOWLEDGEMENTS
[10] a) J. M. Thomas, R. Raja, C. Sankar, R. G. Bell, Acc. Chem. Res.
2001, 34, 191; b) E. Breynaert, I. Hermans, B. Lambie, G. Maes,
J. Peeters, A. Maes, P. Jacobs, Angew. Chem., Int. Ed. 2006, 45,
7584; c) R. Zhao, D. Ji, G. Lv, G. Qian, L. Yan, X. Wang, J. Suo,
Chem. Commun. 2004, 904; d) Y. Liu, H. Tsunoyama, T. Akita,
S. Xie, T. Tsukuda, ACS Catal. 2011, 1, 2.
We acknowledge Tarbiat modares University for partial
support of this work.
ORCID
[11] a) A. Corma, H. García, F. X. Llabrés i Xamena, Chem. Rev. 2010,
110, 4606; b) M. Yoon, R. Srirambalaji, K. Kim, Chem. Rev. 2012,
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Meghdad Karimi https://orcid.org/0000-0001-5350-9861
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How to cite this article: Mohebali H, Mahjoub
AR, Karimi M, Heydari A. Oxidative amidation of
benzyl alcohol, benzaldhyde, benzoic acid styrene
and phenyl acetylene catalyzed by ordered
mesoporous HKUST‐1‐Cu: Effect of surface area on
oxidative amidation reaction. Appl Organometal
Chem. 2019;e4822. https://doi.org/10.1002/aoc.4822
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