Acylation of aromatic compounds using moisture insensitive mesoporous Si-MCM-41 supported Ga2O3 catalyst

Article abstract of DOI:10.1081/SCC-120006469

Mesoporous Si-MCM-41 supported Ga₂O₃ is a highly active catalyst for the acylation of aromatic compounds with different acyl chlorides. Moreover, this catalyst is not deactivated by water and hence does not require moisture-free reaction conditions.

Full text of DOI:10.1081/SCC-120006469

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: http://www.tandfonline.com/loi/lsyc20
ACYLATION OF AROMATIC COMPOUNDS USING
MOISTURE INSENSITIVE MESOPOROUS Si-MCM-41
SUPPORTED Ga O CATALYST
2
3
Vasant R. Choudhary & Suman K. Jana
To cite this article: Vasant R. Choudhary & Suman K. Jana (2002) ACYLATION OF AROMATIC
COMPOUNDS USING MOISTURE INSENSITIVE MESOPOROUS Si-MCM-41 SUPPORTED
Ga O CATALYST, Synthetic Communications, 32:18, 2843-2848, DOI: 10.1081/SCC-120006469
2
3
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SYNTHETIC COMMUNICATIONS
Vol. 32, No. 18, pp. 2843–2848, 2002
ACYLATION OF AROMATIC
COMPOUNDS USING MOISTURE
INSENSITIVE MESOPOROUS Si-MCM-41
SUPPORTED Ga O CATALYST
2
3
Vasant R. Choudhary* and Suman K. Jana
Chemical Engineering Division, National Chemical
Laboratory, Pune-411 008, India
ABSTRACT
Mesoporous Si-MCM-41 supportedGa O is a highly active
2
3
catalyst for the acylation of aromatic compounds with differ-
ent acyl chlorides. Moreover, this catalyst is not deactivated
by water andhence do es not require moisture-free reaction
conditions.
Key Words: Acylation of aromatic compounds; Si-MCM-41
supportedgallium ox ied; Moisture insensitive catalyst;
Benzoylation of aromatic compounds
INTRODUCTION
Friedel–Crafts type acylation of aromatic compounds with acyl chlo-
rides using anhydrous AlCl , as a catalyst is a commonly practicedsynthetic
3
*Corresponding author. Fax: (þ91)-20-5893041/5893355; E-mail: vrc@ems.ncl.
res.in
2
843
DOI: 10.1081/SCC-120006469
Copyright & 2002 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

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2
844
CHOUDHARY AND JANA
[
1]
methodfor the preparation of aromatic ketones.
AlCl as a homogeneous catalyst in the acylation, however, poses several
The use of anhydrous
3
serious problems, such as requirement of the catalyst in more than stoichio-
metric amounts, difficulty in the separation and recovery of the catalyst,
disposal of the spent catalyst, corrosion problems, etc. Moreover, this
catalyst is highly moisture sensitive and hence demands moisture-free reac-
tants andsolvent andalso dr y atmosphere for its han dl ing. Because of its
higher moisture sensitivity, the results obtainedwith this catalyst are seldom
reproducible. Hence development of easily separable solid catalysts having
high activity but little or no moisture sensitivity for the acylation reactions
is, therefore, of great practical importance. A number of solidacidcatalysts,
[
2–4]
[5]
such as Hb, HY andH-ZSM-5 zeolites,
heteropoly acids, modified
[6]
ZrO2 have been reportedearlier for the acylation reactions. However,
these catalysts have poor activity for the acylation.
[7]
Our earlier studies reveal that Ga O (or In O )/Si-MCM-41 has
2
2
3
3
very high activity with little or no moisture sensitivity in the benzylation
of benzene. We report here the synthesis of different aromatic ketones in
high yields at a short reaction period (3 h), by the acylation of different
aromatic compounds even in the presence of moisture using Ga O /
2
3
Si-MCM-41, which can be separatedsimply by filtration.
RESULTS AND DISCUSSION
Results showing the influence of solvent, moisture in solvent andload-
ing of Ga O on Si-MCM-41 on the yieldof methoxy benzophenone in the
2
3
ꢀ
benzoylation of anisole by benzoyl chloride (at 80 C) over the Ga O /
2
3
Si-MCM-41 catalyst are presentedin Table 1. The pro du ct yieldfor the
different solvents is in the following order: n-heptane<acetonitrile<dichlor-
oethane. As expected, the yield is also increased with increasing the Ga O
2
3
loading. It is interesting to note that, the presence of moisture in the solvent
has a beneficial effect on the product yield; it has caused a significant increase
in the product yield.
The results showing the product yields in the acylation of different
ꢀ
aromatic compounds with different acyl chlorides (at 80 C) over the
Ga O (20%)/Si-MCM-41 catalyst in the presence or absence of moisture
2
3
in the reaction mixture are presentedin Table 2. From the results, following
important observations can be made:
–
In all the cases, the product yield is quite high, indicating high
acylation activity of the catalyst.

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MESOPOROUS Si-MCM-41 SUPPORTED Ga O CATALYST
2
2845
3
Table 1. Effect of Solvent, Moisture in Solvent, andGa O Loading
2
3
on the Yieldin the Benzoylation of Anisole over Ga
ꢀ
2
O
3
/Si-MCM-41
Catalyst at 80Æ1 C (Reaction Period ¼ 3 h)
Ga
(
2
O
wt%)
3
Loading
IsolatedYield(%)
Methoxy Benzophenone
Solvent Used
0
5
.0
.0
Dichloroethane
Dichloroethane
Dichloroethane
Dichloroethane
Dichloroethane
Acetonitrile
0
37
63
76
80
75
25
1
2
2
2
2
0.0
0.0
0.0
0.0
0.0
a
n-Heptane
a
Solvent saturatedwith water at room temperature.
–
–
Because of the presence of moisture in the substrate or catalyst
i.e., in the reaction mixture) the product yield is not decreased;
in fact it is increasedsignificantly in di cating a beneficial effect of
the moisture in the reaction mixture.
In the benzoylation of different aromatic compounds, the product
yield depends on the substituent group(s) present in the aromatic
substrate. The order of the product yield for the different substituents
is as follows.
(
For substitutedbenzenes: without substituent<methyl< id- methyl<tri-
methyl<methoxy. For substitutednaphthalenes: without substituent<
methyl<methoxy. The above order is consistent with that observed
[1]
earlier.
The observedhigh acylating activity of Ga O /Si-MCM-41 catalyst in
the presence of moisture suggests that Lewis acids of the Ga O catalyst
2
3
2
3
does not play significant role in the acylation. The standard reduction
0
potential for gallium, E
of the Ga O /Si-MCM-41 catalyst are expectedto play an important role in
3þ
1þ is À0.44 V andhence the re do x properties
ðGa =Ga
Þ
2
3
the acylation. A probable redox mechanism for the acylation reactions over
the Ga O /Si-MCM-41 catalyst is given below.
2
3
3
þ
þÁ
2
RCOCl þ Ga ! 2RCOCl þ Ga1þ
ð1Þ
½
2
R ¼ C H ; C H CH ; C H or C H ꢁ
6
5
6
5
2
2
5
3
7
þÁ
þ
Á
RCOCl ! 2RCO þ 2Cl
ð2Þ
ð3Þ
ð4Þ
Á
1þ
3þ
2
Cl þ Ga ! Ga þ 2ClÀ
þ
þ
RCO þ ArH ! RCOAr þ H

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2
846
CHOUDHARY AND JANA
Table 2. Results on the Acylation of Different Aromatic Compounds over Ga O
2
3
ꢀ
(
20%)/Si-MCM-41 Catalyst at 80 C (Solvent: Dichloroethane, reaction period ¼ 3 h)
Acylating
Agent
Entry Substrate
Product
Yield (%)
1
2
3
4
5
6
7
8
9
0
1
2
3
Anisole
Anisole
Anisole
Benzene
Benzene
Toluene
Toluene
p-Xylene
p-Xylene
Mesitylene
Mesitylene
C
C
C
6
6
6
H
H
H
5
5
5
COCl
COCl
COCl
4-Methoxy benzophenone
4-Methoxy benzophenone
4-Methoxy benzophenone
Benzophenone
76
79
80
42
43
50
52
64
66
71
73
54
62
a
b
C H COCl
C
C
C H COCl
C
C
C H COCl
C
C
6
6
6
5
5
5
b
H
H
COCl
COCl
Benzophenone
4-Methyl benzophenone
4-Methyl benzophenone
2,5-Dimethyl benzophenone
2,5-Dimethyl benzophenone
2,4,6-Trimethyl benzophenone
2,4,6-Trimethyl benzophenone
2-Benzoyl naphthalene
1-Benzoyl 2-methyl
b
6
6
6
5
5
5
H
H
COCl
COCl
b
1
1
1
1
6
6
6
5
5
5
b
H
H
COCl
COCl
Naphthalene
2-Methyl
C H COCl
6
5
naphthalene
2-Methoxy
naphthalene
Anisole
naphthalene
1-Benzoyl 2-methoxy
naphthalene
4-Methoxy propiophenone
4-Methoxy propiophenone
1-Propio 2-methoxy
naphthalene
4-Methoxy butyrophenone
4-Methoxy butyrophenone
1
4
C
6
H
5
COCl
79
1
1
1
5
6
7
C H COCl
C
C
79
82
81
2
2
2
5
5
5
b
Anisole
H
H
COCl
COCl
2-Methoxy
naphthalene
Anisole
1
1
2
8
9
0
C
C
3
H
H
7
COCl
COCl
77
80
61
b
Anisole
Anisole
3
7
C H CH COCl 4-Methoxy phenyl
6
5
2
acetophenone
COCl 4-Methoxy phenyl
acetophenone
b
2
1
Anisole
C
H
6 5
CH
2
63
a
Moist catalyst (the catalyst storedover water at room temperature for 12 h).
Aromatic compoundsaturatedwith water.
b
[
(
Ar ¼ C H , (CH )C H , (CH ) C H , (CH ) C H , (CH O)C H , C H ,
6
5
3
6
4
3 2
6
3
3 3
6
2
3
6
4
10
7
CH )C H or (CH O)C H ]
3 10 6 3 10 6
þ
À
H þ Cl ! HCl
The above mechanism is similar to that proposedearlier by Brio et al. for
ð5Þ
[
8]
the acylation reactions over cation-exchangedclays.
In summary, the Si-MCM-41 supportedGa O is a highly active cat-
alyst for the acylation of aromatic compounds by acyl chlorides and the
2
3

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MESOPOROUS Si-MCM-41 SUPPORTED Ga O CATALYST
2
2847
3
catalysts do not demand stringent moisture-free conditions for them to be
active in the acylation process. Moreover, because of the presence of mois-
ture, the yieldof acylatedaromatic compoundis increasedwhich is of great
practical importance.
EXPERIMENTAL PROCEDURE
Catalyst Preparation
SupportedGa O catalysts (loading of Ga O ¼ 5–20 wt%) were pre-
2
3
2
3
paredby impregnating Si-MCM-41 (high silica mesoporous MCM-41
2
À1
having surface area of 1140 m g ) with gallium nitrate (Aldrich) from its
aqueous solution by incipient wetness technique, evaporating the water in
ꢀ
ꢀ
vacuum oven at 120 C for 8 h andthen calcining in static air at 500 C for
ꢀ
5 h. Before use, the catalyst was pretreatedat 150 C in a flow of moisture-
free nitrogen for 1 h to remove the adsorbed moisture.
General Procedure for Friedel–Crafts Type Acylation Reaction
The acylation reaction over the supportedGa O catalyst was carried
2
3
3
out in a magnetically stirredglass reactor (capacity: 25 cm ) fittedwith a
reflux condenser, having a low dead volume, mercury thermometer and
3
arrangement for continuously bubbling moisture-free N (30 cm min
À1
)
2
through the liquidreaction mixture at the following reaction con di tions by
[
7]
the procedure described earlier: reaction mixture ¼ 20.0 mmol of moisture-
free aromatic compound þ 11.0 mL of moisture-free solvent þ 8.6 mmol
ꢀ
of acyl chloride, amount of catalyst ¼ 0.4 g, andtemperature ¼ 80 ꢂ 1 C
(
under reflux).
The reaction work-up involvedfiltration andwashing the filtrate twice
with distilled water (15 mL) and 0.1 M NaOH solution (40 mL). The product
was purifiedby column chromatography using silica gel (SRL 60–120 mesh)
as a stationary phase andbenzene as an eluent. The structure of the product
was determined by NMR and MASS spectroscopy.
ACKNOWLEDGMENT
S. K. Jana is grateful to CSIR, New Delhi for the awardof Research
Fellowship.

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2
848
CHOUDHARY AND JANA
REFERENCES
. Olah, G.A. Friedel-Crafts and Related Reactions; Wiley-Interscience
Publ.: New York, 1963.
1
2
3
. Singh, A.P.; Bhattacharya, D. Catal. Lett. 1995, 32, 327.
. Paul, V.; Sudalai, A.; Daniel, T.; Srinivasan, K.V. Tetrahedron Lett.
1994, 35, 2601.
4. Harvey, G.; Vogt, A.; Kouwenhoven, H.W.; Prins, R. Proc. Int. Zeolite
Conf. 1992, 2, 363.
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6
. Izumi, Y.; Ogawa, M.; Urabe, K. Appl. Catal. A: Gen. 1995, 132, 127.
. Quaschning, V; Deutsch, J.; Druska, P.; Niclas, H.J.; Kemnitz, E.
J. Catal. 1998, 177, 164.
7
8
. Choudhary, V.R.; Jana, S.K.; Kiran, B.P. J. Catal. 2000, 192, 257.
. Brio, K.; Bekassy, S.; Agai, B.; Figueras, F.J. Mol. Catal. A: Chem.
2000, 151, 179.
Receivedin the UK July 6, 2001