The chemoselective preparation of the substituted phenyl benzoates using re-Y zeolite as catalyst

Article abstract of DOI:10.1081/SCC-120005422

A practical and chemoselective method for the synthesis of substituted phenyl benzoates using rare earth zeolite as catalyst was described, its recycle procedure offers high total yield.

Full text of DOI:10.1081/SCC-120005422

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THE CHEMOSELECTIVE PREPARATION OF THE
SUBSTITUTED PHENYL BENZOATES USING RE–Y ZEOLITE
AS CATALYST
Yixiang Ding a , Rui Wu a & Qiang Lin b
a Shanghai Institute of Organic Chemistry, Shanghai, 200032, China
b Hainan University, Haikou, 570000, China
To cite this article: Yixiang Ding , Rui Wu & Qiang Lin (2002) THE CHEMOSELECTIVE PREPARATION OF THE SUBSTITUTED
PHENYL BENZOATES USING RE–Y ZEOLITE AS CATALYST, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 32:14, 2149-2153, DOI: 10.1081/SCC-120005422
To link to this article: http://dx.doi.org/10.1081/SCC-120005422
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SYNTHETIC COMMUNICATIONS
Vol. 32, No. 14, pp. 2149–2153, 2002
THE CHEMOSELECTIVE PREPARATION
OF THE SUBSTITUTED PHENYL
BENZOATES USING RE–Y
ZEOLITE AS CATALYST
2
Yixiang Ding,1, Rui Wu,1 andQiang Lin
*
1Shanghai Institute of Organic Chemistry,
Shanghai 200032, China
2Hainan University, Haikou, 570000, China
ABSTRACT
Apractical and chemoselective method for the synthesis of
substituted phenyl benzoates using rare earth zeolite as cata-
lyst was described, its recycle procedure offers high total yield.
The substituted phenyl benzoates have wide application in the manu-
facture of fine chemicals[1–5] such as insecticide antioxidant, photosensitizer,
liquid crystals, magnetic recording materials and so on. They are also
intermediates for the synthesis of the important fine chemicals hydroxy-
benzophenone.
Esterification is a common reaction. Esters are usually prepared from
acid and alcohol industrially. Due to the poor nucleophility of phenol,
phenolic esters are not formed from free carboxylic acids and generally
*Corresponding author. E-mail: dingyx@pub.sioc.ac.cn
2149
DOI: 10.1081/SCC-120005422
Copyright & 2002 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

2150
DING, WU, AND LIN
prepared from the corresponding phenol and strong acylating agent such as
acid chloride or anhydride, unless some catalysts such as trifluoroacetic
anhydride, trifluoromethanesulphonic anhydride or polyphosphoric acid
are used. Dicyclohexylcarbodiimide etc. has also been used as efficient con-
densing agents. About that Whiting has a good review.[6] These method
present serious environmental problem or need expensive agents. So, the
developments of clear and efficient synthetic routs are challenging.
Solid acids have been developed to promote and esterification,[7–9] but
the preparation of phenyl benzoates catalyzed with zeolite is not satisfactory
so far. Hoefinagel[10] reported that the reaction of resorcinol with benzoic
acid catalyzed with H-ꢀ zeolite gave mixed product of ester and hydroxy-
phenone. Later Guisnet et al.[11,12] suggested o- and p-hydroxyacetophenone
resulted from different pathways in the acylation of phenol by acetic acid on
zeolite ZSM-5. In the present work, we found that phenyl benzoates can be
prepared easily by the catalysis of RE–Y zeolite without C-acylation or fries
rearrangement products. RE–Y zeolite has long been used in the oil industry
for petroleum cracking, which is special thermal stable.
RESULTS AND DISCUSSION
Amixture of benzoic acid and phenol in o-dichlorobenzene was heated
in the presence of zeolite catalyst RE–Y at reflux temperature for 1–10 h to
give phenyl benzoate as summarized in Table 1. As the esterification is
equilibrium reaction, to make this reaction more efficient removal of water
by azeotropic distillation or addition of dehydrating agent is necessary.
The effects of the different zeolites on esterification of phenol with
4-hydroxy-benzoic acid were studied. The zeolites USY, ZSM-5 and
ZCM-7 have only low catalytic activity. The reaction catalyzed by H-ꢀ
formed more Fries rearrangement product hydroxyphenone. The zeolite
(RE–Y) gave best result with middle yield and high chemoselectivity. The
yield increased with increasing catalyst loading, generally 10% w/w of the
mass of benzoic acid gave satisfactory results already.
Table 2 gave the results of the reaction of 4-hydroxy-benzoic acid with
phenol in various solvents. The esterification reaction is dependent on the

SUBSTITUTED PHENYL BENZOATES WITH RE–Y ZEOLITE
2151
Table 1. The Preparation of Phenyl Benzoatea on RE–Y Zeolite
Time
(h)
Yield
(%)
Total Yield/
Times of Recycle
No.
X
Y
1
2
3
4
5
6
7
8
9
H
H
H
H
H
4-NO2
3-Cl
4-H
10
10
5
0.5
6
2
5
10
10
1
5
10
35
63
53
64
57
22
10
55
68
25/3
70/3
84/2
76/2
85/2
80/2
50/3
25/3
87/3
87/2
4-OH
4-OMe
4-OMe
4-OMe
4-OMe
4-OMe
4-OH
4-t-Bu
3-Me
2,4-Cl2
4-NO2
3-Me
XPh¼ꢁ-
naphthol
10
11
4-OMe
7
aAll products were characterized by 1H NMR, IR and physical constants are in
b
agreement with the literature data. Isolated yield.
Table 2. Effect of Solvents on the Yield of Ester 4
Dielectri
Constant c
Bp.
ꢀC
Yield
%
No.
Solvents
1
2
3
4
o-Cl2-benzene
Chlorobenzene
Toluene
6.83
5.65
2.24
2.23
170
132
110
80
63
33
18
10
Benzene
removal of water from the reaction mixture. The efficiency of the removal of
water from the channels of the zeolite is probably related to the temperature
and solvent diplobility mainly.
The reaction of p-hydroxybenzoic acid with phenol formed small
amount of Fries rearrangement product 4-hydroxybenzophenone under
170ꢀC reflux temperature for over 1 h, after 8 h about 20% 4-hydroxy-
benzophenone was formed. Other preparations were not found to form
hydroxybenzophenone. This fact shows that RE–Y is not good catalyst
for C-acylation or Fries rearrangement.
To increase the yield a recycle procedure was developed. After reaction
completed RE–Y catalyst was first collected by hot filtration. The product

2152
DING, WU, AND LIN
ester was isolated by extraction with nonpolar or low polar solvent from the
reaction mixture. The raffinate containing starting materials was subjected
again to the esterification condition. Atwo recycles procedure of 4 offered
81% total yield. The recovered catalyst was washed with solvent (e.g.
Acetone, freed from water and any organic pollutant) and reactivated by
calcination at 450ꢀC. Upon reuse the catalyst exhibits its original activity
and chemoselectivity. The catalyst reusability for ester 4 was studied three
times, their yields were 63, 62, and 63% respectively.
The results in Table 1 show that an electron-donating substituent on
benzoic acid which will stabilize the acylium ion structure favors the ester-
ification reaction and an electron-attracting substituent decreases the yield,
the fact is consistent with acylium ion mechanism. An electron-donating
substituent on phenol increases the nucleophility of phenol, so it also
favors the formation of esters. Fortunately, most of the useful phenyl
benzoates industrially have electron-donating substituents, so the new
chemoselective procedure can meet industry demand.
In conclusion, the esterification reaction of phenols with benzoic acids
can be catalyzed by zeolite RE–Y via an acylium ion mechanism, RE–Y is
an effective catalyst for esterification but not good for the Fries rearrange-
ment. Arecycle procedure of esterification provides a chemoselective, effi-
cient and clean method of preparation of substituted phenyl benzoates.
EXPERIMENTAL
The RE–Y zeolite (SiO2/Al2O3 ¼ 5.0, mixture of rare earth
oxide ¼ 17%) and other zeolites were purchased from Wenzhou HuaHua
Zeolite Com. Ltd. and they are activated at 450ꢀC for 2 h before use. All
chemicals were commercially available. Chemical grade agents were used
without further purification. The products were identified by isolating the
1
products and checking their melting point, MS, IR and H NMR.
A General Procedure
Amixture of benzoic acid (0.1 mol), phenol (0.11 mol), freshly acti-
vated zeolite (RE–Y, 10% w/w of acid) and dichlorobenzene (200 mL) was
stirred at reflux temperature. The water formed was removed by azeotropic
distillation. The course of the reaction was followed by TLC analysis.
When the reaction was completed, the reaction mixture was filtered, the
filtrate was concentrated and chromatographed on silica gel to give the
pure product.

SUBSTITUTED PHENYL BENZOATES WITH RE–Y ZEOLITE
A Recycle Procedure
2153
The reaction of benzoic acid, phenol was carried out according to
above. After reaction was completed, the catalyst was collected by filtration,
washed with acetone and then reactivated at 450ꢀC for 2 h. The reaction
mixture was concentrated and diluted with CH2Cl2 then filtered. The insol-
uble portion was mixture of phenol, benzoic acid and small amount of ester,
and can be reused in a subsequent preparation. The filtrate gave the crude
product after removal of the solvent. The pure phenyl benzoate was
obtained by recrystallization with ethyl acetate.
ACKNOWLEDGMENT
We are grateful to financial support of Shanghai Qunli Chemical
Co. Ltd.
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Received in Japan February 27, 2001