An efficient procedure for acetalization of carbonyl compounds with P 2O5/SiO2

Article abstract of DOI:10.1080/10426500490463583

P₂O₅ as a dehydrating agent can be used for acetalization of carbonyl compounds. This reaction is very fast with high yield and also comparable with acetal formation by using microwave irradiation.

Full text of DOI:10.1080/10426500490463583

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Phosphorus, Sulfur, and Silicon and the Related
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AN EFFICIENT PROCEDURE FOR ACETALIZATION OF
CARBONYL COMPOUNDS WITH P2O5/SiO2
Bibi Fatemeh Mirjalili a , Mohammad Ali Zolfigol b , Abdolhamid Bamoniri c , Mohammad Ali
Amrollahi a & Azizeh Hazar a
a Yazd University , Yazd, Iran
b Bu-Ali Sina University , Hamadan, Iran
c Kashan University , Kashan, Iran
Published online: 16 Aug 2010.
To cite this article: Bibi Fatemeh Mirjalili , Mohammad Ali Zolfigol , Abdolhamid Bamoniri , Mohammad Ali Amrollahi & Azizeh
Hazar (2004) AN EFFICIENT PROCEDURE FOR ACETALIZATION OF CARBONYL COMPOUNDS WITH P2O5/SiO2 , Phosphorus, Sulfur,
and Silicon and the Related Elements, 179:7, 1397-1401, DOI: 10.1080/10426500490463583
To link to this article: http://dx.doi.org/10.1080/10426500490463583
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Phosphorus, Sulfur, and Silicon, 179:1397–1401, 2004
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Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490463583
AN EFFICIENT PROCEDURE FOR ACETALIZATION
OF CARBONYL COMPOUNDS WITH P2O5/SiO2
Bibi Fatemeh Mirjalili,a Mohammad Ali Zolfigol,b
Abdolhamid Bamoniri,c Mohammad Ali Amrollahi,a
and Azizeh Hazara
Yazd University, Yazd, Iran;a Bu-Ali Sina University, Hamadan,
Iran;b and Kashan University, Kashan, Iranc
(Received October 23, 2003; in final form November 13, 2003)
P2O5 as a dehydrating agent can be used for acetalization of carbonyl
compounds. This reaction is very fast with high yield and also compa-
rable with acetal formation by using microwave irradiation.
Keywords: Acetalization; dehydrating agent; diphosphorus pentoxide
The carbonyl function, as present in aldehydes and ketones, is the most
versatile functional group in organic synthesis. A major problem in
a synthesis of any lengths is to shield a carbonyl function from nu-
cleophilic attack until such time as its electrophilic properties must
be exploited. One of the most useful protecting methods for carbonyl
compounds is acetalization and thioacetalization.1 Acetals are not only
the most widely used protecting groups but are also efficient chiral
auxiliary groups for enantioselective synthesis.2 The most convenient
and practical methods for acetalization are reaction of carbonyl com-
pounds with ethylene glycol in the presence of an appropriate catalyst,
with removal of water formed polyanillin-supported sulfuric acid,3 pyri-
dinium salts,4 SbCl53, rhodium, ruthenium and iridium complexes,6 sil-
ica gel supported metallic sulfates,7 Tungsten hexachloride,8 zirconium
tetrachloride,9 DDQ,10 NBS,11 Envirocat EPZG,12 hydroxy complexes of
palladium(II) and platinium(II),13 iodine,14 titanium cation-exchange
montmorillonite15 are usually utilized as catalyst.
Financial support for this work by Research Affairs, Yazd University, Yazd, Iran and
Bu-Ali Sina University, Hamadan, Iran, is gratefully acknowledged.
Address correspondence to Bibi Fatemeh Mirjalili, Department of Chemistry, Col-
lege of Science, Yazd University, PO Box 89195-741, Yazd, Iran. E-mail: fmirjalili@
yazduni.ac.ir
1397

1398
B. F. Mirjalili et al.
Dehyrating agents such as calcium sulfate, aluminum oxide, copper
sulfate and molecular sieve are also used for the acetal formation.16
Literature survey shows that phosphorus pentoxide (phosphoric anhy-
dride) as a dehydrating agent was used for formation of anhydride from
two molecules of an ordinary acid, ketenimine from amide, vinyl ether
from acetal, nitrile from amide,17 amide from oxime,18 phenolic ester
from carboxylic acid19 and so on. On the basis of the above mentioned
ability of P2O5 we decided to use it for the acetalization of some di-
ols. Therefore, we have been used silica supported form of P2O5 due to
advantages which was reported by Eshghi et al.19
RESULTS AND DISCUSSION
We report herein that acetals and ketals can be prepared very fast and
in excellent yields by the direct condensation of any diols with aldehy-
des/ketones under heterogeneous condition by employing of P2O5/SiO2
(w/w 75%) at room temperature (Scheme 1).
SCHEME 1
Various aldehydes and ketones with different kinds of diols were
subjected to acetalization reaction in the presence of P2O5/SiO2 (w/w
75%) (Table 1). Reaction is exothermic, simple and work-up procedures
are very easy and convenient. In this procedure, did not need tedious
neutralization during work-up and azeotropically removing of water by
Dean-stark apparatus. Although for liquid starting materials, did not
need a solvent, but for solid materials, acetonirile were used as solvent.
This Procedure is very fast and is comparable with acetalization under
microwave irradiation.20,21
EXPERIMENTAL SECTION
General: Chemicals such as carbonyl compounds, ethylene glycol,
phenyl ethylene glycol, guaiacol glyceryl ether, diphosphorus pentox-
ide, acetonitrile, and silica gel were purchased from Fluka, Merck, and

Acetalization
1399
TABLE I Rapid Acetalization/Ketalization of Aldehydes and Ketones(I) by
P2O5/ SiO2 (w/w, 75%) at Room Temperature
Carbonyl
compound (I)
P2O5/SiO2
Diol (II)
Acetonitrile (w/w,75%) Yielda
Entry (10 mmole)
(10–12 mmole)
Product (III)
(mL)
(gr)
(%)
85
90
88
1
2
3
HOCH2 CH2OH
HPCH2 CH2OH
—
2
—
1.5
2
3
4
PhCHOH-CH2OH
HOCH2 CH2OH
3
2
84
5
6
—
1.5
2
89
85
3
7
8
5
5
1.5
2
90
84
9
HOCH2 CH2OH
—
1.5
2
90
87
10
3
11
5
2
85
12
13
3
5
2
2
83
85
14
3
1.5
88
15
PhCHOH-Ch2OH
3
5
1.5
2
85
82
16
aIsolated yield.

1400
B. F. Mirjalili et al.
Aldrich chemical companies. 5-Norbornene-2,2-dimethylol was synthe-
sized according to our previously reported procedure.20 The acetaliza-
tion products were characterized by comparison of their spectral IR,
1H-NMR, TLC, and physical data with authentic samples.
General Procedure for the Preparation of Acetals
or Ketals
To a stirred mixture of carbonyl compound and diol in acetonirile or
without solvent was added a mixture of P2O5/SiO2 (w/w75%) rapidly
(Table I). The reactions are exothermic and after 1–2 min were com-
pleted. The reaction vessel was cooled and the heterogeneous mixture
washed with dichloromethane and decanted. After removal of solvent,
we worked-up and isolated the pure product.
Preparation of Acetal(7) from 4-Nitro Benzaldehyde.
A Typical Procedure
To a stirred and hot mixture of 4-nitrobenzaldehyde( 1.51 g, 10 mmol),
5-norbornene 2,2-dimethylol (1.55 g, 10 mmol) and acetonitrile (5 mL),
P2O5/SiO2 [(w/w 75%), 1.5 g] were added. Reaction is exothermic and
completed after 60 sec. The reaction vessel was cooled and the heteroge-
neous mixture washed with dichloromethane and then decanted. After
removal of solvent, by addition of ethanol and water, the acetal as pure
crystal was obtained. Yield: 2.3 g (90%), m.p: 123–125◦C. [Lit.20 m.p.:
124◦C]
CONCLUSION
Acetals and ketals can be prepared very fast and in excellent yields by
the direct condensation of any diol with aldehydes/ketones under het-
erogeneous condition by employing P2O5/SiO2 (w/w 75%) at room tem-
perature. The cheapness and availability of the reagent, easy procedure
and work-up make this method attractive for the organic chemists.
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