Chemoselective synthesis of 1,1-diacetates from aldehydes in the presence of Al(HSO4)3 under mild solvent-free conditions

Article abstract of DOI:10.1134/S1070428007060085

A novel efficient procedure has been developed for the preparation of acylals in high yields by reaction of the corresponding aldehydes with acetic anhydride in the presence of Al(HSO₄)₃ as catalyst under mild (room temperature) solvent-free conditions.

Full text of DOI:10.1134/S1070428007060085

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2007, Vol. 43, No. 6, pp. 852–854. © Pleiades Publishing, Ltd., 2007.
Published in Russian in Zhurnal Organicheskoi Khimii, 2007, Vol. 43, No. 6, pp. 855–857.
Chemoselective Synthesis of 1,1-Diacetates
from Aldehydes in the Presence of Al(HSO ) under Mild
4
3
Solvent-Free Conditions*
a
b
c
a
a
B. F. Mirjalili , M. A. Zolfigol , A. Bamoniri , M. A. Amrollahi , and N. Sheikhan
a
Department of Chemistry, College of Science, Yazd University, P.O. Box 89195-741,Yazd, Iran
e-mail: fmirjalili@yazduni.ac.ir
b
Department of Chemistry, College of Science, Bu-Ali Sina University, Hamadan, Iran
c
Department of Chemistry, College of Science, Kashan University, Kashan, Iran
Abstract—A novel efficient procedure has been developed for the preparation of acylals in high yields by
reaction of the corresponding aldehydes with acetic anhydride in the presence of Al(HSO
4 3
) as catalyst under
mild (room temperature) solvent-free conditions.
DOI: 10.1134/S1070428007060085
Acylals attract interest as an alternative to acetals
for the protection of aldehyde group due to their stabil-
ity in basic and neutral media. From the synthetic
viewpoint, 1,1-diacetates are important as precursors
of 1-acetoxy dienes for Diels–Alder reactions [1] and
intermediate products in various transformations, in-
cluding nucleophilic substitution reactions [2–6].
tions. Although publications on the use of these salts
in synthetic practice are few in number, in the recent
years more attention has been given to their synthetic
potential in organic chemistry. To the best of our
knowledge, there are no published data on the syn-
thesis of acylals with the aid of Al(HSO ) . Alumi-
num(III) hydrogen sulfate is a stable nonhygroscopic
crystalline substance that is insoluble in most organic
solvents.
4
3
Known syntheses of acylals from aldehydes and
acetic anhydride involve strong protic acids, such as
sulfuric, methanesulfonic, and phosphoric, and Lewis
acids, e.g., WCl [7] or ZrCl [8]. In the recent years,
In continuation of our studies on the application of
metal hydrogen sulfates in organic synthesis, the
present communication describes a convenient method
for the preparation of acylals from the corresponding
aldehydes and acetic anhydride in the presence of
6
4
several reagents and catalysts have been proposed, in
particular P O /SiO [9], NBS [10], Bi(NO ) ·5H O
2
5
2
3 3
2
[
11], In(OTf) [12], Bi(OTf) ·xH O [13], zirconium
3 3 2
sulfophenyl phosphonate [14], H NSO H [15], LiBF
Al(HSO ) . The reactions were carried out at room
2
3
4
4 3
[
16], zinc montmorillonite [17], and heteropolycom-
temperature without a solvent using 4–9 mol % of the
catalyst (Scheme 1, see table).
pounds such as Wells–Dawson acid [18] or aluminum
dodecatungstophosphate [19].
Scheme 1.
According to recently reported data, many reactions
proceed more effectively in the solid state than in solu-
tion. Solvent-free techniques offer such advantages as
reduced pollution, low cost, simplicity of handling, and
easy workup. These factors are especially important
for large-scale processes. Analogous advantages (spe-
cifically, reduced reactor and plant corrosion and en-
vironmentally safe disposal) are inherent to the use of
solid acids instead of, e.g., sulfuric acid. Inorganic
acidic salts such as Al(HSO ) [20, 21] may be recom-
Al(HSO ) , Ac O
4 3
2
room temperature
R–CHO
R–CH(OAc)2
R = Ar, Alk (see table).
The catalytic effect of Al(HSO ) may be rational-
ized in terms of the presence of a hydrogen sulfate ion
as a source of proton and of an Al cation acting as
a Lewis acid. The proposed procedure combines chem-
ical and environmental advantages of solvent-free
reactions. Our results show that Al(HSO ) effectively
4
3
3
+
4
3
mended as reagents and catalysts in the above reac-
4
3
*
The text was submitted by the authors in English.
catalyzes transformations of aromatic aldehydes, in-
852

CHEMOSELECTIVE SYNTHESIS OF 1,1-DIACETATES FROM ALDEHYDES
Chemoselective transformation of aldehydes into the corresponding acylals in the presence of Al(HSO
853
4 3
)
Ratio RCHO– Al(HSO
mmol
4
)
3
–Ac
2
O,
a
b
Run no.
Aldehyde
Reaction conditions Time, min Yield, %
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
4-Nitrobenzaldehyde
3-Nitrobenzaldehyde
2-Chlorobenzaldehyde
4-Chlorobenzaldehyde
Benzaldehyde
3:0.138:3
3:0.138:3
3:0.276:3
3:0.276:3
3:0.276:3
3:0.276:3
3:0.138:3
3:0.276:3
3:0.138:3
3:0.138:3
3:0.276:3
3:0.276:3
3:0.138:3
3:0.138:3
3:0.138:3
3:0.138:3
3:0.138:3
A
A
A
A
05
05
05
05
05
60
20
05
05
05
05
05
30
15
05
05
85
80
83
86
75
68
72
60
88
80
75
82
A
c
2-Ethoxybenzaldehyde
2-Nitrocinnamaldehyde
3-Methoxybenzaldehyde
2,4-Dichlorobenzaldehyde
2,6-Dichlorobenzaldehyde
2-Cyanobenzaldehyde
4-Cyanobenzaldehyde
Vanillin
c
A
A
A
A
A
B
A
A
A
d
e
68 (22)
f
2-Furaldehyde
40
g
Hydrocinnamaldehyde
20
30
00
g
Isobutyraldehyde
4-Dimethylaminobenzaldehyde
A
B
05
30
h
3–5
a
b
c
d
e
f
A: grinding in a mortar at room temperature; B: heating at the boiling point.
Yield of isolated product.
The reaction was carried out in hexane at room temperature.
Triacetate.
4
-Acethoxy-3-methoxybenzaldehyde.
Unidentified polymeric product.
The reaction was accompanied by aldol condensation.
Calculated on the reacted aldehyde.
g
h
cluding those having electron-withdrawing substituents
in the benzene ring, into the corresponding acylals (see
table, run nos. 1–4, 9–12). It should be noted that the
yields of acylals with electron-withdrawing substit-
uents in analogous reactions catalyzed by AlPW O
room temperature. Presumably, the reactivity of that
aldehyde is strongly reduced due to strong donor effect
of the dimethylamino group. It should also be noted
that the reaction with vanillin gave the corresponding
triacetoxy derivative (run no. 13), i.e., the phenolic
hydroxy group underwent acetylation as well.
1
2
40
[
19] were much poorer.
Some aliphatic and aromatic ketones were also tried
Thus we have developed a convenient and effective
catalytic procedure for the chemoselective transforma-
tion of various aldehydes into the corresponding
acylals at room temperature without a solvent using
a relatively nontoxic and inexpensive catalysts.
in this reaction. However, cyclohexanone, 5-methyl-
hexan-2-one, acetophenone, and 4-nitroacetophenone
failed to react with acetic anhydride on grinding in
a mortar over a period of 5 min at room temperature or
on heating at the boiling point over a period of 60 min.
Probably, the proposed procedure ensures chemoselec-
tive protection of an aldehyde group in the presence of
a ketone group. No expected acylal was obtained from
EXPERIMENTAL
All reagents were purchased from Fluka, Merck, or
Aldrich. Aluminum(III) hydrogen sulfate was prepared
by the procedure described in [20]. The products were
4
-dimethylaminobenzaldehyde and acetic anhydride in
the presence of Al(HSO ) on grinding in a mortar at
4
3
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 43 No. 6 2007

8
54
MIRJALILI et al.
identified by their physical constants and spectral data
5. Sandberg, M. and Sydnes, L.K., Org. Lett., 2000, vol. 2,
1
p. 687.
(
IR, H NMR).
6
7
8
9
. Yadav, J.S., Reddy, B.V.S., and Srihari, P., Synlett,
001, no. 5, p. 673.
. Karimi, B., Ebrahimian, G.R., and Seradj, H., Synth.
Commun., 2002, vol. 32, p. 669.
. Smitha, G. and Sanjeeva, R., Tetrahedron, 2003,
vol. 59, p. 9571.
. Mirjalili, B.F., Zolfigol, M.A., and Bamoniri, A.H.,
Phosphorus, Sulfur Silicon, 2004, vol. 179, p. 19.
3
-Nitrobenzylidene diacetate. A mixture of
2
0
.453 g (3 mmol) of 3-nitrobenzaldehyde, 0.3 ml
(
(
3 mmol) of acetic anhydride, and 0.043 g
0.138 mmol) of Al(HSO ) was ground in a mortar
4
3
over a period of 5 min at room temperature. The prog-
ress of the reaction was monitored by TLC using
methylene chloride–petroleum ether (3:2) as eluent.
After 5 min, the conversion was more than 99%. When
the reaction was complete, the mixture was treated
with diethyl ether, the precipitate was filtered off, the
filtrate was washed with a saturated aqueous solution
1
1
1
1
1
0. Karimi, B., Seradj, H., and Ebrahimian, G.R., Synlett,
000, no. 5, p. 623.
2
1. Aggen, D.H., Arnold, J.N., Hayes, P.D., Smoter, N.J.,
and Mohan, R.S., Tetrahedron, 2004, vol. 60, p. 3675.
2. Ghosh, R., Maiti, S., Chakraborty, A., and Halder, R.,
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3. Carrigan, M.D., Eash, K.J., Oswald, M.C., and Mo-
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4. Curini, M., Epifano, F., Marcotullio, M.C., Rosati, O.,
and Nocchetti, M., Tetrahedron Lett., 2002, vol. 43,
p. 2709.
5. Jin, T.-S., Sun, G., Li, Y-W., and Li, T.-S., Green
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6. Yadav, J.S., Reddy, B.V.S., Venugopal, C., and Rama-
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Appl. Clay Sci., 2002, vol. 21, p. 213.
18. Romanelli, G.P., Thomas, H.J., Baronetti, G.T., and
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19. Firouzabadi, H., Iranpoor, N., Nowrouzi, F., and
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of NaHCO (2×25 ml) and water (30 ml), and the
3
organic phase was dried over anhydrous Na SO ,
2
4
filtered, and evaporated. Yield 0.58 g (86%), colorless
crystalline substance, mp 65–66°C; published data
[
12]: mp 64–66°C. The other acylals were synthesized
in a similar way.
The authors thank the Research Affairs at the Yazd
University, Bu-Ali Sina University, and Kashan Uni-
versity for the financial support to this work.
1
1
1
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RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 43 No. 6 2007