An efficient method for the synthesis of acylals from aldehydes under solvent-free conditions catalyzed by antimony trichloride

Article abstract of DOI:10.1080/00397910701651284

A mild and efficient method has been developed for the preparation of acylals from aldehydes catalyzed by antimony trichloride under solvent-free conditions in very good to excellent yields. The easy availability, low cost, and ease of handling of the catalyst make this procedure especially attractive for large-scale synthesis. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910701651284

This article was downloaded by: [National Sun Yat-Sen University]
On: 08 January 2015, At: 01:35
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office:
Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An International
Journal for Rapid Communication of
Synthetic Organic Chemistry
Publication details, including instructions for authors and subscription
information:
http://www.tandfonline.com/loi/lsyc20
An Efficient Method for the Synthesis of
Acylals from Aldehydes under Solvent‐Free
Conditions Catalyzed by Antimony Trichloride
Dr. Asish K. Bhattacharya a , Mohammad Mujahid a & Arvind A. Natu a
a Combi Chem‐Bio Resource Centre and Division of Organic Chemistry
(Synthesis) , National Chemical Laboratory , Pune, Maharashtra, India
Published online: 25 Jan 2008.
To cite this article: Dr. Asish K. Bhattacharya , Mohammad Mujahid & Arvind A. Natu (2007) An Efficient
Method for the Synthesis of Acylals from Aldehydes under Solvent‐Free Conditions Catalyzed by Antimony
Trichloride, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 38:1, 128-134, DOI: 10.1080/00397910701651284
To link to this article: http://dx.doi.org/10.1080/00397910701651284
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”)
contained in the publications on our platform. However, Taylor & Francis, our agents, and our
licensors make no representations or warranties whatsoever as to the accuracy, completeness, or
suitability for any purpose of the Content. Any opinions and views expressed in this publication
are the opinions and views of the authors, and are not the views of or endorsed by Taylor &
Francis. The accuracy of the Content should not be relied upon and should be independently
verified with primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities
whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial
or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or
distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use
can be found at http://www.tandfonline.com/page/terms-and-conditions

Synthetic Communicationsw, 38: 128–134, 2008
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910701651284
An Efficient Method for the Synthesis of
Acylals from Aldehydes under Solvent-Free
Conditions Catalyzed by Antimony
Trichloride
Asish K. Bhattacharya, Mohammad Mujahid,
and Arvind A. Natu
Combi Chem-Bio Resource Centre and Division of Organic Chemistry
(Synthesis), National Chemical Laboratory, Pune, Maharashtra, India
Abstract: A mild and efficient method has been developed for the preparation of
acylals from aldehydes catalyzed by antimony trichloride under solvent-free conditions
in very good to excellent yields. The easy availability, low cost, and ease of handling of
the catalyst make this procedure especially attractive for large-scale synthesis.
Keywords: acetic anhydride, acylals, aldehydes, antimony trichloride, solvent-free
conditions
INTRODUCTION
Protection and deprotection of functional groups plays a pivotal role in the
synthesis of multifunctional targets, and tolerance of other functional
groups present in the substrates necessitates selective reagents for these type
of transformations.[1] Acylal formation is one of the most widely used
processes for protection of aldehydes because of the remarkable stability of
acylals (1,1-diacetates) against a variety of reaction conditions, such as
aqueous acids and neutral and basic media.[2] Acylals have also found
Received in the USA May 23, 2007
Address correspondence to Dr. Asish K. Bhattacharya, Combi Chem-Bio Resource
Centre and Division of Organic Chemistry (Synthesis), National Chemical Laboratory,
Dr. Homi Bhabha Road, Pune, 411 008, Maharashtra, India. E-mail: ak.bhattacharya@
ncl.res.in
128

Synthesis of Acylals from Aldehydes
129
applications as cross-linking reagents for cellulose in cotton[3] and bleaching
activators in wine-stained fabrics.[4]
Usually, acylal formation involves the reaction of aldehydes with acetic
anhydride in the presence of an acid catalyst,[5,6] which include heterogeneous
solid acids,[7] metal halides,[8] metal tetrafluoroborates,[9] metal triflates,[10]
and silica-supported reagents.[11]
However, many of these existing methodologies suffer from one or more of
the following disadvantages: (i) prolonged reaction times (e.g., up to 120 h in the
case of 2-furyl aldehyde with PCl3[5a]); (ii) low yields (e.g., 30% in case of cinna-
maldehyde with PCl3[5a]); (iii) high temperatures;[9a] (iv) use of harmful organic
solvents;[5b,6c,10a,10d] (v) use of moisture-sensitive and costly catalysts
(e.g., triflates[10]); (vi) special efforts required to prepare the catalyst (e.g.,
Nafion-H,[7a] H2SO4-SiO2,[11a] HClO4-SiO2,[11b] HBF4-SiO2,[11c] and FeCl3-
SiO2[11d]); (vii) use of excess Ac2O; and (viii) requirement of special appara-
tus.[9c] We report use of SbCl3 under solvent-free conditions as an efficient
catalyst for the acylal formation in high yields in substrates with structural
diversity.
RESULTS AND DISCUSSION
As a Lewis acid, SbCl3 has been extensively used as a catalyst in various organic
transformations.[12] To the best of our knowledge, there is no report of the use of
SbCl3 for these types of reactions. It is easier to handle[12b] than other metal
halides such as InCl3, GdCl3, and TiCl4, and it is also mild and cost-effective.
Thus, the reaction of an aldehyde (1.0 mmol), acetic anhydride (5.0 mmol),
and SbCl3 (10 mol%) under solvent-free conditions at room temperature
furnished the corresponding acylal in good to excellent yields (Scheme 1).
To establish the generality of the present reaction and to examine the
tolerance of the other functional groups present in the substrates, diverse
aldehydes including aromatic and a,b-unsaturated moiety (Table 1) were
subjected to acylal formation by the treatment of Ac2O under the catalytic
influence of SbCl3. In almost all cases, the reactions are faster than those
reported,andthe yieldsarequite high. Asanticipated, thepresenceofsubstituents
on the aromatic ring at the para position (entries b, c, f, g, h, k, n, and p) increases
the yield and also enhances the rate of the reaction, whereas the presence of sub-
stituents at meta position (entries i and j) decreases the yield and reactions are
sluggish. Tolerance to various functional groups in the substrates was evident
from the substrates bearing methylenedioxy, methoxy, and olefinic groups.
Scheme 1.

130
A. K. Bhattacharya, M. Mujahid, and A. A. Natu
Table 1. SbCl3-catalysed acylal formation of different aldehydes with Ac2Oa
Time
(min)
Yield
(%)b
Entry
a
Substrate
Product
5
96
b
c
15
10
96
95
d
e
5
92
96
10
f
10
15
96
98
g
h
i
15
30
92
80
j
30
30
5
72
85
88
k
l
(continued)

Synthesis of Acylals from Aldehydes
131
Table 1. Continued
Time
(min)
Yield
(%)b
Entry
Substrate
Product
m
n
CH3(CH)2CHO
CH3(CH)2CH(OAc)2
10
25
91
92
o
p
20
5
90
96
q
—
24 h
—
1
aAll products were characterized by IR, H NMR, and mass spectral data.
bIsolated yields of the corresponding acylal.
The case of cinnamaldehyde (entry d) is worth mentioning because it
furnished a yield of 92% (5 min) by this method, in contrast to a yield of
30% (24 h) with PCl3.[5a] In the case of aliphatic aldehydes (entry m), one
also observes high yields in short reaction times. Hydroxy groups in the sub-
strates (entries k, l, n, o, p) were also acetylated to furnish the corresponding
triacetates under the present reaction conditions. Failure of 4-dimethylamino-
benzaldehyde (entry q) to furnish the corresponding acylal even after 24 h
may be ascribed to the strong electron-donating dimethylamino group. Also,
tautomerization may occur with the formation of a quininoid structure and
thereby deactivate the reactivity of the aldehydic group.[5e]
CONCLUSION
In conclusion, SbCl3 has been found to be a cost-effective and highly efficient
Lewis acid catalyst for the preparation of acylals from aldehydes under mild
conditions.
TYPICAL PROCEDURE
A mixture of aldehyde (2 mmol), freshly distilled Ac2O (10 mmol), and SbCl3
(10 mol%) was stirred magnetically at room temperature until complete

132
A. K. Bhattacharya, M. Mujahid, and A. A. Natu
consumption of the aldehyde (by thin-layer chromatography, TLC). The
reaction mixture was diluted with water (30 mL) and extracted with dichlor-
omethane (3 ꢀ 30 mL). The combined dichloromethane extracts were
washed successively with 10% sodium bicarbonate and H2O, dried
(Na2SO4), and concentrated under reduced pressure. In all the cases, the
product obtained after the usual workup gave satisfactory spectral data
without any further purification.
Selected Spectral Data
1,1-Diacetoxy-1-(4-methylphenyl)methane (3b): mp: 82–838C (lit.[11b]
1
848C); IR (neat): 1762 cm21; H NMR (200 MHz, CDCl3): d 7.64 (s, 1H),
7.43–7.23 (m, 4H), 2.37 (s, 3H), 2.11 (s, 6H); MS (ESI): m/z ¼ 222 [Mþ],
245 [Mþ þ Na].
1,1-Diacetoxy-1-(3-bromophenyl)methane (3i): mp: 84–858C (lit.[11b] 83 8C);
IR (neat): 1760 cm21; 1H NMR (200 MHz, CDCl3): d 7.63 (s, 1H), 7.32–7.20
(m, 4H), 2.14 (s, 6H); MS (ESI): m/z ¼ 286 [Mþ], 309 [Mþ þ Na].
1,1-Diacetoxy-1-(3-chlorophenyl)methane (3j): gummy; IR (neat):
1757 cm21 1H NMR (200 MHz, CDCl3): d 7.63 (s, 1H), 7.38–7.26
;
(m, 4H), 2.14 (s, 6H); MS (ESI): m/z ¼ 242 [Mþ], 265 [Mþ þ Na].
1,1-Diacetoxy-1-(2-acetoxy,3-methoxyphenyl)methane (3l): gummy; IR
1
(neat): 1772 cm21; H NMR (200 MHz, CDCl3): d 7.88 (s, 1H), 7.49–7.26
(m, 3H), 3.89 (s, 3H), 2.41 (s, 3H), 2.13 (s, 6H); MS (ESI): m/z (%) ¼ 296
[Mþ], 319 [Mþ þ Na].
ACKNOWLEDGMENT
A. K. B. isgratefulto S. Sivaram, director, NationalChemicalLaboratory (NCL),
Pune, India, for financial support (MLP008626) and to Krishna N. Ganesh,
J. C. Bose fellow and director, Indian Institute of Science Education and
Research (IISER), Pune, for constant encouragement and support.
REFERENCES
1. Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis, 3rd edn.;
John Wiley and Sons: New York, 1999; p. 306.
2. Gregory, M. J. Evidence for a cyclic AA11 mechanism in the hydrolysis of
benzylidene diacetates. J. Chem. Soc. B 1970, 1201.

Synthesis of Acylals from Aldehydes
133
3. Frick, J. G., Jr.; Harper, R. J., Jr. Acetals as crosslinking reagents for cotton.
J. Appl. Polymer Sci. 1984, 29, 1433.
4. Eanderson, W. R Eur. Pat. Appl. EP 125 781, 1985; Chem, Abstr. 1985, 102,
P64010K.
5. (a) Michie, J. K.; Miller, J. A. Phosphorus trichloride as catalyst in preparation of
1,1-diacetates from aldehydes. Synthesis 1981, 824; (b) Deka, N.; Kalita, D. J.;
Borah, R.; Sarma, J. C. Iodine as acetylation catalyst in the preparation of 1,1-dia-
cetates from aldehydes. J. Org. Chem. 1997, 62, 1563; (c) Karimi, B.; Seradj, H.;
Ebrahimian, G. R. Mild and efficient conversion of aldehydes to 1,1-diacetates
catalyzed with N-bromosuccinimide (NBS). Synlett 2000, 623; (d) Deka, N.;
Borah, R.; Kalita, D. J.; Sarma, J. C. Synthesis of 1,1-diacetates from aldehydes
using trimethylchlorosilane and sodium iodide as catalyst. J. Chem. Res., Synop.
1998, 94; (e) Jin, T.-S.; Sun, G.; Li, Y.-W.; Li, T.-S. An efficient and convenient
procedure for the preparation of 1,1-diacetates from aldehydes catalyzed by
H2NSO3H. Green Chem. 2002, 4, 255.
6. (a) Jin, T.-S.; Du, G.-Y.; Li, T.-S. An efficient and convenient procedure for the
synthesis of 1,1-diacetates of aldehydes catalysed by anhydrous ferrous sulfate.
Ind. J. Chem. Sect. B 1998, 37, 939; (b) Roy, S. C.; Banerjee, B. A mild and
efficient method for the chemoselective synthesis of acylals from aldehydes and
their deprotection catalysed by ceric ammonium nitrate. Synlett 2002, 1677;
(c) Aggen, D. H.; Arnold, J. N.; Smoter, N. J.; Mohan, R. S. Bismuth
compounds in organic synthesis: bismuth nitrate catalyzed chemoselective
synthesis of acylals from aromatic aldehydes. Tetrahedron 2004, 60, 3675–3679.
7. (a) Olah, G. A.; Mehrotra, A. K. Catalysis by solid superacids: improved Nafion-H
catalyzed preparation of 1,1-diacetates from aldehydes. Synthesis 1982, 962;
(b) Ballini, R.; Bordoni, M.; Bosica, G.; Maggi, R.; Sartori, G. Solvent-free
synthesis and deprotection of 1,1-diacetates over a commercially available
zeolite
Y as a reusable catalyst. Tetrahedron Lett. 1998, 39, 7587;
(c) Kumar, P.; Hegde, V. R.; Kumar, T. P. An efficient synthesis of diacetates
from aldehydes using beta-zeolite. Tetrahedron Lett. 1995, 36, 601;
(d) Jankovic, L.; Komadel, P. Metal cation-exchanged montmorillonite
catalyzed protection of aromatic aldehydes with Ac2O. J. Catal. 2003, 218, 227.
8. (a) Smitha, G.; Reddy, C. S. A facile and efficient ZrCl4 catalyzed conversion of
aldehydes to geminal-diacetates and dipivalates and their cleavage. Tetrahedron
2003, 59, 9571; (b) Yin, L.; Zhang, Z.; Wang, Y. Indium tribromide as a highly
efficient and versatile catalyst for chemoselective synthesis of acylals from
aldehydes under solvent-free conditions. Synlett 2004, 1727; (c) Yadav, J. S.;
Reddy, B. V. S.; Srinivas, C. Indium trichloride catalyzed chemoselective conver-
sion of aldehydes to gem-diacetates. Synth. Commun. 2002, 32, 1175, and refer-
ences cited therein.
9. (a) Sumida, N.; Nishioka, K.; Satu, T. Conversion of aldehydes into geminal dicar-
boxylates (acylals) catalyzed by lithium tetrafluoroborate. Synlett 2001, 1921;
(b) Chakraborti, A. K.; Thilagavathi, R.; Kumar, R. Copper(II) tetrafluoro-
borate–catalyzed formation of aldehyde-1,1-diacetates. Synthesis 2004, 831, and
references cited therein.
10. (a) Carrigan, M. D.; Eash, K. J.; Oswald, M. C.; Mohan, R. S. An efficient method
for the chemoselective synthesis of acylals from aromatic aldehydes using bismuth
triflate. Tetrahedron Lett. 2001, 42, 8133; (b) Ghosh, R.; Maiti, S.;
Chakraborty, A.; Halder, R. Indium triflate: a reusable catalyst for expeditious
chemoselective conversion of aldehydes to acylals. J. Mol. Catal. A 2004, 215,
49; (c) Karimi, B.; Maleki, J. Lithium trifluoromethanesulfonate (LiOTf) as a

134
A. K. Bhattacharya, M. Mujahid, and A. A. Natu
recyclable catalyst for highly efficient acetylation of alcohols and diacetylation of
aldehydes under mild and neutral reaction conditions. J. Org. Chem. 2003, 68,
4951; (d) Chandra, K. L.; Saravanan, P.; Singh, V. K. An efficient method for
diacetylation of aldehydes. Synlett 2000, 359.
11. (a) Desai, U. V.; Thopate, T. S.; Pore, D. M.; Wadgaonkar, P. P. An efficient,
solvent-free method for the chemoselective synthesis of acylals from aldehydes
and their deprotection catalyzed by silica sulfuric acid as a reusable solid acid
catalyst. Catal. Commun. 2006, 7, 508; (b) Kumar, R.; Tiwari, P.; Maulik, P. R.;
Misra, A. K. HClO4-SiO2 catalyzed chemoselective synthesis of acylals from
aldehydes under solvent-free conditions. J. Mol. Catal. A 2006, 247, 27;
(c) Kamble, V. T.; Bandgar, B. P.; Joshi, N. S.; Jamodeb, V. S. A remarkable
HBF4-SiO2-catalyzed synthesis of acylals from aldehydes under solvent-free
conditions. Synlett 2006, 2719; (d) Wang, C.; Li, M. A novel and efficient conver-
sion of aldehydes to 1,1-diacetates catalyzed with FeCl3/SiO2 under microwave
irradiation. Synth. Commun. 2002, 32, 3469.
12. (a) Ren, P.; Pan, S.; Dong, T.; Wu, S. The novel reduction systems: NaBH4-SbCl3
or NaBH4-BiCl3 for conversion of nitroarenes to primary amines. Synth. Commun.
1995, 25, 3799; (b) Maiti, G.; Kundu, P. Imino Diels–Alder reactions: an efficient
one-pot synthesis of pyrano and furanoquinoline derivatives catalyzed by SbCl3.
Tetrahedron Lett. 2006, 47, 5733, and references cited therein.