Oxidative removal of acetal protection by the action of KHSO5 and AlCl3 under mild heterogeneous conditions

Full text of DOI:10.1023/A:1019644013230

Russian Journal of Organic Chemistry, Vol. 38, No. 5, 2002, pp. 761 762. From Zhurnal Organicheskoi Khimii, Vol. 38, No. 5, 2002, pp. 797 798.
Original English Text Copyright 2002 by Mirjalili, Zolfigol, Bamoniri.
Oxidative Removal of Acetal Protection
by the Action of KHSO5 and AlCl3 under Mild
Heterogeneous Conditions*
1
2
3
B. F. Mirjalili , M. A. Zolfigol , and A. Bamoniri
1
University of Yazd, Yazd, Iran
2
Bu-Ali Sina University, P.O.Box 4135, Hamadan, 65174 Iran
e-mail: Zolfi@basu.ac.ir
3
University of Kashan, Kashan, Iran
Received January 23, 2002
Protection [1] and deprotection [2] of carbonyl
functionalities are key problems in organic chemistry.
Numerous methods for removal of acetal protection
are known. These are based mostly on acid hydrolysis
of the acetal moiety in aqueous medium [3]. Less
common nonaqueous procedures utilize phosphorus
triodide and diphosphorus tetraiodide [4], iodotri-
methylsilane [5], chlorotrimethylsilane sodium iodide
[6], K10 montmorillonite [7], cobalt and manganese
salts in the presence of oxygen [8], cerium(III)
chloride [9], triphenylphosphine and CBr4 [10], as
well as oxidative systems, e.g. cerium ammonium
nitrate [11], Fe(NO3)3 1.5N2O4 [2], and Cu(NO3)2
N2O4 [2]. We recently showed that heterogeneous
systems are considerably more advantageous than
homogeneous, for they are characterized by experi-
mental simplicity, mild reaction conditions, and
minimal wastes [12 17]. To our knowledge, Oxone
(potassium peroxymonosulfate, KHSO4 2KHSO5
K2SO4, pKa 1) is a widely used oxidant [18] which
has never been applied to deprotect acetals.
of using them in smaller than stoichiometric amounts.
However, high yields of carbonyl compounds were
obtained only when the ratio Oxone:AlCl3 :substrate
was 1:3.8:6. Thus we have found that Oxone is
an effective reagent ensuring fast removal of acetal
protection.
Carbonyl compounds, ethylene glycol, aluminum
chloride, and acetonitrile were purchased from Fluka,
Merck, and Aldrich. Commercial potassium peroxy-
monosulfate was used (KHSO4 2KHSO5 K2SO4,
from Merck). Acetals and 5,5-bis(hydroxymethyl)-
2-norbornene were synthesized by the procedure
described by us in [1]. The deacetalization products
were identified by comparing their spectral (IR and
1H NMR) and TLC data and physical properties with
those of authentic samples.
In the present work various acetals (compounds
Ia Ik, see table) were subjected to deacetalization in
the presence of Oxone and AlCl3 in acetonitrile under
reflux. According to the TLC data, the conversion of
the initial acetal and the yield of the corresponding
carbonyl compound were quantitative.
Deacetalization of compounds I was carried out in
various solvents, such as acetonitrile, tetrahydrofuran,
and methylene chloride. The most appropriate solvent
was acetonitrile. We also examined the possibility
of catalytic action of Oxone and AlCl3 or at least
____________
Deacetalization of compound Ig to 4-hydroxy-3-
methoxybenzaldehyde (typical procedure). A mix-
ture of 0.07 g (0.25 mmol) of compound Ig, 0.3 g of
Oxone, and 0.2 g of AlCl3 in 5 ml of acetonitrile was
refluxed for 60 min. The precipitate was filtered off
and washed with methylene chloride, and the filtrate
was evaporated under reduced pressure. Addition of
ethanol and water to the residue gave 4-nitrobenzalde-
hyde in quantitative yield.
The authors are grateful to the Reserach Depart-
ments at the University of Yazd (Yazd, Iran) and
Bu-Ali Sina Universitety (Hamadan, Iran) for the
financial support of this work.
*
The original article was submitted in English.
1070-4280/02/3805-0761$27.00 2002 MAIK Nauka/Interperiodica

762
MIRJALILI et al.
Deacetalization with Oxone and AlCl3 in acetonitrile
Comp.
no.
Comp.
no.
Formula
Product
Formula
Product
Ia
Ig
Ih
Ii
Ib
Ic
Id
Ij
Ie
If
Ik
REFERENCES
10. Johnstone, C., Kerr, W.J., and Scott, J.S., J. Chem.
Soc., Chem. Commun., 1996, p. 341.
1. Pourjavadi, A. and Mirjalili, B.F., J. Chem. Res.,
Synop., 1999, p. 562.
2. Firouzabadi, H., Iranpour, N., and Zolfigol, M.A.,
11. Ates, A., Gautier, A., Leroy, B., Plancher, J.M.,
Quesnel, Y., and Marko, I.E., Tetrahedron Lett.,
1999, vol. 40, p. 1799.
Bull. Chem. Soc. Jpn., 1998, vol. 71, p. 2169.
12. Zolfigol, M.A., Synth. Commun., 1999, vol. 29, p. 905.
3. Chaves, F., Suarez, S., and Diaz, M.A., Synth.
Commun., 1994, vol. 24, p. 2325.
13. Zolfigol, M.A., Nematollahi, D., and Mallak-
pour, S.E., Synth. Commun., 1999, vol. 29, p. 2277.
4. Denis, J.N. and Krief, A., Angew. Chem., Int. Ed.
Engl., 1980, vol. 19, p. 1006.
14. Zolfigol, M.A. and Mallakpour, S.E., Synth. Com-
mun., 1999, vol. 29, p. 4061.
5. Jung, M.E., Andrew, W.A., and Ornstein, P.L.,
Tetrahedron Lett., 1977, no. 28, p. 4175.
6. Olah, G.A., Hussain, A., Singh, B.P., and Mal-
15. Zolfigol, M.A., Kiany-Borazjani, M., Sadeghi, M.M.,
Mohammadpool-Baltork, I., and Memarian, H.R.,
Synth. Commun., 2000, vol. 30, p. 551.
hotra, A.K., J. Org. Chem., 1983, vol. 48, p. 3667.
16. Zolfigol, M.A., Synth. Commun., 2000, vol. 30,
p. 1593.
7. Gautier, E.C.L., Graham, A.E., McKillop, A.,
Standen, S.P., and Taylor, R.J.K., Tetrahedron Lett.,
1997, vol. 38, p. 1881.
17. Zolfigol, M.A., Kiany-Borazjani, M., Sadeghi, M.,
Sadeghi, M.M., Memarian, H.R., and Mohammad-
poor-Baltork, I., J. Chem. Res., Synop., 2000, p. 167.
8. Hashemi, M. and Kalantari, F., Synth. Commun.,
2000, vol. 30, p. 1857.
9. Marcantoni, E. and Nobili, F., J. Org. Chem., 1997,
18. Zolfigol, M.A., Bagherzaden, M., Madrakian, E.,
Ghaemi, E., and Taqian-Nasab, A., J. Chem. Res.,
Synop., 2001, p. 140.
vol. 62, p. 4183.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 38 No. 5 2002