A simple method for mild oxidation of α-hydroxysilanes to provide aroylsilanes

Article abstract of DOI:10.1081/SCC-100105124

Potassium permanganate supported onto alumina in hexane-water is a good oxidizing agent to convert α-hydroxysilanes into acylsilanes. This mild oxidation afforded aroylsilanes having electron-donating groups attached to the aromatic ring, in 70-86% yield.

Full text of DOI:10.1081/SCC-100105124

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A SIMPLE METHOD FOR MILD OXIDATION OF α-
HYDROXYSILANES TO PROVIDE AROYLSILANES
a
b
Amauri F. Patrocínio & Paulo J. S. Moran
a
Universidade Estadual de Campinas, Instituto de Química, Campinas, SP, 13083-970,
Brazil
b
Universidade Estadual de Campinas, Instituto de Química, Campinas, SP, 13083-970,
Brazil
Published online: 09 Nov 2006.
To cite this article: Amauri F. Patrocnio & Paulo J. S. Moran (2001) A SIMPLE METHOD FOR MILD OXIDATION OF
α-HYDROXYSILANES TO PROVIDE AROYLSILANES, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 31:16, 2457-2461, DOI: 10.1081/SCC-100105124
To link to this article: http://dx.doi.org/10.1081/SCC-100105124
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SYNTHETIC COMMUNICATIONS, 31(16), 2457–2461 (2001)
A SIMPLE METHOD FOR MILD
OXIDATION OF a-HYDROXYSILANES
TO PROVIDE AROYLSILANES
´
Amauri F. Patrocınio and Paulo J. S. Moran*
Universidade Estadual de Campinas, Instituto de Quı
´
mica,
13083-970 Campinas-SP, Brazil
ABSTRACT
Potassium permanganate supported onto alumina in hexane-
water is a good oxidizing agent to convert a-hydroxysilanes
into acylsilanes. This mild oxidation afforded aroylsilanes
having electron-donating groups attached to the aromatic
ring, in 70–86% yield.
The versatile employment of acylsilanes in organic synthetic routes
1
2
3
such as cyclizations, radical reactions, stereocontrol induction, bioreduc-
4
tion and others, has stimulate a search for new methodologies for their
5
6
synthesis.
Different from various routes for the acylsilanes synthesis that employ
expensive reagents or numerous steps, the oxidation of a-hydroxysilanes 1 is
simple and practical. Moreover, the preparation of acylsilanes via oxidation
of a-hydroxysilanes is sometimes the sole option specifically when a silyl
alcohol is a critical intermediate of a synthetic route, for example in chiral
*
Corresponding author.
2
457
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

ORDER
REPRINTS
´
PATROCINIO AND MORAN
2
458
7
3a
induction and racemate resolution (Scheme 1). However, the drawback of
this protocol is that ordinary oxidizing agents like aqueous permanganate
Scheme 1.
and chromic acid in general lead to silanols and aldehydes as major products
5
a
(
Scheme 2). Accordingly, the oxidation of a-silyl alcohols to acylsilanes is
Scheme 2.
8
restrict to some mild conditions, such as Swern-oxidation.
In this communication, we present the results for the oxidation of
9
secondary a-hydroxysilanes 1 to acylsilanes 2 by a mild procedure using
potassium permanganate supported onto neutral alumina. Since acylsi-
lanes are easily converted into ester or carboxylic acid by oxidizing
1
0
1
1
reagents, a biphasic mixture of hexane-water was used as solvent in
order to limit contact between the inorganic reagent and the produced
acylsilane.
Aryl-a-hydroxysilanes having electron-donating groups attached
to the aromatic ring (as 1b–d) were rapidly converted into acylsilanes
2
without significant C-Si cleavage. The replacement of CH3 by C H
6 5
groups attached to the silicon in the silyl alcohols 1a–c has not great
influence on the yield. On the other hand, the alkyl-a-hydroxysilanes
1f and 1g are practically inert toward KMnO4 under these reaction
conditions (see Table). As a comparative study, the oxidation of 1f was
carried out by K Cr O -H SO in water-hexane. Although this reaction
2
2
7
2
4
is very fast (10 min.), it afforded more than 50% of products from C-Si
bond cleavage.

ORDER
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OXIDATION OF a-HYDROXYSILANES
Table. Oxidation of a-Hydroxysilanes into Acylsilanes
2459
1
2,13
a
b
Total a-hydroxysilane conversion (except when indicated); Isolated yield (except
when indicated); Around 15% of cleavage was detected; Estimated by GC/MS;
c
d
e
f
2 2 7 2 4 2
The a-hydroxysilane was recovered; Oxidation by K Cr O -H SO -H O.
In summary, we have reported a mild and practical method of a-
hydroxysilanes oxidation, which enlarges the choice of methodologies avail-
able to prepare aroylsilanes.
REFERENCES
1. (a) Saleur, D.; Bouillon, J.-P.; Portella, C. Tetrahedron Lett. 1999, 40,
321. (b) Saleur, D.; Bouillon, J.-P.; Portella, C. Tetrahedron Lett. 2000,
41, 1885. (c) Tsai, Y.M.; Cherng, C.D.; Nieh, H.C.; Sieh, J.A.
Tetrahedron 1999, 55, 14587. (d) Takeda, K.; Ohtani, Y. Org. Lett.
999, 1, 677.
1
2
. (a) Chuang, T.-H.; Fang, J.-M.; Jiaang, W.-T.; Tsai, Y.-M. J. Org.
Chem. 1996, 61, 1794. (b) Chang, S.Y.; Jiaang, W.T.; Cherng, C.D.;
Tang, K.H.; Huang, C.H.; Tsai, Y.M. J. Org. Chem. 1997, 62, 9089.
(
7
c) Tsai, Y. M; Tang, K.H.; Jiaang, W.T. Tetrahedron Lett. 1996, 37,
767.

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REPRINTS
´
PATROCINIO AND MORAN
2
460
3. (a) Nakada, M.; Urano, Y.; Kobayashi, S.; Ohno, M. Tetrahedron Lett.
1
1
994, 35, 741. (b) Fleming, I.; Barbero, A.; Walter, D. Chem. Rev.
997, 97, 995. (c) Bonini, B.F.; Comes-Franchini, M.; Laboroi, F.;
Mazzanti, G.; Ricci, A.; Varchi, G. J. Org. Chem. 1999, 64, 8008. (d)
Huang, A.X.; Xiong, Z.; Corey, E.J. J. Am. Chem. Soc. 1999, 121, 9999.
. (a) Patrocınio, A.F.; Correˆ a, Jr., I.R.; Moran, P.J.S. J. Chem. Soc.
´
4
Perkin Trans. 1 1999, 3133. (b) Tacke, R.; Linoh, H. In: Patai, S.;
Rappoport, Z. (eds). ‘‘The Chemistry of Organic Silicon Compounds’’,
1989, Chap.18. John Wiley & Sons Ltd. (c) Syldatk, C.; Stoffregen, A.;
Wuttke, F.; Tacke, R. Biotech. Letters 1988, 10, 731. (d) Fischer, L.;
Wagner, S.A.; Tacke, R. Appl. Microbiol. Biotechnol. 1995, 42, 671.
(e) Tacke, R.; Wagner, S.A.; Brakmann, S.; Wuttke, F. J. Organomet.
Chem. 1993, 458, 13.
5
. (a) Brook, A.G. In: Stone, F.G.A.; West, R. eds. Advance Organo-
metallic Chemistry. Ac. Press, N.Y. 1968, 7, 95. (b) Page, P.C.B.;
Klair, S.S.; Rosenthal, S. Chem. Soc. Rev. 1990, 19, 147. (c) Ricci,
A.; Degl’Innocenti, A. Synthesis 1989, 647. (d) Ricci, A. J. Organomet.
Chem. 1998, 567, 181. (e) Patrocinio, A.F.; Moran, P.J.S. J. Braz.
Chem. Soc. 2001, 12, 7.
6. For some examples of acylsilanes synthesis methodologies see Ref. 5
and for other more recents see (a) Patrocınıo, A.F.; Moran, P.J.S.
´ ´
J. Organomet. Chem. 2000, 603, 220. (b) Tius, M.A.; Hu, H.
Tetrahedron Lett. 1998, 39, 5937. (b) Stergiades, I.A.; Tius, M.A.
J. Org. Chem. 1999, 64, 7547. (c) Geng, F.; Maleczka, Jr., R.E.
Tetrahedron Lett. 1999, 40, 3113. (d) Fleming, I.; Ghosh, U.
J. Chem. Soc. Perkin Trans. 1 1994, 257. (e) Paredes, M.D.; Alonso,
R. Tetrahedron Lett. 1999, 40, 3973. (f ) Bonini, B.F.; Franchini, M.C.;
Mazzanti, G.; Passamonti, U.; Ricci, A.; Zani, P. Synthesis 1995, 92.
. Sakaguchi, K.; Mano, H.; Ohfune, Y. Tetrahedron Lett. 1998, 39, 4311.
. Sommer, L.H.; Bailey, D.L.; Golberg, G.M.; Buck, C.E.; Bye, T.S.;
Evans, F.J.; Whitmore, F.C. J. Am. Chem. Soc. 1954, 76, 1613. (b)
Ireland, R.E.; Norbeck, D.W. J. Org. Chem. 1985, 50, 2198. (c)
Linderman, R. J.; Suhr, Y. J. Org. Chem. 1998, 53, 31569. (d)
Danheiser, R.L.; Fink, D.M.; Okano, K.; Tsai, Y.-M.; Szczepanski,
S.W. J. Org. Chem. 1985, 50, 5393. (e) Huber, P.; Bratovanov, S.;
Bienz, S.; Syldatk, C.; Pietzsch, M. Tetrahedron: Asymmetry 1996,
7
8
7
, 69.
9.
The a-silyl alcohols where prepared by addition of trimethyl- or
dimethylphenylsilyl lithium to aldehydes. For preparation details and
other methods see: (a) Mori, A.; Fujita, A.; Ikegashira, K.;
Nishihara, Y.; Hiyama, T. Synlett 1997, 693. (b) Wilson, S.R.; Hague,
M.S.; Misra, R.N. J. Org. Chem. 1982, 47, 747. (c) Barretm, A.G.M.;

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OXIDATION OF a-HYDROXYSILANES
2461
Hill, J.M.; Wallace, E.M.; Flygare, J.A. Synlett 1991, 764. (d) Hudrlik,
P.F.; Abdallah, Y.M.; Kulkarni, A.K.; Hudrlik, A.M. J. Org. Chem.
1992, 57, 6552. (e) Hiyama, T.; Obayashi, M. J. Org. Chem. 1983, 48,
912. (f ) Linderman, R.J.; Ghannam, A. J. Am. Chem. Soc. 1990, 112,
2392. (g) Linderman, R.J.; Chen, K. Tetrahedron Lett. 1992, 33, 6767.
1
0. The efficiency of supported reagents for better performance in oxida-
tions is known. Examples are: molecular sieves-permanganate (Regen,
S. L.; Koteel, C. J. Am. Chem. Soc. 1977, 99, 3837), copper sulfate-
permanganate (Menger, F. M.; Lee, C. J. Org. Chem. 1979, 44, 3446),
montmorillonite-acylnitrates (Oliveira Filho, A.P.; Moreira, B.G.;
Moran, P.J.S.; Rodrigues, J.A.R. Tetrahedron Lett. 1996, 37, 5029).
Also, it is known that potassium permanganate supported onto acidic
alumina is a good procedure to obtain aldehydes from olefins cleavage
(Lee, D.G.; Chen Tao; Zhao Wang. J. Org. Chem. 1993, 58, 2918).
1. Patrocınio, A. F.; Moran, P. J. S. Synth. Commun. 2000, 30, 1419.
1
1
´
2. General procedure for supported two-phase oxidation. A powdered
KMnO (0.35 g) and neutral Alumina (0.45 g) were added to water
4
(
3.0 mL) and this mixture was stirred by 3 min. followed by addition
of hexane (7.0 mL). Thus, the a-silyl alcohol (0.58 mmol) dissolved in
.0 mL of hexane was added, at room temperature. The mixture was
1
stirred for more 1–5 hours and then filtered under reduced pressure.
The organic phase was isolated and the desired product purified
by filtration in a short chromatograph column, using hexane-ethyl
acetate (9:1).
1
3. Physical data of the aroylsilane 4-methoxybenzoyldimethylphenylsilane
0
–1
2
b (R ¼ Ph), yellow oil, n
(KBr)/cm 1588 (C ¼ O), 1423, 1511, 1253,
max
1
8
36. NMR H (300 MHz, CDCl ): 0.61 (s, 6H, SiMe ); 3.82 (s, 3H,
3
2
OMe); 6.86 (d, J ¼ 9.4 Hz, 1H
); 7.30–7.61 (m, 5H, SiPh); 7.75 (d,
meta
.
þ
J ¼ 9.4 Hz, 1H
). m/z: 270 (M , 10%); 269 (31); 255 (5); 239 (16);
ortho
þ
1
2
35 (100). HRMSfound m/z 269.09961; calcd. for C H O Si [M-H] :
1
6
17
2
69.09978. Physical data of the aroylsilane 3,4-dimethoxybenzoyldi-
0
–1
methylphenylsilane 2c (R ¼ Ph), yellow oil, n
(KBr)/cm
1573
max
1
(
6
C ¼ O), 1506, 1413, 1259, 826. NMR H (300 MHz, CDCl ): 0.61 (s,
3
H, SiMe ); 3.78 (s, 3H, OMe); 3.88 (s, 3H, OMe); 6.80 (dd, J ¼ 14.5
2
and 1.9, lH
); 7.30–7.41 (m, 5H, SiPh); 7.57–7.63 (m, 2H
). m/z:
ortho
meta
.
þ
3
3
2
00 (M , 10%); 299 (22); 285 (5); 269 (41); 135 (100). HRMSfound m/z
þ
00.11814; calcd. for C H O Si [M] : 300.11817. The other acylsilanes
1
7
20
3
were analyzed by GC/MScomparing the retention time and MSspectra
with genuine samples. The physical data of these acylsilanes are found in
Ref. 4a, 4e, 5a and references cited therein.
Received in the USA November 10, 2000

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