LETTER
Direct Trifluoroacetylation
441
of trifluoroacetylation on the nature of the external halide
used, as well as the formation of only 2-O-trifluoro-
acetylated halohydrins 5–8 (Scheme 1, route A) with de-
fined stereochemistry, and the lack of an intramolecular
acyl rearrangement, are in agreement with this mecha-
nism.
(2) Stamatov, S. D.; Stawinski, J. Tetrahedron Lett. 2006, 47,
543.
2
(
3) de Haas, G. H.; van Deenen, L. L. M. Recl. Trav. Chim.
Pays-Bas 1961, 80, 951.
(
(
4) Boguslavskaya, L. S. Russ. Chem. Rev. 1972, 41, 740.
5) (a) Azzena, F.; Calvani, F.; Crotti, P.; Gardelli, C.; Macchia,
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S.; Anderson, R. C. Tetrahedron Lett. 1991, 32, 3021.
An alternative scenario that would invoke a nucleophilic
attack by a trifluoroacetate anion on silicon seems less
plausible, as halide ions are apparently more effective as
a nucleophile for silicon than trifluoroacetate. This is also
consistent with the experimental data that trifluoroacety-
lation was significantly faster in the presence of external
halides.
(
c) Righi, G.; Pescatore, G.; Bonadies, F.; Bonini, C.
Tetrahedron 2001, 57, 5649. (d) Kotsuki, H.; Shimanouchi,
T.; Ohshima, R.; Fujiwara, S. Tetrahedron 1998, 54, 2709.
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(
(7) (a) Onaka, M.; Sugita, K.; Takeuchi, H.; Izumi, Y. J. Chem.
Soc., Chem. Commun. 1988, 1173. (b) Chini, M.; Crotti, P.;
Gardelli, C.; Macchia, F. Tetrahedron 1992, 48, 3805.
Finally, to demonstrate feasibility of the removal of tri-
fluoroacetyl groups from halohydrins 5–8 under mild con-
ditions, these compounds were treated in CH Cl –pentane
(
8) (a) Gao, L.-X.; Murai, A. Chem. Lett. 1989, 357. (b) Gao,
L.-X.; Murai, A. Chem. Lett. 1991, 1503.
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Lett. 1992, 33, 7093. (b) Sharghi, H.; Eskandari, M. M.
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M.; Ghavami, R. J. Mol. Catal. A: Chem. 2004, 215, 55.
2
2
with pyridine (10 equiv) and methanol (250 equiv) at
room temperature. The reactions were quantitative
(
completion within 20 min) and, after removal of volatile
(
d) Sharghi, H.; Eskandari, M. M. Synthesis 2002, 1519.
products, afforded positional homogenous vicinal halo-
(
(
10) Bonini, C.; Righi, G. Synthesis 1994, 225.
1
13
alkanols 9–12 (purity >99%, by H NMR and C NMR
11) (a) Soroka, M.; Goldeman, W.; Malysa, P.; Stochaj, M.
Synthesis 2003, 2341. (b) Solladie-Cavallo, A.; Lupattelli,
P.; Marsol, C.; Isarno, T.; Bonini, C.; Caruso, L.; Maiorella,
A. Eur. J. Org. Chem. 2002, 1439.
spectroscopy) without any supplementary purification
2
7
(
route B, Scheme 1).
In conclusion, we have developed a general, simple and
efficient synthetic strategy for a direct conversion of tri-
methylsilylated halohydrins 1–4 to 2-O-trifluoroacetylat-
ed derivatives 5–8, from which the corresponding C3-
vicinal haloalkanols (9–12), that bear acyl residues sen-
sitive to migration, can be retrieved directly and without
recourse to additional work-up or purification steps.
(
12) (a) Sabitha, G.; Babu, R. S.; Rajkumar, M.; Reddy, C. S.;
Yadav, J. S. Tetrahedron Lett. 2001, 42, 3955. (b) Kwon,
D. W.; Cho, M. S.; Kim, Y. H. Synlett 2003, 959.
(13) (a) Tamami, B.; Mahdavi, H. React. Funct. Polym. 2002, 51,
. (b) Niknam, K.; Nasehi, T. Tetrahedron 2002, 58, 10259.
c) Hara, S.; Hoshio, T.; Kameoka, M.; Sawaguchi, M.;
Fukuhara, T.; Yoneda, N. Tetrahedron 1999, 55, 4947.
d) Sharghi, H.; Naeimi, H. Synlett 1998, 1343.
7
(
(
The reactions are clean, entirely chemo- and regio-
specific, and afford the target products under mild condi-
tions in practically quantitative yields. The method makes
use of commercially available reagents and is potentially
tolerant toward the presence of other, more stable silyl
groups.
(14) Leung, W.-H.; Wong, T. K. T.; Tran, J. C. H.; Yeung, L.-L.
Synlett 2000, 677.
(
15) (a) Kricheldorf, H. R.; Morber, G.; Regel, W. Synthesis
981, 383. (b) Andrews, G. C.; Crawford, T. C.; Contillo, L.
1
G. Tetrahedron Lett. 1981, 22, 3803. (c) Detty, M. R.;
Seidler, M. D. Tetrahedron Lett. 1982, 23, 2543. (d) Iqbal,
J.; Amin Khan, M.; Ahmad, S. Synth. Commun. 1989, 19,
641.
(16) Dodd, G. H.; Golding, B. T.; Ioannou, P. V. J. Chem. Soc.,
Chem. Commun. 1975, 249.
Acknowledgment
(
17) (a) Lalonde, M.; Chan, T. H. Synthesis 1985, 817.
Financial support from the Swedish Natural Science Research
Council and the Swedish Foundation for Strategic Research is
gratefully acknowledged.
(
1
b) Zhang, W.; Robins, M. J. Tetrahedron Lett. 1992, 33,
177. (c) Bajwa, J. S.; Vivelo, J.; Slade, J.; Repic, O.;
Blacklock, T. Tetrahedron Lett. 2000, 41, 6021.
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239. (b) Serdarevich, B. J. Am. Oil Chem. Soc. 1967, 44,
(
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(
(
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(
1
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