S. Kanta De / Tetrahedron Letters 45 (2004) 2919–2922
Table 4. RuCl3 catalyzed acylation of alcohols at room temperaturea
2921
nol was acetylated by Sc(OTf)3 at ꢀ20 ꢁC using 3 equiv
of acetic anhydride, Bi(OTf)3 catalyzed acetylation of
the same compound required 10 equiv of acetic anhy-
dride. The RuCl3 catalyzed acetylation of the above
mentioned compound requires only 1.2 equiv of acetic
anhydride and it works at room temperature. The
5-TBSO-pentanol was acetylated in 72% yield in 4 h in
the presence of Bi(OTf)3 with 10 equiv of acetic anhy-
dride, where as the same compound was acetylated in
81% yield in 1 h in the presence of RuCl3 with 1.2 equiv
of acetic anhydride.
Entry
1
Substrate
Time
Yieldb
Ph
OH
10 min
95
MeO
NO2
2
3
4
10 min
30 min
25 min
94
89
95
OH
In conclusion, a simple and efficient method for acetyl-
ation of all types of phenols, alcohols, thiols, and amines
using a catalytic amount of ruthenium chloride has been
developed. The method has advantages in terms of
yields, short reaction times, ease of operation, and
compatibility with other protecting groups and will
make a useful and important addition to the present
methodologies.
OH
OMe
OH
MeO
O
5
6
7
50 min
2 h
82
85
87
OH
References and notes
Ph
1. Greene, T. W.; Wuts, P. G. M. Protective groups in
Organic Synthesis, 3rd ed.; Wiley: New York, 1999;
p 150.
OH
2. Vedejs, E.; Diver, S. T. J. Am. Chem. Soc. 1993, 115, 3358.
3. (a) Ishihara, K.; Kubota, M.; Kurihara, H.; Yamamoto,
H. J. Am. Chem. Soc. 1995, 117, 4413; (b) Ishihara, K.;
Kubota, M.; Kurihara, H.; Yamamoto, H. J. Org. Chem.
1996, 61, 4560.
Ph
OH
6 h
OH
4. Ishihara, K.; Kubota, M.; Yamamoto, H. Synlett 1996,
265.
5. (a) Procopiou, P. A.; Baugh, S. P. D.; Flack, S. S.; Inglis,
G. G. A. J. Org. Chem. 1998, 63, 2342; (b) Procopiou, P.
A.; Baugh, S. P. D.; Flack, S. S.; Inglis, G. G. A. Chem.
Commun. 1996, 2625.
6. (a) Saravanan, P.; Singh, V. K. Tetrahedron Lett. 1999, 40,
2611; (b) Chandra, K. L.; Saravanan, P.; Singh, R. K.;
Sing, V. K. Tetrahedron 2002, 58, 1369.
7. Chakroborty, A.; Gulhane, R. Tetrahedron Lett. 2003, 44,
6749.
8
9
7 h
92
91
OH
25 min
10
11
12
13
14
4-Methyl-1-pentanol
R-(ꢀ)-2-Butanol
R-(ꢀ)-2-Hexanol
1-Adamantol
40 min
2 h
3 h
92
83
93
87
82
4 h
2 h
8. Chauhan, K. K.; Frost, C. G.; Love, I.; Waite, D. Synlett
1999, 1743.
(1R,2S,2R)-(ꢀ)Menthol
9. (a) Orita, A.; Tanahashi, C.; Kakuda, A.; Otera, J. Angew.
Chem., Int. Ed. 2000, 39, 2877; (b) Orita, A.; Tanahashi,
C.; Kakuda, A.; Otera, J. J. Org. Chem. 2001, 66, 8926; (c)
Carrigan, M. D.; Freiberg, D. A.; Smith, R. C.; Zerth, H.
M.; Mohan, R. S. Synthesis 2001, 2091.
OH
15
35 min
1 h
91
O
16
95
OH
10. Chandrasekhar, S.; Ramchander, T.; Takhi, M. Tetrahe-
dron Lett. 1998, 39, 3263.
11. Ballini, R.; Bosica, G.; Carloni, S.; Ciaralli, L.; Maggi, R.;
Sartori, G. Tetrahedron Lett. 1998, 39, 6049.
12. (a) Bhaskar, P. M.; Loganathan, D. Tetrahedron Lett.
1998, 39, 2215; (b) Li, A.-X.; Li, T.-S.; Ding, T.-H. Chem.
Commun. 1997, 1389.
()5
OH
17
18
1 h
2 h
81
89
TBSO
()6
Br
OH
13. Nakae, Y.; Kusaki, I.; Sato, T. Synlett 2001, 1584.
14. Typical procedure: To a mixture of 6-bromo-1-hexanol
(905 mg, 5 mmol) and acetic anhydride (610 mg, 6 mmol)
in acetonitrile (10 mL) was added ruthenium chloride
(53 mg, 5 mol %) at room temperature. After completion
of reaction (TLC), then reaction mixture was diluted with
water (50 mL) and extracted with ethyl acetate (2 · 50 mL).
The organic layer was washed with satd NH4Cl solution
(30 mL), 1 N NaHCO3 solution (25 mL), and brine
a 1.2 equiv of acetic anhydride, 5 mol % catalyst were used.
b Yields refer to pure isolated products.
over the metal triflates may be explained through com-
parison of the results of a few representative examples of
acid-sensitive substrates. Thus, 1-ethynyl-1-cyclohexa-