Selective acetylation of aliphatic hydroxyl group in the presence of phenolic hydroxyl group using silica gel supported BF3 catalyst

Article abstract of DOI:10.1081/SCC-120002009

Selective acetylation of aliphatic hydroxyl group in the presence of phenolic hydroxyl group was achieved conveniently and efficiently by treatment with EtOAc in the presence of silica gel supported BF₃ catalyst.

Full text of DOI:10.1081/SCC-120002009

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SELECTIVE ACETYLATION OF ALIPHATIC HYDROXYL
GROUP IN THE PRESENCE OF PHENOLIC HYDROXYL
GROUP USING SILICA GEL SUPPORTED BF3 CATALYST
Biswanath Das a , B. Venkataiah a & P. Madhusudhan a
a Organic Chemistry Division-I, Indian Institute of Chemical Technology, Hyderabad, 500
007, India
Published online: 16 Aug 2006.
To cite this article: Biswanath Das , B. Venkataiah & P. Madhusudhan (2002) SELECTIVE ACETYLATION OF ALIPHATIC
HYDROXYL GROUP IN THE PRESENCE OF PHENOLIC HYDROXYL GROUP USING SILICA GEL SUPPORTED BF3 CATALYST,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:2,
249-252, DOI: 10.1081/SCC-120002009
To link to this article: http://dx.doi.org/10.1081/SCC-120002009
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SYNTHETIC COMMUNICATIONS, 32(2), 249–252 (2002)
SELECTIVE ACETYLATION OF
ALIPHATIC HYDROXYL GROUP IN
THE PRESENCE OF PHENOLIC
HYDROXYL GROUP USING SILICA
GEL SUPPORTED BF3 CATALYST
Biswanath Das,* B. Venkataiah, and
P. Madhusudhan
Organic Chemistry Division-I, Indian Institute of
Chemical Technology, Hyderabad, 500 007, India
ABSTRACT
Selective acetylation of aliphatic hydroxyl group in the pre-
sence of phenolic hydroxyl group was achieved conveniently
and efficiently by treatment with EtOAc in the presence of
silica gel supported BF3 catalyst.
Selective acetylation of aliphatic hydroxyl group in the presence
of phenolic hydroxyl group is an useful procedure in synthetic organic
chemistry.2 Such conversion has recently been carried out2 by applying
the process of transesterification using EtOAc in the presence of hetero-
genous catalyst, silica gel supported NaHSO4. The catalyst is reported to
work under heating condition.
*Corresponding author.
249
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

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DAS, VENKATAIAH, AND MADHUSUDHAN
Table 1. Selective Acetylation of Aliphatic Hydroxyl Groupsy

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ACETYLATION OF ALIPHATIC HYDROXYL GROUP
251
In continuation of our recent studies3 on important methodologies useful
for synthesis of bioactive compounds and their intermediates we have
applied silica gel supported BF3 catalyst at room temperature for selective
acetylation of aliphatic hydroxyl groups. BF3 is a versatile Lewis acid cat-
alyst frequently used in organic synthesis.4 Recently the silica gel supported
BF3 system has bee reported.4 This heterogenous catalyst can easily be
recovered and also minimise the production of waste formed during BF3
recovery. However, the catalytic activity of the system has not yet been
properly explored. We have observed that the system can efficiently be util-
ized for selective acetylation of aliphatic hydroxyl group in the presence of
aromatic hydroxyl group. Previously BF3 has not been reported to be
employed for selective acetylation.
Different aliphatic alcohols have now been converted to the corre-
sponding acetates by treatment with EtOAc in the presence of silica gel sup-
ported BF3 catalyst at the room temperature (Table 1). Phenolic hydroxyl
groups were uneffected under similar reaction conditions. The conversion of
primary hydroxyl groups was achieved with very high yields (78–86%) but
the compounds with secondary hydroxyl group afforded the desired acetates
in poor yields (4–8%) along with some side products. The catalyst
has effectively been utilized for the conversion of the natural antitumour
coumarino-lignoid, cleomiscosin A into its analogue, venkatasin5 (Entry
no. 10). The structures of all the reaction products were settled from their
analytical and spectral data.6 Unsupported BF3 decreased the yields of the
products; primary alcohols produced the acetates with an yield of 37–45%.
In conclusion, a simple, mild and efficient method has been developed
for selective acetylation of aliphatic hydroxyl group in the presence of phe-
nolic hydroxyl group. The primary hydroxyl groups showed much higher
reactivity compared to the secondary hydroxyl groups towards acetylation
under similar reaction conditions. The common solvent EtOAc has been
utilized for acetylating agent. The catalyst (silica gel supported BF3)
which has been used here for the first time for such conversion can easily
be prepared from the readily available materials and conveniently be
handled. The catalyst can also be recovered from the reaction mixture
through simple filteration. The experimental procedure is simple and the
conversion occurs at room temperature.
General Procedure: p-Hydroxyphenylethanol (Entry 2, 69 mg,
0.5 mmole) was dissolved in EtOAc (20 ml). Silica gel supported BF3
[100 mg, prepared by reported method3 using BF3ꢀOEt2 and silica gel (finer
than 200 mesh)] was added. The mixture was stirred at room temperature
under N2 atmosphere for 9 h and filtered. The filterate was concentrated
and subjected to column chromatography over silica gel to afford
p-hydroxyphenylethyl acetate (73 mg, 81.1%).

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DAS, VENKATAIAH, AND MADHUSUDHAN
ACKNOWLEDGMENT
The authors thank CSIR, New Delhi for financial assistance.
REFERENCES
1. Part 6 in the series Studies on Novel Synthetic Methodologies, for part 5
see Das, B.; Venkataiah, B. Synthesis 2000 (accepted). IICT Commu-
nication No. 4503.
2. Breton, G.W. J. Org. Chem. 1997, 62, 8952; references cited therein.
3. a) Das, B.; Madhusudhan, P.; Venkataiah, B. Synlett 1999, 1569. b) Das,
B.; Venkataiah, B.; Madhusudhan, P. Synlett 2000, 59.
4. Wilson, K.; Clark, J.H. J. Chem. Soc., Chem. Commun. 1998, 2135;
references cited therein.
5. Das, B.; Venkataiah, B.; Kashinatham, A. Nat. Prod. Lett. 1999, 13, 293.
6. The spectral and analytical data of the two unknown acetates (entry nos.
4 and 5) are given below.
3-(4-Hydroxyphenyl)propyl Acetate: Viscous mass, 1H NMR
(CDCl3) : d 7.05 (2H, d, J ¼ 8.0 Hz), 6.73 (2H, d, J ¼ 8.0 Hz), 4.11
(2H, t, J ¼ 7.0 Hz), 2.62 (2H, t, J ¼ 7.0 Hz), 2.08 (3H, s), 1.08–0.88
(2H, m); MS: m/z 194 (Mþ); Anal. calcd. for C11H14O3: C, 68.04; H,
7.22. Found C, 68.12; H, 7.17.
3-(3-Methoxy-4-hydroxyphenyl)-propyl Acetate: Viscous mass,
1H NMR (CDCl3) : d 6.87 (1H, d, J ¼ 8.0 Hz), 6.75–6.66 (2H, m), 4.13
(2H, t, J ¼ 7.0 Hz), 3.90 (3H, s), 2.65 (2H, t, J ¼ 7.0 Hz), 2.10 (3H, s),
1.05–0.90 (2H, m); MS: m/z 224 (Mþ); Anal. calcd. for C12H16O4: C,
64.29; H, 7.14. Found C, 64.21; H, 7.08.
7. da Graca Nascimento, M.; Zanotto, S.P.; Scremin, M.; Rezende, M.C.
Synth. Commun. 1996, 26, 2715.
8. Das, B.; Takhi, M.; Kumar, H.M.S.; Srinivas, K.V.N.S.; Yadav, J.S.
Phytochemistry 1993, 32, 697.
9. Rubinstein, I.; Goad, L.J.; Clague, A.D.H.; Mucheirn, L.J.
Phytochemistry 1976, 15, 195.
Received in the UK July 25, 2000

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