Phosphomolybdic acid: Mild and efficient catalyst for acetylation of alcohols, phenols, and amines under solvent-free conditions

Article abstract of DOI:10.1055/s-2007-1000859

Phosphomolybdic acid (PMA) has been found to be a simple and efficient catalyst for the acetylation of alcohols, phenols, and amines. Acetylation reactions with acetic anhydride (1.0 equiv) proceed in excellent yield in the presence of a catalytic amount (0.2 mol%) of PMA at ambient temperature within a relatively short reaction time (<10 min). Structurally diverse alcohols, phenols, and amines undergo acetylation under solvent-free conditions. Georg Thieme Verlag Stuttgart.

Full text of DOI:10.1055/s-2007-1000859

PAPER
267
Phosphomolybdic Acid: Mild and Efficient Catalyst for Acetylation of
Alcohols, Phenols, and Amines under Solvent-Free Conditions
P
hosphomolyb
a
dic
A
cid:
C
n
atalyst for
A
t
cetylat
o
ion sh T. Kadam, Sung Soo Kim*
Department of Chemistry, Inha University, Incheon 402-751, Korea
Fax +82(32)8675604; E-mail: sungsoo@inha.ac.kr
Received 19 September 2007; revised 23 October 2007
reaction times, the use of halogenated solvents, and the
use of hazardous materials. Perchlorates are explosive,9 4-
(N,N-dimethylamino)pyridine is highly toxic, and tribu-
tylphosphine is flammable and air-sensitive. Triflates are
Abstract: Phosphomolybdic acid (PMA) has been found to be a
simple and efficient catalyst for the acetylation of alcohols, phenols,
and amines. Acetylation reactions with acetic anhydride (1.0 equiv)
proceed in excellent yield in the presence of a catalytic amount (0.2
mol%) of PMA at ambient temperature within a relatively short re- expensive and some of them are applicable only to alco-
action time (<10 min). Structurally diverse alcohols, phenols, and
amines undergo acetylation under solvent-free conditions.
hols and phenols. Many catalysts need special conditions
for their preparation [Bi(OTf)3, Naflon-H, yttria-zirconia,
Key words: acetylation, phosphomolybdic acid, alcohols, amines,
green catalysis
N-heterocyclic carbene]. Some method require the use of
an excess of acylating agent. Thus, the development of
new catalytic methods is highly desirable.
Phosphomolybdic acid (PMA) belongs to the class of het-
eropolyacids (HPAs). Recently, HPAs have attracted
much attention as catalysts for various organic transfor-
mations as well as processes related to fine-chemical syn-
thesis.10 HPAs have several advantages that make them
economically and environmentally attractive catalysts.
Considering the importance of environmental awareness
in chemical technology, it is important to minimize the
prevalence of undesirable hazardous chemical substances
that are dangerous to human health and the environment.
Considering this demand, HPAs have emerged as green
catalysts for chemical technology owing to their high cat-
alytic activity in low concentration and being environ-
mentally friendly.11 HPAs are stronger acids than
conventional acids, yet noncorrosive and work in low
concentrations, thus avoiding disposal problems.12 A va-
riety of synthetic methods have been developed and com-
mercialized in which HPAs are used as catalysts.13 PMA
is a stronger acid than sulfuric acid, and this makes it pos-
sible to carry out reactions at low concentrations and at
ambient temperature. PMA has been used as a catalyst in
various methods, such as the Friedel–Crafts acylation of
phenol,14 the Fries rearrangement of phenyl acetate,15 the
oxidation of hydroxyl groups,16 the regioselective open-
ing of N-tosylaziridine,17 and selective deprotection of
tert-butyldimethylsilyl ethers.18
Functional-group protection and deprotection is the heart
and soul of multifunctional and multistep syntheses of tar-
get molecules. The protection of alcohol and phenol moi-
eties represents one of the most ubiquitous steps in
chemistry,1 because of the high prevalence of these func-
tionalities in drugs and pharmaceuticals. Their protection
is usually achieved through acetylation with acetic anhy-
dride.2 Acetyl is the most common group in view of easy
introduction, being stable under acidic conditions, and be-
ing easily removable by mild alkaline hydrolysis. The
poor nucleophilic properties of hydroxy compounds ne-
cessitate activation of the anhydride. Various activators
employed for this purpose include the nucleophilic 4-
(N,N-dimethylamino)pyridine,3 tributylphosphine,4 and
other catalytic systems such as cobalt(II) chloride,5a tanta-
lum(V) chloride/silica,5b zinc(II) chloride,5c zirconi-
um(IV) chloride,5d indium(III) chloride,5e ruthenium(III)
chloride,5f copper(II) chloride/palladium(II) chloride,5g
iodine,5h,i nitrobenzeneboronic acid,5j and polytungstic ac-
id.5k Recently, the use of many triflates and perchlorates
has also been reported, e.g. scandium(III) triflate,6a bis-
muth(III) triflate,6b copper(II) triflate,6c indium(III) tri-
flate,6d aluminum(III) triflate,6e cerium(III) triflate,6f
gadolinium(III) triflate,6g erbium(III) triflate,6h lithium
perchlorate,7a copper(I) perchlorate,7b magnesium per-
chlorate,7c iron(III) perchlorate,7d and perchloric acid/sili-
ca.7e Other catalyst such as montmorillonite,8a
benzenesulfonamide,8b lanthanum(III) nitrate,8c yttria-zir-
conia,8d trichloroisocyanuric acid,8e Naflon–H,8f and N-
heterocyclic carbene,8g,h have also been used for the acety-
lation of alcohols.
In view of these properties and the wide application of
PMA, we wish to report herein the acetylation of alcohols,
phenols, and amines (RXH) with acetic anhydride (1.0
equiv) in the presence of a catalytic amount of PMA (0.2
mol%) at ambient temperature under solvent-free condi-
tions (Scheme 1). The reactions proceed in excellent
yields within quite short reaction times. For the generali-
zation of this catalysis, a large-scale (10.0 g) acetylation
of alcohol was also carried out, in which the same amount
of the catalyst was used, and the reaction proceeded rap-
idly in excellent yield. To evaluate the efficiency of PMA
Although there is currently a number of methods avail-
able, they have one or more disadvantages, such as long
SYNTHESIS 2008, No. 2, pp 0267–0271
x
x
.
x
x
.2
0
0
7
Advanced online publication: 18.12.2007
DOI: 10.1055/s-2007-1000859; Art ID: F17007SS
© Georg Thieme Verlag Stuttgart · New York

268
S. T. Kadam, S. S. Kim
PAPER
Table 1 Catalytic Acetylation of Alcohols, Phenols, and Amines
as catalyst, the general applicability and scope of the
method was studied by use of various alcohols, phenols,
and amines (Table 1). Structurally diverse alcohols such
as primary, secondary, allylic, and heterocyclic alcohols
underwent smooth acetylation in excellent yields. Various
benzylic alcohols with electron-donating and electron-
withdrawing substituents also undergo smooth acetylation
in quite high yields. This method is also compatible with
alcohols containing double bonds, e.g. cinnamyl alcohol
and geraniol (Table 1, entries 6 and 9).
with PMAa (continued)
Entry Starting material RXH
Reaction time Yieldb (%)
2 min
12 h
12 h
95
OH
995j
658b
977b
8
10 min
Me
10 min
1 h
96
OH
9
907e
Me
Me
OH
OH
H3[P(Mo3O10)4]·nH2O (0.2 mol%)
RXH
RXAc
Ac2O, r.t., 2–10 min
X = O, NH
10
11
12
2 min
3 min
4 min
93
98
93
Cl
Scheme 1
Table 1 Catalytic Acetylation of Alcohols, Phenols, and Amines
with PMAa
Entry Starting material RXH
Reaction time Yieldb (%)
OPh
OH
4 min
15 s
95
986e
816g
905j
958b
978e
967e
938c
958b
24 h
10 h
1 h
75 h
1 h
OH
1
OH
OH
18 min
1 h
13
8 min
95
OH
2
6 min
94c
CH2
14
15
10 min
2 min
97
97
OH
S
OH
3 min
7 h
4.3 h
98
OH
3
948e
938b
Me
OH
OH
Me
4 min
30 min
18 min
96
16
17
7 min
93
4
986i
958c
10 min
15 s
2 h
97
OMe
OH
966e
987b
955k
926g
968c
977b
OH
1 h
5 min
8 h
96
5
708e
45 min
15 min
1–5 min
F
OH
7 min
11 h
2.5 h
2 h
10–15 min
94
10 min
25 s
8 h
1.5 h
1.5 h
1 h
25 min
20 min
97
955j
985f
965k
977b
956e
907e
896i
915e
976g
956h
968c
OH
6
7
18
6 min
8 h
97
NO2
908b
Me
OH
Synthesis 2008, No. 2, 267–271 © Thieme Stuttgart · New York

PAPER
Phosphomolybdic Acid: Catalyst for Acetylation
269
Table 1 Catalytic Acetylation of Alcohols, Phenols, and Amines
vent-free conditions are the optimal conditions with PMA.
In contrast, 10 mol% lanthanum(III) nitrate is required,8c
whereas with nitroboronic acid 2.5 mol% of catalyst and
3–10 equivalents acylating agent are necessary for reac-
tion times of 7–12 hours. With copper(II) triflate, 2.5
mol% catalyst and 2.0 equivalents reagent are required in
an organic solvent for completion of the reaction. Some
comparative results are collected in Table 1. From these
results it is evident that acetic anhydride and PMA pro-
vide a suitable combination for the acetylation of alco-
hols, phenols, and amines under solvent-free conditions.
with PMAa (continued)
Entry Starting material RXH
Reaction time Yieldb (%)
OH
5 min
30 s
1.5 h
96
19
966e
895e
CN
OH
20
3 min
87
In conclusion, PMA is an efficient, eco-friendly catalyst
for the acetylation of alcohols, phenols, and amines when
acetic anhydride is used as the acetylating agent under
mild and solvent-free conditions. The noncorrosive and
solvent-free conditions are environmentally friendly. The
catalyst is also suitable for large-scale acetylation, and it
is useful for industrial applications.
CHMe2
OH
10 min
10 s
97
21
996e
Cl
OH
The 1H NMR (200 MHz) spectra of samples in CDCl3 (with TMS
as internal standard) were recorded on a Varian Gemini 200 spec-
trophotometer. 13C NMR (100 MHz) data were collected on a Vari-
an Gemini 400 spectrophotometer. HRMS (EI) and GCMS (EI, 70
eV) determinations were carried out on Jeol DMX 303 and Singal
Quadropole GC/MS system with 3800GC/Varian instruments, re-
spectively.
22
7 min
98
OMe
NH2
3 min
15 min
94
23
886g
NH2
Acetylation of Alcohols, Phenols, and Amines; General Proce-
dure
3 min
1 h
15 min
97
24
926g
988c
H3[P(Mo3O10)4]·nH2O (PMA; 3.6 mg, 0.2 mol%) was added to a
mixture of alcohol or amine RXH (1 mmol) and Ac2O (1.0 mmol).
The reaction mixture was stirred at r.t. for the appropriate amount
of time (see Table 1). After completion of the reaction (by TLC), the
reaction mixture was diluted with NaHCO3 (15 mL) and extracted
with EtOAc (3 × 20 mL). Concentration of the combined organic
layer under vacuum gave a crude mass, which was purified by col-
umn chromatography (silica gel); this gave the corresponding
acetylated product RXAc (see Table 1 for further details).
NH2
25
2 min
2 min
95
97
26
NH2
a Reagents and conditions: RXH (1 equiv), Ac2O (1 equiv), PMA (0.2
Benzyl Acetate (Table 1, entries 1 and 2)
1H NMR (200 MHz, CDCl3): d = 2.00 (s, 3 H), 5.01 (s, 2 H), 7.32–
7.37 (m, 5 H).
13C NMR (100 MHz, CDCl3): d = 20.94, 66.19, 128.04, 128.06,
128.14, 128.36, 135.76, 170.58.
mol%), r.t.
b Isolated yield.
c Large-scale reaction (10.0 g).
This catalytic system is applicable to a heterocyclic alco- HRMS (EI): m/z [M + H]+ calcd for C9H10O2: 150.0684; found:
150.0680.
hol, and it gives the corresponding acetate in quite high
GCMS (EI, 70 eV): m/z (%) = 107.83 (100), 149.90 (100) [M + H]+.
yield (Table 1, entry 14). A sterically hindered alcohol
also yields the corresponding acetate under these condi-
tions (Table 1, entry 8). Interestingly, phenols undergo the
acetylation smoothly in the presence of PMA (Table 1,
entries 17–22). Phenols with activating and deactivating
groups also underwent acetylation rapidly in high yields.
The strongly deactivated nitro- and cyanophenols afford-
ed the corresponding acetates within 10 and 5 minutes, re-
spectively (Table 1, entries 18 and 19). It is very
interesting to note that this method is also applicable to
amines (Table 1, entries 23–26). Aromatic, benzylic, and
aliphatic amines undergo acetylation in high yields and in
short reaction times. These results clearly indicate that a
low catalyst loading with a minimum amount of acylating
reagent (1.0 equiv) and a short reaction time under sol-
4-Methylbenzyl Acetate (Table 1, entry 3)
1H NMR (200 MHz, CDCl3): d = 2.10 (s, 3 H), 2.37 (s, 3 H), 5.09
(s, 2 H), 7.20–7.26 (m, 4 H).
13C NMR (100 MHz, CDCl3): d = 20.87, 65.963, 128.107, 128.895,
132.701, 137.658, 170.398.
HRMS (EI): m/z [M + H]+ calcd for C10H12O2: 164.0837; found:
164.0837.
4-Methoxybenzyl Acetate (Table 1, entry 4)
1H NMR (200 MHz, CDCl3): d = 2.42 (s, 3 H), 4.15 (s, 3 H), 5.39
(s, 2 H), 7.22–7.26 (m, 2 H), 7.60–7.67 (m, 2 H).
13C NMR (100 MHz, CDCl3): d = 20.78, 55.96, 114.23, 127.21,
127.78, 128.12, 13.475, 17.32.
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S. T. Kadam, S. S. Kim
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4-Fluorobenzyl Acetate (Table 1, entry 5)
Cyclohex-3-enylmethyl Acetate (Table 1, entry 15)
1H NMR (200 MHz, CDCl3): d = 2.37 (s, 3 H), 5.28 (s, 2 H), 7.21–
7.30 (m, 2 H), 7.54–7.59 (m, 2 H).
1H NMR (200 MHz, CDCl3): d = 1.56 (d, J = 6 Hz, 3 H), 2.08 (s, 3
H), 5.92 (q, 1 H), 7.30–7.37 (m, 4 H).
13C NMR (100 MHz, CDCl3): d = 20.87, 65.43, 115.16, 115.37,
130.01, 131.63, 163.61, 170.51.
13C NMR (100 MHz, CDCl3): d = 21.22, 22.13, 72.14, 125.86,
126.07, 128.25, 141.45, 169.95.
(E)-3-Phenylprop-2-enyl Acetate (Table 1, entry 6)
1H NMR (200 MHz, CDCl3): d = 1.98 (s, 3 H), 4.60 (t, J = 6.2 Hz,
2 H), 6.20–6.22 (m, 1 H), 6.54 (d, J = 1.7 Hz, 1 H), 7.17–7.30 (m, 5
H).
13C NMR (100 MHz, CDCl3): d = 20.95, 64.97, 123.00, 126.432,
127.88, 128.42, 133.99, 136.01, 170.55.
1-Phenylethyl Acetate (Table 1, entry 16)
1H NMR (200 MHz, CDCl3): d = 2.29 (s, 3 H), 7.21–7.28 (m, 2 H),
8.19–8.24 (m, 3 H).
13C NMR (100 MHz, CDCl3): d = 21.14, 122.33, 125.09, 145.17,
155.21, 168.20.
Phenyl Acetate (Table 1, entry 17)
n-Hexyl Acetate (Table 1, entry 7)
1H NMR (200 MHz, CDCl3): d = 2.49 (s, 3 H), 7.21–7.28 (m, 2 H),
7.51–7.56 (m, 2 H).
1H NMR (200 MHz, CDCl3): d = 0.81 (q, 3 H), 1.23 (m, 4 H), 1.61
(m, 2 H), 2.04 (s, 3 H), 4.01 (t, J = 2.6 Hz, 2 H).
13C NMR (100 MHz, CDCl3): d = 20.95, 122.77, 129.23, 130.93,
148.92, 168.88.
13C NMR (100 MHz, CDCl3): d = 13.97, 20.97, 22.58, 28.56, 31.43,
64.57, 170.95.
4-Nitrophenyl Acetate (Table 1, entry 18)
1H NMR (200 MHz, CDCl3): d = 2.34 (s, 3 H), 7.28–7.30 (m, 2 H),
8.23–8.28 (m, 2 H).
13C NMR (100 MHz, CDCl3): d = 20.98, 109.25, 118.01, 122.24,
132.59, 152.65, 169.29.
Benzhydryl Acetate (Table 1, entry 8)
1H NMR (200 MHz, CDCl3): d = 2.48 (s, 3 H), 6.98.62 (s, 1 H),
7.66–7.70 (m, 10 H).
13C NMR (100 MHz, CDCl3): d = 21.17, 76.72, 126.88, 127.68,
128.28, 140.00, 169.66.
4-Cyanophenyl Acetate (Table 1, entry 19)
1H NMR (200 MHz, CDCl3): d = 2.33 (s, 3 H), 7.21–7.28 (m, 2 H),
7.6–67.71 (m, 2 H).
13C NMR (100 MHz, CDCl3): d = 20.98, 109.12, 118.42, 122.53,
133.39, 153.63, 170.18.
HRMS (EI): m/z [M + H]+ calcd for C9H7NO2: 161.0477, found:
161.0487.
(E)-3,7-Dimethylocta-2,6-dienyl Acetate (Table 1, entry 9)
1H NMR (200 MHz, CDCl3): d = 1.59 (s, 3 H), 1.82 (s, 1 H), 1.98–
2.03 (q, 4 H), 2.04 (s, 3 H), 4.55 (d, J = 6 Hz, 2 H), 5.06 (m, 1 H),
5.31 (dd, J = 14 Hz, 2 H).
13C NMR (100 MHz, CDCl3): d = 16.40, 17.63, 25.61, 26.26, 39.47,
61.27, 118.13, 123.57, 131.57, 141.97, 170.78.
4-Chlorobenzyl Acetate (Table 1, entry 10)
1H NMR (200 MHz, CDCl3): d = 2.07 (s, 3 H), 5.02 (s, 2 H), 7.42–
7.58 (m, 4 H).
13C NMR (100 MHz, CDCl3): d = 20.92, 65.35, 128.56, 129.45,
133.93, 134.30, 170.48.
4-Isopropylphenyl Acetate (Table 1, entry 20)
1H NMR (200 MHz, CDCl3): d = 1.24 (d, J = 4.6 H), 2.26 (s, 3 H),
2.98 (m, 1 H), 7.01–7.20 (m, 2 H), 7.20–7.22 (m, 2 H).
13C NMR (100 MHz, CDCl3): d = 21.08, 24.00, 33.58, 121.05,
127.14, 146.10, 148.40, 169.43.
4-Phenoxyphenyl Acetate (Table 1, entry 11)
1H NMR (200 MHz, CDCl3): d = 2.30 (s, 3 H), 5.26 (s, 2 H), 7.22–
7.32, (m, 5 H), 7.51–7.55 (m, 3 H).
13C NMR (100 MHz, CDCl3): d = 20.55, 65.36, 117.94, 118.65,
122.32, 129.41, 129.49, 137.68, 156.51, 157.08, 170.04.
4-Chlorophenyl Acetate (Table 1, entry 21)
1H NMR (200 MHz, CDCl3): d = 2.49 (s, 3 H), 7.21–7.24 (m, 2 H),
7.51–7.56 (m, 2 H).
13C NMR (100 MHz, CDCl3): d = 20.95, 122.77, 129.236, 130.93,
148.92, 168.88.
4-Hydroxybenzyl Acetate (Table 1, entry 12)
3-Methoxyphenyl Acetate (Table 1, entry 22)
1H NMR (200 MHz, CDCl3): d = 2.25 (s, 3 H), 3.76 (s, 3 H), 6.65–
6.79 (m, 3 H), 7.22–7.28 (m, 1 H).
13C NMR (100 MHz, CDCl3): d = 20.86, 55.13, 107.39, 111.31,
113.50, 129.50, 151.35, 160.15, 169.96.
1H NMR (200 MHz, CDCl3): d = 2.2 (s, 3 H), 2.02 (s, 1 H), 4.59 (s,
2 H), 7.02–7.05 (m, 2 H), 7.30–7.34 (m, 2 H).
13C NMR (100 MHz, CDCl3): d = 20.10, 64.48, 121.44, 121.46,
127.91, 138.36, 149.76, 169.50.
(S)-(4-Methyl-4-vinylcyclohex-1-enyl)methyl Acetate (Table 1,
entry 13)
N-Phenylacetamide (Table 1, entry 23)
1H NMR (200 MHz, CDCl3): d = 2.25 (s, 3 H), 7.41–7.49 (m, 3 H),
7.66–7.70 (m, 2 H), 8.45 (s, 1 H)
1H NMR (100 MHz, CDCl3): d = 1.68–2.01 (ms, 6 H), 2.02 (s, 3 H),
4.40 (s, 2 H), 2.31 (m, 1 H), 4.44 (s, 2 H), 4.67 (d, J = 4 Hz, 2 H),
5.71 (t, J = 18 Hz, 1 H).
13C NMR (100 MHz, CDCl3): d = 24.23, 120.09, 124.21, 128.66,
137.81, 169.10.
13C NMR (100 MHz, CDCl3): d = 20.87, 26.32, 27.25, 30.38, 40.75,
68.32, 108.62, 125.62, 125.56, 132.39, 149.21, 170.62.
N-Benzylacetamide (Table 1, entry 24)
1H NMR (200 MHz, CDCl3): d = 1.85 (s, 1 H), 4.38 (d, J = 5.8 Hz,
2 H), 6.66 (br s, 1 H), 7.28–7.37 (m, 5 H).
(2-Thienyl)methyl Acetate (Table 1, entry 14)
1H NMR (200 MHz, CDCl3): d = 2.52 (s, 3 H), 5.43 (s, 2 H), 7.11
(dd, J = 16 Hz, 2 H), 7.50 (m, J = 6 Hz, 1 H).
13C NMR (100 MHz, CDCl3): d = 22.99, 43.51, 127.17, 127.51,
128.39, 138.09, 169.98.
13C NMR (100 MHz, CDCl3): d = 20.97, 60.42, 125.87, 126.54,
126.69, 134.76, 170.48.
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Phosphomolybdic Acid: Catalyst for Acetylation
271
N-Cyclohexylacetamide (Table 1, entry 25)
1H NMR (200 MHz, CDCl3): d = 0.98–1.98 (m, 10 H), 2.02 (s, 3 H),
3.59–3.70 (m, 1 H), 5.96 (br s, 1 H).
13C NMR (100 MHz, CDCl3): d = 23.30, 24.82, 25.98, 32.98, 48.17,
169.10.
Synlett 1999, 1743. (e) Kamal, A.; Khan, M. A.; Reddy, S.
Y.; Srikant, V. V.; Krishnaji, T. Tetrahedron Lett. 2007, 48,
3813. (f) Dalpozzo, R.; De Nino, A.; Maiuolo, L.; Procopio,
A.; Nardi, M.; Bartoli, G.; Romeo, R. Tetrahedron Lett.
2003, 44, 5621. (g) Alleti, R.; Perambudura, M.; Samantha,
S.; Reddy, V. P. J. Mol. Catal. A: Chem. 2005, 226, 57.
(h) Antonio, P. R.; Dalpozzo, R.; De Nino, A.; Maiuolo, L.;
Russo, B.; Sindona, G. Adv. Synth. Catal. 2004, 346, 1465.
(i) Herari, M.; Behbahani, F. K.; Bamoharram, F. F. J. Mol.
Catal. 2006, 253, 16.
N-tert-Butylacetamide (Table 1, entry 26)
1H NMR (200 MHz, CDCl3): d = 1.22–1.41 (m, 9 H), 2.02 (s, 3 H),
5.43 (br s, 1 H).
13C NMR (100 MHz, CDCl3): d = 24.46, 28.76, 51.16, 169.51.
(7) (a) Nakae, Y.; Kusaki, I.; Sato, T. Synlett 2001, 1584.
(b) Kondasamy, J. K.; Chaand, D. K. J. Mol. Catal. A: Chem.
2006, 255, 275. (c) Bartoli, G.; Bosco, M.; Dalpozzo, R.;
Marcantoni, E.; Massaccesi, M.; Rinaldi, S.; Sambri, L.
Synlett 2003, 39. (d) Heravi, M. M.; Behbahani, F. K.;
Shoar, R. H.; Oskooie, H. A. Catal. Commun. 2006, 7, 136.
(e) Chakraborti, A. K.; Gulhane, F. K. Chem. Commun.
2003, 1896.
Acknowledgments
The authors thank the Centre for Biological Modulators for the fi-
nancial support. BK21 was also provided.
(8) (a) Li, A.-X.; Li, T.-S.; Ding, T.-H. Chem. Commun. 1997,
1389. (b) Khazaei, A.; Rostami, A.; Tanbakouchian, Z.;
Zinati, Z. Catal. Commun. 2006, 7, 214. (c) Reddy, T. S.;
Narasimhulu, M. N.; Suryakiran, K.; Mahesh, C.; Ashalatha,
K.; Venkateswarlu, Y. Tetrahedron Lett. 2006, 47, 6825.
(d) Kumar, P.; Pandey, R. K.; Bodas, M. S.; Dongare, M. K.
Synlett 2001, 206. (e) Zolfigol, M. A.; Khazaei, A.;
Choghamarani, A. G.; Rostai, A.; Hajjami, M. Catal.
Commun. 2006, 7, 399. (f) Kumareswaran, R.; Pachamuthu,
K.; Vakar, Y. D. Synlett 2000, 1652. (g) Grasa, G. A.;
Guveli, T.; Singh, R.; Nolan, S. P. J. Org. Chem. 2003, 68,
2812. (h) Grasa, G. A.; Kissling, R. M.; Nolan, S. P. Org.
Lett. 2002, 4, 3583.
(9) (a) Schumacher, J. C. Perchlorates – Their Properties,
Manufacture, and Use; ACS Monograph Series, Reinhold:
New York, 1996. (b) Long, J. Chem. Health Safety 2002, 9,
12.
(10) (a) Kozhevnikov, I. V. Chem. Rev. 1998, 98, 171.
(b) Mizuno, N.; Misono, M. Chem. Rev. 1998, 98, 199.
(11) Makoto, M.; Izumi, O.; Gaku, K.; Atsushi, A. Pure Appl.
Chem. 2000, 72, 1305.
References
(1) (a) Green, T. W.; Wuts, P. G. M. In Protective Groups in
Organic Synthesis, 3rd ed.; Wiley: New York, 1999, 150.
(b) Otera, J. Chem. Rev. 1993, 93, 1449. (c) Franklin, A. S.
J. Chem. Soc., Perkin Trans. 1 1998, 2451. (d) Franklin, A.
S. J. Chem. Soc., Perkin Trans. 1 1999, 3537.
(2) (a) Zhdanov, R. I.; Zhenodarova, S. M. Synthesis 1975, 222.
(b) Strok, G.; Takahashi, T.; Kawamoto, I.; Suzuki, T. J. Am.
Chem. Soc. 1978, 100, 8272. (c) Dauban, W. G.; Bune, R.
A.; Gerdes, J. M.; Henger, K. E.; Cunningham, A. M. Jr.;
Ottoboni, T. B. Tetrahedron Lett. 1983, 24, 5709.
(3) (a) Hofle, G.; Steglich, W.; Vorbruggen, H. Angew. Chem.,
Int. Ed. Engl. 1978, 17, 569. (b) Steglich, W.; Hofle, G.
Angew. Chem., Int. Ed. Engl. 1969, 8, 981.
(4) (a) Vedejs, E.; Diver, S. T. J. Am. Chem. Soc. 1993, 115,
3358. (b) Vedejs, E.; Bennett, N. S.; Conn, L. M.; Diver, S.
T.; Gingras, M.; Lin, S.; Oliver, P. A.; Petrson, M. J. J. Org.
Chem. 1993, 58, 7286.
(5) (a) Iqbal, J.; Srivastava, R. R. J. Org. Chem. 1992, 57, 2001;
and references cited therein. (b) Chandrasekhar, S.;
Ramaeshandar, T. T. Indian J. Chem., Sect. B: Org. Chem.
Incl. Med. Chem. 2004, 43, 83; and references cited therein.
(c) Backer, R. H.; Bordewell, F. G. Org. Synth. 1995, 3, 141.
(d) Chakraborti, A. K.; Gulhane, R. Synlett 2004, 657.
(e) Chakraborti, A. K.; Gulhane, R. Tetrahedron Lett. 2003,
44, 3521. (f) Shirini, F.; Zolfigol, M. A.; Abedini, M.
Monatsh. Chem. 2004, 135, 279. (g) Bosco, J. W. J.; Saikia,
A. K. Chem. Commun. 2004, 1116. (h) Bosco, J. W. J.;
Agrahari, A.; Saikia, A. K. Tetrahedron Lett. 2006, 47,
4065. (i) Phukan, P. Tetrahedron Lett. 2004, 45, 4785.
(j) Tale, R. H.; Adude, R. N. Tetrahedron Lett. 2006, 47,
7263. (k) Heravi, M. M.; Behbahani, K. F.; Bamoharram, F.
F. J. Mol. Catal. A: Chem. 2006, 253, 16.
(12) (a) Izumi, Y.; Hasebe, R.; Urabe, K. J. Catal. 1983, 84, 402.
(b) Kozhevnikov, I. V. Russ. Chem. Rev. 1987, 56, 811.
(c) Okuhara, T.; Mizuno, N.; Misono, M. Adv. Catal. 1996,
41, 113.
(13) Izumi, Y.; Urabe, K.; Onaka, M. Zeolite Clay and
Heteropoly Acid in Organic Reactions; Kodansha/VCH:
Tokyo, 1992, 99.
(14) Kaur, J.; Griffin, K.; Harrison, B.; Kozhevnikov, I. V. J.
Catal. 2002, 208, 448.
(15) Kozhevnikova, E. F.; Derouane, E. G.; Kozhevnikov, I. V.
Chem. Commun. 2002, 1178.
(16) Firouzabadi, H.; Iranpoor, N.; Amani, K. Synthesis 2003,
408.
(6) (a) Ishihara, K.; Kubota, M.; Kurihara, H.; Yamamoto, H. J.
Org. Chem. 1996, 61, 4560. (b) Orita, A.; Tanahashi, C.;
Kakuda, A.; Otera, J. Angew. Chem. Int. Ed. 2000, 39, 2877.
(c) Saravanan, P.; Singh, V. K. Tetrahedron Lett. 1999, 40,
2611. (d) Chauhan, K. K.; Frost, C. G.; Love, I.; Waite, D.
(17) Kishore Kumar, G. D.; Baskaran, S. Synlett 2004, 1719.
(18) Kishore Kumar, G. D.; Baskaran, S. J. Org. Chem. 2005, 70,
4520.
Synthesis 2008, No. 2, 267–271 © Thieme Stuttgart · New York