Saccharinsulfonic acid: An efficient and recyclable catalyst for acetylation of alcohols, phenols, and amines

Article abstract of DOI:10.1007/s00706-009-0214-7

Saccharinsulfonic acid is an efficient catalyst of the protection of alcohols, phenols, and amines with acetic anhydride. All reactions were performed under mild and completely heterogeneous reaction conditions. with excellent yields.

Full text of DOI:10.1007/s00706-009-0214-7

Monatsh Chem (2009) 140:1495–1498
DOI 10.1007/s00706-009-0214-7
ORIGINAL PAPER
Saccharinsulfonic acid: an efficient and recyclable catalyst
for acetylation of alcohols, phenols, and amines
•
Farhad Shirini Mohammad Ali Zolfigol
•
Masoumeh Abedini
Received: 13 June 2009 / Accepted: 14 October 2009 / Published online: 11 November 2009
Ó Springer-Verlag 2009
Abstract Saccharinsulfonic acid is an efficient catalyst of
the protection of alcohols, phenols, and amines with acetic
anhydride. All reactions were performed under mild and
completely heterogeneous reaction conditions. with excel-
lent yields.
trihydrate [14], NBS [15], alumina-supported MoO3 [16],
Gd(OTf)3 [17], NbCl5 [18], HBF4-SiO2 [19], manga-
nese(III) bis(2-hydroxyanil)acetylacetonato complex [20],
fluorous distannoxane [21], 3-nitrobenzene boronic acid
[22], bis(cyclopentadienyl)zirconium dichloride [23],
polymer-supported gadolinium triflate [24], N,N-dibromo-
4-methylbenzenesulfonimide [25], N,N-dichloro-4-methyl-
benzenesulfonimide [26], Al(OTf)3 [27], silica sulfuric
acid [28], Al(HSO4)3 [29], V(HSO4)3 [30], and o-benzen-
edisulfonimide [31] have also been used as catalysts for
acetylation of alcohols. However, some of these methods
suffer from one or more of the following disadvantages:
long reaction times, harsh reaction conditions, tedious
work-up procedure, use of reagents with unpleasant odors,
use of highly flammable and expensive reagents, formation
of by-products, and low yields of the desired products.
Therefore, introduction of new methods and catalysts for
the preparation of acetates is still in demand.
Keywords Saccharinsulfonic acid Á Acetylation Á
Alcohols Á Acetic anhydride Á Heterogeneous
reaction conditions
Introduction
Acetylation is one of the most important methods widely
used for protection of the alcoholic hydroxyl group. This
method is important because of the ease of introduction of
the acetyl group, the stability of the product to acidic
conditions, and ease of removal of the protecting group by
alkaline hydrolysis [1]. In general, acetylation takes place
by treatment of the alcohols with acid anhydrides or acid
chlorides in the presence of tertiary amines such as tri-
ethylamine and pyridine [2]. 4-(Dimethylamino)pyridine
[3, 4], p-toluenesulfonic acid [5], sulfamic acid [6], scan-
dium triflate [7], indium triflate [8], copper triflate [9],
bismuth triflate [10], Me3SiOTf [11], electron-deficient
tin(IV) porphyrin [12], silica gel supported sodium
hydrogen sulfate [13], potassium dodecatungstocobaltate
Results and discussion
We recently reported the preparation of saccharinsulfonic
acid (SaSA) as a stable derivative of saccharin, and its
application in acceleration of the chemoselective trimeth-
ylsilylation of alcohols with hexamethyldisilazane [32]. In
continuation of this study we have observed that this
reagent is also a highly effective catalyst of acetylation of
alcohols with acetic anhydride. All reactions were per-
formed in CH2Cl2 under reflux, with good to high yields
(Scheme 1; Table 1).
F. Shirini (&) Á M. Abedini
Department of Chemistry, College of Science,
University of Guilan, 41335 Rasht, Iran
e-mail: shirini@guilan.ac.ir
A wide variety of alcohols, including benzylic, primary,
secondary, and tertiary aliphatic alcohols underwent acet-
ylation with acetic anhydride in the presence of catalytic
amounts of SaSA in CH2Cl2 under reflux in good to high
M. A. Zolfigol
College of Chemistry, Bu-Ali Sina University, Hamadan, Iran
123

1496
F. Shirini et al.
O
Ac2O, SaSA
Su
Pr
(SaSA)
SO3H
N
Ac2O /
CH2Cl2, r. t.
S
O
O
Su= ArOH; Pr= ArOAc
ROH
ROAc
Su= R1NHR2; Pr= R1N(Ac)R2
CH2Cl2, reflux
Scheme 1
Scheme 2
yields. Primary benzylic, including electron-donating or
withdrawing groups, and aliphatic alcohols were acetylated
with excellent yields (Table 1, entries 1–11, 13–16). The
protection of benzylic, cyclic, and linear secondary alco-
hols was also achieved satisfactorily (Table 1, entries 12,
17, 18). It is in general known that diaryl carbinols can
easily dimerize or dismutate in the presence of a Lewis
acid catalyst [33]. However, benzhydrol itself, as model
compound, was acetylated in 85% yield using Ac2O in the
presence of SaSA without any dimerisation (Table 1, entry
Table 1 Acetylation of
alcohols, phenols, and amines
catalyzed by SaSA
Entry
1
Substrate
2-ClC6H4CH2OH
Product
2-ClC6H4CH2OAc
Time (h) Yield (%)
2
95
92
90
92
92
92
90
85
90
85
92
2
3
4-ClC6H4CH2OH
2-BrC6H4CH2OH
2-MeC6H4CH2OH
2-MeOC6H4CH2OH
3-MeOC6H4CH2OH
2-NO2C6H4CH2OH
3-NO2C6H4CH2OH
4-NO2C6H4CH2OH
Ph2CHOH
4-ClC6H4CH2OAc
2-BrC6H4CH2OAc
2-MeC6H4CH2OAc
2-MeOC6H4CH2OAc
3-MeOC6H4CH2OAc
2-NO2C6H4CH2OAc
3-NO2C6H4CH2OAc
4-NO2C6H4CH2OAc
Ph2CHOAc
2
1.5
1.5
1
4
5
6
1
7
5.8
4.5
4
8
9
10
11
2
0.5
CH2OH
CH2OAc
12
13
14
15
PhCH2CH2OH
PhCH2CH2CH2OH
PhCH(Me)CH2OH
OH
PhCH2CH2OAc
PhCH2CH2CH2OAc
PhCH(Me)CH2OAc
OAc
2
90
87
90
92
2
1.5
1.5
16
1.5
90
OH
OAc
17
18
PhCH2C(OH)Me2
PhCH2C(OAc)Me2
1
92
89
1.5
OH
Ph3COH
OAc
Ph3COAc
19
20
21
2
85
90
92
2- (CH2=CH)C6H4OH
OH
2- (CH2=CH)C6H4OAc
OAc
0.5
0.8
22
23
OH
OAc
0.5
3
90
Products were characterized by
their physical constants,
comparison with authentic
samples, IR and NMR
spectroscopy [12, 13, 16, 17, 20,
23, 24, 26, 30, 34, 35], isolated
yield, phenols and amines are
acetylated at room temperature
90a
OH
OH
OAc
OAc
24
25
26
PhNH2
4-MeC6H4NH2
PhNHMe
PhNHAc
4-MeC6H4NHAc
PhN(Ac)Me
1
1
92
90
85
a
Reaction was performed using
2.4 mmol of acetic anhydride
0.25
123

Saccharinsulfonic acid
1497
Scheme 3
(MeCO)2O
O
O
O
O
O S N
O
OH
O
S
O
Me
Me
N S OH
O
S
O
O
O
O
MeCO2H + MeCO(X)R
RXH; X=O, N
O
H
O
X R
O S N
O
Me
Me
OH
S
O
O
O
O
General procedure
12). It is noteworthy that in the case of optically active
alcohols the reaction proceeded well with complete reten-
tion of configuration (Table 1, entry 17). Interestingly,
hindered tertiary alcohols such as 1-phenyl-2-methyl-2-
propanol, 1-adamantanol, and triphenyl carbinol, as models
for acetylation of tertiary alcohols, were also converted to
the corresponding acetates in CH2Cl2 under reflux in good
to excellent yields (Table 1, entries 19–21). Our investi-
gation showed that SaSA is also able to catalyze the
acetylation of phenols and amines in CH2Cl2 at room
temperature in good to high yields (Scheme 2; Table 1,
entries 22–33).
A mixture of 1 mmol substrate, 0.12 cm3 acetic anhydride
(1.2 mmol), and 13 mg SaSA (0.05 mmol) in 3 cm3
CH2Cl2 was stirred at room temperature or heated at reflux.
The progress of the reaction was monitored by TLC. After
completion of the reaction, the mixture was filtered and the
solid residue was washed with 5 cm3 CH2Cl2 and then
dried. The recovered catalyst can be used for two further
reactions. The organic layer was washed with 2 9 5 cm3
saturated NaHCO3 and 10 cm3 water and dried over
MgSO4. Evaporation of the solvent followed by column
chromatography on silica gel afforded the pure acetate.
We have found that SaSA is a reusable catalyst and
even after three runs for the acetylation of the substrates
with acetic anhydride the catalytic activity of SaSA was
almost the same as that of the freshly used catalyst.
Although the actual role of SaSA is not clear, the
mechanism shown in Scheme 3 is selected as highly
probable.
Acknowledgment We are thankful to the University of Guilan
Research Council for partial support of this work.
References
In conclusion, the acetylation of alcohols, phenols, and
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of SaSA, a newly prepared melamine-based reagent. High
yields of the products, relatively short reaction times, ease
of the preparation, stability and reusability of the reagent,
heterogeneous reaction conditions, and easy work-up are
among the other advantages of this new method which
make this procedure a useful and attractive addition to the
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