Chemoselective dithioacetalization of carbonyl compounds using magnesium hydrogensulfate as efficient heterogeneous catalyst

Article abstract of DOI:10.1080/10426500801967740

Carbonyl compounds have been successfully converted into their corresponding dithiolanes and dithianes derivatives with 1,2-ethanedithiol and 1,3-propanedithiol in excellent yield at room temperature and short reaction times using a catalytic amount of ma

Full text of DOI:10.1080/10426500801967740

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Chemoselective
Dithioacetalization of Carbonyl
Compounds Using Magnesium
Hydrogensulfate as Efficient
Heterogeneous Catalyst
Hamid Reza Shaterian a , Asghar Hosseinian a , Majid
Ghashang a & Fahimeh Khorami a
a Department of Chemistry, Faculty of Sciences ,
University of Sistan and Baluchestan , Zahedan, Iran
Published online: 24 Sep 2008.
To cite this article: Hamid Reza Shaterian , Asghar Hosseinian , Majid Ghashang
& Fahimeh Khorami (2008) Chemoselective Dithioacetalization of Carbonyl
Compounds Using Magnesium Hydrogensulfate as Efficient Heterogeneous Catalyst,
Phosphorus, Sulfur, and Silicon and the Related Elements, 183:10, 2490-2501, DOI:
10.1080/10426500801967740
To link to this article: http://dx.doi.org/10.1080/10426500801967740
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Phosphorus, Sulfur, and Silicon, 183:2490–2501, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500801967740
Chemoselective Dithioacetalization of Carbonyl
Compounds Using Magnesium Hydrogensulfate as
Efficient Heterogeneous Catalyst
Hamid Reza Shaterian, Asghar Hosseinian,
Majid Ghashang, and Fahimeh Khorami
Department of Chemistry, Faculty of Sciences, University of Sistan and
Baluchestan, Zahedan, Iran
Carbonyl compounds have been successfully converted into their correspond-
ing dithiolanes and dithianes derivatives with 1,2-ethanedithiol and 1,3-
propanedithiol in excellent yield at room temperature and short reaction times
using a catalytic amount of magnesium hydrogensulfate. The synthetic simple
procedures reported in this paper constitute an exceptionally mild procedure for
carbonyl protection in ambient conditions.
Keywords 1,3-dithiane; 1,3-dithiolane; dithioacetalization; heterogeneous catalyst;
Mg(HSO4)2
INTRODUCTION
Since the introduction of 1,3-dithianes as nucleophilic acylating
reagents by Corey and Seebach,1 dithioacetals have become widely used
tools for the formation of C C bonds. In addition, the stability exhib-
ited by 1,3-dithiolanes under acidic or basic conditions has led to their
synthetic utility as carbonyl protecting groups2 and as intermediates
in the conversion of a carbonyl function to a hydrocarbon derivative.3,4
They are generally obtained by protic acid or Lewis acid cat-
alyzed condensation of carbonyl compounds with thiols or dithi-
ols. Several Brønsted and Lewis acid catalysts such as: Sc(OTf)3,5
InCl3,6 iodine supported on natural phosphate7 CoCl2,8 NiCl2,9 NBS,10
In(OTf)3,11 MoO2(acac)2,12 [bmim]HSO4,13 p-dodecyl benzenesulfonic
Received 2 December 2007; accepted 4 January 2008.
We are thankful to the Sistan and Baluchestan University Research Council for the
partial support of this research.
Address correspondence to Hamid Reza Shaterian, Department of Chemistry, Faculty
of Sciences, University of Sistan and Baluchestan, P. O. Box 98135-674, Zahedan, Iran.
E-mail: hrshaterian@hamoon.usb.ac.ir
2490

Carbonyl Compounds as Heterogeneous Catalyst
2491
acid (DBSA),14 TiCl4,15 LaCl3,16 hydrobromic acid,17 ZnCl2,18 Y(OTf)139
Iron(III) fluoride,20 and VO(OTf)221 have been used in thioacetalization
reactions. Many of these methods require long reaction times, reflux
conditions, stoichiometric amounts of catalyst, unwanted side products,
and show low selectivity when applied to the mixtures of aldehydes and
ketones. Therefore, there is still a need to develop a simple and efficient
method for dithioacetalization of carbonyl groups. Thus, in continuation
of our previous work on heterogeneous catalysts,22 we wish to report
an efficient method for the dithioacetalization of carbonyl compounds
in high to excellent yields by employing Mg(HSO4)2 as active heteroge-
neous catalyst (Scheme 1). We believe that our method is very simple,
mild, rapid and new to the literature.
O
Mg(HSO4)2 (Catalyst)
n
HSCH2(CH2)nCH2SH
+
S
S
R1
R2
CH3CN
R.T
R1
R2
n= 0,1
R1, R2= Alkyl, Aryl, H
SCHEME 1
This catalyst is safe and easy to handle; environmentally benign;
presents fewer disposal problems; and it is stable in reaction media.
Magnesium hydrogensulfate has been used in some organic reactions,
such as acetylation and formylation of alcohols,23 cleavage of C N,24
and oxidation of thiols.25
RESULTS AND DISCUSSION
In the first reaction, benzaldehyde (1 mmol) was converted to its corre-
sponding 2-phenyl-1,3-dithiane using Mg(HSO4)2 (0.05 g, 20 mol%) as
catalyst in the presence of various solvents at room temperature (Table
I). The results in Table I show that amongst these solvents, acetonitrile
was the solvent of choice in terms of time and product yield.
To find out the optimum quantity of the catalyst, the reaction of
benzaldehyde with 1,3-propandithiol was carried out using different
quantities of Mg(HSO4)2 under ambient conditions in acetonitrile as
solvent (Table II). As can be seen from Table II, best results were ob-
tained when using 0.025 g (10 mol%) of the catalyst.
Next, we prepared a range of cyclic dithioacetals under the following
reaction conditions: aldehydes or ketones (1 eq), 1,3-propandithiol or
1,2-ethanedithiol (1.1 eq), and acetonitrile (as solvent, 2 mL) in the
presence of Mg(HSO4)2 (0.025 g, 10 mol%) (Table III).

2492
H. R. Shaterian et al.
TABLE I Conversion of Benzaldehyde (1mmol) to
2-Phenyl-1,3-dithiane Using 1,3-Propanedithiol (1.1 mmol) in the
Presence of Mg(HSO4)2 (0.05 g, 20 mol%) as Catalyst Under a Variety
Solvents (2 mL) at Room Temperature
Entry
Solvent
Time (min)
Yield (%)a
1
2
3
4
5
6
7
Chloroform
Dichloromethane
Ethylacetate
n-Hexane
17
16
60
15
60
60
0.5
96
93
Incompletely
91
Incompletely
Incompletely
97
EtOH
H2O
Acetonitrile
aYields refer to the pure isolated products.
As shown in Table III, several different aliphatic and aromatic alde-
hydes with both electron-withdrawing and donating substituents pro-
duced corresponding cyclic dithioacetal without the formation of any
side products, in high to excellent yields within a few minutes at room
temperature (Table III, entries 1–29). The reaction was performed with
benzaldehyde containing withdrawing as well as electron donating
groups, but benzaldehydes with electron-donating groups are generally
more reactive than their corresponding benzaldehydes with electron-
withdrawing groups and provided the desired product at short reaction
time with excellent yield (Table III, entries 3–10). As reported in the
literature,26 this observation clearly shows that the reactivity of ben-
zaldehydes in thioacetalization reaction is more strongly affected by the
electronic and steric hindrance factors. We also performed dithioac-
etalization reactions with aromatic and aliphatic ketones at room
temperature. Benzophenone, cyclohexanone, cyclopentanone, and ethyl
TABLE II Optimization of the Amount of Mg(HSO4)2 in the
Reaction of Benzaldehyde with 1,3-Propandithiol Under Ambient
Conditions in Acetonitrile as Solvent
Entry
Catalyst (g)
Time (min)
Yield (%)a
1
2
3
4
5
0.1
Immediately
95
97
98
97
96
0.05
0.025
0.01
0.005
0.5
1.5
4
11
aYields refer to pure isolated product.

Carbonyl Compounds as Heterogeneous Catalyst
2493
TABLE III Conversion of Aldehydes and Ketones to the
Corresponding 1,3-Dithiane and 1,3-Dithiolane Using Mg(HSO4)2
as Catalyst in Acetonitrile as Solvent Under Ambient Conditions
Entry
1
Substrate
Product
Time (min) Yield (%)a
1.5
98
2
3
2
96
91
1.5
4
5
6
1.5
3
92
97
96
1.2
7
8
1.1
95
90
2
(Continued on next page)

2494
H. R. Shaterian et al.
TABLE III Conversion of Aldehydes and Ketones to the
Corresponding 1,3-Dithiane and 1,3-Dithiolane Using Mg(HSO4)2 as
Catalyst in Acetonitrile as Solvent Under Ambient Conditions
(Continued)
Entry
9
Substrate
Product
Time (min)
2
Yield (%)a
89
10
11
3
4
88
97
12
13
6
95
95
23
14
15
27
27
92
93
16
4
98
(Continued on next page)

Carbonyl Compounds as Heterogeneous Catalyst
2495
TABLE III Conversion of Aldehydes and Ketones to the
Corresponding 1,3-Dithiane and 1,3-Dithiolane Using Mg(HSO4)2
as Catalyst in Acetonitrile as Solvent Under Ambient Conditions
(Continued)
Entry
17
Substrate
Product
Time (min)
11
Yield (%)a
97
18
4
95
19
20
5
3
95
96
21
22
5
4
94
98
(Continued on next page)

2496
H. R. Shaterian et al.
TABLE III Conversion of Aldehydes and Ketones to the
Corresponding 1,3-Dithiane and 1,3-Dithiolane Using
Mg(HSO4)2 as Catalyst in Acetonitrile as Solvent Under
Ambient Conditions (Continued)
Entry
23
Substrate
Product
Time (min) Yield (%)a
4
89
24
25
8
2
91
87
26
27
28
29
30
8
8
93
91
89
88
92
7
6
12

Carbonyl Compounds as Heterogeneous Catalyst
2497
TABLE III Conversion of Aldehydes and Ketones to the
Corresponding 1,3-Dithiane and 1,3-Dithiolane Using Mg(HSO4)2 as
Catalyst in Acetonitrile as Solvent Under Ambient Conditions
(Continued)
Entry
31
Substrate
Product
Time (min) Yield (%)a
9
97
32
10
97
33
34
15
9h
92
40% GC Yield
35
36
37
9h
9h
20% GC Yield
43% GC Yield
92
9hb
(Continued on next page)

2498
H. R. Shaterian et al.
TABLE III Conversion of Aldehydes and Ketones to the
Corresponding 1,3-Dithiane and 1,3-Dithiolane Using Mg(HSO4)2 as
Catalyst in Acetonitrile as Solvent Under Ambient Conditions
(Continued)
Entry
38
Substrate
Product
Time (min) Yield (%)a
10hb
93
39
10hb
60% GC Yield
aYields refer to the pure isolated products. All known products have been reported
previously in the literature and were characterized by comparison of IR and 1H NMR
spectra with authentic samples.5−21 bThe reaction was performed at 80◦C under reflux
conditions.
3-oxobutanoate converted to the corresponding 1,3-dithianes at ambi-
ent conditions (Table III, Entries 30–33). But, the reaction of acetophe-
none and its derivatives with 1,3-propanedithiol were not completed
after 9 h at room temperature (9 h, 20–43% GC yield); thus, we per-
formed these reactions at 80oC in an oil bath (Table III, entries 36–38).
In order to show the ability of magnesium hydrogensulfate to act
as chemoselective catalyst for dithioacetalization reactions, we stud-
ied dithioacetalization of benzaldehyde and 4-methoxybenzaldehyde
in the presence of acetophenone. The benzaldehyde and 4-
methoxybenzaldehyde were exclusively protected, whereas acetophe-
none was intact in the same experimental conditions (Scheme 2).
To show the merit of the present work in comparison with reported
results in the literature, we compared results of magnesium hydrogen-
sulfate with CoCl2,8 NiCl2,9 MoO2(acac)122, and Y(OTf)139 in the synthe-
sis of 2-phenyl-1,3-dithiane. As shown in Table IV, magnesium hydro-
gensulfate can act as effective catalyst with respect to reaction times,
yields, and the obtained products.
In conclusion, we have demonstrated that magnesium hydrogen-
sulfate is a new, efficient, mild and heterogeneous catalyst for dithioac-
etalization of various aldehydes and ketones at room temperature. This

Carbonyl Compounds as Heterogeneous Catalyst
2499
SCHEME 2
simple and efficient method is a chemoselective procedure for protection
of aldehydes in the presence of ketones. This synthetic mythology is
important from an environmental point of view and economic consid-
erations, because it produces little waste.
EXPERIMENTAL
All reagents were purchased from Merck and Aldrich and used with-
out further purification. Mg(HSO4)2 was prepared via a literature
procedure.24 All yields refer to isolated products after purification.
Products were characterized by comparison of spectroscopic data (IR,
1H NMR spectra) with authentic samples. The NMR spectra were
recorded on a Bruker Avance DEX 400 MHz instrument. IR spectra
were recorded on a Perkin-Elmer 781 spectrophotometer. TLC was per-
formed on Silica-gel polygram SIL G/UV 254 plates.
TABLE IV Comparison of the Efficiency of Metal Catalysts for the
Synthesis of 2-Phenyl-1,3-dithiane
Entry
Catalyst
Conditions
Time
Yield (%)ref
1
2
3
4
5
CoCl2
NiCl2
MoO2(acac)2
Y(OTf)3
CH3CN; r.t.; Cat (5 mol%)
CH2Cl2-MeOH (5:1), r.t.; Cat (10 mol%)
CH3CN; r.t.; Cat (10 mol%)
1 h
2.5 h
3 h
45 min
1.5 min
918
949
9412
8919
98
CH3CN; r.t.; Cat (5 mol%)
CH3CN; r.t.; Cat (10 mol%)
Mg(HSO4)2

2500
H. R. Shaterian et al.
General Procedure for the Dithioacetalization of Carbonyl
Compounds
To a mixture of a carbonyl compound (1 mmol) and 1,3-propanedithiol
or 1,2-ethanedithiol (1.1 mmol) in acetonitrile (2 mL) was added 0.025
g of Mg(HSO4)2. The reaction mixture was stirred at room tempera-
ture for time indicated in Table III. The progress of the reaction was
monitored by TLC or GC. After completion of the reaction acetonitrile
was evaporated from the reaction mixture. The reaction mixture was
combined with chloroform and filtered. The organic layer was extracted
with 10% NaHCO3 solution (10 ml) followed by water (10 ml) and brine
solution (5 ml). Organic layer dried with anhydrous CaCl2 and filtered,
solvent evaporated under reduced pressure, and the pure product was
obtained. The desired pure product(s) was characterized by comparison
of their physical data with those of known the dithioacetals.5−21 Spec-
troscopic analysis confirmed the molecular structures of the products.
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