Ferric hydrogensulfate as effective and recyclable catalyst for mild dithioacetalization of aldehydes and ketones

Article abstract of DOI:10.1080/10426500701569422

Ferric hydrogensulfate has been found to be an extremely efficient and recyclable heterogeneous catalyst for dithioacetalization reactions. Carbonyl compounds have been successfully converted into their corresponding dithiolanes and dithianes derivatives

Full text of DOI:10.1080/10426500701569422

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Phosphorus, Sulfur, and Silicon
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Ferric Hydrogensulfate as
Effective and Recyclable
Catalyst for Mild
Dithioacetalization of
Aldehydes and Ketones
Hamid Reza Shaterian a , Hamid Reza Ahmadian a
, Majid Ghashang a , Razieh Doostmohammadi a &
Hossein Yarahmadi a
a Department of Chemistry, Faculty of Sciences ,
University of Sistan and Baluchestan , Zahedan, Iran
Published online: 09 May 2008.
To cite this article: Hamid Reza Shaterian , Hamid Reza Ahmadian , Majid Ghashang ,
Razieh Doostmohammadi & Hossein Yarahmadi (2008) Ferric Hydrogensulfate as
Effective and Recyclable Catalyst for Mild Dithioacetalization of Aldehydes and
Ketones, Phosphorus, Sulfur, and Silicon and the Related Elements, 183:5, 1099-1108,
DOI: 10.1080/10426500701569422
To link to this article: http://dx.doi.org/10.1080/10426500701569422
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Phosphorus, Sulfur, and Silicon, 183:1099–1108, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701569422
Ferric Hydrogensulfate as Effective and Recyclable
Catalyst for Mild Dithioacetalization of Aldehydes
and Ketones
Hamid Reza Shaterian, Hamid Reza Ahmadian,
Majid Ghashang, Razieh Doostmohammadi,
and Hossein Yarahmadi
Department of Chemistry, Faculty of Sciences, University of Sistan
and Baluchestan, Zahedan, Iran
Ferric hydrogensulfate has been found to be an extremely efficient and recyclable
heterogeneous catalyst for dithioacetalization reactions. Carbonyl compounds have
been successfully converted into their corresponding dithiolanes and dithianes
derivatives in excellent yields at ambient conditions. The synthetic simple proce-
dures reported in this paper constitute an exceptionally mild procedure for selective
carbonyl protection.
Keywords 1,3-dithiane; 1,3-dithiolane; dithioacetalization; Fe(HSO4)3; heterogeneous
catalyst
INTRODUCTION
Thioacetalization of carbonyl compounds plays an important role in or-
ganic synthesis.1Since the introduction of 1,3-dithianes as nucleophilic
acylating reagents by Corey and Seebach, dithioacetals have become
widely used tools for C C bond formation.2 Furthermore, the stabil-
ity exhibited by cyclic and acyclic dithioacetal under acidic and ba-
sic conditions has led to their synthetic utility as carbonyl protecting
groups and as intermediates for the conversion of carbonyl compounds
to their parent hydrocarbons.3,4 Several Brønsted and Lewis acid cata-
lysts 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 acid (DBSA),14 TiCl4,15 LaCl3,16 hydrobromic
Received 18 June 2007; accepted 22 June 2007.
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, PO Box 98135-674, Zahedan, Iran.
E-mail: hrshaterian@hamoon.usb.ac.ir
1099

1100
H. R. Shaterian et al.
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. Although some Lewis acid catalysts
have been reported to show chemoselectivity, these catalysts are de-
stroyed in the work-up procedure and cannot be recovered and reused.14
Some methods failed to protect deactivated aromatic substrates. There-
fore, there is still a need to develop a simple and efficient method for
dithioacetalization of carbonyl groups and chemoselective protection
of aldehydes. In this research, ferric (III) hydrogensulfate as the solid
heterogeneous acid catalyst shows special mention and also can be re-
covered and reused again. This catalyst is safe, easy to handle, envi-
ronmentally benign, presents fewer disposal problems and is stable in
reaction media. Ferric hydrogensulfate has been used in some organic
reactions, such as Schmidt reaction of ketones to amides22 and Friedel-
Crafts acylation of alkoxy benzenes by aliphatic anhydrides.23
RESULTS AND DISCUSSION
Recent progress in the catalysis by Brønsted and Lewis acids is worthy
of note. Among these, heterogeneous catalysts have been attracting
much attention, because they offer a viable approach to the preparation
of invaluable organic compounds.24 These catalysts have been used in
high demand in terms of minimizing waste generation side product and
provide environmentally benign processes.
In continuation of our interest to develop protection and deprotection
of carbonyl groups,25 herein, we wish to report an efficient method for
the dithioacetalization of carbonyl compounds in good to high yields, as
well as the chemoselective protection of various carbonyl compounds
by employing Fe(HSO4)3 as active heterogeneous catalyst (Scheme 1).
We believe that our method is very simple, mild, rapid and new to the
literature.
SCHEME 1

Ferric Hydrogensulfate as Effective Catalyst
1101
TABLE I Conversion of Benzaldehyde (1mmol) to
2-Phenyl-1,3-dithiane Using 1,3-Propanedithiol (1.05 mmol) in the
Presence of Different Amounts of Solid Fe(HSO4)3 as a Catalyst
under a Variety of Solvents (2 mL) at Room Temperature
Entry
Solvent
Catalyst (mol %)
Time (min)
GC Yield (%)
1
2
3
4
5
6
7
8
9
Chloroform
Dichloromethane
Ethylacetate
n-Hexane
Diethyl ether
Acetonitrile
Acetonitrile
Acetonitrile
Acetonitrile
Acetonitrile
Acetonitrile
10
10
10
10
10
10
20
5
25
20
15
40
20
2
100
100
100
100
100
100
100
96
Immediately
8
20
60
24 h
2
1
0
90
85
—
10
11
First, we tried to convert benzaldehyde (1 mmol) to its corresponding
2-phenyl-1,3-dithiane with various amounts of 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 and the quantity of Fe(HSO4)3 was
chosen to be 10 mol%.
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 (1.05 eq) and acetonitrile (as solvent, 2 mL) in the
presence of Fe(HSO4)3 (10 mol%) (Table II).
As shown in Table II, several different aliphatic, aromatic aldehy-
des 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 II, entries 1–12). 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 reac-
tion time with excellent yield (Table II, entries 3–10). As reported in
the literature,26 this observation clearly shows that the reactivity of
benzaldehydes in thioacetalization reaction is more strongly affected
by the electronic factors. We also performed dithioacetalization reac-
tions with aromatic and aliphatic ketones at room temperature (Table
II, entries13–19). The reaction of acetophenone with 1,3-propanedithiol

1102
H. R. Shaterian et al.
TABLE II Conversion of Aldehydes and Ketones to the
Corresponding 1,3-Dithiane and 1,3-Dithiolane Using Fe(HSO4)3 as s
Catalyst in Acetonitrile as a Solvent at Room Temperature
Entry
1
Substrate
Product
Time (min)
2
Yielda (%)
97b
2
5
98
3
4
7
95
96
10
5
6
20
24
94
91
7
24
93
8
9
7
5
3
2
93
95
97
89
10
11
12
13
4
97
10
94c
14
9
99

Ferric Hydrogensulfate as Effective Catalyst
1103
TABLE II Conversion of Aldehydes and Ketones to the
Corresponding 1,3-Dithiane and 1,3-Dithiolane Using Fe(HSO4)3 as s
Catalyst in Acetonitrile as a Solvent at Room Temperature
(Continued)
Entry
15
Substrate
Product
Time (min)
10
Yielda (%)
96
16
17
10
10
97
90
18
19
8
91
24h
0.0
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
;
bIsolated yield after third cycle with reused catalyst. cThe reaction was performed at
50◦C.
was not completed after 24 h at room temperature (24 h, 60% GC yield),
thus we performed this reaction at 50◦C in oil bath (10 min, 100% GC
yield) (Table II, entry 13). The condensation reaction of 9H-fluoren-9-
one with dithiols was not successful in the reaction conditions (Table
II, Entry 19).
In a typical experiment, after the reaction was completed, in the
work-up stage, acetonitrile was evaporated from the reaction mixture.
The reaction mixture was combined with chloroform, the ferric hydro-
gensulfate as catalyst was isolated from the reaction mixture by sim-
ple filtration. The purified catalyst was achieved by washing the solid
residue catalyst by ethyl acetate followed by drying in an oven at 100◦C
for 30 min. In every experiment, more than 98% of the ferric hydro-
gensulfate was easily recovered from the reaction mixture. Catalytic
activity of the recovered catalyst was tested and showed activity same
as ferric hydrogensulfate that it was used in the first time.
In order to show the ability of ferric hydrogensulfate to act as selec-
tive catalyst, we studied dithioacetalization of aldehydes and ketones
with 1,3-propanedithiol (Table III). By this method, benzaldehyde was

1104
H. R. Shaterian et al.
TABLE III Selective Dithioacetalization of Different Aldehydes and
Ketones in the Presence Fe(HSO4)3 as Catalyst Using
1,3-Propanedithiol
Entry
Carbonyl compound
Product
Time (min)
Yielda,b (%)
1
90
10
10
100
2
3
10
10
0
100
0
100
4
5
10
10
0
100
0
6
100
0
10
a
GC yield using n-octane as internal standard. bThe molar ratio of substrate1/su-
bstyrate2 /1,3-propanedithiol/Fe(HSO4)3 was chosen 1/1/1.05/0.1.

Ferric Hydrogensulfate as Effective Catalyst
1105
protected in the presence of 3-nitrobenzaldehyde with the ration of
90/10 (Table III, entry 1). Benzaldehyde in the presence of acetophe-
none and benzophenone was exclusively protected (Table III, entries
2, 3). Heptanal was quantitatively converted to its S, S-cyclic acetal,
whereas acetophenone and benzophenone remained intact (Table III,
entries 5, 6). Thus, the excellent chemoselectivity observed for dithioac-
etalization of aldehydes and ketones make the presented method useful
contribution in organic synthesis.
In conclusion, we have demonstrated that ferric hydrogensulfate is a
new, efficient, mild and heterogeneous catalyst for dithioacetalization of
various aldehydes and ketones at room temperature. This simple and ef-
ficient 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 considerations, because
it produces little waste. Ferric hydrogensulfate has excellent activity
and can be recovered from reaction mixtures and reused. Greener con-
ditions, simple work-up procedure, high yields and short reaction times
are other advantages of this method.
EXPERIMENTAL
All reagents were purchased from Merck and Aldrich and used without
further purification. Ferric hydrogensulfate was prepared according to
the reported procedure.22,23 All yields refer to isolated products after pu-
rification. 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 spec-
tra were recorded on a Perkin-Elmer 781 spectrophotometer. TLC was
performed on Silica-gel polygram SIL G/UV 254 plates.
Preparation of Ferric Hydrogensulfate22
A 50 mL suction flask was equipped with a dropping funnel. The gas
outlet was connected to a vacuum system through an alkaline solution
trap. Anhydrous ferric chloride (10 mmol) was charged into the flask
and concentrated sulfuric acid 98% (30 mmol) was added dropwise over
a period of 30 min at room temperature. HCl evolved immediately. After
completion of the addition, the mixture was shaken for 30 min at 100◦C,
while the residual HCl was eliminated by suction. Finally, a pale-brown
solid Fe(HSO4)3 was obtained.22

1106
H. R. Shaterian et al.
FIGURE 1 FT-IR spectrum of Fe(HSO4)3.
FT-IR Spectrum of Fe(HSO4)3
The FT-IR spectrum of the catalyst was shown in Figure 1. The cata-
lyst is solid and solid-state IR spectrum was recorded using the KBr
disk technique. The spectrum shows a broad OH stretching absorp-
tion around 3500 and 3100 cm−1. For sulfuric acid functional group in
Fe(HSO4)3, the FTIR absorption of the O S O stretching modes lies in
1113 cm−1, and that of the S O stretching mode lies in 600–700 cm−1
.
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 (1.05 mmol) ) in acetonitrile (2 mL) was added 10
mol% of Fe(HSO4)3. The reaction mixture was stirred at room temper-
ature for time indicated in Table II. 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 catalyst washed with chlo-
roform and recovered catalyst can be used again. The organic layer
was extracted with 10% sodium hydroxide 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 pres-
sure and the pure product was obtained. The desired pure product(s)

Ferric Hydrogensulfate as Effective Catalyst
1107
was characterized by comparison of their physical data with those of
known the dithioacetals.5–21 The spectral data of some representative
dithioacetals are given below.
2-Phenyl-1,3-dithiane (Table II, entry 1)
1H NMR (CDCl3, 400 MHz): δ = 1.92–1.96 (1H, m), 2.15–2.17 (1H, m),
2.88–3.10 (4H, m), 5.17 (1H, s), 7.29–7.48 (5H, m) ppm; IR (KBr, cm−1):
3063, 3022, 2929, 2894, 1685, 1598, 1487, 1445, 1429, 1276, 1240, 1158,
1071, 845, 698.
2-Phenyl-1,3-dithiolane (Table II, Entry 2)
1H NMR (CDCl3, 400 MHz): δ = 2.32 (1H, s), 3.29–3.52 (4H, m), 5.62
(1H, s), 7.10 (2H, d,J = 6.5 Hz), 7.40 (2H, d, J = 6.5 Hz) ppm; IR (KBr,
cm−1): 3004, 1510, 1437, 1411, 1277, 1177, 1165, 830, 777.
3>2-(4-Chlorophenyl)-1,3-dithiane (Table II, entry 3)
1H NMR (CDCl3, 400 MHz): δ = 1.89–1.94 (1H, m), 2.87–2.94 (2H,
m), 3.00–3.09 (2H, m), 2.87–3.09 (4H, m), 5.13 (1H, s), 7.30 (2H, d, J =
9.0 Hz), 7.40 (2H, d, J = 9.0 Hz) ppm; IR (KBr, cm−1): 3081, 3036, 2901,
1912, 1490, 1425, 1276, 1174, 1115, 1088, 1016, 885, 854, 819, 788, 761,
675, 513.
2-(3-Nitrophenyl)-1,3-dithiane (Table II, entry 5)
1H NMR (400 MHz, CDCl3): δ = 1.75–2.05 (m, 1H), 2.10–2.25 (m,
1H), 2.80–3.15 (m, 4H) 5.20 (s, 1H), 7.49 (1H, t, J = 8 Hz), 7.77 (1H,
d, J = 8 Hz), 8.13 (1H, d, J = 8 Hz), 8.31 (s, 1H) ppm; IR (KBr, cm−1):
3059, 2942, 1533, 1477, 1440, 1353, 1269, 1186, 1086, 931, 877, 815,
774, 728, 696, 447.
2-(4-N,N-dimethylphenyl)-1,3-dithiane (Table II, entry 8)
1H NMR (CDCl3, 400 MHz): δ = 1.88–1.91(1H, m), 2.12–2.17 (1H,
m), 2.87–3.08 (4H, m), 2.94 (6H, s), 5.11 (1H, s), 6.67 (2H , d, J = 8.8
Hz),7.33(2H, d, J = 8.8Hz) ppm; IR (KBr, cm−1): 3066, 2949, 2898, 2801,
1608, 1520, 1349, 765.
2-(2-Phenyl ethenyl)- 1,3-dithiane (Table II, entry 11)
1H NMR (CDCl3, 400 MHz): δ = 1.89–1.95 (1H, m), 2.11–2.16 (1H,
m), 2.83–2.99 (4H, m), 4.82 (1H, d, J = 7.6 Hz), 6.26 (1H, dd, J =16.0
and 7.6 Hz), 6.76 (1H, d, J = 16.0 Hz), 7.30–7.40 (5H, m) ppm; IR (KBr,
cm−1): 3066, 2941, 1677, 1649, 1616, 1579, 1496, 1451, 1424, 1275, 1246,
1206, 1172, 1044, 964, 911, 869, 767, 896, 677, 509.

1108
H. R. Shaterian et al.
2-Methyl-2-phenyl-1,3-dithiane (Table II, entry 13)
1H NMR (CDCl3, 400 MHz): δ = 1.80 (1H, s), 1.94–1.98 (2H, m), 2.72–
2.75 (4H, m), 7.20–7.40 (3H, m), 7.94–7.96 (2H, m) ppm; IR (KBr, cm−1):
3059, 2905, 2362, 1645, 1489, 1446, 1370, 1511, 1278, 1254, 1181, 1067,
1029, 909, 869, 766, 701, 625, 554.
1,5-Dithiaspiro[5.5] undecane (Table II, entry 14)
1H NMR (CDCl3, 400 MHz): δ = 1.25–1.45 (2H, m), 1.58–1.66 (4H,
m), 1.96–2.00 (6H, m), 2.80–2.82 (4H, m) ppm; IR (KBr, cm−1): 2936,
2851, 1645, 1443, 1352, 1317, 1275, 1243, 1190, 1132, 1011, 824, 769,
559.
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