A facile and efficient procedure for the transdithioacetalization of 1,1-diacetates using POCl3-montmorillonite as catalyst

Article abstract of DOI:10.1081/SCC-200036588

A rapid and efficient method for the transdithioacetalization of 1,1-diacetates with 1,2-dithioglycol was described in good to excellent yield catalyzed by POCl₃-montmorillonite.

Full text of DOI:10.1081/SCC-200036588

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A Facile and Efficient
Procedure for the
Transdithioacetalization
of 1,1‐Diacetates Using
POCl ‐Montmorillonite as
3
Catalyst
a
a
a
Tong‐Shou Jin , Guang Sun , Yan‐Wei Li
&
a
Tong‐Shuang Li
a
Department of Chemistry , College of Chemistry
and Environmental Science, Hebei University , No.
88 Hezuo Road, Baoding, 071002, Hebei Province,
P.R.China
Published online: 10 Jan 2011.
To cite this article: Tong‐Shou Jin , Guang Sun , Yan‐Wei Li & Tong‐Shuang
Li (2004) A Facile and Efficient Procedure for the Transdithioacetalization of
1
,1‐Diacetates Using POCl ‐Montmorillonite as Catalyst, Synthetic Communications:
3
An International Journal for Rapid Communication of Synthetic Organic Chemistry,
4:22, 4105-4110, DOI: 10.1081/SCC-200036588
3
To link to this article: http://dx.doi.org/10.1081/SCC-200036588
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SYNTHETIC COMMUNICATIONS
Vol. 34, No. 22, pp. 4105–4110, 2004
A Facile and Efficient Procedure for the
Transdithioacetalization of 1,1-Diacetates
Using POCl -Montmorillonite as Catalyst
3
*
Tong-Shou Jin, Guang Sun, Yan-Wei Li, and Tong-Shuang Li
Department of Chemistry, College of Chemistry and Environmental
Science, Hebei University, Baoding, P.R.China
ABSTRACT
A rapid and efficient method for the transdithioacetalization of 1,1-
diacetates with 1,2-dithioglycol was described in good to excellent
3
yield catalyzed by POCl -montmorillonite.
3
Key Words: Transdithioacetalization; 1,1-Diacetates; POCl -montmor-
illonite; Thioacetals.
Protection of carbonyl groups as thioacetals are quite often a necessary
[1]
requirement in the synthesis of multiple functional organic molecules.
*
Correspondence: Tong-Shou Jin, College of Chemistry and Environmental Science,
Hebei University, No. 88 Hezuo Road, Baoding 071002,Hebei Province, P.R.China;
E-mail: orgsyn@mail.hbu.edu.cn.
4
105
DOI: 10.1081/SCC-200036588
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

4
106
Jin et al.
Thioacetals are quite stable toward a wide variety of reagents and are also
useful in organic synthesis as acyl carbanion equivalents in C 22 C bond
forming reactions. Moreover, S,S-acetals could be used as intermediates for
[3]
the conversion of the carbonyl function to parent hydrocarbons. In the litera-
[
4–8]
ture, several types of lewis acid catalysts were introduced previously for
the preparation of thioacetals from carbonyl compounds. Mixed reagent
[9–12]
systems
have also been developed for the formation of thioacetals. As
a faster and cleaner reaction compared with thioacetalization of cabonyl com-
pounds, transthioacetalization of acetals is a useful transformation for the
[13]
preparation of S,S-acetals that have been reported in the literature.
However, many of these reported methods require long reaction times, stoi-
chiometric use of expensive and hazardous reagent and lack general applica-
bility. After a literature survey, we found that the transthioacetalization of
[
14]
1
,1-diacetate has also been reported,
but only a few kinds of diacetates
are studied. In this article, we have introduced POCl -mont as an efficient
3
catalyst for the transthioacetalization of 1,1-diacetates (Scheme. 1).
When various types of aromatic 1,1-diacetates 1 are heated with 1,2-
dithioglycol 2 in refluxing dichloromethane or at room temperature in the
presence of POCl -mont, the corresponding dithiolanes 3 are obtained in
3
good to excellent yield. The result is summarized in Table 1.
From Table 1, we found that 1,1-diacetates of benzaldehyde and cinna-
maldehyde and with electron-donating groups (1a, 1g, 1b, 1c, and 1j) were
easily converted to the corresponding dithiolanes at room temperature in
the presence of POCl -mont. Howerery, 1,1,-diacetates with electron-
3
withdrawing group (1d, 1e, 1f, 1h, and 1i) take longer reaction time at room
temperature; therefore, complete conversion of the reactions need in refluxing
temperature. For example, the transthioacetalization of 1f need 45 min in
dichloromethane at room temperature under catalyst of POCl -mont and
3
give the corresponding yield 83%, when it is proceeded in refluxing CH Cl
2
2
only need 15 min and the yield is 90% (as shown in Table 1). It is pointed
out that 1h and 1i provide poor conversion rate (,40%) at room temperature
for the time 2 hr, whereas over 72% yield were obtained in refluxing CH Cl
2
2
for 60 min, possibly due to the strong electron withdrawing nitro substituent.
In summary, we have developed a facile and efficient procedure for the
transthioacetalization of 1,1-diacetates with 1,2-dithiaglycol under the catalyst
Scheme 1.

Transdithioacetalization of 1,1-Diacetates
4107

4
108
Jin et al.
of POCl -mont. For this method has operational simplicity, high yield, short
3
reaction time and using a reusable catalyst.
EXPERIMENTAL
The POCl -mont catalyst was obtained by mixing POCl and montmoril-
3
3
lonite clays in CH Cl then solvent was removed under reduced pressure and
2
2
finally stored in desiccator until use. The products were characterized by
1
H NMR spectra and comparison of their melting or boiling points with
literature values.
General Procedure for the Transthioacetalization
of 1,1-Diacetate
A mixture of 1,1-diacetate l. (2.00 mmol, synthesized as described
[
15]
previously ), HSCH CH SH (2.4 mmol), CH Cl (8 mL), and POCl -mont
2
2
2
2
3
(
150 mg) was stirred in refluxing CH Cl or at room temperature for the
2 2
time indicated in Table 1. The reaction was monitored by TLC. After
completion of the reaction, CH CI (10 mL) was added to the reaction
mixture and the POCl -mont was filtered off. The catalyst was washed with
2
2
3
CH Cl (2 Â 8 mL); after that, the filtrate was washed with 5% HCl
2
2
(
dried with MgSO . The solvent was evaporated under reduced pressure, and
15 mL), 5% NaHCO (15 mL) and brine (2 Â 15 mL) successively and
3
4
residue was chromatographed on silica gel (petroleum-ether as eluent) to
1
give the corresponding dithiolanes 3 (Table 1). H NMR spectra were deter-
mined in D-chloroform solution on a FT-NMR Bruker 300 (300 MHz), and
reported in d ppm using tetramethylsilane as the standard.
4
-MeOC H CH(SCH ) 3c
6 4 2 2
d 3.30–3.45 [4H, m, 4-CH OC H CH (SCH ) ], 3.80[3H, s, 4-CH OC
6-
H
3
6
4
2 2
3
H CH(SCH ) ], 5.60[1H, s, 4-CH OC H CH(SCH )2], 6.87–7.47[4H, m,
4
2 2
3
6
4
2
4
-CH OC H CH(SCH ) ].
3 6 4 2 2
4
-ClC H CH(SCH ) 3d
6 4 2 2
d , 3.30–3.60 [4H, m, 4-ClC H CH(SCH ) ], 5.60[1H,s, 4-ClC H CH
H
6
4
2 2
6 4
(
SCH ) ], 7.30–7.50 [4H, m, 4-ClC H CH (SCH ) ].
2 2 6 4 2 2

Transdithioacetalization of 1,1-Diacetates
4109
PhCH 55 CHCH(SCH ) 3g
2
2
d 3.22–3.42 [4H, m, C H CH 55 CHCH (SCH ) ], 5.22 [1H, d, C H
6 5-
H
6
5
2 2
CH 55 CHCH(SCH ) ], 6.15–6.22[1H, dd, C H CH 55 CHCH (SCH ) ],
2 2
2
2
6
5
6
CH 55 CHCH (SCH ) ].
.52[1H, d, C H CH 55 CHCH (SCH ) ], 7.22–7.46 [5H, m, C H
6 5 2 2 6 5-
2
2
4
-O NC H CH(SCH ) 3h
2 6 4 2 2
dH3.35–3.60 [4H, m, 4-NO C H CH (SCH ) ], 5.60 [1H, s,
2 2
2
6
4
4
-NO C H CH (SCH ) ], 7.67–8.15 [4H, m, 4-NO C H CH (SCH ) ].
2 6 4 2 2 2 6 4 2 2
ACKNOWLEDGMENTS
The project was supported by National Natural Science Foundation of
China (29872011 and 29572039), Educational Ministry of China, Educational
Department of Hebei Province (990104), Science and Technology Commis-
sion of Hebei Province.
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2
3
Received in the UK July 29, 2004