A mild method for conversion of alcohols to dialkyl sulfites by use of Na2SO3/SOCl2

Article abstract of DOI:10.1080/10426500490262577

Alcohols are easily converted to their corresponding dialkyl sulfite under mild reaction conditions using Na₂SO₃/SOCl₂ in moderate to good isolated yields.

Full text of DOI:10.1080/10426500490262577

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Phosphorus, Sulfur, and Silicon and the Related
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A MILD METHOD FOR CONVERSION OF ALCOHOLS TO
DIALKYL SULFITES BY USE OF Na2SO3/SOCl2
Ali Reza Kiasat a , Foad Kazemi a & Froogh Khosravian a
a Shahid Chamran University, Ahvaz, Iran
Version of record first published: 11 Aug 2010.
To cite this article: Ali Reza Kiasat , Foad Kazemi & Froogh Khosravian (2004): A MILD METHOD FOR CONVERSION OF
ALCOHOLS TO DIALKYL SULFITES BY USE OF Na2SO3/SOCl2 , Phosphorus, Sulfur, and Silicon and the Related Elements, 179:2,
427-431
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Phosphorus, Sulfur, and Silicon, 179:427–431, 2004
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Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500490262577
A MILD METHOD FOR CONVERSION
OF ALCOHOLS TO DIALKYL SULFITES
BY USE OF Na2SO3/SOCl2
Ali Reza Kiasat, Foad Kazemi, and Froogh Khosravian
Shahid Chamran University, Ahvaz, Iran
(Received June 26, 2003; in final form August 26, 2003)
Alcohols are easily converted to their corresponding dialkyl sulfite un-
der mild reaction conditions using Na2SO3/SOCl2 in moderate to good
isolated yields.
Keywords: Dialkyl sulfite; sodium sulfite; sulfurous acid diester;
thionyl chloride
Sulfurous acid diesters, dialkyl sulfites, are of particular interest in
preparative organic chemistry.1 They serve as useful alkylating agent
and react much faster than alkyl halides,1 because the monoalkyl
sulfite anion (ROSO2)− is more effective as a leaving group than a
halide ion. In 1986, a report by Kim et al.2 outlined the applica-
tion of di-2-pyridyl sulfite as a useful reagent for the preparation of
N-sulfinylamines, nitriles, isocyanides, and carbodiimides. The elim-
ination processes of dialkyl sulfites occur upon heating and produce
olefines, ethers, or other oxygenated products.1 Sulfites are similar to
phosphites in transestrification3 and isomerization4 reactions.
Dialkyl sulfites are typically prepared by the reaction of thionyl chlo-
ride with alcohol in the presence of a base such as pyridine.5 This
method was improved by Ogata et al.6 who used N,Nꢁ-thionyldiimidazol
for the synthesis of diphenyl sulfite. A report of the synthesis of dialkyl
sulfites by iodine or bromine in pyridine with liquid sulfur dioxide at
20◦C also has appeared in the literature.1 In 1966, a patent7 described
the preparation of dialkyl disulfites by heating the adduct of ethylene
oxide and sulfur dioxide with primary alcohols in the presence of alkali
Authors acknowledge the partial support of this work by Shahid Chamran Ahvaz
University Research Council.
Address correspondence to Ali Reza Kiasat, Chemistry Department, College of Sci-
ence, Chamran University, Ahvaz 6137-4-3169, Iran.
427

428
A. R. Kiasat et al.
hydrides or a transition metal halide. Another method that applied for
the synthesis of methyl alkyl sulfites consists of the reaction of dia-
zomethane with alcoholic solutions of sulfur dioxide.1 However, many
of these methods met with some limitations, including low yields, la-
borious procedures, expensive or not readily accessible reagents, harsh
reaction conditions, or tedious work-up. Consequently, it seems that
there is still a great demand for a new and efficient method. In our
development of new methods for functional group transformations,8
we especially are interested in developing the application of modified
forms of thionyl chloride in organic synthesis.8f−h In this line, very
recently8h we have found that aldoximes undergo rapid dehydration
using Na2SO3/SOCl2 under mild reaction condition to afford the cor-
responding nitriles. Now we report conditions whereby various types
of dialkyl sulfite can be synthesized conveniently from the correspond-
ing alcohol under mild reaction conditions by sodium sulfite/thionyl
chloride.
RESULTS AND DISCUSSION
The reagent easily was prepared by the reaction of thionyl chloride
with stiochiometric amount of sodium sulfite at room temperature.
Dialkyl sulfite was simply synthesized by adding the related alcohol
to the reagent in CH2Cl2. For 1 mmol of alcohol, 1.5 eqiv. each of
thionyl chloride and sodium sulfite were used. The plausible mech-
anism for this reaction is as follow: at first, (I) is probably formed;
this kind of mechanism has been proposed in the reaction of thionyl
chloride and polyvinylpyrrolidone,8h 1,4-diazabicyclo[2.2.2]octane,14g
N-methyl-pyrolidone,9 or N,N-dimethylformamide.10 Representative
alcohols were treated with (I) in CH2Cl2 at room temperature.
The reaction proceeded probably via O-substituted alcohol (II),
which forms dialkyl sulfite with the nucleophilic addition of a sec-
ond alcohol followed by elimination of sulfur dioxide as shown in
Scheme 1.
The effects of other solvents such as CCl4, n-hexane, ether, and THF
also were studied, but in comparison with CH2Cl2, the reaction times
were longer and the yields were considerably lower. The procedure
turned out to be general for a range of structurally diverse alcohols.
As shown in Table I primary alcohols reacted faster than secondary

Dialkyl Sulfites
429
SCHEME 1
and tertiary alcohols and phenol. Most of the obtained product were
purified by plate chromatography eluted with n-hexan and ether (4:1).
The structure of all the products were confirmed by their analytical and
spectral (IR, 1H NMR) data.
Compared to some previously reported reagents with major or minor
drawbacks, several noteworthy features of this system are apparent.
TABLE I Conversion of Alcohols to Dialkyl Sulfites Using Na2SO3/Thionyl
Chloridea
Entry
Substrate
Product
(CH3O)2SO
[CH3(CH2)2CH2O]2SO
[(CH3)2CHCH2O]2SO
[(CH3)3CO]2SO
Time (min) Yield (%)b,c
1
2
3
4
5
6
7
CH3OH
10
15
30
60
10
5
60
80
71
43
82
80
73
CH3(CH2)2CH2OH
(CH3)2CHCH2OH
(CH3)3COH
CH3(CH2)5CH2OH
CH3CH(CH3)CH2OH
[CH3(CH2)5CH2O]2SO
[CH3CH(CH3)CH2CH2]2SO
CH3(CH2)5CHOHCH3 [CH3(CH2)5(CH3)CHO]2SO
40
8
10
15
20
30
81
53
64
34
9
10
11
aMolar ratio of reagent to substrate was 1.5:1. The reaction performed at r.t.
bYields refer to pure isolated products.
cProducts were characterized by comparision of their physical data, IR, NMR spectra
with known samples.

430
A. R. Kiasat et al.
These are: availability of the reagent, operational simplicities, and use
of inexpensive reagents.
CONCLUSION
We believe that the present procedure provides an easy, mild, and effi-
cient methodology for the preparation of dialkyl sulfites from different
classes of alcohols; it may be a suitable addition to methodologies al-
ready present in the literature.
EXPERIMENTAL
General
Progress of the reactions was followed by TLC using silica gel with fluo-
rescent indicator coated on aluminum sheets. IR spectra were recorded
on a Shimadzo 450 spectrophotometer. Sodium sulfite and thionyl chlo-
ride were purchased from Fluka Company. Alcohols were purchased
from Fluka and Merck. Products were characterized by comparison of
1
their physical data, IR, and H NMR spectra with authentic samples.
The purity determination of the products and reaction monitoring were
accomplished by TLC on silica gel polygram SILG/UV 254 plates.
General Procedure for the Conversion of Alcohols
to Sulfite with Na2SO3/SOCl2 in CH2Cl2
To a mixture of sodium sulfite (1.5 mmol, 0.189 g) and freshly distilled
thionyl chloride (1.5 mmol, 0.179 g) was added a solution of alcohol
(1 mmol) in dry CH2Cl2 (5 ml). The reaction mixture was stirred at
room temperature for 5–60 min (Table I). The progress of the reaction
was followed by TLC. The mixture was then filtered and the residue
washed thoroughly with CH2Cl2 (5 ml). Evaporation of solvent under
reduced pressure furnished the crude dialkyl sulfite which were purified
by plate chromatography.
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Dialkyl Sulfites
431
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