The first effective procedure for the direct esterification and thiolysis of sulfinic acids

Article abstract of DOI:10.1055/s-0028-1083205

Alkyl arenesulfinates and S-thiosulfinates are readily accessible in good yields by the reaction of sulfinic acids and alcohols or thiols, respectively, in the presence of lanthanide(III) triflates as catalysts. Georg Thieme Verlag Stuttgart · New York.

Full text of DOI:10.1055/s-0028-1083205

SHORT PAPER
3563
The First Effective Procedure for the Direct Esterification and Thiolysis of
Sulfinic Acids
D
irec
t
Est
ó
erification an
z
dThiolysis
e
of Sulfinic
f
A
cids Drabowicz,* Małgorzata Kwiatkowska, Piotr Kiełbasiński*
Department of Heteroorganic Chemistry, Centre of Molecular and Macromolecular Studies, Polish Academy of Sciences,
Sienkiewicza 112, 90-363 Łódź, Poland
E-mail: draj@bilbo.cbmm.lodz.pl; E-mail: piokiel@bilbo.cbmm.lodz.pl
Received 22 July 2008
direct acylation of alcohols with carboxylic acids8 or acid
anhydrides.9 The present paper describes a successful lan-
thanide(III) triflate catalyzed direct esterification and thi-
olysis of sulfinic acids.
Abstract: Alkyl arenesulfinates and S-thiosulfinates are readily ac-
cessible in good yields by the reaction of sulfinic acids and alcohols
or thiols, respectively, in the presence of lanthanide(III) triflates as
catalysts.
Key words: sulfinates, S-thiosulfinates, esterification, thiolysis, A series of sulfinic acids were reacted with alcohols and
lanthanide(III) triflates
thiols in the presence of catalytic amounts of scandi-
um(III) or ytterbium(III) triflates. The reaction was per-
formed in dichloromethane at room temperature and was
usually complete within a few hours, which could easily
be monitored by TLC. As a result, the corresponding sul-
finates or S-thiosulfinates were formed in good to high
yields (Table 1). All products, except for propyl p-tolu-
enesulfinate (entry 4), are known in the literature and the
appropriate references are shown in Table 1.
Esters and thiolesters of sulfinic acids have proven to be
key compounds for investigations of the synthesis and
transformations of a variety of sulfinyl derivatives.1
Therefore, the development of new, efficient, and general
methods for their synthesis remains an ongoing subject of
research for organic chemists.
Among a few approaches to the synthesis of sulfinates and
S-thiosulfinates, the most versatile is the reaction of sulfi-
nyl chlorides with alcohols2 and thiols,3 respectively, in
the presence of a base. The main drawback to this proce-
dure is, however, the fact that many sulfinyl chlorides
may be obtained only via chlorination of sulfinic acids.
Hence, it would be desirable and advantageous to develop
a methodology that would make it possible to synthesize
sulfinates and S-thiosulfinates directly from sulfinic acids.
In this context, it should be mentioned that the alkylation
of sulfinate anions with simple alkylating agents takes
place only at the sulfinyl sulfur atom to produce sulfones.4
Procedures leading to the prevailing formation of the O-
alkylation products are scarce and they require the appli-
cation of hard alkylating agents, such as diazoalkanes,5
oxonium salts,6 or O-alkylisoureas.7 On the other hand,
simple acid-catalyzed esterifications and thiolyses fail
due to the instability of sulfinic acids under the reaction
conditions. There are very few successful procedures for
the esterification of sulfinic acids described in the litera-
ture; moreover they are based on the use of quite expen-
sive and scarcely available activating agents that must be
used in equimolar proportions.2
Table 1 Direct Synthesis of Sulfinates and S-Thiosulfinates from
Sulfinic Acidsa
O
O
catalyst
R1-S-OH
R2-XH
R1-S-X-R2
+
(1)
Entry R1
R2
X
Catalyst
Time Yield
(h)
(%)Ref.
6311
5612
7111
73
1
2
p-Tol
p-Tol
p-Tol
p-Tol
p-Tol
Ph
Et
O
O
O
O
O
Sc(OTf)3
Sc(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
48
i-Pr
Et
48
72
3
4
Pr
10
5
i-Pr
10
7212
7913
8414
8015
9416
8717
trace
trace
6
CH2t-Bu
O
O
O
S
72
7
Ph
Et
44
8
Ph
i-Pr
t-Bu
t-Bu
Et
44
9
Ph
68
10
11
p-Tol
t-Bu
p-Tol
S
60
O
O
240
240
Looking for new, useful procedures that would enable
sulfinic acids to be transformed directly into their esters or 12
thiolesters, we focused our attention on the lanthanide(III)
triflates as potential catalysts for these reactions. It should
be added that this type of catalyst has been applied in the
t-Bu
a CH2Cl2, r.t.
Inspection of Table 1 clearly shows that, although arene-
sulfinic acids reacted with primary and secondary alco-
hols very easily (entries 1–8), no such reaction was
observed for 2-methylpropane-2-sulfinic acid (R1 = t-Bu,
SYNTHESIS 2008, No. 22, pp 3563–3564
Advanced online publication: 23.10.2008
DOI: 10.1055/s-0028-1083205; Art ID: P08108SS
x
x.
x
x
.
2
0
0
8
© Georg Thieme Verlag Stuttgart · New York

3564
J. Drabowicz et al.
SHORT PAPER
nD20 1.5214.
1H NMR (200 MHz, CDCl3): d = 0.9 (t, J = 7.0 Hz, 3 H), 1.60 (sex-
entry 11). Similarly, a very low yield of the appropriate
product was obtained when p-toluenesulfinic acid was
treated with tert-butyl alcohol (R2 = t-Bu, entry 12). This tet, J = 7.0 Hz, 2 H), 2.32 (s, 3 H), 3.74–3.86 (ABX2, JAB = 8.5 Hz,
JAX = JBX = 7.0 Hz, 2 H), 7.2–7.4 (AA¢BB¢, 4 H).
indicates that the reaction must be very sensitive to the
steric hindrance exerted by each substrate. Interestingly,
sterically hindered 2-methylpropane-2-thiol was found to
react readily with arenesulfinic acids to give the corre-
sponding S-thiosulfinates in high yields (R2 = t-Bu, entries
9 and 10). The latter result seems particularly interesting
as it represents the first direct thiolysis of an acid leading
to a thiolester; this transformation is unknown both for
sulfinic and carboxylic acids.
Anal. Calcd for C10H14SO2: C, 60.46; H, 7.13; S, 16.13. Found: C,
60.36; H, 7.30; S, 15.83.
References
(1) Drabowicz, J.; Kiełbasiński, P.; Mikołajczyk, M. The
Chemistry of Sulfinic Acids, Esters and Their Derivatives;
Patai, S., Ed.; J. Wiley & Sons: Chichester, 1990, 351–429.
(2) Zoller, U. The Chemistry of Sulfinic Acids, Esters and Their
Derivatives; Patai, S., Ed.; J. Wiley & Sons: Chichester,
1990, 217–237.
(3) Takata, T.; Endo, T. The Chemistry of Sulfinic Acids, Esters
and Their Derivatives; Patai, S., Ed.; J. Wiley & Sons:
Chichester, 1990, 527–575.
(4) Schank, K. Syntheses of Sulphones, Sulphoxides and Cyclic
Sulfides; Patai, S.; Rappoport, Z., Eds.; J. Wiley & Sons:
Chichester, 1994, 1–67.
(5) Meek, J. S.; Fowler, J. S. J. Org. Chem. 1968, 33, 3422.
(6) Kobayashi, M. Bull. Chem. Soc. Jpn. 1966, 39, 1296.
(7) Kiełbasiński, P.; Żurawiński, R.; Drabowicz, J.;
Mikołajczyk, M. Tetrahedron 1988, 44, 6687.
(8) Barrett, A. G. M.; Braddock, C. Chem. Commun. 1997, 351.
(9) Ishihara, K.; Kubota, M.; Kurihara, H.; Yamamoto, H.
J. Org. Chem. 1996, 61, 4560.
(10) Mikołajczyk, M.; Drabowicz, J.; Kiełbasiński, P. Chiral
Sulfur Reagents: Applications in Asymmetric and
Stereoselective Synthesis; CRC Press: Boca Raton, 1997.
(11) Furukawa, N.; Noguchi, Y.; Nishikawa, M. Synthesis 1978,
441.
(12) Drabowicz, J. Chem. Lett. 1981, 1753.
(13) Norton, R. V.; Douglass, J. B. Org. Magn. Res. 1974, 6, 89.
(14) Michalski, J.; Modro, T.; Wieczorkowski, J. J. Chem. Soc.
1960, 1665.
Since enantiomerically enriched sulfinates and S-thiosul-
finates constitute valuable substrates in the synthesis of
optically active sulfinyl derivatives,10 an attempt was
made to prepare them by asymmetric induction using the
above reaction. To this end, two model reactions were
performed. First, p-toluenesulfinic acid was reacted with
(–)-menthol in the presence of ytterbium(III) triflate in the
hope of obtaining diastereomerically enriched menthyl p-
toluenesulfinate, the compound known for its application
in the synthesis of enantiopure sulfoxides. Second, p-tolu-
enesulfinic acid was treated with propan-2-ol catalyzed by
scandium(III) or ytterbium(III) triflate mixed with select-
ed optically active amines. Unfortunately, in no case was
the diastereomeric excess or enantiomeric excess of the
products higher than 5%.
All products, except for propyl p-toluenesulfinate, are known in the
literature (Table 1).
Propyl p-Toluenesulfinate (Table 1, Entry 4); Typical Proce-
dure
p-Toluenesulfinic acid (0.78 g, 5 mmol), PrOH (0.4 g, 6.7 mmol),
and Yb(OTf)3 (124 mg, 0.2 mmol, 4 mol% with respect to the
sulfinic acid) were mixed together in CH2Cl2 (10 mL) and the soln
was stirred at r.t. for 10 h. After completion of the reaction, Et2O (20
mL) was added and the organic phase was washed with 5% aq
NaOH (10 mL) and H2O (10 mL). The organic layer was dried
(MgSO4) and the solvents were removed to give pure propyl p-tolu-
enesulfinate (0.683 g, 73%) as a liquid; bp 106–107 °C/4 mbar.
(15) Nokami, J.; Fujita, Y.; Okawara, R. Tetrahedron Lett. 1979,
20, 3659.
(16) Maricichi, T. J.; Angeletakis, C. N. J. Org. Chem. 1984, 49,
1931.
(17) Mikołajczyk, M.; Drabowicz, J. J. Am. Chem. Soc. 1978,
100, 2510.
Synthesis 2008, No. 22, 3563–3564 © Thieme Stuttgart · New York