Unexpected Reactivity of the Burgess Reagent
with Thiols: Synthesis of Symmetrical Disulfides
thiol (1) with 1 equivalent of the Burgess reagent. Instead, a
nearly quantitative yield of disulfide 2 was isolated. Examination
of other thiols (Table 1) reveals the reaction to be a general
and high-yielding method, except for branched aliphatic thiols
Scott C. Banfield, Alvaro Takeo Omori, Hannes Leisch, and
Tomas Hudlicky*
(
entries 5 and 8), which react to afford both symmetrical
7
8
disulfides and trisulfides.
Department of Chemistry and Center for Biotechnology,
Brock UniVersity, 500 Glenridge AVenue,
St. Catharines, Canada L2S 3A1
The reaction of decane-1-thiol was optimized, as shown in
Table 2, and we attempted to determine the mechanism of the
reaction and to identify the reduced component in the sequence.
Although the oxidation proceeded cleanly at 50 °C in 1 h, we
found that higher yields could be obtained at room temperature
in 1 h. The reaction was further accelerated by forming the
thiolate anion first (entries 5-8, Table 2). The order of addition
of the Burgess reagent and the thiol was shown to be
inconsequential as long as there was a slight excess of the
Burgess reagent. The use of polar solvents such as DMF (entry
ReceiVed January 26, 2007
4
) hindered the rate of oxidation.
A tentative proposalsand at this stage speculativesfor this
transformation is shown in Scheme 1. In the first step the thiol
reacts with the Burgess reagent either in an acid-base reaction
to form thiolate 23 or via substitution to form inner salt 25.
Intermediates 25 or 27, required for intramolecular E2 elimina-
tion, are likely to be protonated by mercaptans to generate
Reaction of the Burgess reagent with a series of aliphatic
and aromatic thiols led to the corresponding symmetrical
disulfides in high yields. No olefins were detected in the
reactions of aliphatic thiols.
9
thiosulfonyl carbamate 26. Instead, it is likely that thiosulfonyl
carbamate 26 is attacked by either thiol or its conjugate base to
form the disulfide and intermediate 28 or its tautomer 29. We
attempted to isolate compound 29 but were only able to
characterize the triethylammonium salt 31 (in crystalline form),
probably resulting from the immediate air oxidation of the labile
intermediate 30. NMR experiments in d6-benzene showed the
formation of a new species, which did not correspond to either
Since its discovery in the late 1960s, the Burgess reagent1
has been used primarily for dehydration of secondary and tertiary
alcohols and for the preparation of nitriles and carbamates.
2
Epoxides were thought to be inert to the action of the reagent
until 2003 when we demonstrated that sulfamidates are easily
3
prepared from its reaction with various oxiranes. Since then,
Nicolaou reported the synthesis of sulfamidates from diols as
(6) We are grateful to Prof. Graham J. Bodwell (Memorial University
of Newfoundland), who suggested to us during the 12th LTOS Symposium
in August 2006 that we examine the formation of alkenes from aliphatic
thiols with the Burgess reagent.
(7) (a) Sathe, M.; Ghorpade, R.; Kaushik, M. P. Chem. Lett. 2006, 35,
1048. (b) Hashemi, M.; Ghafuri, H.; Karimi-Jaberi, Z. J. Sulfur Chem. 2006,
27, 165. (c) Akdag, A.; Webb, T.; Worley, S. D. Tetrahedron Lett. 2006,
well as other compounds,4 and the reagent is enjoying a
renaissance in the exploration of new reactive options, including
the first disclosure, published by us in 2006, of its asymmetric
version and its application to the synthesis of chiral amino
alcohol derivatives.5 Extension of the reactivity studies to
47, 3509. (d) Joshi, A. V.; Bhusare, S.; Baidossi, M.; Qafisheh, N.; Sasson,
primary, secondary, and tertiary thiols was logical and has been
suggested as a possible means of forming alkenes from such
Y. Tetrahedron Lett. 2005, 46, 3583. (e) Arisawa, M.; Sugata, C.;
Yamaguchi, M. Tetrahedron Lett. 2005, 46, 6097. (f) Leino, R.; Loennqvist,
J.-E. Tetrahedron Lett. 2004, 45, 8489. (g) Khodaei, M. M.; Salehi, P.;
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A. K.; Agnihotri, G. Synth. Commun. 2004, 34, 1079. (i) Hashemi, M. M.;
Karimi-Jaberi, Z. Monatsh. Chem. 2004, 135, 41. (j) Zeynizadeh, B. J. Chem.
Res., Synop. 2002, 11, 564. (k) Ali, M. H.; McDermott, M. Tetrahedron
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J. Synthesis 2002, 7, 856. (m) Ledung, G.; Bergkvist, M.; Quist, A. P.;
Gelius, U.; Carlsson, J.; Oscarsson, S. Langmuir 2001, 17, 6056. (n) Zhong,
P.; Guo, M.-P. Synth. Commun. 2001, 31, 1825. (o) Kesavan, V.; Bonnet-
Delpon, D.; Begue, J.-P. Synthesis 2000, 2, 223. (p) Abele, E.; Abele, R.;
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M.; Vadivel, S. Kumara; Bhalerao, U. T. Synth. Commun. 1998, 28, 1499.
(s) Wu, X.; Ricke, R. D.; Zhu, L. Synth. Commun. 1996, 26, 191. (t) Ho,
T.-L.; Hall, T. W.; Wong, C. M. Synthesis 1974, 12, 872. (u) Nakayama,
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G.; Cappericci, A.; Degl’Innicenti, A.; Duce, D. R.; Menichetti, S.
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6
compounds. We were, however, surprised to find no evidence
of olefin or carbamate formation when we reacted decane-1-
*
To whom correspondence should be addressed. Phone: (905) 688-5550
ext 4956. Fax: (905) 984-4841.
1) (a) Atkins, G. M.; Burgess, E. M. J. Am. Chem. Soc. 1968, 90, 4744.
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(
(
9
6
3
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(
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2
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1
0.1021/jo070099t CCC: $37.00 © 2007 American Chemical Society
Published on Web 06/01/2007
J. Org. Chem. 2007, 72, 4989-4992
4989