Fundamental reactivity of sulfur with organotins: Underexploited Ar-S bond formation under aqueous and aerobic conditions

Article abstract of DOI:10.1055/s-2004-829166

This work describes a comprehensive study on the reactivity of organotins with elemental sulfur for producing organosulfur compounds and Ar-S bonds. Elemental sulfur, fluoride ions and organotins reacted under aqueous, aerobic and almost neutral conditions to selectively generate disulfides, without forming thiols or thioethers (or sometimes trisulfides). Several parameters were examined in depth: organotins, carbon ligands, fluoride sources, temperatures, solvents and equivalents of sulfur.

Full text of DOI:10.1055/s-2004-829166

2
052
FEATURE ARTICLE
Fundamental Reactivity of Sulfur with Organotins: Underexploited Ar-S
Bond Formation under Aqueous and Aerobic Conditions
F
M
undamental Reactivit
a
yof
S
ulfur
r
with
O
rg
c
anotins Gingras,* Yoann M. Chabre, Jean-Manuel Raimundo
Chemical Laboratory of Organic and Metallic Materials (CMOM), Faculty of Sciences, University of Nice-Sophia Antipolis,
8 Avenue Valrose, 06108 Nice Cedex 2, France
2
Fax +33(4)92076578; E-mail: gingras@unice.fr
Received 20 September 2003; revised 19 March 2004
bonates or its variant requires high temperatures for sev-
eral hours.9
Abstract: This work describes a comprehensive study on the reac-
tivity of organotins with elemental sulfur for producing organosul-
fur compounds and Ar-S bonds. Elemental sulfur, fluoride ions and For the above reasons, we present an innovative, but sim-
organotins reacted under aqueous, aerobic and almost neutral con-
ple, sulfuration method for making Ar-S bonds and aryl
ditions to selectively generate disulfides, without forming thiols or
disulfides. This method uses inexpensive elemental sulfur
thioethers (or sometimes trisulfides). Several parameters were ex-
under atmospheric, aqueous and almost neutral condi-
amined in depth: organotins, carbon ligands, fluoride sources, tem-
tions, in open vessels. Preliminary reports by Schumann
peratures, solvents and equivalents of sulfur.
10
and coworkers opened up this field in 1962–3, but under
less favorable conditions, without fluoride ions. High
temperatures (200 °C), lower reactivity, lower selectivity
and undesirable mixtures of products (thioethers, disul-
fides, organotin sulfides, aromatic compounds, etc.) re-
sulted. Electron-rich C-Sn bonds can be activated by
generating hypercoordinated nucleophilic species with
Key words: sulfur, organotins, fluoride ions, hypercoordination,
aryl disulfides
Introduction
11
After nearly 150 years, since the discovery of diethyltin fluoride ions. Here, we contributed to the first compre-
diiodide in 1849 by Sir Edward Frankland, a comprehen- hensive study on the reactivity of organotins with elemen-
sive study on the reactivity of elemental sulfur with orga- tal sulfur in the presence of fluoride ions for selectively
notins was achieved for selectively producing aryl producing organosulfur compounds (disulfides).
1
disulfides, and most notably Ar-S bonds.
Incorporation of elemental sulfur into organic molecules
is important and there is a need for simple protocols for
2
Development of the Sulfuration Method
making Ar-S bond under neutral, moist and aerobic con-
ditions. Strong bases (Grignard or organolithium re-
agents) used in classical methods are cumbersome
because of their standardization, their pyrophoric, mois-
ture- and air-sensitive nature, and their incompatibility
with many functional groups. Moreover, arylthiols are of-
ten formed in moderate yields along with undesirable
1
2
A preliminary communication was limited to some elec-
trophilic sulfur sources with our reagent (n-
Bu N)(Ph SnF ). In this work, we showed that water can
1
3
4
3
2
modify the course of the reaction. We greatly simplified
and generalized the method by making hypercoordinated
species in situ. We analyzed in depth several reaction pa-
rameters: a) solvents, b) amount of water, c) temperatures
and reaction time, d) fluoride sources, e) sulfur/organotin
molar ratio and f) classes of substrates and ligands trans-
ferred. Scheme 1 summarizes the conditions for the selec-
tive preparation of aryl disulfides, at the expense of thiols,
thioethers and sometimes trisulfides.
3
polysulfides. Purification by distillation is often the only
issue.
Ar-S bond formation by metal-catalyzed reactions (Pd,
4
Cu, Ni) with aryl halides or boronic acids have some lim-
its imposed by the electron-withdrawing or donating na-
ture of the substituents on the aromatic ring. Most high-
yielding methods refer to reactions with organic iodides as
substrates. Otherwise, yields over 95% from Pd catalysts
5
are occasionally observed. Moreover, several research
groups can testify to the air sensitivity of most classical
5
,6,7
Pd, Ni or Cu catalysts.
We also experienced some lim-
8
its for making poly(p-phenylene sulfide) oligomers.
Finally, the Newman-Kwart rearrangement of thionocar-
Scheme 1 Simple and selective sulfuration of organotins
SYNTHESIS 2004, No. 12, pp 2052–2057
x
x.
x
x
.
2
0
0
4
Advanced online publication: 02.08.2004
DOI: 10.1055/s-2004-829166; Art ID: Z14003SS
Georg Thieme Verlag Stuttgart · New York
©

FEATURE ARTICLE
Fundamental Reactivity of Sulfur with Organotins
2053
Solvents and Rate Enhancement with Water
vent did not lead to even a trace of product (Table 1, entry
0). Weakly or non-coordinating solvents like THF or xy-
1
The first important parameter is the choice of solvents. In lene were inefficient. The exact reasons for rate and yield
Table 1, coordinating polar solvents like DMF and enhancement with H O is unclear. However, it has been
2
CH CN were best when combined with H O (entries 2–5 reported that diaquo cationic triorganotin species can be
3
2
and 8 in Table 1). However, the amount of H O should not formed from triorganotin halides.14 It is also known that
2
exceed 10–15% v/v, or the yield drops drastically. It is the dielectric constant of a solvent can increase exponen-
known that the coordinating ability of solvents on organo- tially with a small percentage of water. The debate is open
tins increases the rates and the yields. Surprisingly, dried on this effect; i.e. the coordinating ability of water mole-
DMF (Table 1, entry 1) or CH CN (Table 1, entry 7), lead cules on tin or the increase of the solvent polarity (or both
3
to unsatisfactory results. Methanol as a polar protic sol- effects).
Biographical Sketches
Marc Gingras was born in St- joined the team of Pr. Edwin Vedejs then took up a faculty position
Jérôme, Québec, Canada in 1962. He as an NSERC Postdoctoral Fellow at (chargé de cours) at the Université
studied chemistry from 1981–84 at the University of Wisconsin-Madi- Libre de Bruxelles. In 1999, he was
the University of Sherbrooke, son. In 1992, he continued for anoth- appointed as professor at the Univer-
Québec, Canada where he obtained er postdoctoral year at the same sity of Nice-Sophia Antipolis,
his BSc degree. From 1985–89, he university with Pr. Laura L. Kiessling France, where his interests include
completed a PhD degree at McGill in the field of glycochemistry and synthetic methodologies, advanced
University, Montréal, Canada under ROMP. After obtaining a French organic materials and supramolecular
the co-direction of Pr. T. H. Chan and scholarship (séjour scientifique de chemistry toward nanotechnology
Pr. David N. Harpp. His graduate haut niveau), he joined the Laborato- (sulfurated molecular asterisks, den-
work involved the development and ry of Supramolecular Chemistry at drimers, helicenes, etc.).
use of organometallic reagents of the Strasbourg under the guidance of Pr.
main group elements. In 1989, he Jean-Marie Lehn (1993–1995). He
Yoann M. Chabre was born in Nice, his PhD work under the guidance of are in the field of organic synthesis,
France, in 1979. He received his mas- Pr. Marc Gingras at the same univer- in particular sulfur chemistry and su-
ter and DEA degrees at the Universi- sity, in the Chemical Laboratory of pramolecules.
ty of Nice-Sophia Antipolis, Nice, Organic and Organometallic Materi-
France. He is currently completing als (CMOM). His research interests
Jean-Manuel Raimundo was born In 2000, he did some postdoctoral collaboration with TotalFina Elf
in Redon, France, in 1973. He ob- studies in the laboratory of Pr. (2002). He was appointed, at the Uni-
tained a BSc in biochemistry from François Diederich at ETH, Zürich, versity Nice Sophia-Antipolis, as
the University of Rennes, France, Switzerland. He spent one year in a Maître de Conférence in 2003. His
and his PhD from the University of temporary
academic
position research interests include organic
Angers (France) under the guidance (ATER) at the University of Angers synthesis, new synthetic reactions
of Dr. Jean Roncali on new organic (2001). He did a second postdoctoral and the development of advanced or-
materials for optoelectronic devices. stay at the same university during a ganic materials.
Synthesis 2004, No. 12, 2052–2057 © Thieme Stuttgart · New York

2
054
M. Gingras et al.
FEATURE ARTICLE
a,b,c
Table 1 Solvent, Temperature and Water Effects on Yield, Reactivity and Selectivity in the Sulfuration of Ph SnCl
3
Yieldf,g (%)
Entry
Solventd,e
DMF
Ratio H O– solvent T (°C)
Time (h)
0.42
0.42
0.42
0.42
19
(PhS)2
23
(PhS)2S
2
1
2
3
4
5
6
7
8
9
0/100
5/95
150
150
150
150
90
8
DMF
69
83
55
62
30
Trace
75
8
8
DMF
10/90
20/80
10/90
10/90
0/100
10/90
20/80
0/100
9
DMF
7
DMF
12
11
–
DMF
60
19
CH CN
90
10
3
CH CN
90
19
7
3
CH CN
90
19
3
3
1
0
MeOHh
80
80
–
–
a
b
c
d
e
f
Ph SnCl (1.20 mmol).
Elemental sulfur (3.74 mmol).
KF (3.72 mmol).
3
DMF dried over 4 Å molecular sieves.
CH CN dried over 3 Å molecular sieves.
3
Products were characterized by H NMR, 13C NMR and GC/MS.
1
g
Isolated mixture, ratios analyzed by GC.
The water content of MeOH was estimated to be 0.05%.
h
Sulfur/Organotin Molar Ratio
Table 2 Variation of Sulfur–Organotin Molar Ratio and the Effect
on Yield and Selectivity
b,c,d,e
A second variable was the sulfur–organotin molar ratio. In
Table 2, we show that a ratio of 3:1 (Table 2, entry 3) was
the best. Higher ratios provided more trisulfide and less
selectivity. However, in spite of an excess of sulfur, we
were not able to produce trisulfides in good yield
Yieldf,g (%)
a
b
Entry
Sulfur – organotin
(PhS)2
71
(PhS)2S
1
2
3
4
5
6
7
8
9
8.0
4.5
3.1
2.9
2.8
2.7
2.6
2.5
1.25
0.50
25
16
9
(
Table 2, entry 1). Diminishing the ratio to 0.50 gave no
66
trace of thioether, but traces of thiol for the first time. Se-
lectivity for disulfide formation is astonishing despite the
possibility for producing thioether, trisulfide and thiol.
83
74
4
75
6
Fluoride Ion Sources
74
2
A third parameter was the source of fluoride ions, as
shown in Table 3. They are all commercially available
and inexpensive. Cryolite (Na SiF ) or fluorite (CaF )
67
2
60
–
2
6
2
were of special interest due to their natural abundance.
Without fluoride ion, no sulfuration occurs (Table 3, entry
25
–
1
0h
33
–
6
). It was shown that hypercoordinated (n-
Bu N)(Ph SnF ) was equally reactive in this sulfuration. It
was then postulated that penta- or hexacoordinated
organotins might be involved as the reactive species. Flu-
a
b
c
d
e
f
4
3
2
Elemental sulfur (according to the molar ratio mentioned).
Ph SnCl (1.20 mmol).
3
KF (3.72 mmol).
H O–DMF (10:90), 25 min, 150 °C.
oride ions incorporated in a complex or CaF gave poor
2
2
DMF dried over 4 Å molecular sieves.
yields (Table 3, entries 3–5). In spite of the presence of
Products were characterized by H NMR, 13C NMR and GC/MS.
1
protic KHF , no thiol was produced (Table 3, entry 2). In
g
h
2
Isolated mixture, ratios analyzed by GC.
short, the simplest efficient fluoride source was inexpen-
sive KF.
3% PhSH detected.
Synthesis 2004, No. 12, 2052–2057 © Thieme Stuttgart · New York

FEATURE ARTICLE
Fundamental Reactivity of Sulfur with Organotins
2055
Table 3 Variation of Fluoride Ion Sources and the Effect on Yield
and Selectivity in the Sulfuration of Triphenyltin Chloride
late that the increase of fluorine ligands on the organotin
complex decreases its carbon nucleophilicity. A good
compromise could be achieved with hypercoordinated
triphenyltin and tetraphenyltin species. It was only under
forcing conditions, after 44 hours at 150 °C, that diphe-
nyltin dichloride (Table 5, entry 2) could possibly deliver
a phenyl group in a 88% yield. A higher lack of reactivity
was found for phenyltin trichloride (Table 5, entry 1).
Those observations were necessary for ruling out any sig-
nificant organotin disproportionation within 25 minutes at
a,b,c
Yieldd,e (%)
Entry Fluoride
source
Ratio H O– Time
2
DMFc
10/90
10/90
10/90
10/90
10/90
10/90
(h)
(PhS) (PhS) S
2
2
1
2
3
4
5
6
KF
0.42
22
83
31
29
–
9
7
–
–
–
–
KHF2
96
2
Na SiF6
CaF2
0.42
0.42
0.42
1
50 °C for an in situ generation of triphenyltin or tetraphe-
NaBF4
–
nyltin species. An important dynamic exchange of phenyl
ligands on tin seems unlikely here. A second important
point is the number of carbon ligands reacting with sulfur
under those conditions. Due to the kinetics, it is probable
that diphenyltin species mainly delivered one ligand, from
comparison with phenyltin species (entry 1). However,
the delivery of two ligands from triphenyltin species is ap-
parently favorable, otherwise a yield of 166% would be
reached when assuming a stoichiometry with one carbon
ligand transferred. In the case of tetraphenyltin, a combi-
nation of one or two ligands transferred cannot be exclud-
ed.
-
–
a
b
c
d
e
3
.72 mmol fluoride source; 1.2 mmol Ph SnCl.
3
Elemental sulfur (3.74 mmol).
DMF dried over 4 Å molecular sieves. 150 °C.
Products were characterized by H NMR, 13C NMR and GC/MS.
1
Isolated mixture, ratios analyzed by GC.
Reaction Time, Temperatures and Yields
We next turned our attention to reaction time and temper-
atures in DMF and in CH CN (Tables 1 and 4). The tem-
3
Table 5 Reactivity of Mono-, Di-, Tri- and Tetraorganotins toward
Sulfur and Fluoride Ions: Determination of the Number of Carbon
perature was lowered to 90 °C in CH CN or DMF, but at
3
the expense of a longer reaction time (Table 1, entries 5, Ligands Delivered from the Organotin Substrate a
8
). The reaction progressed even at 60 °C, but provided
Yieldb,c,d (%)
Time (h) (PhS)2 (PhS)2S
only 30% yield of disulfide (Table 1, entry 6). The opti-
mized time in 10% water–DMF and a sulfur–organotin ra-
tio of 3.1 was about 25 minutes at 150 °C. A distinct
brown color was indicative of a quick and successful re-
action.
Entry
Organotin
PhSnCl
1
2
3
44
44
– (18)
– (10)
1 (2)
9 (18)
–
3
Ph SnCl
44 (88)
83 (166)
50 (100)
2
2
Table 4 Variation of Reaction Time and Yields for the Reaction of
Ph SnCl
0.42
3
Triphenyltin Chloride in the Presence of Sulfur and Fluoride Ionsa
4
Ph Sn
5
4
Yieldb,c (%)
a
Organotin (1.2 mmol), elemental sulfur (3.74 mmol), KF (3.72
Entry
Time (min)
(PhS)2
42
(PhS)2S
mmol), H
2
O–DMF (10:90, DMF dried over 4 Å molecular sieves),
1
50 °C.
b
Products were characterized by H NMR, 13C NMR and GC/MS.
1
1
2
3
15
25
–
–
–
–
c
Isolated mixture, ratios analyzed by GC.
Yields in parentheses are calculated from the stoichiometric release
60
d
of one phenyl ligand. Other yields are based on the transfer of two
phenyl ligands.
60
78
4
120
66
a
Ph SnCl (1.2 mmol), elemental sulfur (3.00 mmol), KF (3.72
3
Substrate Studies, Substituent Effects and Relative
Rates of Carbon Ligand Delivery
mmol), H O–DMF (10:90, DMF dried over 4Å molecular sieves),
2
1
50 °C.
b
Products were characterized by H NMR, 13C NMR and GC/MS.
1
c
Isolated mixture, ratios analyzed by GC.
Another important parameter was the electronic signifi-
cance of the para-substitution on the aromatic ring of tet-
raphenyltin compounds, as shown in Table 6. In short, it
was found that electron-withdrawing substituents were
Organotins and the Number of Carbon Ligands De-
livered
15
the most reactive, leading to a quick reaction for Cl sub-
stitution (entry 2). There was almost no reactivity for a do-
The next variable was the number of carbon ligands liber- nor MeO group (entry 4).
ated from tin, as shown in Table 5. The best substrates
At last, aryl, primary and secondary alkyl ligands reacted
selectively with sulfur, as shown in Table 7. Relative rates
of carbon ligand transfer are: Ph >> cyclohexyl > butyl.
were triphenyltin chloride and tetraphenyltin (Table 5, en-
tries 3, 4). Under fluorinating conditions, one may specu-
Synthesis 2004, No. 12, 2052–2057 © Thieme Stuttgart · New York

2
056
M. Gingras et al.
FEATURE ARTICLE
Table 6 Variation of Substituents on Tetraaryltins and Their Rela-
tive Reactivity with Elemental Sulfur in the Presence of Fluoride Ions
atmosphere, might come from the dimerization of PhS
moieties. This postulate is consistent with the common in-
termediate and the independence of the electrophilic sul-
Yieldc,d (%)
fur source described in a previous communication.12
A
Entry
Tetraorganotin
Time (h) (PhS)2
(PhS)2S
mechanism involving the insertion of a sulfur atom be-
1
6
tween a tin-carbon bond has been documented with SO2
1a
Ph Sn
5.0
50
58
33
–
–
4
17
and SO , and some organotin sulfide by-products were
3
1
0
2b
found by Schumann et al. in their sulfuration method
which was carried out in the absence of fluoride ions). A
(p-ClPh) Sn
0.42
5.0
–
4
(
3b
(p-CH Ph) Sn
Trace
–
3
4
similar mechanism could be evoked here with elemental
sulfur, with a dimerization following. One should also
note that a thermodynamic disproportionation of trisulfide
into disulfide is possible at high temperature, often above
4b
(p-CH OPh) Sn 5.0
3
4
a
Organotin (1.20 mmol), elemental sulfur (3.74 mmol), KF (3.72
mmol), H O–DMF (10:90, DMF dried over 4 Å molecular sieves),
2
2
00 °C. However, our results in CH CN at 90 °C do not
3
1
50 °C.
b
suggest this as a logical possibility. Moreover, after only
15 minutes in DMF at 150 °C, there was no trisulfide ob-
served (Table 4, entry 1). The polymeric nature and the in-
solubility of the organotin fluoride by-products
complicate the characterization of intermediates and the
elucidation of the reaction mechanism. However, these
by-products could be removed by a simple filtration on a
silica gel column, using only EtOAc as solvent. This sol-
vent helps in the precipitation of the organotin fluoride
polymer.
Organotin (0.60 mmol), elemental sulfur (1.87 mmol), KF (1.86
mmol), H O–DMF (10:90, DMF dried over 4 Å molecular sieves),
2
1
50 °C.
c
Products were characterized by H NMR, 13C NMR and GC/MS.
1
Isolated yields, purity >95% as checked by GC.
d
Yield are based on the transfer of two ligands.
The reactivity difference between aromatic and alkyl
groups is noteworthy. Only under forcing conditions (22
h at 150 °C) could cyclohexyl ligands be transferred to
provide disulfide in 50% yield (Table 7, entry 2). With
mixed organotin derivatives such as n-Bu SnPh or n-
3
Conclusion: A Simple Sulfuration of Organotins that
Provides a High Selectivity for Aryl Disulfide Forma-
tion under Aqueous and Atmospheric Conditions
Bu SnCl, there was a significant lack of reactivity.
3
In this paper, we have delineated, for the first time, impor-
tant parameters for the reactivity of organotins with ele-
mental sulfur, although an exact mechanism is still
unknown. Those studies are fundamental in organotin
chemistry. However, a surprising fact is that fluorodestan-
nylation-protonation under aqueous (and even protic)
conditions at 150 °C is not a major reaction pathway in
DMF; neither is the formation of thiols from trapping an
intermediate complex. Selectivity for disulfide formation,
even in the presence of excess sulfur or under a nitrogen
In summary, we report herein a comprehensive study on
the sulfuration of organotins with inexpensive elemental
sulfur, under almost neutral, aqueous and aerobic condi-
tions, to make Ar-S bonds. Fluoride ions and water en-
hanced the reactivity and the efficiency of the method. It
avoids strong bases and the associated disadvantages.
Eventually, disufides could be easily reduced to thiols, if
needed. Hypercoordinated tin species might be involved
in this reaction, as we have already shown similar reactiv-
1
3
Table 7 Variation of Carbon Ligands on Tetra- and Triorganotins
ity to occur with Gingras’ reagent (nBu N)(Ph SnF ).
4
3
2
and Their Reactivity with Elemental Sulfur in the Presence of Fluo-
a
ride Ions
1H and 13C NMR spectra were recorded on a Bruker AC-200 instru-
Yieldb,c (%)
ment at 200 MHz and 50 MHz, respectively, in CDCl . Chemical
3
shifts (d) are reported in part per million (ppm) downfield from
TMS. GC analyses were achieved on a Hewlett Packard 5890 Series
II, a FID detector and an apolar HP5 column (0.25 mm ID, 25 m).
GC/MS spectra were recorded on a Thermoquest Finnigan Trace
GC/Automass III Multi equipped with a DB5MS column [(5% phe-
nyl)-methylpolysiloxane; 0.25 mm ID, 25 m], an EI source and a
quadrupole analyzer. Characterization and analysis of the mixture
of products was achieved by comparison to authentic samples and/
Entry
Organotin
Time (h)
0.42
22
(RS)2
(RS)2S
1
2
3
Ph SnCl
83 (166)d
9 (18)d
3
50 (99)d
Cy SnCl
Traces
Traces
Traces
3
n-Bu SnCl
48
Traces
Traces
3
4
n-Bu SnPh
48
1
13
3
or from GC/MS, H and C NMR spectroscopy. Characterization
of the isolated mixture of PhSSPh and PhSSSPh was achieved by
a
Organotin (1.20 mmol), elemental sulfur (3.74 mmol), KF (3.72
1
13
H, C NMR and GC/MS. GC analyses of PhSPh, PhSSPh and
mmol), H O–DMF (10:90, DMF dried over 4 Å molecular sieves),
2
PhSH were done with reference to authentic samples. Anhydrous
reactions were run in an inert atmosphere with oven-dried glass-
ware, a Teflon stirring bar and a condenser equipped with a rubber
septum. Reactions were monitored with analytical TLC using pre-
1
50 °C.
b
Products were characterized by H NMR, 13C NMR and GC/MS.
1
c
Isolated mixture, ratios analyzed by GC.
Hypothetical yields in parentheses are calculated from the stoichio-
d
coated aluminium sheets (SiO 60F254, SDS; thickness 0.2
2
metric release of one phenyl ligand.
mm, 15–60 microns). TLC visualization was achieved by UV (254,
3
12 nm) and/or development with a molybdenum–cerium acidic so-
Synthesis 2004, No. 12, 2052–2057 © Thieme Stuttgart · New York

FEATURE ARTICLE
Fundamental Reactivity of Sulfur with Organotins
2057
lution (10 mL H SO , 900 mL H O, 25 g (NH ) Mo O ·4H O, 10
11598. (h) Baranano, D.; Hartwig, J. F. J. Am. Chem. Soc.
1995, 117, 2937. (i) Harayama, H.; Kozera, T.; Kimura, M.;
Tanaka, S.; Tamaru, Y. Chem. Lett. 1996, 543.
2
4
2
4 6
7
24
2
g NH Ce(SO ) ). Purification by flash chromatography was per-
4
4 2
formed using Merck silica gel (230–400 mesh, 60 Å). Molecular
sieves were activated (250 °C, 3 h). DMF and CH CN (99%, Acros
(j) Rajagopalan, S.; Radke, G.; Evans, M.; Tomich, J. M.
Synth. Commun. 1996, 26, 1431. (k) Still, I. W. J.; Toste, F.
D. J. Org. Chem. 1996, 61, 7677. (l) Zheng, N.;
McWilliams, J. C.; Fleitz, F. J.; Armstrong, J. D. III;
Volante, R. P. J. Org. Chem. 1998, 63, 9606. (m)Mann, G.;
Baranano, D.; Hartwig, J. F.; Rheingold, A. L.; Guzei, I. A.
J. Am. Chem. Soc. 1998, 120, 9205. (n) Schopfer, U.;
Schlapbach, A. Tetrahedron 2001, 57, 3069. (o) Nandi, B.;
Das, K.; Kundu, N. G. Tetrahedron Lett. 2000, 41, 7259.
3
Organics) were distilled under reduced pressure over CaH and kept
2
over 4 Å and 3 Å MS, respectively. MeOH (Prolabo) was used as
received (estimated water content <0.05%). Most organotins (Sig-
ma-Aldrich) and elemental sulfur were used as received. Fluoride
sources: KF, NaBF (Acros Organics), CaF , Na SiF , KHF (Sig-
4
2
2
6
2
ma-Aldrich), were used as supplied or vacuum-dried.
Typical Procedure: Into a 10 mL oven-dried round-bottom flask
was weighed the organotin (1.20 mmol). A fluoride ion source (3.72
mmol) and elemental sulfur (0.60 to 9.60 mmol) were added. Dry
DMF and a controlled amount of distilled water (0% to 20% relative
to DMF) were injected for a total volume of 3.0 mL. After installing
a water condenser, the mixture was immersed in an oil bath at
(
6
(
p) Li, G. Y.; Zheng, G.; Noonan, A. F. J. Org. Chem. 2001,
6, 8677. (q) Li, G. Y. J. Org. Chem. 2002, 67, 3643.
r) Egi, M.; Liebeskind, L. S. Org. Lett. 2003, 5, 801.
(
6) Cu catalysts: (a) Adams, R.; Reifschneider, W.; Nair, D.
Croatia Chim. Acta 1957, 29, 277. (b) Adams, R.; Ferretti,
A. J. Am. Chem. Soc. 1959, 81, 4927; and references
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1
50 °C under atmospheric conditions, while vigorously stirring for
the required time. Appearance of a brown color was often indicative
of a successful sulfuration. After cooling down to r.t., the mixture
was filtered while rinsing with EtOAc (10 mL). Into the filtrate was
(
d) Adams, R.; Reifschneider, W.; Ferretti, A. Org. Synth.
1962, 42, 22. (e) Suzuki, H.; Abe, H.; Osuka, A. Chem. Lett.
1980, 1363. (f) Yamamoto, T.; Sekine, Y. Can. J. Chem.
1984, 62, 1544. (g) Hickman, R. J. S.; Christie, B. J.; Guy,
poured H O (100 mL) and the aqueous phase was extracted with
2
EtOAc (80 mL or less). The organic phase was washed with H O
2
(
3 × 30 mL). The organic phase was dried over MgSO then filtered,
4
R. W.; White, T. J. Aust. J. Chem. 1985, 38, 899.
h) Kalinin, A. V.; Bower, J. F.; Riebel, P.; Snieckus, V. J.
and the solvent was removed under reduced pressure. The crude
(
product was purified on a short chromatography column (SiO ; hex-
2
Org. Chem. 1999, 64, 2986. (i) Herradura, P. S.; Pendola, K.
A.; Guy, R. K. Org. Lett. 2000, 2, 2019. (j) Savarin, C.;
Srogl, J.; Liebeskind, L. S. Org. Lett. 2002, 4, 4309.
(k) Bates, C. G.; Gujadhur, R. K.; Venkataraman, D. Org.
Lett. 2002, 4, 2803. (l) Kwong, F. Y.; Buchwald, S. L. Org.
Lett. 2002, 4, 3517. (m) Wu, Y.-J.; He, H. Synlett 2003,
ane) to provide the corresponding disulfide as a major component,
1
13
as shown by GC, GC/MS, H NMR and C NMR analyses and
comparisons to authentic samples of thioethers, disulfides or thiols.
1
13
Trisulfides were characterized by GC/MS, H NMR and C NMR.
1
789. (n) Taniguchi, N.; Onami, T. J. Org. Chem. 2004, 69,
Acknowledgment
915.
We (I or the authors) thank the Ministère de la Jeunesse, de l’Edu-
cation Nationale et de la Recherche de France and Mrs. Claire
Gratay for a specific reaction. Dr. André Loupy from the Université
of Paris-Sud, Orsay is thanked for helping us at the initial stage of
this study.
(
7) Ni catalysts: (a) Cristau, H. J.; Chabaud, B.; Chêne, A.;
Christol, H. Synthesis 1981, 892. (b) Foà, M.; Santi, R.;
Garavaglia, F. J. Organomet. Chem. 1981, 206, C29.
(
c) Cristau, H. J.; Chabaud, B.; Labaudiniere, R.; Christol,
H. Organometallics 1985, 4, 657. (d) Takagi, K. Chem.
Lett. 1986, 1379. (e) Takagi, K. Chem. Lett. 1987, 2221.
(
2
f) Meyer, G.; Troupel, M. J. Organomet. Chem. 1988, 354,
49.
8) (a) Pinchart, A.; Dallaire, C.; Gingras, M. Tetrahedron Lett.
998, 39, 543. (b) Gingras, M.; Pinchart, A.; Dallaire, C.
Angew. Chem. Int. Ed. 1998, 37, 3149.
9) Newman, M. S.; Hetzel, F. W. Org. Synth. 1971, 51, 139.
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Synthesis 2004, No. 12, 2052–2057 © Thieme Stuttgart · New York