Syntheses, oxidations, and palladium complexes of fluorous dialkyl sulfides: New precursors to highly active catalysts for the Suzuki coupling

Article abstract of DOI:10.1016/S0040-4020(02)00275-2

Reactions of R_f8(CH₂)_nI (R_f8=CF₃(CF₂)₇) with Li₂S give the fluorous dialkyl sulfides (R_f8(CH₂)_n)₂S (n=2, 1, 71%; 3, 2, 67%) as low melting white solids that are soluble in most fluorous and organic solvents. Reactions of 1 and 2 with CH₃CO₃H yield the corresponding sulfoxides (R_f8(CH₂)_n)₂S=O (85; 80%), which are soluble in CF₃C₆F₅ at room temperature, but insoluble in most other solvents. At higher temperatures, solubilities can become appreciable. Reactions of 1 and 2 with Na₂PdCl₄ (ca. 0.5equiv.) give palladium complexes [(R_f8(CH₂)_n)₂S]₂PdCl ₂ (5, 94%; 6, 95%), which are soluble in only a limited range of fluorinated solvents at room temperature. The CF₃C₆F₁₁/toluene partition coefficients of 1 and 2 are 98.7:1.3 and 96.6:3.4 (24°C). The Suzuki coupling of aryl bromides and PhB(OH)₂ to biaryls is catalyzed by 5 and 6 (0.02mol%) in CF₃C₆F₁₁/DMF/H₂O in the presence of K₃PO₄, generally at room temperature. Turnover numbers of 4500-5000 are easily achieved. However, activities decrease under fluorous biphase recycling conditions, and implications for the nature of the catalytically active species are discussed.

Full text of DOI:10.1016/S0040-4020(02)00275-2

TETRAHEDRON
Pergamon
Tetrahedron 58 #2002) 4007±4014
Syntheses, oxidations, and palladium complexes of ¯uorous
dialkyl sul®des: new precursors to highly active catalysts
for the Suzuki coupling
p
Christian Rocaboy and J. A. Gladysz
Institut f uÈ r Organische Chemie, Friedrich-Alexander Universit aÈ t Erlangen-N uÈ rnberg, Henkestrasse 42, 91054 Erlangen, Germany
Received 20 December 2001; revised 30 January 2002; accepted 31 January 2002
AbstractÐReactions of Rf8#CH
low melting white solids that are soluble in most ¯uorous and organic solvents. Reactions of 1 and 2 with CH CO H yield the corresponding
2
)
n
I #Rf8ˆCF
3
#CF
2
)
7
) with Li
2
S give the ¯uorous dialkyl sul®des #Rf8#CH
2
)
n
)
2
S #nˆ2, 1, 71%; 3, 2, 67%) as
3 3
sulfoxides #Rf8#CH
2
)
n
)
2
SvO #85; 80%), which are soluble in CF
3
C
6
F
5
at room temperature, but insoluble in most other solvents. At higher
PdCl #ca. 0.5 equiv.) give palladium complexes
temperatures, solubilities can become appreciable. Reactions of 1 and 2 with Na
#R #CH ) ) S] PdCl #5, 94%; 6, 95%), which are soluble in only a limited range of ¯uorinated solvents at room temperature. The
2
4
[
CF C F /toluene partition coef®cients of 1 and 2 are 98.7:1.3 and 96.6:3.4 #248C). The Suzuki coupling of aryl bromides and PhB#OH)
f8
2 n 2
2
2
3
6
11
2
to biaryls is catalyzed by 5 and 6 #0.02 mol%) in CF
3
6
C F
2
11/DMF/H O in the presence of K
3
PO
4
, generally at room temperature. Turnover
numbers of 4500±5000 are easily achieved. However, activities decrease under ¯uorous biphase recycling conditions, and implications for
the nature of the catalytically active species are discussed. q 2002 Elsevier Science Ltd. All rights reserved.
1
. Introduction
by-products that are not commonly recycled, usually for
lack of a convenient protocol. This intrinsic waste problem
and poor atom economy has led to increasing interest in
Over the past eight years, many new compounds with high
af®nities for per¯uoroalkane and related `¯uorous' solvents
1
0,11
recyclable sulfur reagents.
1
,2
have been synthesized. This has been prompted by the
emergence of `¯uorous biphase chemistry',1a a current
overview of which is offered by this special issue of
Tetrahedron. As traditionally implemented, this technique
exploits the strongly temperature dependent miscibilities of
Accordingly, we set out to develop ef®cient syntheses of
simple ¯uorous dialkyl sul®des, characterize their solu-
bilities and ¯uorous phase af®nities, and explore their
basic chemistry. In contrast to ¯uorous phosphines and
amines, only two pony tails are possible in the absence of
branching. Thus, slightly lower af®nities for ¯uorous
solvents might be expected. We also sought to assay the
use of such ligands in catalysis, and describe palladium
complexes that are excellent catalyst precursors for the
Suzuki couplingÐa representative carbon±carbon bond
3
organic and ¯uorous solvents. At room temperature, most
combinations give two phases. However, with moderate
4
heating, a single phase forms. Reactions can be conducted
under monophasic conditions at higher temperatures.
Organic products and ¯uorous catalysts or spent reagents
can then be separated under biphasic conditions at lower
temperatures. High ¯uorous phase af®nities are achieved
by appending suf®cient numbers of `pony tails' of the
formula CF #CF ) #CH ) #abbreviated R #CH ) .
1
2
forming reaction of aryl halides. Other types of ¯uorous
1
1,13,14
organosulfur compounds have been reported, as well
as an elegant ¯uorous version of the DMSO-based Swern
3
2 n21
2 m
fn
2 m
1
oxidation of alcohols. These are detailed in Section 3.
1
Many applications of ¯uorous chemistry in catalysis involve
5
,6
7,8
metal adducts of organophosphorus or nitrogen donor
ligands. However, sulfur donor ligands also play extensive
roles in catalysis. Organosulfur compounds furthermore
see widespread use as stoichiometric reagents in organic
2
. Results
.1. Syntheses of ¯uorous compounds
THF solutions of Li S were generated as described pre-
2
9
synthesis. Many of these procedures give organosulfur
2
1
5
viously, and treated with the ¯uorous iodides R #CH ) I
f8
and R #CH ) I. The former is commercially available, and
f8
the latter is easily synthesized from the corresponding
alcohol. As shown in Scheme 1, workups gave the ¯uorous
2 2
Keywords: sul®des; sulfoxides; Suzuki reactions; catalysis; ¯uorous
chemistry.
2 3
p
Corresponding author. Tel.: 149-9131-8522540; fax: 149-9131-
8526865; e-mail: gladysz@organik.uni-erlangen.de
1
6
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020#02)00275-2

4008
C. Rocaboy, J. A. Gladysz / Tetrahedron 58 ꢀ2002) 4007±4014
Scheme 1. Syntheses of ¯uorous dialkyl sul®des and sulfoxides #Rf8ˆCF
3 2 7
#CF ) ).
Scheme 2. Syntheses of palladium complexes of ¯uorous dialkyl sul®des #Rf8ˆCF
3 2 7
#CF ) ).
dialkyl sul®des #R CH CH ) S #1) and #R CH CH CH ) S
2 2
CF ClCCl F. NMR spectra were recorded in the ®rst two
2 2
f8
2
2 2
f8
2
2
2
1
#
measurements showed no phase transitions other than
2) in 67±71% yields as analytically pure white solids. DSC
1
solvents, and 4 was always more soluble than 3. In
contrast, 3 and 4 were insoluble or very poorly soluble in
CF C F , CF C H , and organic solvents such as hexanes,
7
melting #67 and 568C). Sul®des 1 and 2 were further charac-
3
6
11
3
6
5
1
13
terized by NMR spectroscopy # H, C). They showed good
solubility in a broad range of ¯uorous, `hemi'-¯uorous
and non-¯uorous solvents, such as CF C F #per¯uoro-
toluene, CHCl , CH Cl , ether, THF, acetone, methanol, and
3 2 2
ethanol. The ¯uorous sulfoxide R CH CH S#vO)CH
3
f6
2
2
#R ˆ CF #CF ) ) has been shown to be insoluble in
3
6
11
f6
3
2 5
1
1
#
methylcyclohexane)),
CF C F
#per¯uorotoluene),
CF C H #a,a,a-tri¯uorotoluene or `benzotri¯uoride'),
CH Cl at low temperature. The solubilities of ¯uorous
2 2
compounds can be markedly temperature dependent.
Accordingly, 3 and 4 were soluble in acetone at 508C, and
3
6
5
3
,22
3
6
5
hexanes, toluene, CHCl , CH Cl , ether, and THF. They
3
2
2
were slightly soluble in methanol, ethanol, and acetonitrile.
slightly soluble in CF C F , hexanes, toluene, CHCl , THF,
3
6
11
3
acetone, and ethanol. Solubilities further increased at re¯ux
temperatures, in some cases dramatically.
Sul®des have an extensively developed oxidation chemistry,
and ¯uorous phosphines are easily converted to the corre-
5
d,18
sponding ¯uorous phosphine oxides.
In order to improve
Dupont has recently shown that the palladium bis#sul®de)
complex #Et S) PdCl is an effective catalyst precursor
our ability to analyze reactions conducted under aerobic
conditions below, 1 and 2 were treated with peracetic
acid, CH CO H, under conditions reported to give sulf-
2
2
2
2
3
for the Suzuki and Heck reactions. We therefore sought
palladium derivatives of 1 and 2. As shown in Scheme 2,
reactions with Na PdCl gave the target compounds
3
3
1
9
oxides #CHCl , room temperature). White powders,
3
2
4
presumed to be the target compounds #R CH CH ) SvO
f8
[#R CH CH ) S] PdCl #5) and [#R CH CH CH ) S] PdCl
f8 2 2 2 2 2 f8 2 2 2 2 2 2
2
2 2
#
3) and #R CH CH CH ) SvO #4), immediately precipi-
f8
#6) as analytically pure yellow powders in 94±95% yields.
Although trans-#R S) PdCl species are usually more
2
2
2 2
tated #80±85%). Analogous results were obtained with
m-chloroperbenzoic acid. Correct microanalyses were
obtained for these relatively high-melting substances
2
2
2
2
4
stable, cis isomers are often isolated and assignments
require either single crystals or careful far-IR measure-
ments. As with 3 and 4, 5 and 6 dissolved in only a very
limited range of solvents. They were insoluble in CF C F ,
#.1238C), and diagnostic IR n
#1035 and 1089 cm ). However, characterization was
bands were observed
SO
2
1 20
3
6 11
hampered by their peculiar solubility characteristics.
soluble in CF C F , and very slightly soluble in CF C H .
3 6 5 3 6 5
They were insoluble in common organic solvents #hexanes,
toluene, CHCl , CH Cl , ether, THF, acetone, methanol, and
ethanol), failing to impart the slightest hint of color.
At room temperature, 3 and 4 were appreciably soluble only
in CF C F , and slightly soluble in acetic acid and
3
2
2
3
6 5
Quantitative data on ¯uorous phase af®nities were sought.
Accordingly, the CF C F /toluene partition coef®cients of
sul®des 1 and 2 were determined by GC as previously
Table 1. Partition coef®cients #248C, Rf8ˆCF
3
#CF
2 7
) )
3
6 11
Analyte
CF
3
C
6
F
11/toluene
4
reported. These re¯ect relative as opposed to absolute solu-
a
S#CH
S#CH
2
CH
CH
2
R
CH
f8
)
2
1
2
98.7:1.3
96.6:3.4
96.5:3.5
b
a
bilities, and are summarized in Table 1. Values for related
compounds are given, and analyzed in Section 3. Due to the
lack of solubility of sulfoxides 3, 4 and palladium
complexes 5, 6 in CF C F or toluene, analogous partition
2
2
2
R
f8
)
2
b
HN#CH
N#CH CH
2
2
CH
CH
2
CH
2
R
f8
)
2
7
8
2
2
R
f8
)
3
.99.7:,0.3c
.99.7:,0.3
98.8:1.2
P#CH
P#CH
2
CH
CH
2
R
CH
f8
)
3
9
10
3
6 11
c
2
2
2
R
f8
)
3
coef®cients could not be determined. However, metal
complexes containing more than one ¯uorous ligand often
give partition coef®cients higher than the free ¯uorous
a
This work.
Ref. 8a.
Ref. 18b.
b
c
5d,6g
ligand.

C. Rocaboy, J. A. Gladysz / Tetrahedron 58 ꢀ2002) 4007±4014
4009
Chart 1. Suzuki coupling with catalyst precursors 5 and 6.
2
.2. Catalysis
We next sought to probe whether the catalytically active
species or a precursor could be recycled. Thus, analogous
reactions were conducted with a ten-fold higher, 0.2 mol%,
palladium loading. Toluene was then added to give a three-
liquid-phase organic/aqueous/¯uorous system. The upper
two layers were removed, and the denser ¯uorous phase
was extracted with toluene. GC analysis as above showed
comparable conversions and yields, as summarized in Chart
2. However, all reactions were much faster, consistent with
the higher loadings.
Fluorous palladium complexes 5 and 6 were assayed as
catalyst precursors for the Suzuki reaction, using a standard
set of conditions.
sions of 5 or 6 in CF C F were sequentially treated with
1
2,23a
As summarized in Chart 1, suspen-
3
6 11
DMF, an aryl bromide #1.0 equiv.), phenylboronic acid
PhB#OH) , 1.5 equiv.), and an aqueous solution of the
base K PO . Both 5 and 6 #present at 0.02 mol%) dis-
#
2
3
4
solved, and the two-liquid-phase systems were vigorously
stirred at room temperature unless noted. In accord with
other recent studies,25 no efforts were made to exclude air.
The biaryl products precipitated during the reactions,
providing a qualitative measure of conversion. No black
precipitate or other sign of palladium metal formation was
observed.
The recovered ¯uorous phase was charged with fresh reac-
tants. A second cycle of catalysis could always be observed
#Chart 2). However, turnover frequencies diminished, as
evidenced by the slower precipitation of biaryl products,
and in most cases lower conversions and yields after reac-
tion times distinctly longer than those of the ®rst cycles.
When third cycles were conducted, much longer times
were needed, and yields often deteriorated further. When
any given run was allowed to proceed signi®cantly past
complete conversion, it turned gray and then the charac-
teristic color of palladium black.
After workup via ether extraction, reactant conversions
and product yields #based upon the limiting aryl bro-
mide) were determined by GC versus internal standards.
Both 5 and 6 gave comparable results. The reactions of
p-bromoacetophenone and bromobenzene were essen-
tially complete after 24 h at room temperature. The
reactions of p-bromoanisole and p-bromotoluene were
slower, consistent with electronic effects upon reac-
Various scenarios consistent with the preceding behavior
are analyzed in Section 3. To help narrow the possibilities,
the ®rst cycle of the ®rst reaction in Chart 2 was repeated
#p-bromoacetophenone, catalyst 5), and the product-
containing toluene extracts were charged with fresh
1
2,23a
tivity noted earlier,
08C.
and the latter was conducted at
5
For three aryl bromides, the yields of the target biaryls were
greater than 90%. For the fourth #p-bromoanisole), the
yields #71±69%) were only slightly lower than the conver-
sions #77±75%). This implies that yields of ca. 90% would
be attained with higher temperatures and/or longer reaction
times. Minor amounts of biphenyl, a homocoupling product
of the boronic acid, were observed in some cases. More
importantly, turnover numbers approached 5000, indicating
a long-lived catalyst system with excellent prospects for
further optimization.
p-bromoacetophenone, PhB#OH)
solution of K PO . The reaction was closely monitored by
, DMF, and an aqueous
2
3
4
GC, and after 5.5 hÐmuch longer than the times required
for cycles 1 or 2Ðconversion to the biaryl product was
complete. Next, the toluene extract from an identical experi-
ment was treated with aqueous KOH. This system was
1
9
extracted with ether and analyzed by F NMR in the
presence of an internal standard. The ¯uorous sul®de 1
was the only species detected #10±15% of the ligand present
in catalyst 5; range for two runs).

4010
C. Rocaboy, J. A. Gladysz / Tetrahedron 58 ꢀ2002) 4007±4014
Chart 2. Recycling of Suzuki catalysts derived from 5 and 6.
3
. Discussion
The compounds in Scheme 1 are also important because
their physical properties can be compared to those of
many closely related ¯uorous compounds. The sulfoxides
and palladium complexes 3±6 are simply too insoluble for
conventional partition coef®cient measurements. However,
as shown in Table 1, the partition coef®cients of sul®des 1
and 2 indicate very high ¯uorous phase af®nities. They are
slightly lower than those of analogous tertiary amines and
phosphines with three pony tails #1 vs 9; 2 vs 8 and 10).
However, they would be expected to reach .99:,1 with
longer, Rf10-containing pony tails. The sul®de 2 can also
be directly compared to secondary amine HN##CH ) R )
2 3 f8 2
#7), which differs only by a HN/S replacement. Interest-
ingly, the partition coef®cients are very close #96.6:3.4 vs
96.5:3.5).
Scheme 1 establishes that ¯uorous primary iodides with at
least two methylene spacers are easily converted to the
corresponding ¯uorous dialkyl sul®des and sulfoxides.
Closely related sequences leading to sul®des and sulfoxides
of the type R #CH ) S#X)CH #nˆ4, 6; R ˆCF #CF )
)
fn
2 2
3
fn
3
2 n21
1
1
have been recently reported by Crich. A lower homolog of
, #R CH CH ) S, has been sketchily described, together
with other R CH CH SR species. Portella has prepared
1
f6
2
2 2
1
3a
f6
2
2
1
8a
various ¯uorous sul®des with one methylene spacer,
R CH SR, from ¯uorous tosylates, and analogs without
1
3b
fn
2
1
3g
methylene spacers are known. Several ¯uorous thiols and
1
3
disul®des have been synthesized, and two thiols have
recently become commercially available. Hence, despite a
somewhat scattered preparative literature, a wide variety of
¯uorous organosulfur compounds are now readily available.
Applications as scavengers in high-throughput syntheses are
described elsewhere in this issue.
Although none of our data bear upon the electronic proper-
ties of sul®des and sulfoxides 1±4, they can be expected to
be less electron rich than analogous compounds with n-alkyl
2
6

C. Rocaboy, J. A. Gladysz / Tetrahedron 58 ꢀ2002) 4007±4014
4011
8
a
substitutents. Detailed studies of ¯uorous aliphatic amines
show that the electron withdrawing
the palladium ¯uorous phosphine complexes 11±12 are
good catalyst precursors for the Suzuki reaction. At
1
8,27
6l
and phosphines
effect of the Rf8 group has a signi®cant effect upon solu-
tion-phase equilibria and spectroscopic properties through
1.5 mol% palladium loadings, high yields were obtained
through six cycles for a variety of substrates. However, at
0.1 mol% loadings, rates and yields dropped for the second
cycle, and had markedly decreased by the fourth cycle.
Hence, the ¯uorous phosphine and ¯uorous dialkyl
sul®de-based systems show similar characteristics. As
®
ionization potentials, about ten methylene groups are
ve methylene groups #inclusive). With gas-phase vertical
2
7
required before an asymptotic limit is reached.
6
l
The data in Charts 1 and 2 show that palladium complexes 5
and 6 are effective catalyst precursors for the Suzuki reac-
tion. We are particularly struck by the mild conditions and
TON values in Chart 1. As recently as 1999, the scarcity of
ambient-temperature couplings of aryl bromides and
recognized by Bannwarth and emphasized in a recent
3
7
critical analysis, recycling ef®ciency is best quanti®ed
by measuring rate #or TOF) as a function of cycle. When
the time selected for the ®rst cycle is unnecessarily long,
comparable yields can be obtained for subsequent cycles,
even when recycling is only moderately ef®cient.
1
2c,28
PhB#OH) was a point of emphasis.
In the course of
another project involving new catalysts for the Suzuki reac-
2
2
tion, we have measured rates of a benchmark high-activity
9
system, 1:4 Pd#OAc) /P#t-Bu) in toluene at 80±1008C
2
3
8,30
2
#
Chart 1 is distinctly faster.
1 mol% palladium, K PO ).
4
The catalyst system in
3
This in turn poses the question of the active catalyst. The
recycling data in Chart 2 show a progressive loss of activity
#
rate or turnover frequency #TOF)) that is consistent with at
least four possibilities: #1) the generation of a homogeneous
uorous catalyst that is not very ef®ciently recycled #modest
¯
partition coef®cient or ¯uorous phase solubility); #2) the
generation of a homogeneous ¯uorous catalyst that is
ef®ciently recycled but gradually deactivated; #3) the
generation of a non-recyclable heterogeneous or metallic
catalyst at a slow rate from a homogeneous precursor, with
recycling of the remaining precursor until it becomes
exhausted; #4) the generation of a ¯uorous heterogenous or
metallic catalyst that is not very stable or ef®ciently recycled.
Independent of recycling ef®ciency, there are various ways
to probe whether the catalysis in Charts 1 and 2 is due to a
homogeneous species, heterogeneous species, or a mixture
thereof. However, such efforts do not always converge upon
a unique answer, even after intensive study. The aerobic
conditions would necessitate additional control experi-
ments. Thus, our plan is to develop second-generation ¯uor-
ous catalyst precursors with multidentate ligands, such as
cyclometalated species. These are often thought to be less
readily detached during a catalytic cycle, thereby helping to
preserve catalyst integrity. Hence, the data in Charts 1 and 2
can be regarded as a baseline by which the performance of
these new systems can be measured.
The eventual appearance of metallic palladium under the
conditions of Chart 2 leads us to favor possibilities three
and/or four. Dupont also reported that #Et S) PdCl gives
2
2
2
2
3a
palladium black under certain Suzuki conditions. The
signi®cant leaching of ¯uorous sul®de ligand 1 #10±15%
of theory) is consistent with all four scenarios, although
we emphasize that our analysis does not identify the
primary species ®rst transported to the non-¯uorous phase.
The markedly attenuated catalytic activity of the product-
containing organic phases suggests lower levels of active
catalyst, although palladium in catalytically inactive forms
may of course be present.
3
8
In summary, this study has established convenient and
practical syntheses of simple symmetrical ¯uorous dialkyl
sul®des and sulfoxides. Palladium complexes of the former
are precursors to highly active catalysts for the Suzuki
coupling, the characterization and optimization of which
is ongoing. New catalyst systems based upon ¯uorous
cyclometalated sulfur and nitrogen donor ligands will be
Various types of heterogeneous or metallic palladium
species are known to be highly active catalysts for the
3
1±36
Suzuki and Heck reactions.
The so-called `ligand
free' catalysts constitute one intensively investigated
category.3 However, analyses are complicated by recent
evidence that heterogeneous palladium species can under
some conditions serve as precursors to homogeneous
1,32
3
9
described in the near future.
3
4
palladium catalysts. Furthermore, two distinct types of
uorous-phase-soluble palladium nanoparticles have been
¯
reported.
4. Experimental
3
5,36
Both catalyze the Suzuki and Heck reactions,
and can to varying extents be recycled. One is stabilized
by ¯uorous derivative of the enone ligand
OvC#CHvCHC H ) , raising the possibility of a similar
4.1. General
a
6
5 2
Reactions were conducted in air with reagent grade
solvents unless noted. The reagents CF #CF ) CH CH I
3
6b
role for the ¯uorous sul®de ligands.
3
2 7
2
2
#R CH CH I), bromobenzene, p-bromoacetophenone,
p-bromoanisole, p-bromotoluene, PhB#OH)2, K PO
f8 2 2
In very relevant recent work, Bannwarth has reported that
3
4

4012
C. Rocaboy, J. A. Gladysz / Tetrahedron 58 ꢀ2002) 4007±4014
0
0
#
CH CO H #39% in acetic acid; Fluka) were used as
7£Aldrich), Na PdCl
#Strem), LiEt BH #Acros),
2CHH CF ), 3.00±3.12 #m, 2SCHH ), and virtually iden-
2
2
4
3
1
3
1
tical in CD CO D #2.70±2.88, 3.28±3.40); C{ H} #partial)
3 2
25.5 #t, J ˆ22 Hz, 2CH CF ), 44.1 #s, 2SCH ).
3
3
2
received. NMR spectra were recorded on Bruker or Jeol
00 MHz spectrometers at ambient probe temperature and
referenced to residual internal CHCl # H, d 7.27) or CDCl
CF
2
2
2
4
1
4.1.4. Bisꢀ4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadeca-
¯uoroundecyl)sulfoxide or ꢀRf8CH CH CH SvO ꢀ4).
Sul®de 2 #0.219 g, 0.229 mmol), CHCl #6 mL), and
CH CO H #0.055 mL, 0.285 mmol) were combined in a
procedure analogous to that for 3. An identical workup
gave 4 as white solid #0.177 g, 0.182 mmol, 80%), mp
3
3
1
3
19
#
C, d 77.2), or external CFCl # F, d 0.00). IR spectra
3
2
2
)
2 2
were measured on an ASI React-IR spectrometer. Gas
chromatography was conducted on a ThermoQuest Trace
GC 2000 instrument. DSC data were recorded with a
Mettler±Toledo DSC821 instrument and treated by standard
3
3
3
1
7
methods. Elemental analyses were conducted with a Carlo
Erba EA1110 instrument.
123 #capillary), 124.5 #DSC)8C. Calcd for C22
C, 27.23; H, 1.24. Found: C, 27.05; H, 1.46. IR #powder,
H F34SO:
12
2
1
1
cm ): n 1089 m. NMR #d, CDCl /CF C F , 3:1 v/v): H
SO
3
3 6 5
0 0
2.20±2.43 #m, 2CHH CHH CF ), 2.83, 2.85 #two over-
2
4
¯
.1.1. Bisꢀ3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadeca-
uorodecyl)sul®de or ꢀR CH CH ) S ꢀ1). A Schlenk
2
3
lapping dt appearing as an octet; JHHˆ20 Hz, JHHˆ7 Hz,
0 0
2SCHH and 2SCHH );
f8
2
2 2
13
1
¯
N , and LiEt BH #1.0 M in THF; 3.80 mL, 3.80 mmol) was
ask was charged with sulfur #0.058 g, 1.809 mmol) under
C{ H} #partial) 15.0 #s,
), 30.3 #t, JCFˆ22 Hz, 2CH CF ), 51.9 #s,
2
2CH
CH
).
CF
2
2
3
2
2
2
2
1
5
added dropwise with stirring over 15 min. After 20 min, a
solution of R CH CH I #2.080 g, 3.624 mmol) in dry THF
2SCH
2
f8
2
2
#
10 mL, distilled from Na/benzophenone) was added
4.1.5. ꢀRf8CH
was charged with 1 #0.423 g, 0.456 mmol), Na
2
CH
2
)
2
S]
2
PdCl
2
ꢀ5). A round-bottom ¯ask
PdCl
4
dropwise. The yellow solution quickly decolorized, and
was stirred overnight. Water #10 mL) and then aqueous
KOH #10 mL, 1 M) were added. The mixture was extracted
2
#0.059 g, 0.200 mmol), and MeOH #7 mL). The brown
mixture was immersed in a 608C oil bath #melting and dis-
solution of 1). A yellow precipitate rapidly formed. The
mixture was stirred #1 h) and allowed to cool to room
temperature. The precipitate was collected on a fritted
funnel, washed with water #3£10 mL), MeOH #3£10 mL),
and ether #3£10 mL), and dried by oil pump vacuum to give
5 as a light yellow solid #0.381 g, 0.188 mmol, 94%),
mp 178±179 #capillary), 177.1 #DSC)8C. Calcd for
with ether #3£20 mL) and dried #MgSO ). The volatiles
4
were removed by rotary evaporation. The residue was
puri®ed by column chromatography #silica gel, hexanes/
EtOAc, 9:1 v/v). The solvent was removed by rotary
evaporation and oil pump vacuum to give 1 as a white
solid #1.191 g, 1.285 mmol, 71%), mp 67 #capillary), 66.9
#
DSC)8C. Calcd for C H F S: C, 25.93; H, 0.76. Found: C,
20 8 34
1
2
2
2
2
5.85; H, 0.76. NMR #d, CDCl ): H 2.34±2.47 #m,
C H F68Cl S Pd: C, 23.67; H, 0.79. Found: C, 23.83; H,
40 16 2 2
3
3
13
1
1
CH CF ), 2.79 #t, J ˆ8 Hz, 2SCH ); C{ H} #partial)
1.01. NMR #d, CDCl , 1:1 v/v): H 2.80±2.87 #m,
4CH CF ), 3.28 #br s, 4SCH ). MS #m/z, positive FAB) 1032
2
3
/CF
3
C
6
F
5
2
2
HH
2
3
2
3.1 #t, J ˆ5 Hz, 2SCH ), 32.1 #t, J ˆ22 Hz,
2
2
CF
9
2
CF
1
3
1
CH CF ); F 281.1 #t, J ˆ11 Hz, 2CF ), 2113.3 #br
#Pd#1) , 100%).
2
2
HH
3
s, 2CF ), 2122.3 #br s, 6CF ), 2123.0 #br s, 2CF ), 2123.7
2
2
2
4.1.6. ꢀR CH CH CH ) S] PdCl ꢀ6). Sul®de 2 #0.973 g,
f8 2 2 2 2 2 2
#
br s, 2CF ), 2125.3 #br s, 2CF ).
2
2
1.019 mmol), Na PdCl #0.136 g, 0.462 mmol), and MeOH
2 4
#15 mL) were combined in a procedure analogous to that
for 5. An identical workup gave 6 as a light yellow solid
4
¯
.1.2. Bisꢀ4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,11-heptadeca-
uoroundecyl)sul®de or ꢀR CH CH CH ) S ꢀ2). Sulfur
f8
2
2
2 2
#
#
0.917 g, 0.440 mmol, 95%), mp 153±154 #capillary), 155.6
DSC)8C. Calcd for C H F Cl S Pd: C, 25.33; H, 1.16.
#
R CH CH CH I #2.012 g, 3.421 mmol), and THF #15 mL)
were combined in a procedure analogous to that for 1. A
nearly identical workup #silica gel chromatography with
hexanes and then ether) gave 2 as a white solid #1.051 g,
0.052 g, 1.622 mmol), LiEt BH #3.50 mL, 3.50 mmol),
3
44 24 68
2 2
f8
2
2
2
Found: C, 25.64; H, 1.40. NMR #d, CDCl /CF C F , 1:1
3 6 5
3
1
v/v): H 2.30±2.63 #m, 4CH CH CF ), 3.15 #br s, 4SCH );
2
2
2
2
1
3
1
2
C{ H} #partial) 20.3 #s, 4CH CH CF ), 30.5 #t, J ˆ
2 Hz, 4CH CF ), 38.3 #s, 4SCH ). MS #m/z, positive
2 2 2
2
2
2
CF
2
1.101 mmol, 67%), mp 56 #capillary), 56.5 #DSC)8C. Calcd
for C H F S: C, 27.69; H, 1.26. Found: C, 27.83; H, 1.22.
1
FAB) 1061 #Pd#2) , 100%).
2
2
12 34
1
NMR #d, CDCl ): H 1.88±1.99 #m, 2CH CH CF ), 2.19±
3
2
2
2
3
2
.30 #m, 2CH CH CF ), 2.62 #t, JHHˆ8 Hz, 2SCH );
4.2. Catalysis; general procedure
2
2
2
2
1
3
1
2
C{ H} #partial) 20.4 #s, 2CH CH CF ), 30.0 #t, J ˆ
2
2
2
CF
2
2 Hz, 2CH CF ), 31.3 #s, 2SCH ).
2
A 25 mL round bottom ¯ask was charged with a Te¯on
stir bar, 5 or 6 #0.0010 g, 0.0005 mmol), and CF C F
6 11
2
2
3
4
¯
.1.3. Bisꢀ3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadeca-
uorodecyl)sulfoxide or ꢀR CH CH ) SvO ꢀ3). A
round bottom ¯ask was charged with 1 #0.380 g, 0.410
#1.00 mL). Then DMF #3.00 mL), an aryl bromide
#2.500 mmol), PhB#OH)2 #0.724 g, 3.750 mmol), and a
solution of K PO #1.016 g, 5.000 mmol) in water
f8
2
2 2
3
4
mmol) and CHCl #12 mL). Then CH CO H #39% in acetic
3
#2.00 mL) were added. The samples were vigorously stirred
at room temperature #508C for p-bromotoluene) for the time
speci®ed in Chart 1. Then ether #10 mL) and aqueous KOH
#10 mL, 1 M) were added. The ether layer was separated,
and the aqueous layer was extracted twice more with ether
3
3
1
8
acid; 0.100 mL, 0.513 mmol) was added with stirring.
A
white precipitate formed immediately. After 15 min, the
precipitate was collected by ®ltration, washed with ether
#
3£10 mL), and dried by oil pump vacuum to give 3 as a
white solid #0.328 g, 0.348 mmol, 85%), mp 140 #capillary),
40.7 #DSC)8C. Calcd for C H F SO: C, 25.49; H, 0.85.
#10 mL). The extracts were dried #MgSO ) and analyzed by
4
1
GC using hexadecane or tridecane standard #Chart 1).
Authentic samples of all products were purchased from
Aldrich.
2
0
8 34
2
1
Found: C, 25.49; H, 0.92. IR #powder, cm ): n 1035 m.
SO
1
NMR #d, CDCl /CF C F , 2:1 v/v): H 2.65±2.80 #m,
3
3 6 5

C. Rocaboy, J. A. Gladysz / Tetrahedron 58 ꢀ2002) 4007±4014
4013
4
.3. Recycling; general procedure
Acknowledgements
A tube was charged with a Te¯on stirring bar, 5 or 6
0.0041 g, 0.0020 mmol), and CF C F #1.50 mL). Then a
stock DMF solution #2.00 mL) that was 0.50 M in aryl
bromide #1.00 mmol) and 0.75 M in PhB#OH)2 #1.50
mmol) was added, immediately followed by aqueous
We thank the Deutsche Forschungsgemeinschaft #DFG; GL
301/3-1) and Johnson Matthey PMC #palladium loan) for
support.
#
3
6 11
K PO4 #1.33 M; 1.50 mL, 2.00 mmol). Reactions were
3
References
conducted as in the previous procedure for the times speci-
®
#
ed in Chart 2. Stirring was then halted and toluene added
2.00 mL), giving a three phase system. The two upper
layers were carefully removed via syringe, and the bottom
uorous phase extracted once more with toluene #2.00 mL).
1. #a) Horv a th, I. T.; R a bai, J. Science 1994, 266, 72. #b) Horv a th,
I. T. Acc. Chem. Res. 1998, 31, 641.
2. Review literature since 1999: #a) de Wolf, E.; van Koten, G.;
Deelman, B.-J. Chem. Soc. Rev. 1999, 28, 37. #b) Fish, R. H.
Chem. Eur. J. 1999, 5, 1677. #c) Cavazzini, M.; Montanari, F.;
Pozzi, G.; Quici, S. J. Fluorine Chem. 1999, 94, 183.
#d) Diederichsen, U. Nachr. Chem. Tech. Lab. 1999, 47,
805. #e) Hope, E. G.; Stuart, A. M. J. Fluorine Chem. 1999,
100, 75. #f) Hope, E. G.; Stuart, A. M. In Advanced Inorganic
Fluorides, Nakajima, T., Zemva, B., Tressaud, A., Eds.;
Elsevier: Amsterdam, 2000; p. 403, Ch 13. #g) Endres, A.;
Maas, G. Chemie unserer Zeit 2000, 34, 382.
¯
The tube with the ¯uorous phase was recharged with the
DMF solution of aryl bromide and PhB#OH) #2.00 mL),
and then the aqueous solution of K PO #1.50 mL). An
3
identical second cycle was conducted. The upper toluene/
water layers were treated with aqueous KOH and ether as in
the previous procedure, and analyzed by GC #Chart 2).
2
4
4
.4. Leaching tests
3. For a newer protocol that avoids the ¯uorous solvent require-
ment, see: Wende, M.; Meier, R.; Gladysz, J. A. J. Am. Chem.
Soc. 2001, 123, 11490.
A. A tube was charged with 5 #0.0041 g, 0.0020 mmol),
CF C F #1.50 mL), a stock DMF solution #2.00 mL) that
4. Survey of practical considerations and underlying physical
principles: Barthel-Rosa, L. P.; Gladysz, J. A. Coord. Chem.
Rev. 1999, 190±192, 587.
3
6 11
was 0.50 M in p-bromoacetophenone #1.00 mmol) and
.75 M in PhB#OH) #1.50 mmol), and aqueous K PO
4
0
2
3
#
1.33 M; 1.50 mL, 2.00 mmol) as in the previous experi-
5. #a) Rutherford, D.; Juliette, J. J. J.; Rocaboy, C.; Horv a th, I. T.;
Gladysz, J. A. Catal. Today 1998, 42, 381. #b) Juliette, J. J. J.;
Rutherford, D.; Horv a th, I. T.; Gladysz, J. A. J. Am. Chem.
Soc. 1999, 121, 2696. #c) Dinh, L. V.; Gladysz, J. A. Tetra-
hedron Lett. 1999, 40, 8995. #d) So o s, T.; Bennett, B. L.;
Rutherford, D.; Barthel-Rosa, L. P.; Gladysz, J. A. Organo-
metallics 2001, 20, 3079.
ment. An identical reaction and workup gave a toluene
extract, which was recharged in a second tube with the
DMF solution of p-bromoacetophenone and PhB#OH)2
#
2.00 mL), and the aqueous K PO #1.50 mL). The biphasic
3 4
mixture was vigorously stirred. GC data: see text. B. A tube
was charged with the same materials as the previous experi-
ment. After 5 min, stirring was halted and toluene added
6. #a) Betzemeier, B.; Knochel, P. Angew. Chem., Int. Ed. Engl.
1997, 36, 2623 Angew. Chem. 1997, 109 2736. #b) Kling, R.;
Sinou, D.; Pozzi, G.; Choplin, A.; Quignard, F.; Busch, S.;
Kainz, S.; Koch, D.; Leitner, W. Tetrahedron Lett. 1998, 39,
9439. #c) Haar, C. M.; Huang, J.; Nolan, S. P.; Petersen, J. L.
Organometallics 1998, 17, 5018. #d) Smith, Jr., D. C.;
Stevens, E. D.; Nolan, S. P. Inorg. Chem. 1999, 38, 5277.
#e) Hope, E. G.; Kemmitt, R. D. W.; Paige, D. R.; Stuart,
A. M. J. Fluorine Chem. 1999, 99, 197. #f) Richter, B.; Van
Koten, G.; Deelman, B.-J. J. Mol. Catal. ꢀA) 1999, 145, 317.
#g) Richter, B.; Spek, A. L.; Van Koten, G.; Deelman, B.-J. J.
Am. Chem. Soc. 2000, 122, 3945. #h) Schneider, S.;
Bannwarth, W. Angew. Chem., Int. Ed. Engl. 2000, 39, 4142
Angew. Chem. 2000, 112, 4293. #i) Grigg, R.; York, M.
Tetrahedron Lett. 2000, 41, 7255. #j) Zhang, Q.; Luo, Z.;
Curran, D. P. J. Org. Chem. 2000, 65, 8866. #k) Darses, S.;
Pucheault, M.; Gen eà t, J.-P. Eur. J. Org. Chem. 2001, 1121. #l)
Schneider, S.; Bannwarth, W. Helv. Chem. Acta 2001, 84, 735.
7. #a) Pozzi, G.; Montanari, F.; Quici, S. J. Chem. Soc., Chem.
Commun. 1997, 69. #b) Pozzi, G.; Cinato, F.; Montanari, F.;
Quici, S. J. Chem. Soc., Chem. Commun. 1998, 877. #c) Quici,
S.; Cavazzini, M.; Ceragioli, S.; Montanari, F.; Pozzi, G.
Tetrahedron Lett. 1999, 40, 3647. #d) Pozzi, G.; Cavazzini,
M.; Cinato, F.; Montanari, F.; Quici, S. Eur. J. Org. Chem.
1999, 1947. #e) Nishimura, T.; Maeda, Y.; Kakiuchi, N.;
Uemura, S. J. Chem. Soc., Perkin Trans. 1 2000, 4301.
#f) Meseguer, M.; Moreno-Ma nÄ as, M.; Vallribera, A.
Tetrahedron Lett. 2000, 41, 4093. #g) Betzemeier, B.;
Cavazzini, M.; Quici, S.; Knochel, P. Tetrahedron Lett.
#
2.00 mL), giving a three phase system. The two upper
layers were carefully removed via syringe, and the bottom
uorous phase extracted once more with toluene #2.00 mL).
The upper toluene/water layers were treated with ether
10 mL) and aqueous KOH #10 mL, 1 M). The organic
¯
#
layer was dried #MgSO ) and taken to dryness. The white
4
residue was taken up in CDCl #2.50 mL), and a solution of
3
CF C H in CDCl #0.041 M; 0.100 mL, 0.0041 mmol) was
3
6
5
3
1
added. A F NMR spectrum showed only 1, and integration
9
of the CF signal versus that of the standard #d 281.1
3
#2CF ) vs 263.0) indicated 0.0004±0.0006 mmol to be
3
present #two runs; 10±15% of theory).
4
.5. Partition coef®cients
The following is representative. A 10 mL vial was charged
with 1 #0.0303 g, 0.0327 mmol), CF C F #2.000 mL;
distilled from P O ), and toluene #2.000 mL; distilled
2
from Na/benzophenone), equipped with a mininert valve,
vigorously shaken #2 min). After 1 h, a 0.500 mL aliquot
of each layer was added to 0.250 mL of a standard
3
6 11
5
0
.100 M solution of hexadecane in toluene. The solutions
were diluted with ether #4.00±5.00 mL). GC analysis
average of 5±6 injections) showed that 0.00755 mmol of
was in the CF C F aliquot and 0.00010 mmol in the
#
1
3
6 11
toluene aliquot #98.7:1.3; a 2.000/0.500 scale factor gives
a total mass recovery of 0.0283 g, 93%).

4014
C. Rocaboy, J. A. Gladysz / Tetrahedron 58 ꢀ2002) 4007±4014
2
000, 41, 4343. #h) Nakamura, Y.; Takeuchi, S.; Okumura, K.;
21. Similar solubility trends have been noted for other ¯uorous
compounds with two versus three methylene spacers: Curran,
D. P.; Hadida, S.; Kim, S-Y.; Luo, Z. J. Am. Chem. Soc. 1999,
121, 6607.
Ohgo, Y. Tetrahedron 2001, 57, 5565. #i) Colonna, S.;
Gaggero, N.; Montanari, F.; Pozzi, G.; Quici, S. Eur. J. Org.
Chem. 2001, 181.
8
. Syntheses of ¯uorous nitrogen donor ligands: #a) Rocaboy, C.;
Bauer, W.; Gladysz, J. A. Eur. J. Org. Chem. 2000, 2621.
22. Ishihara, K.; Kondo, S.; Yamamoto, H. Synlett 2001, 1371.
23. #a) Zim, D.; Monteiro, A. L.; Dupont, J. Tetrahedron Lett.
2000, 41, 8199. #b) Gruber, A. S.; Pozebon, D.; Monteiro,
A. L.; Dupont, J. Tetrahedron Lett. 2001, 42, 7345.
24. Murray, S. G.; Hartley, F. R. Chem. Rev. 1981, 81, 365 see
section VI-H.
#
b) Rocaboy, C.; Hampel, F.; Gladysz, J. A. J. Org. Chem.,
002, 67, in press.
2
9
. #a) Trost, B. M.; Melvin, Jr., L. S. Sulfur Ylides; Academic:
New York, 1975. #b) Block, E. Reaction of Organosulfur
Compounds; Academic: New York, 1978.
25. #a) Weissman, H.; Milstein, D. J. Chem. Soc., Chem. Commun.
1999, 1901. #b) Bussolari, J. C.; Rehborn, D. C. Org. Lett.
1999, 1, 965. #c) Zim, D.; Gruber, A. S.; Ebeling, G.; Dupont,
J.; Monteiro, A. L. Org. Lett. 2000, 1, 2881.
1
0. #a) Liu, Y.; Vederas, J. C. J. Org. Chem. 1996, 61, 7856.
b) Harris, J. M.; Liu, Y.; Chai, S.; Andrews, M. D.; Vederas,
J. C. J. Org. Chem. 1998, 63, 2407.
#
1
1. Crich, D.; Neelamkavil, S. J. Am. Chem. Soc. 2001, 123, 7449.
2. #a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
26. Zhang, W.; Curran, D. P.; Chen, C. H.-T. Tetrahedron 2002,
58, 3871±3875.
1
#
b) Suzuki, A. In Metal-Catalyzed Cross-Coupling Reactions,
Diederich, F., Stang, P. J., Eds.; Wiley-VCH: Weinheim, 1998
27. Jiao, H.; Le Stang, S.; So o s, T.; Meier, R.; Kowski, K.;
Rademacher, P.; Jafarpour, L.; Hamard, J.-B.; Nolan, S. P.;
Gladysz, J. A. J. Am. Chem. Soc. 2002, 124, 1516.
28. Littke, A. F.; Dai, C.; Fu, G. C. J. Am. Chem. Soc. 2000, 122,
4020.
Chapter 2. #c) Suzuki, A. J. Organomet. Chem. 1999, 576,
147.
1
3. #a) Dialkyl sul®des with one and two pony tails: Szonyi, F.;
Cambon, A. J. Fluorine Chem. 1989, 42, 59. #b) Dialkyl
sul®des with one pony tail: Portella, C.; Shermolovich,
Y. G.; Tschenn, O. Bull. Soc. Chim. Fr. 1997, 134, 697.
29. Eichenseher, S.; Kromm, K.; Delacroix, O.; Gladysz, J. A.
J. Chem. Soc., Chem Commun. 2002, in press.
30. Zapf, A.; Ehrentraut, A.; Beller, M. Angew. Chem., Int. Ed.
Engl. 2000, 39, 4153 Angew. Chem. 2000, 112, 4315.
31. Reetz, M. T.; Westermann, E. Angew. Chem., Int. Ed. Engl.
2000, 39, 165, Angew. Chem. 2000, 112, 170, and earlier
papers referenced therein.
#
c) Dialkyl disul®des with two pony tails, and related
compounds with sulfur±sulfur bonds: Brace, N. O. J. Fluorine
Chem. 2000, 105, 11. #d) Fluorous thiols and dialkyl disul®des
with two pony tails: Mureau, N.; Guittard, F.; G e ribaldi, S.
Tetrahedron Lett. 2000, 41, 2885. #e) Fluorous thiols: Naud,
C.; Calas, P.; Blancou, H.; Commeyras, A. J. Fluorine Chem.
32. #a) LeBlond, C. R.; Andrews, A. T.; Sun, Y.; Sowa, Jr., J. R.
Org. Lett. 2001, 3, 1555. #b) Kabalka, G. W.; Namboodiri, V.;
Wang, L. J. Chem. Soc., Chem. Commun. 2001, 775.
33. Nowotny, M.; Hanefeld, U.; Van Koningsveld, H.; Masch-
meyer, T. J. Chem. Soc., Chem. Commun. 2000, 1877.
34. Bif®s, A.; Zecca, M.; Basato, M. Eur. J. Inorg. Chem. 2001,
2
000, 104, 173. #f) The ¯uorous thiol R CH CH SH: Gong,
f6 2 2
W.; Elitzin, V. I.; Janardhanam, S.; Wilkins, C. L.; Fritsch, I.
J. Am. Chem. Soc. 2001, 123, 769. #g) Kiss, L. E.; R a bai, J.;
Varga, L.; K oÈ vesdi, I. Synlett 1998, 1243.
1
131.
5. #a) Chechik, V.; Crooks, R. M. J. Am. Chem. Soc. 2000, 122,
243. #b) Crooks, R. M.; Zhao, M.; Sun, L.; Chechik, V.;
1
1
1
4. See also Curran, D. P.; Oderaotoshi, Y. Tetrahedron 2001, 57,
3
5
243.
5. Gladysz, J. A.; Wong, V. K.; Jick, B. S. Tetrahedron 1979, 35,
329.
1
Yeung, L. K. Acc. Chem. Res. 2001, 34, 181 and additional
references therein.
2
6. Vincent, J.-M.; Rabion, A.; Yachandra, V. K.; Fish, R. H.
Angew. Chem., Int. Ed. Engl. 1997, 36, 2346 Angew. Chem.
3
6. #a) Moreno-Ma nÄ as, M.; Pleixats, R.; Villarroya, S. Organo-
metallics 2001, 20, 4524. #b) note added in proof: see Moreno-
Ma nÄ as, M.; Pleixats, R.; Villarroya, S. J. Chem. Soc., Chem.
Commun. 2002, 60 for the detailed characterization of palla-
dium nanoparticles stabilized by additional types of ¯uorous
compounds.
1
997, 109, 2438.
7. Cammenga, H. K.; Epple, M. Angew. Chem., Int. Ed. Engl.
995, 34, 1171 Angew. Chem. 1995, 107, 1284.
1
1
1
8. #a) Alvey, L. J.; Meier, R.; So o s, T.; Bernatis, P.; Gladysz, J. A.
Eur. J. Inorg. Chem. 2000, 1975. #b) Alvey, L. J.; Rutherford,
D.; Juliette, J. J. J.; Gladysz, J. A. J. Org. Chem. 1998, 63,
3
7. Gladysz, J. A. Pure Appl. Chem. 2001, 73, 1319.
8. Dupont, J.; Pfeffer, M.; Spencer, J. Eur. J. Inorg. Chem. 2001,
3
6302.
1917.
9. Rocaboy, C.; Gladysz, J. A. Org. Lett. 2002, 4, in press.
19. Madesclaire, M. Tetrahedron 1986, 42, 5459.
20. Davies, J. A. Adv. Inorg. Chem. Radiochem. 1981, 24, 115.
3