Aqueous phase one-electron reduction of sulfonium, selenonium and telluronium salts

Article abstract of DOI:10.1002/ejoc.200400604

Triorganylsulfonium, -selenonium and -telluronium salts were reduced by carbon dioxide radical anions/solvated electrons produced in aqueous solution by radiolysis. The radical expulsion accompanying reduction occurred with the expected leaving group propensities (benzyl > secondary alkyl > primary alkyl > methyl > phenyl), although greater than expected loss of the phenyl group was often observed. Diorganyl chalcogenides formed in the reductions were conveniently isolated by extraction with an organic solvent. Product yields based on the amount of reducing radicals obtained from the γ-source were often higher than stoichiometric (up to 1800 %) in the reduction of selenonium and telluronium compounds; it is likely that this result can be accounted for in terms of a chain reaction with carbon-centred radicals/formate serving as the chain transfer agent. The product distribution was essentially independent of the reducing species for diphenyl alkyl telluronium salts, whereas significant variations were seen for some of the corresponding selenonium salts. This would suggest the intermediacy of telluranyl radicals in the one-electron reduction of telluronium salts. However, pulse radiolysis experiments indicated that the lifetimes of such a species (the triphenyltelluranyl radical) would have to be less than 1 μs. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.

Full text of DOI:10.1002/ejoc.200400604

FULL PAPER
Aqueous Phase One-Electron Reduction of Sulfonium, Selenonium and
Telluronium Salts
[a]
[a]
[b]
[b]
Per Eriksson, Lars Engman,* Johan Lind, and Gabor Merényi
Keywords: Radicals / One-electron reduction / Sulfonium salts / Selenonium salts / Telluronium salts
Triorganylsulfonium, -selenonium and -telluronium salts
were reduced by carbon dioxide radical anions/solvated
electrons produced in aqueous solution by radiolysis. The
radical expulsion accompanying reduction occurred with the
expected leaving group propensities (benzyl Ͼ secondary
alkyl Ͼ primary alkyl Ͼ methyl Ͼ phenyl), although greater
than expected loss of the phenyl group was often observed.
counted for in terms of a chain reaction with carbon-centred
radicals/formate serving as the chain transfer agent. The pro-
duct distribution was essentially independent of the reducing
species for diphenyl alkyl telluronium salts, whereas signifi-
cant variations were seen for some of the corresponding se-
lenonium salts. This would suggest the intermediacy of tellu-
ranyl radicals in the one-electron reduction of telluronium
Diorganyl chalcogenides formed in the reductions were con- salts. However, pulse radiolysis experiments indicated that
veniently isolated by extraction with an organic solvent. Pro-
duct yields based on the amount of reducing radicals ob-
tained from the γ-source were often higher than stoichiomet-
ric (up to 1800 %) in the reduction of selenonium and tellu-
ronium compounds; it is likely that this result can be ac-
the lifetimes of such a species (the triphenyltelluranyl radi-
cal) would have to be less than 1 µs.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
Introduction
anion can be conveniently generated by radiolysis of an ar-
gon-saturated aqueous solution of sodium formate.
Currently, there is a trend in chemistry to develop
“
clean” methodology for carrying out various types of
H O
[
1,2]
2
transformations.
Rather than using complex reagents
–
–
e
aq + N
2
O Ǟ HO· + HO + N
2
(1)
(2)
that could give rise to toxic by-products, the main aspira-
tion of this “green chemistry” is to induce reactions by sim-
ple energy transfer. If solvents are required, they should be
environmentally benign. In this context, the powerful one-
electron reductants (essentially the solvated electron and the
hydrogen atom) produced by radiolysis of water would seem
interesting for carrying out various kinds of reduction reac-
–
–·
HO·/H· + HCO
2
Ǟ CO
2
+ H
2
O/H
2
Reduction of triorganyl onium salts of sulfur, selenium
tions. Under γ-radiolysis conditions, a steady-state concen- and tellurium is followed by rapid decomposition to form
tration of reducing equivalents prevails, and the rate of radi- diorganyl chalcogenides and a carbon-centred radical
cal production is 5 to 8 orders of magnitude lower than in (Eq. 3). We thought that one-electron reductants produced
pulse radiolysis. If the aqueous solution is saturated with by radiolysis of water could be useful for cleanly effecting
N O and sodium formate is added, solvated electrons are such transformations. Chemical reduction of onium species,
2
[
4]
first converted into oxidizing hydroxyl radicals (Eq. 1)and by the use of potassium graphite, for example, is known to
then, together with hydrogen atoms, transformed into the give rise to rather complex mixtures due to further reactions
reducing (Ered = –1.9 V ) carbon dioxide radical anion (coupling, disproportionation, hydrogen abstraction and
Eq. 2). This species is less potent as a reducing agent than alkyl transfer) of the primarily formed carbon-centred radi-
[3]
(
the solvated electron (Ered = –2.9 V). If required, a 1:1 mix- cals. The question of whether this reaction is concerted or
ture of the solvated electron and the carbon dioxide radical proceeds via a stepwise mechanism has been much investi-
[
5]
[6]
gated and debated. If electron transfer (ET) is concerted
[
[
a]
b]
Department of Chemistry, Organic Chemistry, Uppsala Univer- with breaking of the chalcogen–carbon bond (inner sphere
sity,
ET), the mechanism is reduced to that of an S 2 reaction
N
Box 599, 75124 Uppsala, Sweden
Fax: +46-18-4713818
(Eq. 3, path A). If, on the other hand, the electron transfer
is separated from the subsequent step involving cleavage of
the bond to the leaving group, the reduction may be classi-
fied as outer sphere ET (path B).
E-mail: Lars.Engman@kemi.uu.se
Department of Chemistry, Division of Nuclear Chemistry,
Royal Institute of Technology,
1
0044 Stockholm, Sweden
Eur. J. Org. Chem. 2005, 701–705
DOI: 10.1002/ejoc.200400604
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
701

P. Eriksson, L. Engman, J. Lind, G. Merényi
FULL PAPER
lurium. A typical reduction experiment involved γ-radioly-
sis of a 5 × 10–4 m solution of the onium salt for 6–30 min,
extraction of the resulting cloudy (due to formation of in-
soluble diorganyl chalcogenide) aqueous solution with pen-
tane, and gas chromatographic analysis of the products
formed. In one series of experiments (Table 1) the carbon
dioxide radical anion was the principal reductant generated.
In another series of experiments (Table 1) approximately
equal amounts of the carbon dioxide radical anion and the
more strongly reducing solvated electron were generated.
The organochalcogen products formed during homogen-
eous-phase reduction of various alkyl diphenyl onium salts
(
3)
A large variety of sulfonium salts have been reduced by
[
4,7–8]
[9–12]
[13–17]
chemical,
electrochemical,
photochemical
or
pulse radiolytic methods.[ In general, carbon–sulfur bond
cleavage is found to occur irreversibly and leaving group
propensity parallels radical stability (benzyl Ͼ secondary Ͼ
primary Ͼ methyl Ͼ phenyl). At a time resolution of 0.1 µs
18]
1–11 of sulfur, selenium and tellurium (Eq. 5) are shown
inTable 1. The product yields based on the amount of re-
ducing radicals obtained from the γ-source were often
higher than stoichiometric (up to 1800 %) in the reduction
of selenonium and telluronium compounds (entries 2, 3, 6,
there is no experimental evidence for the intermediacy of
a sulfuranyl intermediate.[
18,19]
However, Savéant and co-
7, 11, 16, 17). In contrast, sulfonium compounds were fre-
workers have demonstrated cases of reduction in which the
concerted or stepwise character of the ET bond-breaking
quently incompletely reduced. This suggests a chain reac-
tion in the reduction of onium salts of the two heavier chal-
cogens, with sodium formate serving as the hydrogen atom
donor (Eq. 6). Apparently, the phenyl radical is the best
chain transfer agent (Table 1, entries 2 and 3). Benzene was
detected by GC in the reduction of onium salts 1–3 and
was quantified in one case (entry 2); the yield (86 %) was in
close agreement with that for diphenyl selenide. We believe
that a chain reaction could also be operative for sulfonium
salts, but the reduction of the salts may be too slow for
the process to be efficient. For example, under the ordinary
reduction conditions, no diphenyl ethyl sulfonium tetra-
fluoroborate was reduced. On the other hand, when the re-
duction was performed in argon-saturated, aqueous pro-
pan-2-ol (0.1 m) containing sodium formate and sodium hy-
droxide, stoichiometric amounts (Table 1, entry 8) of re-
duction products were isolated. Five times the stoichiomet-
ric amount of reduction products (based on the amount of
reducing radicals) was formed when the reduction was car-
[
11]
process appears to be related both to molecular structure
and the way in which electron transfer is effected.[
17]
The one-electron reduction of selenonium and tellu-
ronium salts has received only scant attention. A selenur-
anyl radical intermediate was proposed for the reduction of
some cyclic selenonium salts with magnesium or Grignard
selenuranyl and tel-
radicals have also been invoked as intermedi-
ates in homolytic substitution at sulfur, selenium and tel-
lurium (Eq. 4). High-level calculations based on pseudopo-
tential basis sets and electron correlation suggested that the
transient species involved in the methyl radical displace-
[
20,21]
[22–24]
[25]
reagents,
whilst sulfuranyl,
[
25,26]
luranyl
1
3
2
ment at methanetellurol (Eq. 4; R = R = Me; R = H;
X = Te) is an intermediate lying 23.5 kJ mol above the
–
1
[
27]
reactants. On the other hand, the similar reactions at se-
lenium and sulfur were predicted to proceed via symmetri-
–
1
cal transition states with barriers of 63.1 and 87.9 kJ mol ,
respectively.
ried out in N O-purged aqueous propan-2-ol (0.1 m) con-
2
taining sodium hydroxide (Table 1, entry 9).
(
(
5)
6)
(
4)
In view of the many interesting aspects of sulfonium, se-
lenonium and telluronium ion reduction, we thought it
would be interesting to carry out a comparative study using
the one-electron reductants produced in aqueous solution
by radiolysis.
Results and Discussion
Apparently, the deprotonated 2-hydroxy-2-propyl radical
anion formed under these conditions (Eq. 7) is an efficient
The powerful one-electron reductants produced by ra- reducing agent for sulfonium salts (Ered = –2.1 V ) and
diolysis of water turned out to be excellent reducing agents propan-2-ol can act as a hydrogen atom donor for radicals
for water-soluble onium salts of sulfur, selenium and tel- produced to allow a chain reaction to be operative.
[3]
702
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2005, 701–705

Aqueous Phase One-Electron Reductions
FULL PAPER
Table 1. Aqueous phase reduction of onium salts[a] of sulfur, selenium and tellurium
Entry
Compd.
R
X
Reducing agent[b] Ph
2
X (%) PhXR (%)[c] Ph
2
X/PhXR ratio
Reduction yield
[c]
[d]
(%)
–
–
–
–
·
·
·
·
1
2
3
4
5
6
7
8
9
1
2
phenyl
phenyl
phenyl
methyl
methyl
methyl
methyl
ethyl
ethyl
ethyl
ethyl
ethyl
S
CO
CO
CO
CO
2
2
2
2
10
91
81
2
–
–
–
–
–
–
45
Se
Te
Se
Se
Te
Te
S
1800
1400
140
130
360
340
110
500
220
300
160
170
150
100
350
360
130
110
3
4
29
26
21
19
44
73
26
28
0
0
13
9
11
12
0
1:12
1:6.0
3.7:1
3.7:1
1:3.1
1:4.4
1.5:1
1:1
–
·
–
–
4
CO
2
/eaq
4
–
·
5
CO
2
77
71
14
17
38
29
44
45
67
43
84
85
24
27
–
·
5
2
CO /eaq
–
·
·
6
(CH
(CH
3
)
)
2
CO
CO
–
6
S
3
2
–
·
10
11
12
13
14
15
16
17
18
19
7
Se
Se
Te
Te
Se
Se
Te
Te
Te
Te
CO
2
–
·
–
7
CO
2
/eaq
–
·
8
CO
2
1:0
1:0
–
·
–
–
–
–
8
ethyl
CO
2
/eaq
–
·
9
cyclohexyl
cyclohexyl
cyclohexyl
cyclohexyl
benzyl
benzyl
CO
CO
2
5.2:1
5.1:1
7.8:1
7.8:1
2.4:1
2.4:1
–
·
9
2
/eaq
–
·
10
10
11
11
CO
CO
2
–
·
2
/eaq
–
·
[e]
CO
2
–
·
[e]
CO
2
/eaq
0
[
a] Except in the case of compounds 1–3 (chlorides), the counterion is tetrafluoroborate. [b] Carbon dioxide radical anion: γ-radiolysis
of the onium salt in an aqueous sodium formate solution (0.1 m) saturated with N O. Carbon dioxide radical anion/solvated electron: γ-
2
radiolysis of the onium salt in an aqueous sodium formate solution (0.1 m) saturated with Ar. Deprotonated 2-hydroxy-2-propyl radical:
In entry 8 the reduction was performed in an aqueous solution containing sodium formate (0.16 m) and propan-2-ol (0.1 m) with addition
of NaOH (1 mm). The solution was saturated with argon prior to irradiation. In entry 9 the reduction was performed in an aqueous
solution containing sodium hydroxide (1 mm) and propan-2-ol (0.1 m) saturated with N
amount of onium salt and determined by gas chromatography. [d] Yield of chalcogen-containing products based on the amount of
reducing radicals obtained from the γ-source (this is related to the irradiation time). [e] Ph X/bibenzyl ratios are given.
2
O prior to irradiation. [c] Yield based on the
2
hydrolysis for at least one hour in aqueous sodium formate
0.1 m).
(
(7)
For the alkyl diphenyl telluronium salts investigated, ef-
ficient chain reactions were also seen for the methyl and
As an example of a telluronium compound carrying
cyclohexyl derivatives (Table 1, entries 6/7 and 16/17). In three different substituents, ethyl methyl phenyl telluronium
the former case, chain transfer is likely to occur by hydrogen tetrafluoroborate (14) was reduced by the carbon dioxide
abstraction by methyl, whilst in the latter case reduction of radical anion or the mixture of carbon dioxide radical
the telluronium compound by the cyclohexyl radical seems anion/solvated electron. The product of phenyl expulsion,
more likely. However, no attempts were made to detect the volatile ethyl methyl telluride, could not be analysed
cyclohexene thus formed. On reduction, benzyl diphenyl with any certainty in this case. Ethyl radical expulsion was
telluronium tetrafluoroborate (11,Table 1) and the corre- more prevalent than methyl expulsion, and the methyl phe-
sponding sulfur and selenium compounds 12 and 13 ex- nyl telluride/ethyl phenyl telluride ratios in the two experi-
pelled the benzyl radical exclusively. For thermodynamic ments were found to be 3.8:1 and 3.4:1, respectively. The
reasons (low bond dissociation energy of the benzylic C– reduction yields based on the amount of reducing radical
H bond) this species is unlikely to abstract hydrogen from were close to 200 % in both cases.
formate. Accordingly, toluene was never detected and bi-
With some exceptions, the leaving group propensities ob-
benzyl was always formed as a product of dimerization. served during homogeneous phase reduction of diphenyl
Surprisingly, the Ph X/PhCH CH Ph ratio was much larger onium salts of sulfur, selenium and tellurium were as ex-
2
2
2
than expected in the reduction of sulfonium compound 12 pected (benzyl Ͼ secondary Ͼ primary Ͼ methyl Ͼ phe-
and selenonium compound 13,and the yield based on re- nyl). In agreement with earlier findings during chemical re-
[
4]
ducing equivalents was larger than expected for the selenon- duction of diphenyl alkyl sulfonium ions, greater than ex-
ium compound. These apparently conflicting results are due pected loss of the phenyl group was observed. This was es-
to competing hydrolysis of these onium salts, thus generat- pecially true for the reduction of the diphenyl methyl se-
ing diaryl chalcogenide by a non-radical pathway, under the lenonium ion. The expulsion of a larger phenyl radical
experimental conditions. In contrast to compounds 12 and would relieve strain in the transient species involved in the
13, the other onium salts investigated were stable towards reduction reaction. On the other hand, diphenyl ethyl tellu-
Eur. J. Org. Chem. 2005, 701–705
www.eurjoc.org © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 703

P. Eriksson, L. Engman, J. Lind, G. Merényi
FULL PAPER
ronium ion showed only loss of ethyl radical on reduction. The following materials were prepared in analogy with published
procedures (alkyl aryl selenides[ and tellurides ) and were used
38]
[39]
The principal reducing agents present during reduction
of onium salts are the carbon dioxide radical anion or an
equal amount of this species and the solvated electron.
Were these reactions to proceed via intermediates, one
would expect the product distributions to be independent
of the reduction conditions (Eq. 3, path B). On the other
hand, if electron transfer were concerted with breaking of
the chalcogen–carbon bond, the product distribution would
depend on the reducing agent employed (Eq. 3, path A).
From the examples presented in Table 1, it would seem that
in the case of telluronium salts the product distribution is
as reference compounds in the GC analyses: cyclohexyl phenyl sel-
enide,[ cyclohexyl phenyl telluride, ethyl phenyl sulfide, ethyl
40]
[41]
[42]
[43]
[44]
phenyl selenide,
ethyl phenyl telluride,
methyl phenyl selen-
ide[ and methyl phenyl telluride.[44]
45]
Preparation of Onium Tetrafluoroborate Salts. Typical Procedure:
Diphenyl Methyl Selenonium Tetrafluoroborate (4): AgBF (0.86 g,
8 %, 4.30 mmol) was slowly added to a mixture of diphenyl selen-
ide (1.00 g, 4.30 mmol) and methyl iodide (6.10 g, 43 mmol) under
at ambient temperature. After the mixture had been stirred for
7 h in the dark, CH Cl (50 mL) was added and the reaction mix-
ture was filtered. The filtrate was dried (CaCl ) and concentrated
4
9
N
2
1
2
2
2
more or less independent of the reducing agent, whereas to afford an oil, which crystallized upon treatment with ether. After
significant variations are seen for some selenonium salts recrystallization (ether/CH Cl ), the title compound (1.18 g, 87 %)
2
2
1
(
entries 4/5 and 10/11). This could indicate the intermediacy was obtained as white crystals, m.p. 119–121 °C. H NMR δ = 7.59
(
m, 4 H), 7.68 (m, 6 H), 3.40 (s, 3 H). C13
6.61; H, 3.91. Found: C, 46.79; H, 3.82.
4
H13BF Se (335.0): C,
of telluranyl radicals in the one-electron reduction of tellu-
ronium salts. However, when aqueous solutions of tri-
4
phenyltelluronium chloride (3) or triphenylsulfonium chlo- The following compounds were prepared analogously from the cor-
ride (1) containing tert-butyl alcohol as a scavenger of hy- responding chalcogenides and the appropriate iodo compounds.
droxyl radicals were pulse-irradiated in air, a signal at
Diphenyl Ethyl Selenonium Tetrafluoroborate (7): Yield 64 %, m.p.
4
90 nm was detected in both experiments. The new peak
1
66–66.5 °C. H NMR δ = 7.59–7.74 (several peaks, 10 H), 4.06 (q,
–
5
was formed within 5 × 10 s and then disappeared in a J = 7.4 Hz, 2 H), 1.53 (t, J = 7.3 Hz, 3 H). C H BF Se (349.0):
1
4
15
4
9
–1 –1
second-order reaction with a rate of 10 m s . These re- C, 48.18; H, 4.33. Found: C, 48.01; H, 4.24.
sults indicate that a phenyl radical is cleaved off from the
onium salts to form a phenylperoxyl radical almost immedi-
ately after reduction (aryl peroxyl radicals are formed in the 2 H), 1.50 (t, J = 7.5 Hz, 3 H). C H BF Te (397.7): C, 42.28; H,
Diphenyl Ethyl Telluronium Tetrafluoroborate(8): Yield 45 %, oil.
H NMR δ = 7.51–7.65 (several peaks, 10 H), 3.58 (q, J = 7.6 Hz,
1
1
4
15
4
reaction between aryl radicals and molecular oxygen and 3.80. Found: C, 41.48; H, 3.39.
they absorb at 490–600 nm[ ) and then undergoes recom-
28]
Cyclohexyl Diphenyl Selenonium Tetrafluoroborate (9): Yield 51 %,
m.p. 151–153 °C. H NMR δ = 7.85 (m, 4 H), 7.67 (m, 6 H), 4.86
bination. Future work, employing laser flash photolysis
techniques, would hopefully prove useful in the detection of (m, 1 H), 2.08 (m, 2 H), 1.21–1.51 (several peaks, 8 H).
1
short-lived (Ͻ 1 µs) telluranyl radicals.
18 4
C H21BF Se (403.1): C, 53.63; H, 5.25. Found: C, 53.85; H, 5.10.
A signal observed at 280 nm in the reduction of tri-
phenyltelluronium chloride under oxygen-free conditions is
Cyclohexyl Diphenyl Telluronium Tetrafluoroborate(10): Yield 21 %,
m.p. 146–147 °C. H NMR δ = 7.56–7.77 (several peaks, 10 H),
1
likely to be due to diphenyl telluride. In the presence of 4.28 (m, 1 H), 2.17 (m, 2 H), 1.24–1.90 (several peaks, 8 H).
sodium formate, this signal increased by a factor of 15. C H BF Te (451.8): C, 47.86; H, 4.69. Found: C, 47.72; H, 4.58.
1
8
21
4
From the large absorbance it is concluded that a chain reac-
tion also occurs on the pulse radiolysis scale (i.e. tenths of
a µs). The chain length increased with increasing concentra- 7.27 (several peaks, 5 H), 5.24 (s, 2 H). C H BF Se (411.1): C,
Benzyl Diphenyl Selenonium Tetrafluoroborate(13): Yield 26 %, m.p.
1
122–123 °C. H NMR δ = 7.53–7.62 (several peaks, 10 H),7.19–
1
9
17
4
tion of the telluronium salt.
55.51; H, 4.17. Found: C, 55.55; H, 4.12.
In conclusion, the one-electron reductants produced in
aqueous solution by radiolysis have been shown to reduce
sulfonium, selenonium and telluronium salts conveniently
GC analyses were performed on a Varian 3400 GC fitted with a
capillary Rescom SE 54 column and a flame ionization detector.
Calibration curves were made for benzene, methyl phenyl telluride,
and cleanly with expulsion of the most stable radical spe- diphenyl sulfide, diphenyl selenide and diphenyl telluride with pen-
cies. Chain reactions were often observed, with the radical tadecane as internal standard. For all other compounds, a response
species/formate serving as the chain-transfer agents.
factor vs. the corresponding diphenyl chalcogenides was deter-
mined and used for calculation of the product ratios.
Pulse radiolysis was performed at room temperature (22–23 °C)
with the use of doses of 2–15 Gy per pulse, corresponding to 1.2–
Experimental Section
–
6
–3
[46]
9
× 10 mol dm of radicals. The 7 MeV microtron accelerator
Diphenyl diselenide, diphenyl disulfide and diphenyl sulfide are
commercially available. Diphenyl selenide was obtained from the
[47]
and the computerized optical detection system
have been de-
scribed elsewhere. The cell used had an optical path length of 1 cm.
Dosimetry was performed by use of an aerated KSCN solution
[
29]
Eastman Kodak company. Diphenyl ditelluride,
diphenyl tellu-
triphenylselenonium chlo-
and triphenyltelluronium chloride[33] were prepared by lit-
[
30]
[31]
ride,
ride
triphenylsulfonium chloride,
–
2
–3
[48]
–4
2 –1
(
10 mol dm ) taking Gε = 2.23 × 10 m J at 500 nm. γ-Ra-
[
32]
6
0
–1
diolysis was carried out in a Co γ-source at a dose of 0.27 Gy s
corresponding to 0.6 × 10 mol e + OH min dm ) as deter-
mined by the Fricke dosimeter. Irradiation times ranged from 6
to 60 min.
[
34]
erature procedures. Diphenyl ethyl sulfonium tetrafluoroborate,
diphenyl benzyl sulfonium tetrafluoroborate
–
5
–
–1
–3
(
[
34]
and diphenyl
[48]
[35]
benzyl telluronium tetrafluoroborate were prepared by the pro-
[
34]
cedure described by Franzen. Diphenyl methyl telluronium tetra-
[
36]
fluoroborate and ethyl methyl phenyl telluronium tetrafluorobo-
Typical Procedure: Triphenylselenonium chloride (2; 0.0239 g,
[
37]
–5
rate were prepared by literature methods.
1.64 × 10 mol) was dissolved in Millipore-deionized water
704
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2005, 701–705

Aqueous Phase One-Electron Reductions
FULL PAPER
(
50 mL) containing sodium formate (0.1 m) in a reaction flask pos-
sessing a gas inlet through a glass frit and a gas outlet. The solution
was purged with N O for 5 min, stoppered and irradiated in the γ-
[22] J. A. Franz, D. H. Roberts, K. F. Ferris, J. Org. Chem. 1987,
52, 2256–2262.
[
[
[
23] K. F. Ferris, J. A. Franz, C. Sosa, R. J. Bartlett, J. Org. Chem.
992, 57, 777–778.
24] J. E. Lyons, C. H. Schiesser, J. Chem. Soc., Perkin Trans. 2
992, 1655.
25] L. Engman, M. J. Laws, J. Malmström, C. H. Schiesser, L. M.
Zugaro, J. Org. Chem. 1999, 64, 6764–6770 and refs. cited
therein.
2
1
source for 12 min. The cloudy aqueous solution was then extracted
with pentane (3 × 15 mL) and the organic phase was analysed by
gas chromatography.
1
Acknowledgments
[
[
[
[
26] D. H. R. Barton, N. Ozbalik, J. C. Sarma, Tetrahedron Lett.
1
988, 29, 6581–6584.
27] B. A. Smart, C. H. Schiesser, J. Chem. Soc., Perkin Trans. 2
994, 2269–2270.
Financial support by the Swedish Research Council is gratefully
acknowledged.
1
28] X. Fang, R. Mertens, C. von Sonntag, J. Chem. Soc., Perkin
Trans. 2 1995, 1033–1036.
[
[
[
[
[
[
[
[
1] See the following special issues: Pure Appl. Chem. 2000, 72,
29] W. S. Haller, K. J. Irgolic, J. Organomet. Chem. 1972, 38, 97–
1207–1403; Acc. Chem. Res. 2002, 35, 685–816.
103.
2] J. Clark, D. Macquarrie (Eds.), Handbook of Green Chemistry
and Technology, Blackwell Science Ltd.: Oxford, UK, 2002.
3] H. A. Schwarz, R. W. Dodson, J. Phys. Chem. 1989, 93, 409–
14.
4] P. Beak, T. A. Sullivan, J. Am. Chem. Soc. 1982, 104, 4450–
457.
[30] I. D. Sadekov, A. Ya. Bushkov, V. I. Minkin, Zh. Obshch. Khim.
1973, 43, 815–816.
[31] W. A. Bonner, J. Am. Chem. Soc. 1952, 74, 5078–5082.
[32] H. Rheinboldt, in: Methoden der Organischen Chemie,
Houben–Weyl, Vol. IX (Ed.: E. Müller), Georg Thieme Verlag,
Stuttgart, 1955, p. 1039.
[33] K. J. Irgolic, in: Methods of Organic Chemistry, Houben–Weyl,
Vol. E12b (Ed.: D. Klamann), Georg Thieme Verlag, Stuttgart,
1990, p. 678.
4
4
5] B. Speiser, Angew. Chem. Int. Ed. Engl. 1996, 35, 2471–2474
and refs. cited therein.
6] R. A. Marcus, Angew. Chem. Int. Ed. Engl. 1993, 32, 1111–
1121 and refs. cited therein.
7] T. Kataoka, T. Iwama, H. Shimizu, M. Hori, Phosphorus, Sul-
fur Silicon 1992, 67, 169–172.
8] T. Kataoka, Y. Nakamura, H. Matsumoto, T. Isama, H.
Kondo, H. Shimizu, O. Muraoka, G. Tanabe, J. Chem. Soc.,
Perkin Trans. 1 1997, 309–316.
[34] V. Franzen, H-J. Schmidt, C. Mertz, Chem. Ber. 1961, 94, 2942–
2950.
[35] Y. Matano, H. Suzuki, N. Azuma, Organometallics 1996, 15,
3760–3765.
[36] F. H. Musa, W. R. McWhinnie, J. Organomet. Chem. 1978, 159,
[
[
[
9] F. D. Saeva, B. P. Morgan, J. Am. Chem. Soc. 1984, 106, 4121–
37–45.
4125.
[37] T. Shimizu, T. Urakubo, N. Kamigata, J. Org. Chem. 1996, 61,
8032–8038.
10] A. Stasko, P. Rapta, V. Brezová, O. Nuyken, R. Vogel, Tetrahe-
dron 1993, 49, 10 917–10 924.
11] C. P. Andrieux, M. Robert, F. D. Saeva, J.-M. Savéant, J. Am.
Chem. Soc. 1994, 116, 7864–7871.
[38] H. J. Reich, S. K. Shah, J. Org. Chem. 1977, 42, 1773–1776.
[39] D. L. J. Clive, G. J. Chittattu, V. Farina, W. A. Kiel, S. M.
Menchen, C. G. Russell, A. Singh, C. K. Wong, N. J. Curtis, J.
Am. Chem. Soc. 1980, 102, 4438–4447.
[
[
[
12] A. Ghanimi, J. Simonet, New. J. Chem. 1997, 21, 257–265.
13] F. D. Saeva, Tetrahedron 1986, 42, 6123–6129.
14] J. L. Dektar, N. P. Hacker, J. Am. Chem. Soc. 1990, 112, 6004–
[40] H. Duddeck, P. Wagner, A. Biallaß, Magn. Reson. Chem. 1991,
29, 248–259.
6
015.
15] F. D. Saeva, D. T. Breslin, H. R. Luss, J. Am. Chem. Soc. 1991,
13, 5333–5337.
16] X. Wang, F. D. Saeva, J. A. Kampmeier, J. Am. Chem. Soc.
999, 121, 4364–4368.
17] L. Pause, M. Robert, J-M. Savéant, J. Am. Chem. Soc. 2001,
23, 4886–4895.
18] M. Bonifacic, E. Anklam, J. Chem. Soc., Perkin Trans. 2 1991,
43–248.
[41] N. Petragnani, L. Torres, K. J. Wynne, J. Organomet. Chem.
1975, 92, 185–189.
[
[
[
[
[
1
13
1
[42] H NMR and C NMR spectroscopic data were in accordance
1
3
1
with the literature: The Aldrich Library of C and H FT NMR
Spectra (Eds.: C. J. Pouchert, J. Behnke), Aldrich Chemical,
Milwaukee, 1992, 1(2), 432B.
1
1
[43] H. Duddeck, P. Wagner, B. Rys, Magn. Reson. Chem. 1993, 31,
736–742.
2
[44] K. J. Irgolic, P. J. Busse, R. A. Grigsby, J. Organomet. Chem.
1975, 88, 175–180.
[45] L. Engman, J. Persson, C. M. Andersson, M. Berglund, J.
Chem. Soc., Perkin Trans. 2 1992, 1309–1313.
[46] S. Rosander, Thesis, The Royal Institute of Technology, Stock-
holm, Sweden, 1974, TRITAEEP-74–16, p. 28.
[47] T. E. Eriksen, J. Lind, T. Reitberger, Chem. Scr. 1976, 10, 5–7.
[48] E. M. Fielden, in: The Study of Fast Processes and Transient
Species by Electron Pulse Radiolysis (Eds.: J. H. Baxendale, F.
Busi), Reidel, Dordrecht, Holland, 1982, NATO Advanced
Study Institutes Series, pp. 49–62.
19] Simonet demonstrated the first reversible one-electron re-
duction of sulfonium salts at room temperature at normal
[
12]
sweep rates. However, since a strongly electron-withdrawing
substituent (i.e. a nitrophenyl group) was required, the reduced
species is likely to be a nitrophenyl radical anion sulfonium salt
rather than a sulfuranyl radical.
[
20] M. Hori, T. Kataoka, H. Shimizu, K. Tsutsumi, Tetrahedron
Lett. 1989, 30, 981–984.
[21] T. Kataoka, K. Tsutsumi, K. Kano, K. Mori, M. Miyake, M.
Yokota, H. Shimizu, M. Hori, J. Chem. Soc., Perkin Trans. 1
1990, 3017–3025.
Received: August 26, 2004
Eur. J. Org. Chem. 2005, 701–705
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
705