Photoinduced nucleophilic substitution of aryl halides with potassium thioacetate - A one-pot approach to aryl methyl and diaryl sulfides

Article abstract of DOI:10.1002/ejoc.200500955

Aryl methyl sulfides and diaryl sulfides were prepared by photoinduced reactions of potassium thioacetate with aryl halides under entrainment conditions. Without isolation, the arene thiolates obtained by the aromatic substitution were quenched with methyl iodide to afford the aryl methyl sulfides in 26-59% yields in a "one-pot" procedure together with the diaryl sulfides in variable yields (3-31 %). By optimization of the reaction conditions it was possible to improve the formation of the Ar₂S, going from moderate to good yields (64-83%). Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejoc.200500955

FULL PAPER
DOI: 10.1002/ejoc.200500955
Photoinduced Nucleophilic Substitution of Aryl Halides with Potassium
Thioacetate – A One-Pot Approach to Aryl Methyl and Diaryl Sulfides
[a]
[a]
[a]
Luciana C. Schmidt, Valentina Rey, and Alicia B. Peñéñory*
Keywords: Electron transfer / Nucleophilic substitution / Sulfides / Radical anions / Radicals
Aryl methyl sulfides and diaryl sulfides were prepared by
photoinduced reactions of potassium thioacetate with aryl
halides under entrainment conditions. Without isolation, the
arene thiolates obtained by the aromatic substitution were
quenched with methyl iodide to afford the aryl methyl sul-
fides in 26–59% yields in a “one-pot” procedure together
with the diaryl sulfides in variable yields (3–31%). By optimi-
zation of the reaction conditions it was possible to improve
the formation of the Ar
yields (64–83%).
2
S, going from moderate to good
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
with polycyclic or heterocyclic halides.[11] Thioacetate and
thiobenzoate anions react with arenediazonium tetrafluo-
roborates to provide the corresponding aryl thio esters in
moderate yields, and hydrolysis to the arene thiolates and
further treatment with electrophiles provides access to other
Introduction
Aryl sulfides are widely used as intermediates in organic
[
1]
synthesis, and numerous synthetic methods for their prep-
aration have been developed. Polar aromatic nucleophilic
–
–
substitutions by HS or RS anions required strong ring
[
12]
aromatic sulfur derivatives [Equation (1)].
The reactions
[
2]
activation by electron-withdrawing groups (EWGs). For
non-activated aryl halides the use of transition metal cataly-
sis, high temperatures, and long reaction times are neces-
with thioacetate and thiobenzoate anions were attributed to
a radical nucleophilic substitution mechanism, which im-
plies the handling of the usually unstable diazonium salts,
and the yields of the sulfur compounds were modest.
[
3,4]
sary.
Sulfides have also been synthesized by cross-coup-
ling reactions of aryl boronic acid or aryl triflates with thi-
ols.[ Alternatively, the synthesis of aryl sulfides is possible
5]
[6]
by reduction of sulfoxides and sulfones, or by treatment
of organolithium or Grignard compounds with elemental
[
7]
sulfur, while a one-pot synthesis of alkyl aryl sulfides
through reactions between alkyl halides and lithium arene
[
8]
thiolates prepared in situ has also been recently reported.
Sulfur-centered nucleophiles such as thiolate anions have
been shown to react with non-activated aryl halides under
photostimulation conditions to yield new C–S bonds by
radical nucleophilic substitution (SRN1 mechanism) involv-
We have recently reported on the reactivity of the thio-
urea anion in photoinduced aromatic radical nucleophilic
substitution as a “one-pot” method for the synthesis of aryl
thiols, alkyl aryl sulfides, symmetrical or unsymmetrical di-
aryl sulfides, and diaryl disulfides in moderate to good
[9]
ing electron transfer pathways.
While arene thiolate
–
anions (ArS ) afford good yields of substitution products,
–
alkane thiolate anions (RS ) yield mixtures of products
arising from fragmentation of the radical anion intermedi-
ates and straightforward substitution (scrambling prod-
ucts), making these reactions disadvantageous for synthetic
[
13]
yields.
Furthermore, through the use of hydrogen ab-
straction from DMSO as competitive reaction, the absolute
2–
–
rate constants for the addition of S , SCNH(NH2),
and benzenethiolate anions to 1-naphthyl radicals were
[
10]
purpose. However, the expected straightforward substitu-
tion is mainly achieved with compounds bearing EWGs or
9
–1 –1
9
–1 –1
determined to be 0.5·10  s , 1.0·10  s , and
9
–1 –1
[14]
5.1·10  s respectively.
These results encouraged us
to explore further the reactivity and the potential of related
sulfur anions for the synthesis of aromatic sulfur com-
Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad pounds. Here we report the “one-pot” synthesis of aryl
[
a] INFIQC, Departamento de Química Orgánica, Facultad de
Universitaria,
methyl and symmetrical diaryl sulfides by photoinduced re-
actions between thioacetate anion (1) and haloarenes in the
presence of appropriate initiators in DMSO.
5
000 Córdoba, Argentina
Fax: +54-351-4333030
E-mail: penenory@mail.fcq.unc.edu.ar
2210
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 2210–2214

One-Pot Approach to Aryl Methyl and Diaryl Sulfides
FULL PAPER
Results and Discussion
radical trap such as di-tert-butylnitroxide (DTBN) or a
good electron acceptor such as p-dinitrobenzene (p-DNB)
Table 1 summarizes the results obtained in the photoin-
duced reactions between anion 1 and 1-bromonaphthalene
(Table 1, Entries 6–8). The reaction between anion 1 and 2
under entrainment conditions did not occur in the dark.
The yield of biphenyl was considerably increased when the
photochemical reaction of 4-bromobiphenyl was conducted
in liquid ammonia as solvent (Table 1, Entry 9).
(2) in the presence of tert-butoxide anion (3) or the enolate
[
9]
anion of cyclohexenone (4) as entrainment reagents and
after quenching with methyl iodide.
The lack of reaction between anion 1 and 2 alone under
Table 1. Photoinduced reactions between anion 1 with 1-bromo- irradiation conditions, the entrainment reaction in the pres-
naphthalene (2) and 4-bromobiphenyl (9).[
a]
ence of anions 3 or 4 under light catalysis conditions for
both aryl halides 2 and 9, the strong inhibition of the latter
reaction between anion 1 and bromide 9 by DTBN or p-
DNB, and the formation of 8a and naphthalene or biphenyl
as reduction products are all evidence of a radical chain
mechanism for these substitution reactions, and can be in-
terpreted as follows (Scheme 1). Thioacetate anions are
poor electron donors and they are unable to transfer one
electron to the aryl halide to initiate the reaction under irra-
diation conditions. On the other hand, photoinduced elec-
tron transfer (PET) from anions 3 or 4 to the aryl halide
Products yield [%][b]
Entry ArX Ratio
ArX/1
Convn. MB
2
ArH ArSMe Ar S
1[c]
2
9
1:10
1:10
1:10
1:5
2:1
1:5
1:5
1:5
1:5
–
–
–
6
5
6
–
–
2
85
91
85
53
100
44
36
100
71
59
68
93
90
52
64
91
40
35
40
–
38
11
6
14
14
12
32
31
–
[
d]
3
4
5
6
7
8
9
[
[
[
[
[
e][f]
f]
[g]
8
[
16]
21
12
10
41
f][h]
f][i]
j]
7
23
27
–
[
a] ArX: 0.05 , tBuO (3) equimolar with the anion 1, after 3 h of affords the corresponding radical anion [see Equation (3) in
irradiation under nitrogen atmosphere; the reaction was quenched
with MeI. [b] Determined by GC by the internal standard method,
error Ͻ5%. Conversion (convn.) was determined by quantification
of the unreacted substrate. Mass balance (MB). [c] In the absence
Scheme 1]. Fragmentation of this radical anion yields the
aryl radical, which is not reactive towards anions 3 or 4,
and can only couple with anion 1 to generate the radical
·
–
of the entrainment reagents 3 or 4. [d] In the presence of 4. [e] ArX: anion 8 [Equation (4) in Scheme 1]. Two competitive reac-
.25 . [f] Irradiation time1 h. [g] Together with 9% of 1-naphthyl tions are possible for the latter: fragmentation of 8· to af-
–
0
thioacetate (8a). [h] In the presence of 0.01  of p-dinitrobenzene.
ford the thiolate anion 10 and the radical 11 [Equation (5)
in Scheme 1], or ET to the aryl halide to afford product 8
and the radical anion of the aryl halide [Equation (6) in
Scheme 1]. The formation of 8a when the reaction is per-
formed with 2 in excess confirmed this step and the partici-
pation of anion 1 as the nucleophilic species responsible for
the introduction of the sulfur atom.
[i] In the presence of 0.01  DTBN. [j] Reaction performed in liquid
ammonia, with ArX: 0.02 .
There is no reaction between anion 1 and 2 alone (2/1
ratio of 1:10) under irradiation. When the photoinduced
reaction (λmax = 365 nm) was performed in the presence of
[15]
the anions 3 or 4 (good electron donors), it gave 1-(meth-
ylthio)naphthalene (5a) (40%), di(1-naphthyl) sulfide (6a)
(14%), and naphthalene (7a) (6%) [Equation (2)]. Similar
results were obtained when the reaction was performed with
only a fivefold excess of anion 1 relative to 2 (Table 1, En-
tries 1–4). Because of the low recovery of naphthalene after
three hours of irradiation, the mass balances in these reac-
tions were around 70%.
Finally, with a 2/1 ratio of 2:1 and an increased concen-
tration of 2 (0.25 ), it was possible to obtain 1-naphthyl
thioacetate (8a) as intermediate product together with sul-
fide 6a (Table 1, Entry 5). To study the reaction mechanism
further, we explored the reactivity of 4-bromobiphenyl (9)
with anion 1 in the presence of anion 3 under irradiation
conditions. After 1 h conversion was complete, the reaction
afforded a 38% yield of the 4-MeS-substituted product 5b,
a 31% yield of the diaryl sulfide 6b, and a 21% yield of
Scheme 1.
This competition is not observed when the aryl diazo-
biphenyl (7b) [Equation (2)] This photoinduced reaction nium salts are used instead of ArX, because they are easily
was strongly inhibited by the addition of a very efficient reduced. In these reactions, ET from 8– to the aryl diazo-
·
Eur. J. Org. Chem. 2006, 2210–2214
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2211

L. C. Schmidt, V. Rey, A. B. Peñéñory
FULL PAPER
nium salts provides the aryl thioacetate as final product. dides (chlorides are not reactive) and substrates bearing
Our results therefore clearly reveal different behavior for both electron-donating and electron-withdrawing groups. In
thioacetate anion with aryl halides in photoinduced reac- these cases, the arene thiolate anions obtained by the SRN
tions under entrainment conditions, compared to thermal reaction were quenched with MeI to afford the ArSMe de-
1
reactions with the diazonium salts.[
12]
rivatives in moderate to good yields (26–59%) together with
The arene thiolate anion 10, formed in the reaction me- the Ar S in variable yields (3–31%).
2
dia, is able to add to the aryl radical to yield the disubstitu-
tion product 6 after ET to the substrate, following a new Table 2. Photoinduced reactions between anion 1 and aryl ha-
cycle of the SRN1 reaction [Equation (7) in Scheme 1]. Fi- lides.[a]
nally, by hydrogen atom abstraction from the solvent, the
aryl radical gives the corresponding aromatic hydrocarbon
Product yields [%][b]
Entry ArX
Convn.
ArH
ArSMe
Ar2S
(
7) as reduction product [Equation (8) in Scheme 1]. After
1
2
3
4
5
6
7
8
9
1
1
1
1-Br-naphthalene
2-Br-naphthalene
PhI
85
6
5
40
43
56
46
59
41
50
37
41
51 (49)
42 (41)
26
38 (38)[f]
12
27
3
16
–
6
–
29
12
irradiation, the reaction mixture was quenched with methyl
iodide to afford the 1-(methylthio) aryl derivatives 5 [Equa-
tion (9) in Scheme 1]. As has been previously proposed for
the PET reactions with thiourea anion,[ two different
pathways to account for the chain reaction are possible.
Coupling of radical 11 with anion 1 present in excess would
form a new radical anion capable of continuing with the
chain propagation. Another possibility is deprotonation of
[c]
100
100
100
100
100
100
100
100
100
100
100
100
98
[
[
[
d]
d]
d]
4-IC
2-IC
4-IC
2-IC
6
6
6
6
H
4
H
4
H
4
H
4
Me
Me
OMe
OMe
13]
28
17
6
–
–
4-BrC H SMe
6
4
[
c]
4-BrC
4-IC
4-PhCOC
2-MeCOC
4-Br-C H -C H
6
H
4
CN
[
f]
f]
0
1
2
6
H
4
NO
2
–
[
[d]
6
H
4
Br
Br
–
–
–
·
1
1 to afford the radical anion [H C=C=O] , which could
[c]
2
6
H
4
17
31
continue the SRN1 cycle by ET to the aryl halide. In any
case, the products after ET would probably be water-soluble
and hydrolyze during workup.
13[e]
14
21 (20)[f]
6
4
6
5
[d]
9-Br-anthracene
9-Br-phenanthrene 93
12
8
50
46
[d]
1
5
–
Anion 1 thus clearly shows a different reactivity from [a] ArX: 0.05 , 1: 0.25 , tBuO (3) equimolar to the anion 1; the
reaction was quenched with MeI after irradiation for 3 h under
thiourea anion. While the anion 1 is not reactive as electron
donor under photostimulation conditions[
16]
nitrogen in DMSO. [b] Determined by GC by the internal standard
method, error Ͻ5%. The conversion (convn.) was determined by
quantification of the unreacted substrate. [c] In the presence of
and needs an
additional source of electrons to initiate the reaction, but is
reactive in coupling with the aryl radicals, the thiourea enolate anion 4 as entrainment reagent. [d] Not quantified. [e] Irra-
anion is reactive in both pathways.[ This is consistent with diation time 1 h. [f] Isolated yield.
13]
[17]
the pK value of thiourea in DMSO (21.1).
a
Finally, the possibility of a coupling reaction between
In variations of the reaction conditions, ArX/nucleophile
·
·
[12]
SCOMe and Ar to afford Ar–SCOMe,
can be disre- ratio and concentration were adjusted in order to improve
garded because of the followings factors: a) there is no the yields of either ArSMe or Ar S (Table 3). Because of
2
·
source of SCOMe radical under the reaction conditions, as the higher reactivity of the arene thiolate anions formed in
thioacetate anion is not able to transfer one electron to the these reactions in comparison with the thioacetate anion,
substrate to produce the aryl halide radical anion and the the yields of the ArSMe increased moderately with changes
·
SCOMe radical, b) the fact that 1-naphthyl thioacetate (8a) in the reaction conditions. Thus, with a 2/1 ratio of 1:10
is only observed when the reaction is performed with an and a 0.025  concentration of 2, the yield of 1-(methylthio)
excess of 1-bromonaphthalene clearly supports competition naphthalene (5a) increased up to 55% after 3 h, and the
between ET and fragmentation steps as stated in Equa- mass balance improved. (Table 3, Entry 1). Good yields of
tion (5) and (6) (Scheme 1), and c) we were unable to trap the ArSMe were obtained when the intermediate thiolate
the Ar–SCOMe through intramolecular reaction with anions were sterically hindered (Table 3, Entries 2 and 3).
amino or hydroxy groups ortho to the leaving group, the
Conversely, it was also possible to improve the yields of
only products observed in the photoinduced reaction be- Ar S preferentially by optimization of the reaction condi-
2
tween 2-iodoaniline and anion 1, followed by addition of tions. With a 2/1 ratio of 1:1, the photoinduced reaction
MeI, being ArSMe with the amino group mono- and di- between 2 (0.125 ) and anion 1 gave a 42% yield of bis (1-
methylated without any traces of the benzenethiazole deriv- naphthyl) sulfide (6a) as the major product after 3 h. This
ative.
yield could be improved to 83% by increasing the concen-
We further explored the reactivity of anion 1 with a vari- tration to 0.25  with a 2/1 ratio of 1:0.6 (Table 3, Entries 4
ety of aryl halides in photoinduced reactions, and Table 2 and 5). Thus, by use of appropriate reaction conditions it
condenses the results obtained. In general, the thioacetate was possible to obtain the symmetrical diaryl sulfides in
anions are less reactive than the arene thiolate anions gener- yields of up to 83% in a one-pot procedure. Under condi-
ated in the reaction media, and these reactions yield a mix- tions optimized to afford the symmetrical diaryl sulfide
ture of both the mono- and disubstitution products preferentially, the photoinduced reaction between 2 and
(
ArSMe and Ar S respectively) after quenching with MeI. thiourea anion afforded only a 38% yield of the bis (1-
2
[
13]
From Table 2 it is possible to conclude that this methodol- naphthyl) sulfide. This is valuable for the use of thioacet-
ogy is appropriate for non-activated aryl bromides or io- ate anion instead of thiourea anion in the synthesis of sym-
2212
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Eur. J. Org. Chem. 2006, 2210–2214

One-Pot Approach to Aryl Methyl and Diaryl Sulfides
FULL PAPER
plied Photophysics Limited). 1H and 13C NMR spectra were re-
corded at 200 and 50 MHz, respectively, on a Bruker AC 200 spec-
Table 3. One-pot syntheses of aryl methyl sulfides or diaryl sul-
fides.
[
a]
trometer, and all spectra are reported in δ (ppm) relative to Me
4
Si,
Entry ArX
Ratio
ArX/1
Product yields [%][b]
with CDCl as solvent. Gas chromatographic analyses were per-
3
ArH
ArSMe
2
Ar S
formed on a Hewlett–Packard 6890 A instrument with a flame-
ionization detector, either on a HP-5 30 m capillary column of
1[c]
2
1-Br-naphthalene 1:10
2-IC
2-IC
1-Br-naphthalene 1:1
1-Br-naphthalene 1:0.6
PhI
9
7
55
70
79
10
3
22
9
9
42
83
64
33
46
6
6
H
H
4
OMe
Me
1:10
1:10
0
.32 mm×0.25 µm film thickness or on a HP1 5 m×0.53×2.65 µm
film thickness column. GC/MS analyses were carried out on a
Shimadzu GC-MS QP 5050 spectrometer, with
25 m×0.2 mm×0.33 µm HP-5 column.
[
d]
3
4
[
e]
4
5
6
7
8
10
8
a
[d]
1:0.6
1:0.6
1:0.6
5
4-BrC
4-Br-C
6
H
4
CN
-C
6
17
12
5
Materials: tBuOK, potassium thioacetate, cyclohexenone, the aryl
halides, naphthalene, DTBN, thioanisole, diphenyl sulfide, 1-meth-
oxy-4-(methylthio)benzene, 4-(methylthio)nitrobenzene, and 4-
6
H
4
6
H
5
–
[
a] ArX: 0.25 , tBuO (3) equimolar to the anion 1, the reaction
was quenched with MeI after irradiation for 3 h under nitrogen in
DMSO. The conversion was complete in all cases. [b] Determined
by GC by the internal standard method, error Ͻ5%. [c] ArX:
(
methylthio)benzonitrile were all high purity commercial samples,
used without further purification. DMSO was purified by standard
procedures and stored over molecular sieves (4 Å). The cyclohex-
enone enolate anion (4) was generated in situ by acid-base depro-
tonation with tBuOK. All the reaction products were isolated from
the reaction mixture by radial chromatography and characterized
0.025 . [d] Not quantified. [e] ArX: 0.125 .
metrical diaryl sulfides. Table 3 condenses the results ob-
tained.
1
13
by H and C NMR and mass spectrometry. These sulfides are
This methodology has some advantages over the pre- known and had physical properties identical to those reported in
viously reported reactions between thioacetate anions and the literature.
aryl diazonium salts: a) hydrolysis of the aryl thioacetate to
yield the arenethiolates, desirable for further reactions, is
not necessary, b) aryl halides are commercially available
Representative Experimental Procedure: The reactions were carried
out in a 10 mL three-necked Schlenk tube, fitted with nitrogen gas
inlet and magnetic stirrer. The tube was dried under vacuum, filled
and easier to handle than the usually unstable diazonium with nitrogen, and then loaded with dried DMSO (10 mL). tBuOK
salts, and c) the production of arene thiolate anions in the (280.5 mg, 2.5 mmol), potassium thioacetate (285.5 mg, 2.5 mmol),
reaction media, which can further react with the aryl radi- and the aryl halide (0.5 mmol), were added to the degassed solvent
under nitrogen. After 3 h of irradiation with a medium-pressure
cals, allows the symmetrical diaryl sulfides to be obtained
Hg lamp with maximum emission at 365 nm, the reaction was
quenched by addition of methyl iodide (342 µL, 5.5 mmol) and
water (30 mL), and the mixture was then extracted with dichloro-
methane (3×20 mL). The organic extract was washed twice with
in high yields in one-pot procedures. With aryl halides con-
taining EWGs, the arene thiolate anions obtained are less
reactive that the thioacetate anion in the coupling reactions
with the radical, and as a result of such competition the
4
water and dried with anhydrous MgSO , and the products were
diaryl sulfide is obtained in low yield. In spite of this limita-
tion, the possibility to synthesize, for example, bis[4-(cyano)
phenyl] sulfide in a one-pot procedure starting with com-
mercially available reagents in 3 h is very convenient. Alter-
native synthesis of these compounds required the use of ar-
ylmagnesium halides or aryllithium at very low tempera-
tures, or metal catalysis reactions. These procedures imply
a more tedious workup or require the use of expensive cata-
lysts, and are sensitive to the presence of EWGs such as
quantified by GC by the internal standard method or were isolated
from the crude product reaction mixture by radial chromatography.
1
3
7
-(Methylthio)naphthalene:[18] Liquid. H NMR (200 MHz, CDCl
1
3
,
0 °C): δ = 2.60 (s, 3 H, SMe), 7.40–7.75 (m, 5 H, Ar–H), 7.84–
.89 (m, 1 H, Ar–H), 8.31–8.36 (ddd, J = 5.9, 2.2, 0.7 Hz, Ar–
H) ppm. C NMR (50 MHz, CDCl , 30 °C): δ = 16.2, 123.7, 124.3,
3
13
125.6, 125.8, 126.1, 126.2, 128.5, 131.7, 133.6, 135.8 ppm.
Di(1-naphthyl) Sulfide:[19] Liquid. 1H NMR (200 MHz, CDCl
,
3
1
3
30 °C): δ = 7.32–7.96 (m, 14 H, Ar–H) ppm. C NMR (50 MHz,
–
CN, –NO or –COR.
2
CDCl
3
, 30 °C): δ = 126.2, 126.7, 127.4, 127.7, 128.6, 128.9, 129.8,
132.3, 133.1, 133.8 ppm.
Conclusion
[20]
Solid, m.p. 78–79 °C (ref.[20] 78–
1
,4-Bis(methylthio)benzene:
1
We describe for the first time the reactivity of thioacetate 79 °C). H NMR (200 MHz, CDCl
3
1
, 30 °C): δ = 2.45 (s, 6 H,
3
2
3
×SMe), 7.19 (s, 4 H, Ar–H) ppm. C NMR (50 MHz, CDCl
0 °C): δ = 16.4, 127.6, 135.2 ppm.
3
,
anions as nucleophiles in photoinduced reactions with aryl
halides under entrainment conditions, for the synthesis of
aryl methyl and especially for symmetrical diaryl sulfides.
2-(Methylthio)acetophenone:[
21]
Solid, m.p. 44–45 °C (ref.[21] 45–
1
This novel reaction is a very simple and convenient meth- 47 °C). H NMR (200 MHz, CDCl , 30 °C): δ = 2.43 (s, 3 H, SMe),
3
odology for a one-pot synthesis of sulfides in moderate to 2.61 (s, 3 H, CH
3
) 7.15–7.34 (m, 2 H, Ar–H), 7.43–7.51 (ddd, J =
.7, 7.5, 1.1 Hz, 1 H, Ar–H), 7.81–7.86 (dd, J = 7.7, 1.1 Hz, 1 H,
7
good yields, involving the use of commercially available po-
tassium tert-butoxide and thioacetate salts under very mild
conditions.
1
3
Ar–H) ppm. C NMR (50 MHz, CDCl
1
3
, 30 °C): δ = 15.8, 28.1,
23.3, 124.9, 131.0, 132.2, 134.3, 142.5, 198.9 ppm.
4
(
7
-(Methylthio)benzophenone:[22] Solid, m.p. 75–76 °C. 1H NMR
, 30 °C): δ = 2.52 (s, 3 H), 7.26–7.31 (m, 2 H),
200 MHz, CDCl
3
Experimental Section
1
3
.42–7.57 (m, 3 H), 7.71–7.79 (m, 4 H) ppm. C NMR (50 MHz,
, 30 °C): δ = 14.8, 124.8, 128.2, 129.7, 130.6, 132.1, 133.6,
137.8, 145.2, 195.7 ppm.
General Methods: Irradiation was conducted with a 125-W me-
CDCl
3
dium-pressure Hg lamp with its emission maximum at 365 nm (Ap-
Eur. J. Org. Chem. 2006, 2210–2214
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2213

L. C. Schmidt, V. Rey, A. B. Peñéñory
FULL PAPER
Chem. Abstr. Registry Numbers: 1-(Methylthio)naphthalene
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[
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[
10075-72-6], 2-(methylthio)naphthalene
[7433-79-6], di(1-naph-
[613-81-0], 2-
[1441-97-0], 4-(methylthio)benzophe-
[
19]
[24]
thyl) sulfide
[607-53-4], di(2-naphthyl) sulfide
[21]
(
methylthio)acetophenone
[
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[20]
none
[23405-48-3], 1,4-bis(methylthio)benzene
[699-20-7],
[125877-23-8], 4-(methylthio)
[
[
[20]
bis[4-(methylthio)phenyl] sulfide
[
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[12b]
toluene
[623-13-2], di(4-tolyl) sulfide
[620-94-0], 2-(meth-
1
983, 39, 4153–4161.
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3393-77-9], 1-methoxy-2-(methylthio)benzene [2388-73-0], bis[4-
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13]
[27]
sulfide [6554-57-0], 9-(methylthio)anthracene[
28]
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9-(methylthio)
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phenanthrene [120972-30-7].
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Acknowledgments
[15] tert-Butoxide anion and the enolate anion of cyclohexenone
are able to transfer one electron to aryl halides to initiate an
S
RN1 reaction, but they are not reactive in propagation (ad-
This work was supported partly by the Consejo Nacional de Inves-
tigaciones Científicas y Técnicas (CONICET) and FONCYT, Ar-
gentina. L. C. S. and V. R. gratefully acknowledge receipt of a fel-
lowship from CONICET.
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Received: December 6, 2005
Published Online: March 1, 2006
2214
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 2210–2214