Eosin Y (EY) Photoredox-Catalyzed Sulfonylation of Alkenes: Scope and Mechanism

Article abstract of DOI:10.1002/chem.201601000

Alkyl- and aryl vinyl sulfones were obtained by eosin Y (EY)-mediated visible-light photooxidation of sulfinate salts and the reaction of the resulting S-centered radicals with alkenes. Optimized reaction conditions, the sulfinate and alkene scope, and X-ray structural analyses of several reaction products are provided. A detailed spectroscopic study explains the reaction mechanism, which proceeds through the EY radical cation as key intermediate oxidizing the sulfinate salts.

Full text of DOI:10.1002/chem.201601000

DOI: 10.1002/chem.201601000
Full Paper
&
Reaction Mechanisms
Eosin Y (EY) Photoredox-Catalyzed Sulfonylation of Alkenes:
Scope and Mechanism
[a]
[a]
[a, b]
[a]
Andreas Uwe Meyer, Karolína Strakovµ, Tomµ sˇ Slanina,
and Burkhard Kçnig*
Abstract: Alkyl- and aryl vinyl sulfones were obtained by
eosin Y (EY)-mediated visible-light photooxidation of sulfi-
nate salts and the reaction of the resulting S-centered radi-
cals with alkenes. Optimized reaction conditions, the sulfi-
nate and alkene scope, and X-ray structural analyses of sev-
eral reaction products are provided. A detailed spectroscopic
study explains the reaction mechanism, which proceeds
through the EY radical cation as key intermediate oxidizing
the sulfinate salts.
[
2]
[3]
Introduction
sulfinates and alkynes with sulfinic acids gave vinyl sulfones,
[
4]
preserving the SO group. Other approaches to vinyl sulfones
2
[
5]
Sulfinates are interesting reagents for organic transformations.
Many stable alkyl- or aryl sulfinic acids or their sodium or zinc
salts are known or readily available. They are activated for reac-
tion by transition metals or oxidants. Baran and co-workers
used sodium alkyl sulfinates widely for the facile CÀH function-
are the decarboxylative sulfonylation of cinnamic acids or
[
6]
phenylpropiolic acids with sodium sulfinates, and the electro-
[
7]
chemical synthesis from olefins and sodium sulfinates. In
2015, two visible-light photooxidation protocols were de-
scribed for the synthesis of coumarin derivatives from phenyl
[1]
[8]
alization of heterocycles with biological relevance. tert-Butyl
propiolates with aryl sulfinic acids, and the synthesis of aryl
[
9]
hydroperoxide initiates the radical reaction, which provides val-
vinyl sulfones from olefins and aryl sulfinates. However, their
[1]
[10]
uable products under loss of SO2 (Scheme 1a). Transition-
metal-catalyzed reactions of alkenes or alkynes with sodium
scope is limited to aryl vinyl sulfones. Vinyl methyl sulfone
preparation, to date, requires copper-catalyzed reactions of al-
[
11]
[12]
kynes or alkenes with DMSO, or the ammonium iodide-in-
[
13]
duced sulfonylation of olefins with DMSO. Herein, we report
a visible-light-mediated, metal-free synthesis of alkyl and heter-
oaryl vinyl sulfones from alkyl or heteroaryl sulfinates and al-
kenes using green light, the organic dye eosin Y (EY) as photo-
catalyst and nitrobenzene or air as the terminal oxidant
(
Scheme 1b). Alternatively, the oxidative coupling reaction can
be combined with a hydrogen-evolution reaction.
Results and Discussion
Synthesis
In a typical reaction for the photocatalytic reaction, three equi-
valents of the alkyl sulfinate 1a, one equivalent of alkene 2a,
Scheme 1. Comparison of sulfinate oxidations with loss or preservation of
1
0 mol% of EY (A), and one equivalent of nitrobenzene as oxi-
2
SO .
dant in EtOH or a mixture of DMF/H O (3:1) were used to give
2
3
a in 61 and 69% yield, respectively (Table 1, entries 1 and
[
a] A. U. Meyer, K. Strakovµ, Dr. T. Slanina, Prof. Dr. B. Kçnig
University of Regensburg Faculty of Chemistry and Pharmacy
Institute of Organic Chemistry, Universitätsstrasse 31
[14]
5
). Without photocatalyst or without light, no product was
formed (Table 1, entries 2 and 3). Without terminal oxidant, the
yield dropped to 21% (Table 1, entry 4). Air is not a potent oxi-
dant in this reaction, but in oxygen atmosphere, a yield of
9
3053 Regensburg (Germany)
E-mail: Burkhard.Koenig@ur.de
[
b] Dr. T. Slanina
4
8% was obtained (Table 1, entry 6). Sodium persulfate and
Department of Chemistry and RECETOX, Masaryk University
Kamenice 5, 625 00 Brno (Czech Republic)
ammonium persulfate gave 31 and 22%, respectively, of prod-
uct under otherwise identical conditions (Table 1, entries 7 and
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201601000. It contains full experimental
data.
8
). Oxygen present in a typical reaction system serves as
a second terminal oxidant.
Chem. Eur. J. 2016, 22, 8694 – 8699
8694
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
The complex is known to evolve hydrogen upon two-electron
Table 1. Screening of different oxidants.
[
15]
reduction.
entry 9) is comparable to the reaction using oxygen as oxidant
48%, Table 1, entry 6), but in addition, dihydrogen was pro-
The yield of the product 3a (44%, Table 1,
(
duced (10%). The amount of produced dihydrogen deter-
mined by head-space GC is lower than the stoichiometric
equivalent, which may be due to partially dissolved H in the
2
reaction solvent.
The scope of substrates using different alkyl and heteroaryl
sulfinates and olefins was explored by using the general reac-
tion conditions. As depicted in Scheme 2, all expected prod-
ucts 3a–u were obtained in moderate to excellent yields of
Entry
Conditions
Yield (3a)
H
2
[%]
[
a]
[b]
[
%]
[
c]
1
2
3
4
5
6
7
8
PhÀNO
no photocatalyst, PhÀNO
PhÀNO (1 equiv), EtOH, no light
no oxidant, EtOH
PhÀNO (1 equiv), DMF/H
(balloon), EtOH
(1 equiv), EtOH
(1 equiv), EtOH
(py)Cl] (10 mol%),
EtOH (dry), 6h
2
(1 equiv), EtOH
61
0
–
–
–
–
–
–
–
–
5
1–99%. In all cases, the SO2 moiety was preserved in the
2
(1 equiv), EtOH
structure. This is in contrast to the observations of Baran and
2
0
co-workers, in which SO was eliminated upon peroxide oxida-
21
69
48
31
22
44
2
[
d]
2
2
O (3:1)
tion, and CÀH alkylated coupling products were obtained ex-
O
2
[1]
clusively. Applying Baran’s protocol to the model reaction of
Na
(NH
[Co(dmgH)
2
S
2
O
8
Table 1 or the reaction of compound 2a with zinc isopropylsul-
finate did not provide any product with or without preserva-
4
2
) S
2
O
8
[e]
9
2
10
tion of SO (see the Supporting Information). Sulfinate oxida-
2
tions by light or peroxides have therefore a complementary
substrate specificity and are likely to operate by different
mechanisms.
[
[
a] Determined by GC analysis with naphthalene as internal standard.
b] Determined by head space GC analysis with calibration. [c] General re-
action conditions 1: 1a (0.50 mmol, 3 equiv), 2a (0.17 mmol, 1 equiv),
PhÀNO (0.17 mmol, 1 equiv) and EY (10 mol%) in EtOH was irradiated
with green light (l=535 nm) for 18 h. [d] General reaction conditions 2:
1
1
2
The Langlois reagent (sodium trifluoromethanesulfinate)
[
16]
[17]
eliminates SO in copper-catalyzed, other radical, or pho-
2
a (0.50 mmol, 3 equiv), 2a (0.17 mmol, 1 equiv), PhÀNO
2
(0.17 mmol,
[
18]
equiv) and EY (10 mol%) in DMF/H O (3:1) was irradiated with green
2
toredox reactions and gives exclusively CF coupling prod-
3
light for 18 h. [e] Nitrogen atmosphere: degassed by three cycles
vacuum/nitrogen.
ucts. The dual reactivity of sulfonyl radicals (sulfonylative vs.
desulfitative couplings) has been observed previously and was
[
19]
reviewed by Hamze and co-workers.
,2-Dihydronaphthalene (2a) reacted with primary and sec-
1
To provide an oxidant-free CÀS coupling reaction,
ondary alkyl sulfinates to yield the products 3a–g in 56–95%
yield. Even the bulky 10-camphor sulfinate (1h) led to product
[
Co(dmgH) (py)Cl] (10 mol%) was added instead of an oxidant.
2
[
20]
Scheme 2. Scope of vinyl sulfones.
Chem. Eur. J. 2016, 22, 8694 – 8699
www.chemeurj.org
8695
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
3
h in 51% yield. The heteroaryl sulfinates 1i–l with 2a gave
pounds 3 may be caused by their enhanced susceptibility to
polymerization. Products of intramolecular sulfinate radical re-
actions were only observed in traces.
products 3i–l in excellent yields (89–99%). Other styrene deriv-
atives 2b–f reacted with the alkyl sulfinates 1a and b and the
heteroaryl sulfinate 1i to give the products 3m–s in 55–95%
yield. N-Ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ,
Under the conditions for visible-light-mediated [2+2] cyclo-
[
22]
addition reported by Cibulka and co-workers, a diastereo-
meric mixture of bicyclic sulfones 4 and the five-membered
heterocycles 5 were obtained from 3x–ab, whereas compound
3w degraded under the reaction conditions.
2
g), which is an irreversible receptor antagonist and is utilized
[
21]
to study the ontogeny of dopamine receptor function, gave
the alkyl sulfone 3t (59%) and the heteroaryl sulfone product
3
u (79%). The product yield dropped for 3v (11%) derived
from the alkaloid piperine (2h), because the prevailing piper-
ine [2+2] dimer 3v’ (40%, see the Supporting Information)
was formed during irradiation. The molecular structures of
compounds 3j, k, l, m, q, and r were confirmed by X-ray
single-crystal analysis. Electron-donating or electron-withdraw-
ing substituents were generally well tolerated. The bromide
and chloride substituents in products 3k, l, and q allow further
synthetic modifications of the coupling products.
Mechanistic investigations
EY (A) is a known xanthene dye used in photocatalysis, which
often replaces more expensive ruthenium and iridium com-
[
24]
plexes. It can catalyze both oxidations and reductions, and it
has ambivalent reactivity in the excited state. Due to the short
singlet lifetime, the triplet state of EY is usually the photocata-
lytically active state undergoing photoinduced electron trans-
[
24]
Next, we applied the sulfinate oxidation to the synthesis of
complex cyclic sulfones using two sequential visible-light pho-
tocatalytic reactions (Table 2). The reaction of unsaturated sulfi-
nates 1m and n with styrenes 2 gave rapid access to precur-
sors for intramolecular photocatalyzed [2+2] cycloaddition re-
actions. The lower yields observed in the syntheses of com-
fer.
EY can be reductively quenched with good electron donors,
such as alkyl and aryl amines, which was demonstrated by
transient spectroscopic experiments in photocatalytic dehydro-
genative cross-coupling of tetrahydroisoquinoline and nitrome-
[
25]
thane. Some of us recently found that EY undergoes reduc-
[
23]
Table 2. Synthesis of cyclic sulfones 4 and 5.
[
a]
[b]
Analytical scale
Yield of 4
Semi-preparative scale
Isolated yield of 4
[
c,d]
[e,f]
[d]
yield of 5
[g]
3
3
3
x: R’ = OMe
y: R’ = Me
z: R’ = Br
64%
dr > 9:1)
70%
dr ~ 8:1)
57%
25%
(dr ~ 5:4)
30%
(dr ~ 5:4)
28%
(dr ~ 5:4)
35%
(dr ~ 5:4)
33%
56%
(dr > 9:1)
63%
(dr ~ 9:1)
54%
(
(
(
dr > 9:1)
(dr > 9:1)
43%
63%
3
3
aa: R’ = Cl
ab: R’ = F
(
dr ~ 8:1)
53%
(dr ~ 8:1)
[h]
28%
(
dr ~ 5:1)
(dr ~ 10:9)
(dr > 9:1)
[
a] General reaction conditions 3: 0.01 mmol of 3, B (2.5 mol%), 0.5 mL of dry MeCN, 15 min irradiation. [b] General reaction conditions 4: 0.08 mmol of 3,
B (2.5 mol%), 4 mL of dry MeCN, 2 h irradiation. [c] Determined by GC analysis with calibration. [d] Diastereomeric ratio of rel-(1R,5R,7S): rel-(1R,5S,7S). De-
termined by GC and/or NMR analysis. [e] Determined by GC analysis for the same FID response for products 4 and 5. [f] Diastereomeric ratio of rel-(2R,3S) :
rel-(2R,3R). Determined by GC and/or NMR analysis. [g] Shorter reaction time, 10 min for analytical experiments, 80 min for semi-preparative experiments.
[
h] Lower isolated yield due to difficult separation from by-product 5.
Chem. Eur. J. 2016, 22, 8694 – 8699
www.chemeurj.org
8696
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[
26]
tive quenching in catalytic perfluoroarylation. The reduced
reaction intermediates can be found in both parts of Figure 1.
Even the (2,2,6,6-tetramethyl-piperidin-1-yl)oxyl (TEMPO)-trap-
ping experiment forming the derivatives 6 (Figure 2) and 6’
À
form of EY AC was identified by transient spectroscopy in both
cases. Because the reduced EY can be easily re-oxidized by air,
all reactions undergoing reductive quenching cycle must be
accomplished in the absence of O2.
[
9]
(Figure 1) and the determination of potential by-products
(see the Supporting Information) from the radical intermediate
[
9,30]
EY can enter the oxidative quenching cycle in the presence
of good acceptors, for example, electron-poor arenes contain-
ing electron-withdrawing groups. Some examples of the oxida-
tive quenching cycle of EY are photocatalytic desulfonyla-
3C did not exclude one of the possibilities.
The thermody-
namics of both mechanisms were estimated by calculation of
the Gibbs energy of the photoinduced electron transfer be-
tween the triplet state of EY and a model sulfinate. Both pho-
toinduced electron transfers (in oxidative and reductive
quenching cycle) were found to be equally exothermic
[
27]
3À
tion, quenching of the excited EY by [Fe(CN) ] in reverse
6
[
28]
micelles, and the photocatalytic photo-Meerwein arylations
[29]
+
À1
by using diazonium salts. The oxidized form of EY AC was
easily observed by transient spectroscopy, and the reactions
are not so much sensitive to the presence of oxygen.
(DGPeT =À60 kJmol ) by using sodium benzene sulfinate as
substrate. The thermodynamic values did not allow excluding
one of the two reaction mechanisms.
The photocatalytic oxidation of aryl sulfinates has been first
Therefore, EY can enter both quenching cycles in the pres-
ence of either good electron donors or acceptors. The prevail-
ing process, reduction or oxidation, will be determined in such
case by the relative concentration of the donor and acceptor.
This was demonstrated in the photocatalytic reduction of ni-
[
9]
described in 2015. Two different reaction mechanisms were
proposed: 1) A reductive quenching cycle (Figure 1, upper
part); and 2) an oxidative quenching cycle (Figure 1, lower
part). Both mechanisms lead to the same products and similar
[
31]
trobenzenes with triethanolamine (TEOA).
In presence of
TEOA, the reduced form ACÀ was formed exclusively. When ni-
trobenzene was present in the reaction mixture together with
TEOA, and even at concentrations one order of magnitude
+
lower than TEOA, the oxidative quenching forming AC was
the only process occurring. This indicates that nitrobenzene is
a preferred quencher over TEOA. A similar situation has been
demonstrated by Usui and co-workers for a system using
[
32]
methyl viologen as acceptor and TEOA as donor.
This reactivity of photoexcited EY is not exceptional, other
photocatalysts also switch between an oxidative and reductive
2
+
quenching cycle. Compound [Ru(bpy)3]
can enter both
[
33]
mechanisms, which was recently summarized by Tepl y´ . The
2
+
photocatalytic reduction of nitrobenzene with [Ru(bpy)3] as
photocatalyst and hydrazine as sacrificial electron donor pro-
[
34]
ceeds through an oxidative quenching cycle similar to the
[
31]
similar system based on EY.
In summary, nitrobenzene is a strong quencher and usually
preferentially oxidizes the excited catalyst even in the presence
of an excess of excellent electron donors, such as TEOA or hy-
drazine.
The redox potentials of aryl, heteroaryl, and alkyl sulfinates
are given in the Supporting Information. The thermodynamic
limit for the electron transfer between EY and sulfinate is
0
.78 V vs. saturated calomel electrode (SCE) for the oxidative
quenching cycle, and 0.83 V vs. SCE for the reductive quench-
·
À
2
ing, respectively. Sodium alkyl (E [RSO /RSO ]ꢀ +0.45 V vs.
red
2
·
2
À
SCE) and aryl sulfinates (Ered[RSO /RSO ]ꢀ +0.40 V vs. SCE)
2
should be therefore suitable substrates for the proposed cata-
lytic system (see the Supporting Information, Table S7, en-
tries 1–3, 5, 6 and 8–22). Other derivatives, such as zinc sulfi-
·
2
À
nates (Ered[RSO /RSO ]ꢀ +0.9 V vs. SCE; see the Supporting
2
Information, Table S7, entries 4, 7 and 25–28) or Langlois re-
·
À
2
[18]
agent (Ered[RSO /RSO ]ꢀ +1.05 V vs. SCE; see the Support-
2
ing Information, Table S7, entries 23 and 24) are more difficult
to oxidize preventing a clean and complete photocatalytic
transformation (see the Supporting Information, Table S8).
Figure 1. Two possible catalytic cycles for photocatalytic sulfinate oxidation:
a reductive quenching cycle (top) and an oxidative quenching cycle
(
bottom).
Chem. Eur. J. 2016, 22, 8694 – 8699
www.chemeurj.org
8697
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
The reaction mechanism of the photocatalytic mechanism
was elucidated by steady-state (UV/Vis) and transient spectros-
copy (nanosecond pump-probe spectroscopy) measurements.
The details about the steady-state and transient spectroscopy
measurements are given in the Supporting Information.
The quantum yield of the model photocatalytic reaction (see
the Supporting Information for details) was determined to be
F=1.3Æ0.4%. This value corresponds to the rather long reac-
tion times.
butyl hydroperoxide that gave the alkylation of heterocycles. A
wide variety of alkyl and heteroaryl sulfinates are converted in
good to excellent yields. The low reactivity of the sulfinate rad-
ical makes the reaction selective for activated alkenes, such as
styrenes, dihydronaphthalenes, and dihydroquinolines. Com-
plex cyclic sulfones were obtained in a sequence of two photo-
catalytic steps, first producing alkenyl vinyl sulfones that un-
dergo sensitized [2+2] intramolecular photocylization.
An oxidative and a reductive quenching mechanism would
lead to the same products and are both thermodynamically
possible. Transient spectroscopy revealed that the triplet state
of EY exclusively reacts with the terminal oxidant nitrobenzene
giving the EY radical cation. This key intermediate oxidizes the
sulfinate salt giving the corresponding radical and the regener-
ated photocatalyst. Oxygen present in the reaction system
serves as a second terminal oxidant.
The lifetimes of the relevant excited states under various
conditions determined by transient spectroscopy are summar-
ized in Table 3. The triplet state was oxidatively quenched by
+
nitrobenzene to create the radical cation of EY AC , which
reacts with sodium methanesulfinate. This confirms the oxida-
tive quenching to be the key process operating in the photo-
catalytic system. The suggested mechanism is supported by lit-
erature data, and all experiments are shown in Figure 2.
Our photocatalytic oxidation protocol extends the previously
reported applications of sulfinates in synthesis and enables se-
lective reactions with complementary scope to the hydroper-
oxide oxidation. The detailed mechanistic information may fa-
cilitate applications of EY as a photocatalyst in other reactions.
Table 3. Transient species of EY and its lifetimes under various condi-
tions.
[
c]
Transient
Singlet Triplet
425 570
Radical cation
420
[
a]
l [nm]
EY
Acknowledgements
[b]
3.8Æ0.5 480Æ25
n.o.
n.o.
[b]
EY+sulfinate
3.8Æ0.5 480Æ25
[d]
3
This work was supported by the German Science Foundation
(DFG; GRK 1626, Chemical Photocatalysis). A.U.M. thanks the
Fonds der Chemischen Industrie for a scholarship. We thank
Dr. Rudolf Vasold (University of Regensburg) for his assistance
in GC-MS measurements, Regina Hoheisel (University of Re-
gensburg) for her assistance in cyclic voltammetry measure-
ments, and the Laboratory of Organic Photochemistry of Facul-
ty of Science at Masaryk University in Brno, Czech Republic for
transient absorption spectroscopic measurements. The RECE-
TOX research infrastructure used for these measurements was
supported by the projects of the Czech Ministry of Education,
Youth and Sports (LO1214 and LM2015051). We thank Prof.
Radek Cibulka for helpful discussions. The [2+2] cycloaddition
project was supported by the Czech Science Foundation (proj-
ect number 14-09190S).
Lifetime [ns] EY+PhNO
EY+sulfinate+PhNO
2
3.8Æ0.5 330Æ20 (327Æ9)”10
2
3.8Æ0.5 330Æ20
1409Æ77
[
a] Wavelength of detection. [b] Not observed. [c] Radical anion of EY was
not observed. [d] Average value from at least five measurements.
Keywords: alkyl sulfinates
·
photocatalysis
·
reaction
mechanisms · transient spectroscopy · vinyl sulfones
[
1] a) R. Gianatassio, S. Kawamura, C. L. Eprile, K. Foo, J. Ge, A. C. Burns,
M. R. Collins, P. S. Baran, Angew. Chem. Int. Ed. 2014, 53, 9851–9855;
Angew. Chem. 2014, 126, 10009–10013; b) Q. Zhou, A. Ruffoni, R. Giana-
tassio, Y. Fujiwara, E. Sella, D. Shabat, P. S. Baran, Angew. Chem. Int. Ed.
2013, 52, 3949–3952; Angew. Chem. 2013, 125, 4041–4044; c) Q. Zhou,
J. Gui, C.-M. Pan, E. Albone, X. Cheng, E. M. Suh, L. Grasso, Y. Ishihara,
P. S. Baran, J. Am. Chem. Soc. 2013, 135, 12994–12997; d) Y. Ji, T. Brueckl,
R. D. Baxter, Y. Fujiwara, I. B. Seiple, S. Su, D. G. Blackmond, P. S. Baran,
Proc. Natl. Acad. Sci. USA 2011, 108, 14411–14415.
Figure 2. Determined overall mechanism of the reaction.
[
[
[
2] a) N. Taniguchi, Synlett 2011, 1308–1312; b) N. Taniguchi, Tetrahedron
Conclusion
2
014, 70, 1984–1990.
3] W. Wei, J. Li, D. Yang, J. Wen, Y. Jiao, J. You, H. Wang, Org. Biomol. Chem.
014, 12, 1861–1864.
The sodium salts of alkyl and aryl sulfinates reacted in a EY-cat-
alyzed visible-light photooxidation with alkenes to vinyl sul-
2
4] a) A. Noble, D. W. C. MacMillan, J. Am. Chem. Soc. 2014, 136, 11602–
11605; b) C. Poittevin, V. Liautard, R. Beniazza, F. Robert, Y. Landais, Org.
Lett. 2013, 15, 2814–2817; c) Q. Zhu, Y. Lu, Org. Lett. 2009, 11, 1721–
fones. The mild photooxidation preserved the SO moiety in
2
the product in contrast to sulfinate oxidations by using tert-
Chem. Eur. J. 2016, 22, 8694 – 8699
www.chemeurj.org
8698
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
1
724; d) H. Kumamoto, K. Deguchi, T. Wagata, Y. Furuya, Y. Odanaka, Y.
[17] a) Q. Lu, C. Liu, Z. Huang, Y. Ma, J. Zhang, A. Lei, Chem. Commun. 2014,
50, 14101–14104; b) C. Liu, Q. Lu, Z. Huang, J. Zhang, F. Liao, P. Peng,
A. Lei, Org. Lett. 2015, 17, 6034–6037.
[18] D. J. Wilger, N. J. Gesmundo, D. A. Nicewicz, Chem. Sci. 2013, 4, 3160–
3165.
Kitade, H. Tanaka, Tetrahedron 2009, 65, 8007–8013; e) G. Pandey, K. N.
Tiwari, V. G. Puranik, Org. Lett. 2008, 10, 3611–3614; f) M. N. Noshi, A. El-
awa, E. Torres, P. L. Fuchs, J. Am. Chem. Soc. 2007, 129, 11242–11247;
g) J.-N. Desrosiers, A. B. Charette, Angew. Chem. Int. Ed. 2007, 46, 5955–
5
2
957; Angew. Chem. 2007, 119, 6059–6061; h) K. Oh, Org. Lett. 2007, 9,
973–2975; i) D. J. Wardrop, J. Fritz, Org. Lett. 2006, 8, 3659–3662; j) M.
[19] J. Aziz, S. Messaoudi, M. Alami, A. Hamze, Org. Biomol. Chem. 2014, 12,
9743–9759.
Uttamchandani, K. Liu, R. C. Panicker, S. Q. Yao, Chem. Commun. 2007,
5, 1518–1520; k) D. C. Meadows, T. Sanchez, N. Neamati, T. W. North, J.
[20] Ethanol was chosen as the optimal solvent, because the workup of the
reaction mixture is easier with ethanol than with DMF. 1 f lithium sulfi-
1
Gervay-Hague, Bioorg. Med. Chem. 2007, 15, 1127–1137; l) F. Hof, A.
Schütz, C. Fäh, S. Meyer, D. Bur, J. Liu, D. E. Goldberg, F. Diederich,
Angew. Chem. Int. Ed. 2006, 45, 2138–2141; Angew. Chem. 2006, 118,
2
nate, 3e,h,m–s DMF/H O (3:1), 3t, u 42 h, 3v 68 h.
[21] a) A. D. Crocker, D. L. Cameron, Clin. Exp. Pharmacol. Physiol. 1989, 16,
545–548; b) C. A. Crawford, S. A. McDougall, J. K. Rowlett, M. T. Bardo,
Neurosci. Lett. 1992, 137, 265–269; c) T. Der-Ghazarian, A. Gutierrez, F. A.
Varela, M. S. Herbert, L. R. Amodeo, S. Charntikov, C. A. Crawford, S. A.
McDougall, Neuroscience 2012, 226, 427–440; d) S. A. McDougall, J. M.
Valentine, A. E. Gonzalez, D. E. Humphrey, C. B. Widarma, C. A. Crawford,
Psychopharmacology 2014, 231, 1637–1647.
2
193–2196; m) B. A. Frankel, M. Bentley, R. G. Kruger, D. G. McCafferty, J.
Am. Chem. Soc. 2004, 126, 3404–3405; n) G. Wang, U. Mahesh, G. Y. J.
Chen, S. Q. Yao, Org. Lett. 2003, 5, 737–740; o) J. J. Reddick, J. Cheng,
W. R. Roush, Org. Lett. 2003, 5, 1967–1970; p) M. Santelli, H. Doucet, A.
Battace, T. Zair, Synthesis 2006, 3495–3505.
[
[
5] a) Q. Jiang, B. Xu, J. Jia, A. Zhao, Y.-R. Zhao, Y.-Y. Li, N.-N. He, C.-C. Guo, J.
Org. Chem. 2014, 79, 7372–7379; b) Y. Xu, X. Tang, W. Hu, W. Wu, H.
Jiang, Green Chem. 2014, 16, 3720–3723; c) J. Gao, J. Lai, G. Yuan, RSC
Adv. 2015, 5, 66723–66726; d) P. Katrun, S. Hlekhlai, J. Meesin, M. Poh-
makotr, V. Reutrakul, T. Jaipetch, D. Soorukram, C. Kuhakarn, Org.
Biomol. Chem. 2015, 13, 4785–4794.
[22] V. Mojr, E. Svobodovµ, K. Strakovµ, T. Nevesel y´ , J. Chudoba, H. Dvo rˇ µ-
kovµ, R. Cibulka, Chem. Commun. 2015, 51, 12036–12039.
[23] Reaction works also without NaOH, but the yields were slightly higher
upon addition of NaOH. Lithium sulfinates were used, because they can
be easily prepared by the presented method (see the Supporting Infor-
mation). The reactivity of sodium and lithium sulfinates is similar ac-
cording to literature. This is also confirmed by the nearly identical oxi-
dation potentials (see the Supporting Information).
6] G. Rong, J. Mao, H. Yan, Y. Zheng, G. Zhang, J. Org. Chem. 2015, 80,
7
652–7657.
[
[
[
7] Y.-C. Luo, X.-J. Pan, G.-Q. Yuan, Tetrahedron 2015, 71, 2119–2123.
8] W. Yang, S. Yang, P. Li, L. Wang, Chem. Commun. 2015, 51, 7520–7523.
9] A. U. Meyer, S. Jäger, D. P. Hari, B. Kçnig, Adv. Synth. Catal. 2015, 357,
[24] D. P. Hari, B. Kçnig, Chem. Commun. 2014, 50, 6688–6699.
[25] Q. Liu, Y.-N. Li, H.-H. Zhang, B. Chen, C.-H. Tung, L.-Z. Wu, Chem. Eur. J.
2012, 18, 620–627.
2
050–2054.
[26] A. U. Meyer, T. Slanina, C.-J. Yao, B. Kçnig, ACS Catal. 2016, 6, 369–375.
[27] D.-T. Yang, Q.-Y. Meng, J.-J. Zhong, M. Xiang, Q. Liu, L.-Z. Wu, Eur. J. Org.
Chem. 2013, 7528–7532.
[28] E. Joselevich, I. Willner, J. Phys. Chem. 1995, 99, 6903–6912.
[29] D. P. Hari, P. Schroll, B. Kçnig, J. Am. Chem. Soc. 2012, 134, 2958–2961.
[30] Styrene derivatives can form very small quantities of a by-product upon
a nucleophilic attack of ethanol. This can be avoided by using DMF/
[
10] Except Synthesis 2006, 3495–3505, which describes the palladium cata-
lyzed Heck vinylation of methyl vinyl sulfone with aryl halides and is re-
stricted to methyl vinyl sulfones. In some other rare cases sodium
methanesulfinate gets tested as sodium alkyl sulfinate.
[
[
11] Y. Jiang, T.-P. Loh, Chem. Sci. 2014, 5, 4939–4943.
12] J.-Y. Chen, X.-L. Chen, X. Li, L.-B. Qu, Q. Zhang, L.-K. Duan, Y.-Y. Xia, X.
Chen, K. Sun, Z.-D. Liu, Y.-F. Zhao, Eur. J. Org. Chem. 2015, 314–319.
13] X. Gao, X. Pan, J. Gao, H. Huang, G. Yuan, Y. Li, Chem. Commun. 2015,
2
H O (3:1) instead of ethanol.
[
[
[31] X.-J. Yang, B. Chen, L.-Q. Zheng, L.-Z. Wu, C.-H. Tung, Green Chem. 2014,
5
1, 210–212.
16, 1082–1086.
14] GC yield of 3a is slightly lower than the isolated yield of 79%, because
in GC, the dihydronaphthalene moiety of the product gets partially oxi-
dized to the naphthalene core.
15] a) S. Troppmann, B. Kçnig, Chem. Eur. J. 2014, 20, 14570–14574; b) G.
Zhang, C. Liu, H. Yi, Q. Meng, C. Bian, H. Chen, J.-X. Jian, L.-Z. Wu, A. Lei,
J. Am. Chem. Soc. 2015, 137, 9273–9280; c) M. Hansen, S. Troppmann,
B. Kçnig, Chem. Eur. J. 2016, 22, 58–72.
[32] S. D. M. Islam, T. Konishi, M. Fujitsuka, O. Ito, Y. Nakamura, Y. Usui, Photo-
chem. Photobiol. 2000, 71, 675–680.
[33] F. Tepl y´ , Collect. Czech. Chem. Commun. 2011, 76, 859–917.
[34] T. Hirao, J. Shiori, N. Okahata, Bull. Chem. Soc. Jpn. 2004, 77, 1763–1764.
[
[
16] Q. Lu, C. Liu, P. Peng, Z. Liu, L. Fu, J. Huang, A. Lei, Asian J. Org. Chem.
Received: March 2, 2016
2014, 3, 273–276.
Published online on May 11, 2016
Chem. Eur. J. 2016, 22, 8694 – 8699
www.chemeurj.org
8699
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim