Visible-light photocatalytic reduction of sulfonium salts as a source of aryl radicals

Article abstract of DOI:10.1002/adsc.201300040

Triarylsulfonium salts are prompted to undergo efficient homolytic reduction by single electron transfer under mild photocatalytic conditions. The liberated aryl radical can then participate in carbon-carbon bond formation processes with allyl sulfones and activated olefins. Triarylsulfonium salts emerge as a valuable and alternative source of aryl radicals for synthesis. Copyright

Full text of DOI:10.1002/adsc.201300040

COMMUNICATIONS
DOI: 10.1002/adsc.201300040
Visible-Light Photocatalytic Reduction of Sulfonium Salts as
a Source of Aryl Radicals
Simon Donck,a Abdulkader Baroudi,a Louis Fensterbank,a,*
Jean-Philippe Goddard,a,* and Cyril Olliviera,*
a
Institut Parisien de Chimie Molꢀculaire (UMR CNRS 7201), UPMC Univ-Paris 06 – Sorbonne Universitꢀ, 4 Place
Jussieu, C. 229, 75005 Paris, France
Fax : (+33)-1-4427-7360; e-mail: louis.fensterbank@upmc.fr or jean-philippe.goddard@upmc.fr or cyril.ollivier@upmc.fr
Received: January 16, 2013; Published online: && &&, 0000
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201300040.
Abstract: Triarylsulfonium salts are prompted to
undergo efficient homolytic reduction by single
electron transfer under mild photocatalytic condi-
tions. The liberated aryl radical can then participate
in carbon-carbon bond formation processes with
allyl sulfones and activated olefins. Triarylsulfonium
salts emerge as a valuable and alternative source of
aryl radicals for synthesis.
cyclopropyl ketones,[11] halides,[12] N-alkoxyphthal-
AHCTUNGTRENNUNG
imides,[13] keto epoxides/aziridines,[14] azides[15] and di-
azoniums,[16] based on reductive quenching of transi-
tion metal polypyridine complexes or organic dyes
have been developed. However, the use of sulfoniums
as a potential source of carbon-centered radicals has
received only scant attention. We can mention the
pioneering work of Kellogg who reported an acceler-
ating effect of the presence of a photocatalyst such as
[17]
Keywords: carbon-carbon bond formation; photoca-
talysis; radical reactions; reduction; sulfonium salts
[RuACTHUNGTERNNU(G bpy)3]Cl2 or a dye in the reduction of a-keto-
sulfoniums with Hantzsch ester under irradiation.[9a,b]
More recently, Akita and Koike have reported oxytri-
fluoromethylation of alkenes which involves photoca-
talytic reduction of S-(trifluoromethyl)dibenzothio-
phenium tetrafluoroborate (Umemotoꢁs reagent) as
Sulfonium salts have gained increasing attention in or- key step.[18a] Based on a similar approach, Gouverneur
ganic chemistry over the past years.[1] Although the examined the hydrotrifluoromethylation of unactivat-
reactivity of the corresponding ylides is well-devel- ed alkenes[18b] and the trifluoromethylation of allylsi-
oped, their ability to be easily reduced by single-elec- lanes.[18c] However, exploring the reactivity of non-ac-
tron transfer processes and generate carbon-centered tivated sulfonium salts remains a highly challenging
radicals has been less considered.[2] Such a type of ho- task.
molytic cleavage is well-known in Nature and can be
In this context, we investigated the reduction of tri-
observed in the biochemical reduction of the sulfoni- arylsulfoniums under mild photocatalytic conditions
um of S-adenosyl-l-methionine (SAM) by the iron- and the participation of the expelled aryl radicals[19] in
sulfur cluster-containing enzymes.[3] Independently, carbon-carbon bond formations (Scheme 1).
a variety of sulfonium salts bearing alkyl and/or aryl
substituents have been reduced by either pulse radiol- commercially available triphenylsulfonium triflate
ysis,[4] electrochemical,[5] chemical[6] or photochemical (1a) by the [Ru
(bpy)3]Cl2/amine system and we select-
reactions.[7]
ed the allyl sulfone 2a to intercept the intermediate
We initially examined the photoreduction of the
AHCTUNGTRENNUNG
The development of mild and sustainable prepara- phenyl radical. A rapid comparison of the reduction
tive processes limiting the utilization of stoichiometric potential of triphenylsulfonium salts (ca. À1.2 V vs.
toxic metal complexes is needed.[8] A particularly at- SME)[20] and [Ru
ACHTUNGTRENNUNG
tractive approach is the design of new catalytic sys- ports our hypothesis. Visible-light irradiation of a mix-
tems. Recently, photoredox catalysis that combines ture of 1a and 2a (10 equiv.) in acetonitrile in the
visible light and a photocatalyst has seen a renewed presence of [RuACTHNUGTRENNG(U bpy)3]Cl2·CAHUTGNTRNEN(UGN H2O)6 (5 mol%) as the
interest[9] and has proven to be very effective in pro- photocatalyst and Hꢂnigꢁs base [(i-Pr)2NEt] (2 equiv.)
moting single-electron transfer redox reactions in as the reductive quencher for 15 h resulted in the for-
a greener way.[10] For instance, various radical trans- mation of the allylated product 3aa in 55% yield.
formations involving photoreduction of unsaturated/ Control experiments confirmed that no reaction oc-
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1
ÞÞ
These are not the final page numbers!

Simon Donck et al.
COMMUNICATIONS
appearance of a by-product of double aryl radical ad-
dition. Finally, in a typical experiment, triphenylsulfo-
nium triflate (1a) treated with 5 mol% of
[RuACTHNUGTRENNUG(bpy)3]Cl2·ACHTUNGTREN(NUNG H2O)6, 5 equivalents of Hꢂnigꢁs base
in acetonitrile under irradiation and in the presence
of 10 equivalents of allyl sulfone 2a gave the allylation
product 3aa in 64% yield (73% of Ph2S was recov-
ered).
A range of allyl sulfones 2b–f was tested under
these conditions and the results are summarized in
Scheme 2. The unsubstituted allyl sulfone 2b reacts
Scheme 1. Photoreductive generation of phenyl radicals
from triphenylsulfonium salts and subsequent carbon-carbon
bond formation.
curred in the absence of light, photocatalyst or amine, with 1a giving the volatile product 3ab in moderate
and therefore, a simultaneous interaction of the three yield. When the allylation was repeated with phenyl-
reagents is required.
and methyl-substituted allyl sulfones 2c and 2d, re-
With this encouraging result, we set out to optimize sults comparable with that obtained with 2a were
the reaction conditions. Variation of the solvent reached. By contrast, a simple chlorine atom substitu-
nature was detrimental to the reactionꢁs efficiency tion at the internal position dropped the yield to
[40% in N,N-dimethylformamide (DMF) and 47% in 17%. However, the corresponding allyl chloride
dimethyl sulfoxide (DMSO)]. Neither extending the
reaction time up to 48 h nor changing the photocata-
lyst to an iridium polypyridine complex with a more
negative reduction potential {À1.51 V vs. SCE for
[22]
[Ir
G
(ppy)2]PF6
compared to À1.32 V vs.
SCE for [RuACHTUNGTRENNUNG
(bpy)3]Cl2[21]} had a significant impact on
the yield (52% and 57% compared to 55%). By con-
trast, only traces of products were detected with the
less reductive Eosin Y dye (À1.09 V vs. SCE[23] com-
pared to ca. À1.2 V vs. SME[20]) A screening of two
different amines (Et3N and p-MeOC6H4NPh2)[12d] con-
firmed the superiority of Hꢂnigꢁs base as reductive
quencher (Table 1). The use of 5 equivalents of (i-
Pr)2NEt shows further increase in the yield, whereas
no significant improvement was obtained with
10 equivalents. Attempts to reduce the amount of
Scheme 2. Scope for the photoreductive allylation of triphe-
allyl sulfone 2a were unsuccessful and resulted in the nylsulfonium triflate (1a).
Table 1. Optimization of the reaction conditions for the photoreductive allylation of 1a with 2a.[a]
Entry
Catalyst (5 mol%)
Ru(bpy)3Cl2·A(H2O)6
Amine (equiv.)
Equiv. of 2a
Yield [%][b]
1
2
3
4
5
6
7
8
9
10
N
G
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
10
10
10
10
10
10
10
1
55
57
<5
11
6
64
67
14
38
56
[Ir(dtbbpy)(ppy)2]PF6
A
U
Eosin Y
Ru
Ru
Ru
Ru
Ru
Ru
Ru
N
(H2O)6
Et3N (2)
p-MeOC6H4NPh2 (2)
G
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
T
C
3
5
[a]
Reaction conditions: substrate 1a (0.2 mmol, 0.2M in CH3CN), catalyst (5 mol%), amine, allyl sulfone 2a, irradiation with
a 14 W fluorescent light bulb at room temperature over 15 h.
Yield of isolated product.
[b]
2
asc.wiley-vch.de
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!

Visible-Light Photocatalytic Reduction of Sulfonium Salts as a Source of Aryl Radicals
Scheme 3. Addition to 1,1-diphenylethylene and 2-arylacrylates.
showed to be much more reactive and the allylated
compound was isolated in 51% yield.
In a major expansion of scope, we sought to change
the nature of the acceptor by activated olefins such as
styrene, acrylate, methacrylate and acrylonitrile. Dis-
appointingly, the isolated yields were low (5–9%) in
all cases, and all attempts for further improvement
were unsuccessful. Besides, no reaction occurred with
electron-rich olefins such as tert-butyl vinyl ether. We
reasoned that 1,1-diphenylethylene (4a) should be
a more efficient aryl radical trap.[24] The allylation
protocol was tested on 1a with 10 equivalents of 4a
Scheme 4. Scope of the sulfonium salts 1a–g.
and the desired addition product was isolated in 70%
yield (Scheme 3. Decreasing the amount of 4a to only
5 equivalents gave about the same yield. Then, we
Based on these results, we propose the following
proposed to trap the transient radical with 2-phenyl- mechanism (Scheme 5). Under visible-light activation,
ACHTUNGTRENNUNGacrylate 6a and its derivatives 6b and 6c. All products the excited state of the ruthenium(II) complex
2+
were obtained in almost similar yields (53–60% for RuACHTNUTRGNEUNG(bpy)3 is reduced by the amine (DIPEA) to give
5 equiv. of 6, 39–40% for 1 equiv.) whatever the elec- a stronger reductant Ru(I) that transfers an electron
tronic nature of the aryl moiety (electron-rich or elec- to the triphenylsulfonium triflate (1a). The generated
tron-poor).
sulfuranyl radical decomposes into diphenyl sulfide
Finally, the influence of the counter-anion nature and phenyl radical.[7b] The latter is then intercepted
and the substitution of the aryl group on the reactivity by either the allyl sulfone or the activated olefin. The
of sulfoniums was evaluated in the reaction with 1,1- transient radical undergoes a b-fragmentation of the
diphenylethylene (4a) (Scheme 4). A screening of SO2Tol radical to form the allylated product or H-ab-
easily accessible sulfonium salts 1a–c with different straction from the amine radical cation to yield the
counter-anions including triflate, tetrafluoroborate reduced compound, respectively. The difference of re-
and hexafluorophosphate showed no significant activity between allyl sulfones, mono-activated and
impact on the reaction efficiency. On the other hand, gem-diactivated olefins (4a or 6) is still not elucidated
a lower yield was obtained with the bromide 1d prob- and appears more complicated than we imagined. It is
ably due to its low solubility. Introduction of electron- worthy of note that the diphenyl sulfide side product
donating substituents such as methyl or tert-butyl does not react under the photoreductive conditions.[25]
groups (1e and 1f, respectively) provided no signifi-
In conclusion, we have devised a mild and efficient
cant modification in the reactivity of the sulfonium method of the generation of aryl radicals by reduction
salt whereas the strong electron-withdrawing fluorine of various triarylsulfonium salts under visible-light
atom slightly lowered the yield to 58%.
photocatalytic conditions. These transient species
proved to participate in different carbon-carbon bond
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
3
ÞÞ
These are not the final page numbers!

Simon Donck et al.
COMMUNICATIONS
trochemica Acta 2003, 48, 1807–1816; c) P. Martigny, J.
Simonet, G. Mousset, J. Vigneron, Nouv. J. Chimie
1983, 7, 299; d) F. D. Saeva, B. P. Bradley, J. Am. Chem.
Soc. 1984, 106, 4121–4125; e) P. Martigny, J. Simonet, J.
Electroanal. Chem. 1979, 101, 275–279; f) A. Stasko, P.
Rapta, V. Brezova, O. Nuyken, R. Vogel, Tetrahedron
1993, 49, 10917–10924; g) L. Pause, M. Robert, J.-M.
Savꢀant, J. Am. Chem. Soc. 2001, 123, 4886–4895;
h) C. P. Andrieux, M. Robert, F. D. Saeva, J.-M. Sa-
vꢀant, J. Am. Chem. Soc. 1994, 116, 7864–7871; i) J. A.
Kampmeier, A. K. M. M. Hoque, F. D. Saeva, D. K.
Wedegaertner, P. Thomsen, S. Ullah, J. Krake, T. Lund,
J. Am. Chem. Soc. 2009, 131, 10015–10022.
[6] a) S.-K. Chung, K. Sasamoto, Chem. Commun. 1981,
346–347; b) P. Beak, T. A. Sullivan, J. Am. Chem. Soc.
1982, 104, 4450–4457; c) M. Hori, T. Kataoka, H. Shi-
mizu, K. Tsutsumi, Tetrahedron Lett. 1989, 30, 981–984;
d) T. Kataoka, K. Tsutsumi, T. Iwama, H. Shimizu, M.
Hori, Tetrahedron Lett. 1990, 31, 3027–3028; e) T. Ka-
taoka, T. Iwama, H. Shimizu, M. Hori, Phosphorus,
Sulfur and Silicon 1992, 67, 169–172; f) 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; g) T. Kataoka, Y. Nakamura, H.
Matsumoto, T. Iwama, H. Kondo, H. Shimizu, O. Mur-
aoka, G. Tanabe, J. Chem. Soc. Perkin Trans. 1 1997,
309–316; h) J. Kampmeier, T. W. Nalli, J. Org. Chem.
1993, 58, 943–949.
[7] a) F. D. Saeva, Tetrahedron 1986, 42, 6123–6129; b) X.
Wang, F. D. Saeva, J. A. Kampmeier, J. Am. Chem.
Soc. 1999, 121, 4364–4368; c) F. D. Saeva, D. T. Breslin,
H. R. Luss, J. Am. Chem. Soc. 1991, 113, 5333–5337;
d) F. D. Saeva, P. A. Martic, E. Garcia, J. Phys. Org.
Chem. 1993, 6, 333–340; e) R. Schwalm, R. Bug, G.-S.
Dai, P. M. Fritz, M. Reinhardt, S. Schneider, W. Schna-
bel, J. Chem. Soc. Perkin Trans.2 1991, 1803–1808; f) L.
Dektar, N. P. Hacker, J. Am. Chem. Soc. 1990, 112,
6004–6015; g) S. L. Nickol, J. A. Kampmeier, J. Am.
Chem. Soc. 1973, 95, 1908–1915.
[8] a) P. A. Baguley, J. C. Walton, Angew. Chem. 1998, 110,
3272–3283; Angew. Chem. Int. Ed. 1998, 37, 3072–3082;
b) A. Studer, S. Amrein, Synthesis 2002, 835–849;
c) Steamlining Free Radical Green Chemistry, (Eds. T.
Perchyonok, I. Lykakis, A. Postigo), RSC Publishing,
Cambridge, 2012.
[9] For seminal works, see: a) D. M. Hedstrand, W. H.
Kruizinga, R. M. Kellogg, Tetrahedron Lett. 1978, 19,
1255–1258; b) T. J. van Bergen, W. H. Kruizinga, R. M.
Kellogg, J. Org. Chem. 1979, 44, 4953–4962; c) H.
Cano-Yelo, A. Deronzier, J. Chem. Soc. Faraday Trans.
1 1984, 80, 3011–3019; d) H. Cano-Yelo, A. Deronzier,
J. Chem. Soc. Perkin Trans. 2 1984, 1093–1098.
Scheme 5. Proposed mechanism for photoreduction of 1a
and subsequent trapping by allyl sufones or activated ole-
fins.
forming processes including allylation and addition to
activated olefins. Future efforts will be dedicated to
extend the scope to other organylsulfonium salts such
as trialkyl derivatives and to design relevant synthetic
applications.
Acknowledgements
We thank UPMC, CNRS, IUF (L.F.), ANR (grant “Credox”)
and Emergence UPMC 2010. Marion Daniel is acknowl-
edged for the synthesis of 1f. Technical assistance was gener-
ously offered by FR 2769.
References
[1] a) The Chemistry of the Sulfonium Group,
(Eds. C. J. M. Stirling, S. Patai), Wiley, New York, 1981;
b) Onium Ions, (Eds.: G. A. Olah, K. K. Laali, G. K.
Wang, Q. Parkash Surya), John Wiley & Son, USA,
1998; c) V. G. Nenaidenko, E. S. Balenkova, Russ. J.
Org. Chem. 2003, 39, 291–330.
[2] L. Fensterbank, J.-P. Goddard, M. Malacria, C. Ollivier,
Chimia 2012, 66, 425–432.
[10] For recent reviews, see: a) M. Fagnoni, D. Dondi, D.
Ravelli, A. Albini, Chem. Rev. 2007, 107, 2725–2756;
b) D. Ravelli, D. Dondi, M. Fagnoni, A. Albini, Chem.
Soc. Rev. 2009, 38, 1999–2011; c) K. Zeitler, Angew.
Chem. 2009, 121, 9969–9974; Angew. Chem. Int. Ed.
2009, 48, 9785–9789; d) T. P. Yoon, M. A. Ischay, J. Du,
[3] a) C. E. Farrar, K. K. W. Siu, H. P. Lynne, J. T. Jarrett,
Biochemistry 2010, 49, 9985–9996; b) M. Fontecave, J.-
L. Pierre, C. R. Acad. Sci. Paris, Chimie/Chemistry
2001, 4, 531–538; c) S. C. Wang, P. A. Frey, Trends in
Biochemical Sciences 2007, 32, 101–110.
ˇ ´
[4] a) M. Bonifacic, E. Anklam, J. Chem. Soc. Perkin
´
Nature Chem. 2010, 2, 527–532; e) F. Teply, Collect.
Trans. 2 1991, 243–248; b) P. Eriksson, L. Engman, J.
Lind, G. Merꢀnyi, Eur. J. Org. Chem. 2005, 701–705.
[5] a) A. Ghanimi, J. Simonet, New J. Chem. 1997, 21, 257–
265; b) T. Kjaersbo, K. Daasbjerg, S. U. Pedersen, Elec-
Czech. Chem. Commun. 2011, 76, 859–917; f) J. M. R.
Narayanam, C. R. J. Stephenson, Chem. Soc. Rev. 2011,
40, 102–113; g) J. W. Tucker, C. R. J. Stephenson, J.
4
asc.wiley-vch.de
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!

Visible-Light Photocatalytic Reduction of Sulfonium Salts as a Source of Aryl Radicals
Org. Chem. 2012, 77, 1617–1622; h) J. Xuan, W.-J. Xiao,
Angew. Chem. 2012, 124, 6934–6944; Angew. Chem.
Int. Ed. 2012, 51, 6828–6838; i) M. A. Ischay, T. P.
Yoon, Eur. J. Org. Chem. 2012, 3359–3372; j) C.-J. Wal-
lentin, J. D. Nguyen, C. R. J. Stephenson, Chimia 2012,
66, 394–398.
Hisaeda, Chem.Commun. 2011, 47, 6548–6550; aa) T.
Koike, M. Akita, Chem. Lett. 2009, 38, 166–167; ab) M.
Neumann, S. Fꢂldner, B. Kçnig, K. Zeitler, Angew.
Chem. 2011, 123, 981–985; Angew. Chem. Int. Ed. 2011,
50, 951–954; ac) F. R. Bou-Hamdan, P. Seeberger,
Chem. Sci. 2012, 3, 1612–1616; ad) J.-D. Xia, G.-B.
Deng, M.-B. Zhou, W. Liu, P. Xie, J.-H. Li, Synlett
2012, 2707–2713; ae) G.-B. Deng, Z.-Q. Wang, J.-D.
Xia, P.-C. Qian, R.-J. Song, M. Hu, L.-B. Gong, J.-H.
Li, Angew. Chem. 2013, 125, 1575–1578; Angew. Chem.
Int. Ed. 2013, 52, 1535–1538.
[11] a) M. A. Ischay, M. E. Anzovino, J. Du, T. P. Yoon, J.
Am. Chem. Soc. 2008, 130, 12886–12887; b) J. Du, T. P.
Yoon, J. Am. Chem. Soc. 2009, 131, 14604–14605; c) Z.
Lu, M. Shen, T. P. Yoon, J. Am. Chem. Soc. 2011, 133,
1162–1164; d) J. Du, L. Ruiz spelt, I. A. Guzei, T. P.
Yoon, Chem. Sci. 2011, 2, 2115–2119; e) A. E. Hurtley,
M. A. Cismesia, M. A. Ischay, T. P. Yoon, Tetrahedron
2011, 67, 4442–4448; f) E. L. Tyson, E. P. Farney, T. P.
Yoon, Org. Lett. 2012, 14, 1110–1113; g) D. Ravelli, M.
Fagnoni, ChemCatChem 2012, 4, 169–171.
[13] M. Zlotorzynska, G. M. Sammis, Org. Lett. 2011, 13,
6264–6267.
[14] a) E. Hasegawa, S. Takizawa, T. Seida, A. Yamaguchi,
N. Yamaguchi, N. Chiba, T. Takahashi, H. Ikedab, K.
Akiyama, Tetrahedron 2006, 62, 6581–6588; b) M.-H.
Larraufie, R. Pellet, L. Fensterbank, J.-P. Goddard, E.
Lacꢄte, M. Malacria, C. Ollivier, Angew. Chem. 2011,
123, 4555–4558; Angew. Chem. Int. Ed. 2011, 50, 4463–
4466.
[12] a) J. M. R. Narayanam, J. W. Tucker, C. R. J. Stephen-
son, J. Am. Chem. Soc. 2009, 131, 8756–8757; b) J. W.
Tucker, J. M. R. Narayanam, S. W. Krabbe, C. R. J. Ste-
phenson, Org. Lett. 2010, 12, 368–371; c) J. W. Tucker,
J. D. Nguyen, J. M. R. Narayanam, S. W. Krabbe,
C. R. J. Stephenson, Chem. Commun. 2010, 4985–4987;
d) L. Furst, B. S. Matsuura, J. M. R. Narayanam, J. W.
Tucker, C. R. J. Stephenson, Org. Lett. 2010, 12, 3104–
3107; e) L. Furst, J. M. R. Narayanam, C. R. J. Stephen-
son, Angew. Chem. 2011, 123, 9829–9833; Angew.Chem.
Int. Ed. 2011, 50, 9655–9659; f) J. W. Tucker, C. R. J.
Stephenson, Org. Lett. 2011, 13, 5468–5471; g) J. W.
Tucker, Y. Zhang, T. F. Jamison, C. R. J. Stephenson,
Angew. Chem. 2012, 124, 4220–4223; Angew. Chem.
Int. Ed. 2012, 51, 4144–4147; h) C.-J. Wallentin, J. D.
Nguyen, P. Finkbeiner, C. R. J. Stephenson, J. Am.
Chem. Soc. 2012, 134, 8875–8884; i) J. D. Nguyen, E. M.
D’Amato, J. M. R. Narayanam, C. R. J. Stephenson,
Nature Chem. 2012, 4, 854–859; j) J. D. Nguyen, B.
Reiß, C. Dai, C. R. J. Stephenson, Chem. Commun.
2012, DOI: 10.1039/C2CC37206A; k) X. Ju, Y. Liang,
P. Jia, W. Li, W. Yu, Org. Biomol. Chem. 2012, 10, 498–
501; l) T. Courant, G. Masson, Chem. Eur. J. 2012, 18,
423–427; m) N. Iqbal, S. Choi, E. Ko, E. J. Cho, Tetrahe-
dron Lett. 2012, 53, 2005–2008; n) J. B. Edson, L. P.
Spencer, J. M. Boncella, Org. Lett. 2011, 23, 6156–6159;
o) R. S. Andrews, J. J. Becker, M. R. Gagnꢀ, Angew.
Chem. 2010, 122, 7432–7434; Angew. Chem.Int. Ed.
2010, 49, 7274–7276; p) R. S. Andrews, J. J. Becker,
M. R. Gagnꢀ, Org. Lett. 2011, 13, 2406–2409; q) R. S.
Andrews, J. J. Becker, M. R. Gagnꢀ, Angew. Chem.
2012, 124, 4216–4219; Angew. Chem. Int. Ed. 2012, 51,
4140–4143; r) Y. Su, L. Zhang, N. Jiao, Org. Lett. 2011,
13, 2168–2171; s) D. A. Nicewicz, D. W. C. MacMillan,
Science 2008, 322, 77–80; t) D. A. Nagib, M. E. Scott,
D. W. C. MacMillan, J. Am. Chem. Soc. 2009, 131,
10875–10877; u) H.-W. Shih, M. N. V. Wal, R. L.
Grange, D. W. C. MacMillan, J. Am. Chem. Soc. 2010,
132, 13600–1360; v) P. V. Pham, D. A. Nagib, D. W. C.
MacMillan, Angew. Chem. 2011, 123, 6243–6246;
Angew. Chem. Int. Ed. 2011, 50, 6119–6122; w) D. A.
Nagib, D. W. C. MacMillan, Nature 2011, 480, 224–228;
x) M. Pirtsch, S. Paria, T. Matsuno, H. Isobe, O. Reiser,
Chem. Eur. J. 2012, 18, 7336–7340; y) T. Maji, A. Kar-
makar, O. Reiser, J. Org. Chem. 2011, 76, 736–739;
z) H. Shimakoshi, M. Nishi, A. Tanaka, K. Chikama, Y.
[15] Y. Chen, A. S. Kamlet, J. B. Steinman, D. R. Liu,
Nature Chem. 2011, 3, 146–153.
[16] a) D. P. Hari, P. Schroll, B. Kçnig, J. Am. Chem.Soc.
2012, 134, 2958–2961; b) P. Schroll, D. P. Hari, B.
Kçnig, ChemistryOpen 2012, 1, 130–133; c) D. P. Hari,
T. Hering, B. Kçnig, Org. Lett. 2012, 14, 5334–5337;
d) D. Kalyani, K. B. McMurtrey, S. R. Neufeldt, M. S.
Sanford, J. Am. Chem. Soc. 2011, 133, 18566–18569;
e) Y. Ye, M. S. Sanford, J. Am. Chem. Soc. 2012, 134,
9034–9037.
[17] a) K. Kalyanasundaram, Coord. Chem. Rev. 1982, 46,
159–244; b) A. Juris, V. Balzani, F. Barigelletti, S. Cam-
pagna, P. Belser, A. von Zelewsky, Coord. Chem. Rev.
1988, 84, 85–277.
[18] a) Y. Yasu, T. Koike, M. Akita, Angew. Chem. 2012,
124, 9705–9709; Angew. Chem. Int. Ed. 2012, 51, 9567–
9571; b) S. Mizuta, S. Verhoog, K. M. Engle, T. Khota-
vivattana, M. OꢁDuill, K. Wheelhouse, G. Rassias, M.
Mꢀdebielle, V. Gouverneur, J. Am. Chem. Soc. 2013,
135, 2505–2508; c) S. Satoshi, K. M. Engle, S. Verhoog,
O. Galicia-Lꢅpez, M. OꢁDuill, M. Mꢀdebielle, K.
Wheelhouse, G. Rassias, A. Thompson, V. Gouverneur,
Org. Lett. 2013, 15, 1250–1253.
[19] For recent reviews, see: a) M. R. Heinrich, Chem. Eur.
J. 2009, 15, 820–833; b) G. Pratsch, M. R. Heinrich,
Top. Curr. Chem. 2012, 320, 33–60; c) W. R. Bowman,
J. M. D. Storey, Chem. Soc. Rev. 2007, 36, 1803–1822;
d) S. E. Vaillard, B. Schulte, A. Studer, in: Modern Ary-
lation Methods: Radical-Based Arylation Methods,
(Ed.: L. Ackermann), Wiley-VCH, Weinheim, 2009,
p 475–511. For recent examples, see: e) A. Dickschat,
A. Studer, Org. Lett. 2010, 12, 3972–3974; f) M. Hart-
mann, Y. Li, A. Studer, J. Am. Chem. Soc. 2012, 134,
16516–16519; g) A. Wetzel, G. Pratsch, R. Kolb, M. R.
Heinrich, Chem. Eur. J. 2010, 16, 2547–2556; h) G.
Pratsch, C. A. Anger, K. Ritter, M. R. Heinrich, Chem.
Eur. J. 2011, 17, 4104–4108; i) T. Taniguchi, H. Zaimo-
ku, H. Ishibashi, Chem. Eur. J. 2011, 17, 4307–4312;
j) J. Wang, S. Wang, G. Wang, J. Zhang, X.-Q. Yu,
Chem. Commun. 2012, 48, 11769–11771; k) S. Seo, M.
Slater, M. F. Greaney, Org. Lett. 2012, 14, 2650–2653;
l) F. Vallꢀe, J. J. Mousseau, A. B. Charrette, J. Am.
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
5
ÞÞ
These are not the final page numbers!

Simon Donck et al.
COMMUNICATIONS
Chem. Soc. 2010, 132, 1514–1519; m) D. Sustac Roman,
Y. Takahashi, A. B. Charrette, Org. Lett. 2011, 13,
3242–3245; n) Ref.[16]
[24] D. H. R. Barton, J. P. Finet, C. Giannotti, F. Halley, J.
Chem. Soc. Perkin Trans. 1 1987, 241–249.
[25] When a solution of Ph2S and 2a (10 equiv.) in acetoni-
trile in the presence [RuACTHNUTRGENNUG(bpy)3]Cl2·ACHTUNGTRNE(NUGN H2O)6 (5 mol%)
and (i-Pr)2NEt (5 equiv.) was irradiated with a light
bulb 14 W for 15 h, no reaction was observed.
[20] J. Q. Chambers, in: Encyclopdia of Electrochemistry of
the Element (Organic Section), (Eds.: A. J. Bard, H.
Lund), Marcel Dekker, New York, Vol. 12, pp 476–485.
[21] W. F. Wacholtz, R. A. Auerbach, R. H. Schmehl, Inorg.
Chem. 1986, 25, 227–234.
[22] a) L. Flamigni, A. Barbieri, C. Sabatini, B. Ventura, F.
Barigelletti, Top. Curr. Chem. 2007, 281, 143–203;
b) J. D. Slinker, A. A. Gorodetsky, M. S. Lowry, J.
Wang, S. Parker, R. Rohl, S. Bernhard, G. G. Malliaras,
J. Am. Chem. Soc. 2004, 126, 2763–2767.
[26] Non-commercially available triarylsulfonium bromides
can be prepared in one step according to the Imazekiꢁs
procedure by reaction of easily accessible diaryl sulfox-
ides with aryl-Grignard reagents in the presence of
TMSCl. The sulfonium bromide salts were isolated
after HBr treatment, see: S. Imazeki, M. Sumino, K.
Fukasawa, M. Ishihara, T. Akiyama, Synthesis 2004,
1648–1654. Counterion metathesis was accomplished
from the corresponding silver salt (see the Supporting
Information).
[23] X.-F. Zhang, I. Zhang, L. Liu, Photochem. Photobiol.
2010, 86, 492–498.
6
asc.wiley-vch.de
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 0000, 000, 0 – 0
ÝÝ
These are not the final page numbers!

COMMUNICATIONS
Visible-Light Photocatalytic Reduction of Sulfonium Salts
as a Source of Aryl Radicals
7
Adv. Synth. Catal. 2013, 355, 1 – 7
Simon Donck, Abdulkader Baroudi, Louis Fensterbank,*
Jean-Philippe Goddard,* Cyril Ollivier*
Adv. Synth. Catal. 0000, 000, 0 – 0
ꢃ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
7
ÞÞ
These are not the final page numbers!