Photoinduced Oxidative Cross-Coupling for O-S Bond Formation: A Facile Synthesis of Alkyl Benzenesulfonates

Article abstract of DOI:10.1055/s-0036-1588728

We have developed a photoinduced oxidative cross-coupling of thiophenols with alcohols for O-S bond formation. The protocol uses visible light, a metal-free photocatalyst, and oxygen as the oxidant for the selective synthesis of alkyl benzenesulfonates; no ligand co-additive is necessary. Mechanistic studies suggested that the disulfide and alkyl benzenesulfinate are involved as intermediates and that the transformation proceeds by a radical pathway.

Full text of DOI:10.1055/s-0036-1588728

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Photoinduced Oxidative Cross-Coupling for O–S Bond Formation:
A Facile Synthesis of Alkyl Benzenesulfonates
Atul K. Singha
Hong Yia
Guoting Zhanga
Changliang Biana
Pengkun Peia
Aiwen Lei*a,b
a College of Chemistry and Molecular Sciences, The Institute for
Advanced Studies (IAS), Wuhan University, Wuhan, Hubei
430072, P. R. of China
b National Research Center for Carbohydrate Synthesis, Jiangxi
Normal University, Nanchang 330022, Jiangxi, P. R. of China
aiwenlei@whu.edu.cn
Received: 10.01.2017
Accepted after revision: 30.01.2017
Published online: 28.02.2017
compounds play key roles in the activities of some en-
zymes, and these enzymes are often deactivated by active
oxygen species.5 For example, the photooxygenation of me-
thionine causes deactivation of several important en-
zymes.4k,6
DOI: 10.1055/s-0036-1588728; Art ID: st-2017-r0028-c
Abstract We have developed a photoinduced oxidative cross-coupling
of thiophenols with alcohols for O–S bond formation. The protocol uses
visible light, a metal-free photocatalyst, and oxygen as the oxidant for
the selective synthesis of alkyl benzenesulfonates; no ligand co-additive
is necessary. Mechanistic studies suggested that the disulfide and alkyl
benzenesulfinate are involved as intermediates and that the transfor-
mation proceeds by a radical pathway.
Although the photooxidation of organosulfur com-
pounds has been investigated for a long time with a variety
of reagents, the photooxidative cross-coupling of thiols
with alcohols has never been studied, though it is of current
interest. The photooxidation of sulfur with oxygen is com-
plex because of the number of oxidation states of sulfur and
it can give rise to a variety of oxidized oxysulfur com-
pounds, depending on the reaction conditions.7 In continu-
ation of our efforts in photocatalysis and oxidative cross-
coupling reactions,2a–c,2e,g,i we became interested in the de-
velopment of photoinduced oxidative cross-coupling
reactions of thiophenols and alcohols for O–S bond forma-
tion. Here, we report a photooxidative cross-coupling of
thiols with alcohols for a selective and ecofriendly synthe-
sis of alkyl benzenesulfonates (Scheme 1). The sulfonates
are useful intermediates in organic synthesis, medicinal
chemistry, and polyether chemistry.8 They are widely used
as precursors of cyclic crown ethers, aza crown ethers, and
lariat ethers.8 Conventional methodologies, which use tosyl
chloride, tosyl anhydride, or p-toluenesulfonic acid as mois-
ture-sensitive and reactive sulfonylating reagents for the
synthesis of sulfonates, require an equimolar amount of
base or Lewis acid or an expensive alkylating agent, which
generate significant amount of byproducts in the form of
dissolved salts that then require a high level of biological
and chemical oxygen demand.9 The tight restrictions on the
release of waste or toxic emissions, to reduce environmen-
tal pollution, have induced a paradigm shift in the develop-
ment of new synthetic strategies. In this context, a visible-
light-induced cross-coupling reaction that uses oxygen as a
Key words photoredox catalysis, alkyl benzenesulfonates, C–S bond
formation, dioxygen, oxidative coupling.
In the past year, cross-coupling reactions have emerged
as one of the most powerful tools and a fundamental meth-
odology for the construction of carbon–carbon and carbon–
heteroatom bonds in modern synthesis.1 Various conven-
tional coupling reactions of two functionalized starting ma-
terials have been replaced by the improved oxidative cou-
pling reactions, because they are environmentally benign
and do not require prior functionalization of the sub-
strate.1e,2 Numerous oxidative cross-coupling processes
have been developed for the construction of carbon–carbon
and carbon–heteroatom bonds in the last few years. How-
ever, only a few methods are available for the construction
of heteroatom–heteroatom bonds, and these are restricted
to P–N and P–O bonds.1e Therefore, the development of ver-
satile and selective oxidative cross-coupling reactions for
the construction of heteroatom–heteroatom bonds would
offer a useful strategy and would be a welcome move.
Since the first contribution on the photooxidation of a
simple sulfide by Schenck and Krauch in 1962,3 the photo-
oxidation of organosulfur compounds has been extensively
studied, because such compounds are ubiquitous in natural
biological systems.4 In biological systems, organosulfur
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green oxidant would provide an economical, energetically
beneficial opportunity for clean processing and pollution
prevention.2,10
evaluate the scope of the alcohol, various alcohols 2 were
treated with 4-methoxybenzenethiol (1a) under the stan-
dard optimized conditions for oxidative cross-coupling to
give an O–S bond. As shown in Scheme 2, a range of prima-
ry alcohols, including 2,2,2-trifluoroethanol, participated in
the O–S coupling and gave the corresponding benzenesul-
fonates in good yields. The secondary alcohol substrate pro-
pan-2-ol could also be employed in the reaction, giving iso-
propyl 4-methoxybenzenesulfonate (3e) in 69% yield. The
scope with tertiary alcohols was also examined, but the de-
sired product was not obtained under the optimized condi-
tions. We then examined the scope of the reaction for the
synthesis of sulfonates 3h–l by using various thiophenols 1.
A series of functional groups on the thiophenol, including
methyl, methoxy, or fluoro were tolerated under the mild
reaction conditions.
Scheme 1 Visible-light-promoted synthesis of alkyl benzenesulfonates
In the initial stages of our work, we selected 4-methoxy-
benzenethiol (1a) and methanol (2a) as model substrates,
and, on the basis of earlier reports, the 9-mesityl-10-meth-
ylacridinium ion (Acr+–Mes) as a photocatalyst. We chose
Acr+–Mes for our optimization studies because it has been
shown to be an efficient photoredox catalyst in various
photooxidative transformations, as a result of its high oxi-
dizing ability and reducing ability.11 After a series of screen-
ing studies on the reaction conditions (for details, see Sup-
porting Information, Tables S1, S2, S3, and S4), we found
that use of 5 mol% of 9-mesityl-10-methylacridinium per-
chlorate with 3 mL of methanol (2a) and 4-methoxyben-
zenethiol (1a; 1.0 mmol) delivered the maximum yield
(70%) of methyl 4-methoxybenzenesulfonate 3a (see Sup-
porting Information, Table S3, entry 9). In addition, we per-
formed a series of control experiments to confirm the nec-
essary parameters for the reaction, such as catalyst, air, and
visible light (Table 1). Control experiments indicated that
no desired product was observed when light, photocatalyst,
or oxygen were absent.
R2
O
S
–
5 mol% Acr+–Mes ClO4
O2, r.t., blue LED
R2 OH
SH
O
R1
R1
O
1
2
3
O
O
O
O
O
O
S
S
S
O
O
O
O
O
O
3a, 70%, 18h
3b, 52%, 18h
3c, 63 %,48 h
O
O
O
O
S
O
S
O
S
O
O
O
O
O
O
3d, 68%, 50h
3e, 69%, 60h
3f, 61 %, 60 h
Table 1 Control Experiments to Confirm the Necessary Parameters of
the ReactionA
O
O
O
S
O
O
S
O
–
5 mol% Acr+–Mes ClO4
F
O
S
O
O
S
O
MeOH
O
SH
O
O
O
O
F
F
O
r.t., blue light
O
3g, 54%, 72h
3h, 56%, 30h
3i, 53%, 30h
1a
2a
3a
F
O
O
Entry
Photocatalyst
Oxidant
Blue light
Yieldb,c (%)
O
S
O
S
O
S
1
2
3
4
5
+
+
–
+
+
O2
air
O2
O2
N2
+
+
+
–
+
72 (70)
trace
no
O
O
O
O
O
O
3j, 65%, 36h
3k, 45%, 72h
3l, 53%, 18h
Scheme 2 Exploration of the substrate scope for the synthesis of alkyl
benzenesulfones 3. Reagents and conditions: thiophenol 1 (1.0 mmol),
photocatalyst (5.0 mol%), alcohol 2 (3.0 mL), O2, 3 W blue LEDs, r.t.,
18–72 h. Isolated yields were calculated for the conversion of two moles
of the thiophenol 1 into one mole of the corresponding product 3.
no
no
a Reaction conditions: 1a (1.0 mmol), photocatalyst (5.0 mol%), MeOH (2a;
3.0 mL), r.t., oxidant, 3 W blue LED illumination, 18 h.
b Determined by GC using biphenyl as an internal standard; the yield in pa-
rentheses is the isolated yield.
c Yield calculated on the basis of two moles of the thiophenol 1a being re-
quired for conversion into one mole of product 3a.
We conducted a number of experiments to gain a rea-
sonable insight into the reaction mechanism (Scheme 3).
Initially, we studied the progress of reaction with 4-me-
thoxybenzenethiol (1a, 1.0 mmol) and 9-mesityl-10-meth-
ylacridinium perchlorate (5.0 mol%) as model substrate and
photocatalyst, respectively, in methanol (2a, 3 mL) at r.t.,
and we monitored the progress of the reaction by TLC. After
With the optimized reaction conditions in hand, we
next examined the substrate scope and limitations of this
process by changing the alcohol and thiophenol. The results
are illustrated by the examples detailed in Scheme 2.12 To
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–F

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A. K. Singh et al.
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two and eight hours, new spots appeared on TLC, and the
corresponding intermediate products were isolated in 95%
and 42% yield, respectively; these were confirmed to be
1,1′-disulfanediylbis(4-methoxybenzene) (6a) and methyl
4-methoxybenzenesulfinate (10a), respectively (Scheme 3, a).
To confirm that 6a and 10a were intermediates in the
reaction, we subjected these compounds to the standard re-
action conditions and obtained the product methyl 4-me-
thoxybenzenesulfonate (3a) in 47% and 99% yields, respec-
tively (Scheme 3, b). When methyl 4-methoxybenzenesulfi-
(Scheme 3, b). These experiments confirmed that the reac-
tion proceeds via 1,1′-disulfanediylbis(4-methoxybenzene)
(6a) and methyl 4-methoxybenzenesulfinate (10a) as inter-
mediates, and that these compounds participate in the cat-
alytic cycle.
To confirm that a radical process is involved in this reac-
tion, we performed radical-trapping and EPR experiments.
The radical-trapping experiment was performed by adding
the conventional radical scavenger TEMPO under the stan-
dard reaction conditions. The reaction was completely in-
hibited, and methyl 4-methoxybenzenesulfonate (3a) was
nate (10a) was oxidized with dioxygen without
a
photocatalyst, only a trace of product 3a was obtained
a) Synthesis of Intermediate:
SH
OMe
–
5 mol% Acr+–Mes ClO4
S
MeOH
S
O2, r.t., 2 h, blue LEDs
MeO
MeO
MeO
1a
2a
6a, 95%
O
SH
–
5 mol% Acr+–Mes ClO4
S
MeOH
O
O2, r.t., 8 h
blue LEDs
MeO
1a
2a
10a, 42%
b) Intermediate Probe:
OMe
O
S
–
5 mol% Acr+–Mes ClO4
O2, r.t., blue LEDs
S
S
MeOH
MeO
MeO
MeO
O
O
O
O
MeO
6a
2a
3a, 47%
3a, 99%
3a, n.d.
O
S
O
S
5 mol% Acr+–Mes ClO4
O2, r.t., blue LED
–
O
MeOH
O
MeO
10a
10a
2a
O
O
S
S
O
MeOH
O2, r.t., blue LED
O
MeO
2a
c) Evidence in Support of Radical Pathway:
5 mol% Acr+–Mes ClO4
–
O
TEMPO (1.0 equiv)
MeO
S
O
O
MeOH
MeO
SH
O2, r.t., 24 h, blue LEDs
1a
d) 18O-Labelling Experiment:
2a
3a, n.d.
18O
–
5 mol% Acr+–Mes ClO4
S
MeOH
O
MeO
SH
18O2, r.t., 24 h, blue LEDs
MeO
1a
2a
10a, 64%
Scheme 3 Preliminary mechanistic investigations
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–F

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A. K. Singh et al.
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We also performed oxygen-labelling experiments. In
the presence of 18O2 labelled dioxygen, the 18O-labelled
product methyl 4-methoxybenzenesulfinate (10a) (from
the m/z) was obtained in 64% yield, confirming that dioxy-
gen took part in this transformation, and that the S–O bond
originates from the dioxygen (Scheme 3, d).
On the basis of these control experiments, a possible
mechanism for this photoinduced cross-coupling reaction
for the synthesis of alkyl benzenesulfonates is shown in
Scheme 4. The photocatalytic reaction is initiated by intra-
molecular photoinduced electron transfer from the mesity-
lene moiety to the singlet excited state of the Acr+ moiety of
Acr+–Mes, which affords Acr•–Mes•+. The Mes•+ moiety can
oxidize the thiophenol 1 to produce the radical cation 4,
whereas the Acr• moiety can reduce O2 to O2•–. The resulting
thiophenol radical cation 4 gives the corresponding thiyl
radical 5 through deprotonation. The thiyl radical 5 then
undergoes homocoupling to form a disulfide 6. Disulfide 6
undergoes a further one-electron oxidation to form a disul-
fide radical cation 7, which is oxidized to form the thioper-
sulfinate 8. This is simultaneously attacked by the alcohol
to form intermediate 9, which then undergoes photooxida-
tive fragmentation to form alkyl benzenesulfinate 10 and
benzenesulfonic acid 11 (confirmed by HRMS). Benzenesul-
finate 10 is further oxidized to afford the benzenesulfonate
product 3.
Figure 1 EPR studies of radical species in the oxidative reaction
not formed at all (Scheme 3, c). Electron paramagnetic reso-
nance (EPR) experiments were also conducted to gain an in-
sight into the mechanism. The EPR spectrum of a mixture of
4-methoxybenzenethiol (1a, 0.25 mmol), 9-mesityl-10-
methylacridinium perchlorate (5 mol%), and methanol (2a,
3 mL) displayed a resonance characteristic of an organic
H
radical (g = 2.0070, αN = 13.3 G,αβ = 7.9 G) (Figure 1). We
propose that this might correspond to an oxygen-centered
radical–5,5-dimethylpyrroline N-oxide (DMPO) adduct. The
results of the trapping and EPR experiments indicated the
participation of organic radicals in the reaction.
Scheme 4 Plausible mechanism for the photoinduced cross-coupling of thiophenols and alcohols for the synthesis of alkyl benzenesulfonates
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In conclusion, we have described the first photoinduced
oxidative cross-coupling reaction of thiophenols with alco-
hols for the mild synthesis of alkyl benzenesulfonates in
moderate to good yields. A simple and metal-free precata-
lyst is employed, and no ligand co-additive is necessary. A
series of mechanistic studies suggests that the photoin-
duced O−S coupling proceeds through an SET/radical path-
way. An advantage of our method over reported methods is
that it does not require an expensive alkylating agent, a
Lewis acid, or an equimolar amount of base.
1987, 109, 1478. (f) Sawaki, Y.; Ogata, Y. J. Am. Chem. Soc. 1981,
103, 5947. (g) Takata, T.; Tamura, Y.; Ando, W. Tetrahedron 1985,
41, 2133. (h) Akasaka, T.; Ando, W. Tetrahedron Lett. 1985, 26,
5049. (i) Clennan, E. L.; Chen, X. J. Am. Chem. Soc. 1989, 111,
5787. (j) Ando, W.; Kabe, Y.; Miyazaki, H. Photochem. Photobiol.
1980, 31, 191. (k) Ando, W.; Takata, T. In Singlet O2; Vol. III, Part
2; Frimer, A. A., Ed.; CRC Press: Boca Raton, 1985, 1.
(5) (a) Organic Chemistry of Sulfur; Oae, S., Ed.; Plenum Press: New
York, 1977. (b) Block, E. Reactions of Organosulfur Compounds;
Academic Press: New York, 1978.
(6) Sysak, P. K.; Foote, C. S.; Ching, T.-Y. Photochem. Photobiol. 1977,
26, 19.
(7) (a) Banchereau, E.; Lacomhe, S.; Ollivier, J. Tetrahedron Lett.
1995, 36, 8197. (b) Robert-Banchereau, E.; Lacombe, S.; Ollivier,
J. Tetrahedron 1997, 53, 2087. (c) Baciocchi, E.; Crescenzi, C.;
Lanzalunga, O. Tetrahedron 1997, 53, 4469. (d) Lacombe, S.;
Cardy, H.; Simon, M.; Khoukh, A.; Soumillion, J. P.; Ayadim, M.
Photochem. Photobiol. Sci. 2002, 1, 347. (e) Sheu, C.; Foote, C. S.;
Gu, C.-L. J. Am. Chem. Soc. 1992, 114, 3015. (f) Jensen, F. J. Org.
Chem. 1992, 57, 6478. (g) Lacombe, S.; Loudet, M.; Dargelos, A.;
Robert-Banchereau, E. J. Org. Chem. 1998, 63, 2281.
(h) Memarian, H. R.; Mohammadpoor-Baltork, I.; Bahrami, K.
Bull. Korean Chem. Soc. 2006, 27, 106. (i) Lakkaraju, P. S.; Zhou,
D.; Roth, H. D. J. Chem. Soc., Perkin Trans. 2 1998, 1119. (j) Albini,
A.; Bonesi, S. M. J. Photosci. 2003, 10, 1. (k) Baciocchi, E.; Del
Giacco, T.; Ferrero, M. I.; Rol, C.; Sebastiani, G. V. J. Org. Chem.
1997, 62, 4015. (l) Clennan, E. L.; Zhou, W.; Chan, J. J. Org. Chem.
2002, 67, 9368. (m) Latour, V.; Pigot, T.; Simon, M.; Cardy, H.;
Lacombe, S. Photochem. Photobiol. Sci. 2005, 4, 221. (n) Clennan,
E. L. Acc. Chem. Res. 2001, 34, 875.
(8) (a) Larock, R. C. Comprehensive Organic Transformations:
A Guide to Functional Group Preparations; Wiley-VCH: Wein-
heim, 1997. (b) Horning, J. E. C. In Synthetic Organic Chemistry;
Vol. 3; Wagner, R. B.; Zokk, H. D., Eds.; Wiley: New York, 1953.
(c) Sandler, S. R.; Karo, W. Organic Functional Group Prepara-
tions; Academic: New York, 1983, 2nd ed., Vol. 1. (d) Kabalka, G.
W.; Varma, M.; Varma, R. S.; Srivastava, P. C.; Knapp, F. F. Jr.
J. Org. Chem. 1986, 51, 2386. (e) Cragg, P. J. A Practical Guide to
Supramolecular Chemistry; Wiley: Chichester, 2005.
(9) (a) Kurita, K. Chem. Ind. (London) 1974, 345. (b) Yoshida, Y.;
Sakakura, Y.; Aso, N.; Okada, S.; Tanabe, Y. Tetrahedron 1999, 55,
2183. (c) Hartung, J.; Hünig, S.; Kneuer, R.; Schwarz, M.;
Wenner, H. Synthesis 1997, 1433. (d) O’Connell, J. F.; Rapoport,
H. J. Org. Chem. 1992, 57, 4775. (e) Katritzky, A. R.; Zhang, G.;
Wu, J. Synth. Commun. 1994, 24, 205. (f) Kazemi, F.; Massah, A.
R.; Javaherian, M. Tetrahedron 2007, 63, 5083. (g) Asano, K.;
Matsubara, S. Org. Lett. 2009, 11, 1757. (h) Karaman, R.; Leader,
H.; Goldblum, A.; Breuer, E. Chem. Ind. (London) 1987, 857.
(i) Klamann, D.; Weyerstahl, P. Chem. Ber. 1965, 98, 2070.
(j) Nitta, Y.; Arakawa, Y. Chem. Pharm. Bull. 1985, 33, 1380.
(k) Mukaiyama, T.; Hojo, K. Chem. Lett. 1976, 893. (l) Choudary,
B. M.; Chowdari, N. S.; Kantam, M. L. Tetrahedron 2000, 56,
7291. (m) Das, B.; Reddy, V. S.; Reddy, M. R. Tetrahedron Lett.
2004, 45, 6717. (n) Velusamy, S.; Kiran, J. S. K.; Punniyamurthy,
T. Tetrahedron Lett. 2004, 45, 203. (o) Comagic, S.; Schirrmacher,
R. Synthesis 2004, 885. (p) Morita, J.; Nakatsuji, H.; Misaki, T.;
Tanabe, Y. Green Chem. 2005, 7, 711. (q) Morita, J.-i.; Nakatsuji,
H.; Misaki, T.; Tanabe, Y. Adv. Synth. Catal. 2006, 348, 2057.
(10) (a) Yoon, T. P.; Ischay, M. A.; Du, J. Nat. Chem. 2010, 2, 527.
(b) Sun, C.-L.; Shi, Z.-J. Chem. Rev. 2014, 114, 9219. (c) Shi, L.;
Xia, W. Chem. Soc. Rev. 2012, 41, 7687. (d) Prier, C. K.; Rankic, D.
A.; MacMillan, D. W. C. Chem. Rev. 2013, 113, 5322. (e) Xie, Z.;
Wang, C.; deKrafft, K. E.; Lin, W. J. Am. Chem. Soc. 2011, 133,
Acknowledgment
This work was supported by the National Natural Science Foundation
of China (21390400, 21520102003, 21272180, 21302148), the Hubei
Province Natural Science Foundation of China (2013CFA081), the Re-
search Fund for the Doctoral Program of Higher Education of China
(20120141130002), and the Ministry of Science and Technology of
China (2012YQ120060). The Program of Introducing Talents of Disci-
pline to Universities of China (111 Program) is also appreciated.
Supporting Information
Supporting information for this article is available online at
http://dx.doi.org/10.1055/s-0036-1588728.
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References and Notes
(1) (a) New Trends in Cross-Coupling: Theory and Applications;
Colacot, T., Ed.; RSC: Cambridge, 2015. (b) Metal-Catalyzed
Cross-Coupling Reactions and More; de Meijere, A.; Oestreich,
M., Eds.; Wiley-VCH: Weinheim, 2014. (c) Metal-Catalyzed
Cross-Coupling Reactions; de Meijere, A.; Diederich, F., Eds.;
Wiley-VCH: Weinheim, 2004, 2nd ed., Vol. 2. (d) Johansson
Seechurn, C. C. C.; Kitching, M. O.; Colacot, T. J.; Snieckus, V.
Angew. Chem. Int. Ed. 2012, 51, 5062. (e) Lee, C.-F.; Liu, Y.-C.;
Badsara, S. S. Chem. Asian J. 2014, 9, 706. (f) Liu, C.; Zhang, H.;
Shi, W.; Lei, A. Chem. Rev. 2011, 111, 1780.
(2) (a) Liu, C.; Yuan, J.; Gao, M.; Tang, S.; Li, W.; Shi, R.; Lei, A. Chem.
Rev. 2015, 115, 12138. (b) Zhang, G.; Liu, C.; Yi, H.; Meng, Q.;
Bian, C.; Chen, H.; Jian, J.-X.; Wu, L.-Z.; Lei, A. J. Am. Chem. Soc.
2015, 137, 9273. (c) Liu, C.; Liu, D.; Lei, A. Acc. Chem. Res. 2014,
47, 3459. (d) Girard, S. A.; Knauber, T.; Li, C.-J. Angew. Chem. Int.
Ed. 2014, 53, 74. (e) Wang, J.; Liu, C.; Yuan, J.; Lei, A. Angew.
Chem. Int. Ed. 2013, 52, 2256. (f) Liu, Q.; Jackstell, R.; Beller, M.
Angew. Chem. Int. Ed. 2013, 52, 13871. (g) Liu, D.; Liu, C.; Li, H.;
Lei, A. Angew. Chem. Int. Ed. 2013, 52, 4453. (h) Zhang, C.; Tang,
C.; Jiao, N. Chem. Soc. Rev. 2012, 41, 3464. (i) Chen, M.; Zheng, X.;
Li, W.; He, J.; Lei, A. J. Am. Chem. Soc. 2010, 132, 4101. (j) Zhao,
Y.; Wang, H.; Hou, X.; Hu, Y.; Lei, A.; Zhang, H.; Zhu, L. J. Am.
Chem. Soc. 2006, 128, 15048. (k) Li, Z.; Li, C.-J. J. Am. Chem. Soc.
2004, 126, 11810.
(3) Schenck, G. O.; Krauch, C. H. Angew. Chem. 1962, 74, 510.
(4) (a) Straight, R. C.; Spikes, J. D. In Singlet O2; Vol. IV; Frimer, A. A.,
Ed.; Chap. 2; CRC Press: Boca Raton, 1985, 91. (b) Gu, C.-L.;
Foote, C. S.; Kacher, M. L. J. Am. Chem. Soc. 1981, 103, 5949.
(c) Gu, C.-L.; Foote, C. S. J. Am. Chem. Soc. 1982, 104, 6060.
(d) Liang, J.-J.; Gu, C.-L.; Kacher, M. L.; Foote, C. S. J. Am. Chem.
Soc. 1983, 105, 4717. (e) Jensen, F.; Foote, C. S. J. Am. Chem. Soc.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–F

F
A. K. Singh et al.
Cluster
Synlett
2056. (f) Xie, J.; Xue, Q.; Jin, H.; Li, H.; Cheng, Y.; Zhu, C. Chem.
Sci. 2013, 4, 1281. (g) Liu, J.; Liu, Q.; Yi, H.; Qin, C.; Bai, R.; Qi, X.;
Lan, Y.; Lei, A. Angew. Chem. Int. Ed. 2014, 53, 502. (h) Ischay, M.
A.; Anzovino, M. E.; Du, J.; Yoon, T. P. J. Am. Chem. Soc. 2008, 130,
12886. (i) Dirocco, D. A.; Rovis, T. J. Am. Chem. Soc. 2012, 134,
8094. (j) Deng, G.-B.; Wang, Z.-Q.; Xia, J.-D.; Qian, P.-C.; Song, R.-
J.; Hu, M.; Gong, L.-B.; Li, J.-H. Angew. Chem. Int. Ed. 2013, 52,
1535. (k) Cherevatskaya, M.; Neumann, M.; Füldner, S.;
Harlander, C.; Kümmel, S.; Dankesreiter, S.; Pfitzner, A.; Zeitler,
K.; König, B. Angew. Chem. Int. Ed. 2012, 51, 4062. (l) Cai, S.;
Zhao, X.; Wang, X.; Liu, Q.; Li, Z.; Wang, D. Z. Angew. Chem. Int.
Ed. 2012, 51, 8050. (m) Wang, K.; Meng, L.-G.; Zhang, Q.; Wang,
L. Green Chem. 2016, 18, 2864.
(11) (a) Fukuzumi, S.; Ohkubo, K. Chem. Sci. 2013, 4, 561.
(b) Fukuzumi, S.; Ohkubo, K. Org. Biomol. Chem. 2014, 12, 6059.
(12) Alkyl Benzenesulfonates 3; General Procedure
An oven-dried Schlenk tube equipped with a magnetic stirrer
bar was charged with Acr+–Mes ClO4– (5.0 mol%), capped with a
septum, and evacuated. A balloon filled with O2 was connected
to the Schlenk tube through the side arm, and thiophenol 1(1.0
mmol) and alcohol 2 (3.0 mL) were successively injected into
the reaction tube. The mixture was irradiated with light from
blue LEDs (3.0 W) and vigorously stirred at r.t. for 18–72 h (see
Scheme 2). When the reaction was complete (TLC), the product
was purified by flash column chromatography (silica gel, PE–
EtOAc).
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–F