Angewandte
Communications
Chemie
Organocatalysis
Hot Paper
Disulfide-Catalyzed Visible-Light-Mediated Oxidative Cleavage of
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C C Bonds and Evidence of an Olefin–Disulfide Charge-Transfer
Complex
Yuchao Deng, Xiao-Jing Wei, Hui Wang, Yuhan Sun, Timothy Noꢀl, and Xiao Wang*
Abstract: A photocatalytic method for the aerobic oxidative
methods have been reported with the photon as a traceless
reagent and a green source of energy.[8–12] In general, these
methods require UV light, or catalysts that are toxic[8] or
metal-based,[9] or a demandingly oxidative photoredox cata-
lyst to be SET-reduced by the olefin.[10–12] Alternatively, it
would be attractive to seek a non-metal photocatalyst that
functions via a non-redox/sensitization mechanism, and
preferably with a reduced cost than most photocatalysts.
Herein, we report a visible-light aerobic OCO method that
utilizes inexpensive aromatic disulfide as photocatalyst
(Scheme 1).
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cleavage of C C bonds has been developed. Electron-rich
aromatic disulfides were employed as photocatalyst. Upon
visible-light irradiation, typical mono- and multi-substituted
aromatic olefins could be converted into ketones and aldehydes
at ambient temperature. Experimental and computational
studies suggest that a disulfide–olefin charge-transfer complex
is possibly responsible for the unconventional dissociation of
À
S S bond under visible light.
T
he oxidative cleavage of olefins (OCO) is a widely applied
transformation in organic synthesis, since it introduces
oxygen-containing functional groups such as ketones and
aldehydes from inexpensive olefinic feedstock.[1] Despite the
simplicity of the reaction, a practical and mild OCO method is
still one of the long-sought goals in the development of
modern chemical methods. One of the most popular methods
for this transformation is still the old-fashioned ozonolysis,[2]
which requires an ozone generator and displays serious safety
issues owing to the toxicity of O3. Modern OCO reactions
include methods employing stoichiometric metal or non-
metal reagents that are either toxic or strongly oxidizing,[1] or
methods that utilizing molecular oxygen as a safer and cleaner
oxidant in combination of catalytic amount of transition-
metal complexes[3–5] or heat-initiated radical precursors (such
as NHPI[6] or AIBN[7]). Recently, photochemical OCO
Scheme 1. Summary of previous OCO methods.
Several previously reported radical-catalyzed OCO reac-
tions involved the formation of a dioxetane that decomposes
to give the product aldehyde or ketone.[3,6,7] In seeking
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a photoinitiated radical that could reversibly add to the C C
[*] Y. Deng, Prof. H. Wang, Prof. Y. Sun, Prof. X. Wang
CAS Key Lab of Low-Carbon Conversion Science and Engineering
Shanghai Advanced Research Institute
bond, we envisioned that the thiyl radical generated by the
photolysis of disulfide could serve as an ideal catalyst.[13,14]
Recently, examples of disulfide-catalyzed photoreactions
were reported, in which disulfide undergoes photolysis to
catalyze the diboration of terminal alkynes,[15a] or the
reduction of a carbon–halide bond with NHC-borane,[15b] or
the [3+2] cycloaddition.[15c] They required light from the UV
Chinese Academy of Sciences
100 Haike Road, Pudong, Shanghai 201210 (P.R. China)
E-mail: wangxiao@sari.ac.cn
Y. Deng, Prof. Y. Sun
School of Physical Science and Technology, ShanghaiTech University
Shanghai 201210 (P.R. China)
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region because the dissociation of typical aromatic S S bond
Y. Deng
cannot occur under visible light.[16]
University of Chinese Academy of Sciences
Beijing 100049 (P.R. China)
In the hope of establishing a photocatalytic OCO method
with visible light instead of the harmful and equipment-
demanding UV light, we were intrigued by the acceleration
effect in the thiol–olefin co-oxidation (TOCO) reported and
studied in-depth decades ago.[17–21] In the presence of an
olefin, the overall rate for the oxidation–addition sequence is
significantly faster than the SET oxidation of thiol alone,
owing to the formation of an olefin–thiol charge-transfer
complex (CTC; Scheme 2).[17,18] To the best of our knowledge,
the same effect between olefin and disulfide has not been
reported to date. Recently, photochemical activity of electron
donor–acceptor complex (EDA complex) formed in situ[22–24]
X.-J. Wei, Prof. T. Noꢀl
Department of Chemical Engineering and Chemistry
Micro Flow Chemistry and Process Technology
Eindhoven University of Technology
Den Dolech 2, 5612 AZ Eindhoven (The Netherlands)
Prof. X. Wang
Harvard NeuroDiscovery Center
Harvard Medical School and Brigham & Women’s Hospital
65 Landsdowne Street, Cambridge, MA 02139 (USA)
E-mail: xwang21@bics.bwh.harvard.edu
Supporting information for this article can be found under:
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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