Regioselective C-H Phosphorothiolation of (Hetero)arenes Enabled by the Synergy of Electrooxidation and Ultrasonic Irradiation

Article abstract of DOI:10.1021/acs.orglett.1c01161

An electrochemically regioselective C-H phosphorothiolation of (hetero)arenes with thiocyanate as the S source under ultrasonic irradiation has been developed. The synergistic cooperation of electrooxidation and ultrasonication markedly accelerated the C-H phosphorothiolation reaction. This mechanistically different method is distinguished by its wide substrate scope and transition-metal-free and external-oxidant-free conditions, thus complementing the existing metal-catalyzed or peroxide-mediated protocols for the green synthesis of S-(hetero)aryl phosphorothioates.

Full text of DOI:10.1021/acs.orglett.1c01161

pubs.acs.org/OrgLett
Letter
Regioselective C−H Phosphorothiolation of (Hetero)arenes Enabled
by the Synergy of Electrooxidation and Ultrasonic Irradiation
Ze-Yin Meng, Cheng-Tao Feng,* Ling Zhang, Qing Yang, De-Xiang Chen, and Kun Xu*
Cite This: Org. Lett. 2021, 23, 4214−4218
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: An electrochemically regioselective C−H phosphor-
othiolation of (hetero)arenes with thiocyanate as the S source under
ultrasonic irradiation has been developed. The synergistic cooperation
of electrooxidation and ultrasonication markedly accelerated the C−H
phosphorothiolation reaction. This mechanistically different method is
distinguished by its wide substrate scope and transition-metal-free and
external-oxidant-free conditions, thus complementing the existing
metal-catalyzed or peroxide-mediated protocols for the green synthesis of S-(hetero)aryl phosphorothioates.
Scheme 1. Strategies of S-(Hetero)aryl Phosphorothioates
Syntheses
lectrooxidation utilizes electrons as clean oxidants to
afford reactive intermediates under mild conditions. Thus
E
it has been recognized as a green synthetic tool for organic
synthesis.1 For the electrooxidation process, mass transport of
reactants or mediators from a bulk electrolytic solution to an
anode surface always plays a significant role in achieving high
conversions and selectivities.2 Recently, to address mass-
transport limitations, the merger of electrooxidation and flow
technology has provided new opportunities for green syn-
thesis.3 Ultrasonication is known to enhance mass transport
based on a physical phenomenon called acoustic cavitation.4
Consequently, a number of organic reactions can be carried
out with improved efficiency under ultrasonic irradiation.5
From a synthetic standpoint, the merger of electrooxidation
and ultrasonication holds considerable potential to access
previously challenging reactivity in a more efficient and
environmentally friendly way; however, there have been
limited successful examples to tap the full potential of the
sustainability of electrooxidation and the acoustic cavitation of
ultrasonication.6
S-(Hetero)aryl phosphorothioates constitute important
structural motifs of natural products and biological molecules,
which exhibit valuable antibacterial,7 antitumor,8 anticholines-
terase,9 and insecticidal activities.10 Thus impressive efforts
have been made to develop new synthetic methodologies for
constructing S-(hetero)aryl phosphorothioates. Traditional
methods for the preparation of S-aryl phosphorothioates
have mainly relied on the condensation of arylthiols with
prefunctionalized phosphorylation reagents, such as phosphor-
ochloridates and phosphorobromidates (Scheme 1a),11 or the
Michaelis−Arbuzov-type reaction of sulfonyl halides, sulfenyl
halides, disulfides, or other derivatives with phosphites
(Scheme 1b).12 However, the need for prefunctionalized
substrates and the compatibility issues that result from the
harsh conditions remain impediments of these methods. The
cross-dehydrogenative coupling (CDC) of arylthiols with
P(O)−H compounds provides an attractive alternative to
obtain S-aryl phosphorothioates because prefunctionalization
steps are avoided (Scheme 1c).13 However, the limited
availability of arylthiols restricts the structural diversity of the
products. In addition, the smell of arylthiols is very strong and
Received: April 4, 2021
Published: May 13, 2021
https://doi.org/10.1021/acs.orglett.1c01161
© 2021 American Chemical Society
Org. Lett. 2021, 23, 4214−4218
4214

Organic Letters
pubs.acs.org/OrgLett
Letter
unpleasant. Therefore, the employment of suitable aryl
precursors and odorless sulfur-containing reagents as the
equivalent of aryl thiols is highly desirable. Recently, Tang and
coworkers reported a series of Cu-catalyzed or I2/TBHP-
mediated phosphorothiolations of aryl precursors (arylboronic
acids, diaryliodonium, or arenediazonium salts) with P(O)−H
compounds and sulfur powder (Scheme 1d).14 These powerful
methods afforded diversely functionalized S-(hetero)aryl
phosphorothioates in moderate to excellent yields. However,
from the viewpoint of green synthesis, it would be much more
attractive and yet challenging to synthesize S-(hetero)aryl
phosphorothioates from readily available building blocks
without the use of metal catalysts or external chemical
oxidants. In a continuation of our research interest in
electrosynthesis,15 we herein report a green synthesis of S-
(hetero)aryl phosphorothioates enabled by the synergy of
electrooxidation and ultrasonic irradiation (Scheme 1e). This
three-component oxidative cross-coupling strategy employs a
combination of thiocyanate and dimethyl phosphite as the
equivalent of thiophosphate, which has not yet been reported.
The obviation of metal catalysts and chemical redox reagents
makes this protocol attractive for the green synthesis of S-
(hetero)aryl phosphorothioates.
in the formation of the desired product in a trace amount
(entries 2 and 3). When DMSO, DMF, or MeOH was
employed as the solvent, the yield decreased to 74, 65, and
82%, respectively (entries 4−6). Increasing the substrate
concentration improved the yield of 4aa to 90% (entry 7).
When KSCN was used instead of NH4SCN, only a trace
amount of product was observed (entry 8). In addition, control
experiments showed that the base, electrolyte, and electricity
were all crucial for the reaction (entries 9−11). Without
ultrasonication, the yield of 4aa decreased to 44% (entry 12),
which demonstrated the synergy of electrooxidation and
ultrasonic irradiation.
With the optimal reaction conditions in hand, we explored
the substrate scope of this methodology. First, a variety of
imidazo[1,5-a]pyridines were coupled to NH4SCN (2a) and
dimethyl phosphite (3a) under the optimized reaction
conditions, and the results are shown in Scheme 2. The
presence of electron-withdrawing substituents (−F, −Cl, and
−Br) at the pyridine ring of imidazo[1,5-a]pyridines smoothly
Scheme 2. Electrochemical C−H Phosphorothiolation of
a
Imidazo-Fused Heterocycles
Imidazo[1,5-a]pyridine, a N-containing fused heterocycle,
has wide applications in the fields of pharmaceutical and
material sciences.16 As part of our ongoing research on the
synthesis and functionalization of imidazo[1,5-a]pyridines,17
we initiated our study by investigating the electrochemical
coupling of 3-phenylimidazo[1,5-a]pyridine (1a) and
NH4SCN (2a) with dimethyl phosphite (3a) (Table 1).
a
Table 1. Selected Optimization of Reaction Conditions
b
entry
deviation from standard conditions
yield (%)
1
none
84
2
3
4
5
6
7
8
9
n-Bu4NCl instead of n-Bu4NHSO4
n-Bu4NI instead of n-Bu4NHSO4
DMSO as the solvent
DMF as the solvent
MeOH as the solvent
5 mL of CH3CN was used
KSCN instead of NH4SCN
no DBU
trace
trace
74
65
82
90
trace
trace
trace
ND
44
10
11
12
no electrolyte
no electricity
no ultrasonication
a
Reaction conditions: platinum plate anode (1 × 1 cm2), platinum
plate cathode (1 × 1 cm2), 1a (0.3 mmol), 2a (0.6 mmol), 3a (0.9
mmol), n-Bu4NHSO4 (0.25 mmol), DBU (0.4 mmol), CH3CN (7
mL), room temperature, 15 mA, undivided cell, ultrasonic irradiation
b
(50 W, 40 kHz), 2−4 h. Isolated yields. ND, not detected.
When the electrolysis was conducted at a constant current of
15 mA with n-Bu4NHSO4/CH3CN as the electrolytic solution
and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the base in
an undivided cell equipped with platinum electrodes under
ultrasonic irradiation (50W, 40 kHz) at room temperature, the
desired product 4aa was obtained in 84% yield (entry 1).
Changing the electrolyte to n-Bu4NClO4 or n-Bu4NI resulted
a
Reaction conditions: platinum plate anode (1 × 1 cm2), platinum
plate cathode (1 × 1 cm2), 1 (0.3 mmol), 2a (0.6 mmol), 3 (0.9
mmol), n-Bu4NHSO4 (0.25 mmol), DBU (0.4 mmol), CH3CN (5
mL), room temperature, constant current = 15 mA, undivided cell,
ultrasonic irradiation (50 W, 40 kHz), room temperature, 2−4 h (the
reaction time for each substrate is shown in the Supporting
Information); isolated yields.
4215
https://doi.org/10.1021/acs.orglett.1c01161
Org. Lett. 2021, 23, 4214−4218

Organic Letters
pubs.acs.org/OrgLett
Letter
reacted with 2a and 3a to afford the desired products (4ab−
4af) in moderate yields. Imidazo[1,5-a]pyridines bearing
electron-donating groups (−Me and −OMe) also worked
well to give 4ag and 4ah in 78 and 58% yields, respectively.
Next, the effect of the substituent at the C-3 position of the
imidazo[1,5-a]pyridines was examined. The imidazo[1,5-a]-
pyridine moiety with halogen-substituted phenyl rings at the
C-3 position gave the corresponding C-1 phosphorothiolated
products (4ai−4al) in excellent yields. It is noteworthy to
mention that no obvious steric hindrance was observed for this
transformation (4ai and 4ak). When R2 was replaced by
isopropyl or isobutyl, the reactions proceeded smoothly to
produce 4am and 4an in good yields. The benzyl-substituted
imidazo[1,5-a]pyridine was found to be very effective for
phosphorothiolation (4ao). Interestingly, the presence of an
ester group had no obvious influence on the reaction (4ap,
66%). In addition, imidazo[1,5-a]quinolines were amendable
to the standard conditions, affording 4aq in 55% yield.
Furthermore, to extend the scope of this protocol, other
phosphites were also examined under the standard conditions.
It is gratifying that diethyl phosphite and diisopropyl phosphite
also smoothly underwent C−H phosphorothiolation to
provide the phosphorothiolated products (4ar and 4as) in
97 and 95% yields, respectively. However, diphenyl phosphite
failed to afford the target product, mainly due to its relatively
weak nucleophilicity.
lated products (6e and 6f) in good yield. N-Methyl pyrrole, 1-
phenylpyrrole, and 2-methoxythiophene were also well
tolerated in this reaction (6g−6i). However, substrates having
higher oxidation potentials, such as N-Boc indole, N-Ts
pyrrole, and imidazole, failed to give the corresponding
products (6j−6l).
To gain insight into the reaction mechanism, we carried out
a series of control experiments. First, when 1a and 2a were
electrolyzed in the absence of phosphite 3a and DBU,
thiocyanated intermediate A was isolated in 99% yield,
whereas no conversion occurred without electricity (Scheme
4a). When the thiocyanated intermediate A was electrolyzed in
Scheme 4. Control Experiments
To illustrate the general applicability of the sonoelectro-
chemical methodology, we turned our attention to the scope of
other (hetero)arenes (Scheme 3). Free (N−H) indoles
underwent C−H phosphorothiolation, regioselectively afford-
ing C-3 phosphorothiolated products in moderate yields (6a
and 6b). By contrast, N-methylindoles gave the desired
products in excellent yields (6c and 6d). Gratifyingly,
trimethoxybenzene and N,N-dimethylaniline were found to
be suitable substrates for the reaction to give phosphorothio-
Scheme 3. Electrochemical C−H Phosphorothiolation of
a
Other (Hetero)arenes
the absence of phosphite 3a, the disulfide intermediate B was
separated in 83% yield, whereas intermediate A was recovered
without electrolysis (Scheme 4b). As expected, intermediates A
and B could react with phosphite 3a in the presence of DBU
without electrolysis to give the desired product 4aa in 72 and
30% yields, respectively (Scheme 4c,d). These results showed
that A and B were key intermediates of this three-component
coupling reaction. When a radical scavenger such as 2,2,6,6-
tetramethyl-1-piperidinyl-oxy (TEMPO) or 2,6-ditert-butyl-4-
methylphenol (BHT) was added to the reaction mixture, the
reaction was slightly inhibited to give 4aa in 81 and 80% yields,
respectively (Scheme 4e). These results implied that a radical
species was not involved in the rate-determining steps. The
effect of ultrasonic irradiation on different reaction steps was
also investigated. The yields of A, B, and 4aa significantly
decreased in the absence of ultrasonic irradiation (Scheme 4a−
d), which demonstrated that the previously mentioned
reaction steps were all accelerated by ultrasonic irradiation.
a
Standard reaction conditions are shown in Scheme 2; isolated yields.
4216
https://doi.org/10.1021/acs.orglett.1c01161
Org. Lett. 2021, 23, 4214−4218

Organic Letters
pubs.acs.org/OrgLett
Letter
The reaction progress could be clearly monitored by TLC.
(See Figure S2 in the Supporting Information for details.)
When 1a and 2a were electrolyzed in the absence of phosphite
3a and DBU, intermediates A and B appeared successively
with time. When the substrate 1a disappeared, phosphite 3a
and DBU were added to the reaction system. As the reaction
progressed, intermediates A and B gradually disappeared, and
the target products 4aa accumulated.
combination of thiocyanate and phosphite as the equivalent
of thiophosphate, which has not yet been reported. This
mechanistically different method is distinguished by its wide
substrate scope and transition-metal-free and external oxidant-
free conditions.
ASSOCIATED CONTENT
■
sı
* Supporting Information
Cyclic voltammetric (CV) experiments were then carried
out to figure out which coupling component undergoes
electrochemical oxidation first. (See Figures S3−S6 in the
Supporting Information for details.) As shown in Figure S3
and S4, 3-phenylimidazo[1,5-a]pyridine (1a) and NH4SCN
(2a) have similar oxidation potentials, whereas phosphite 3a
remains intact within the tested potential window (Figure S5).
In addition, the CV of NH4SCN shows two oxidation
processes between 0.7 and 1.7 V and a reduction process at
0.25 V, which correspond to the pseudohalide system of
{SCN−(SCN)3−(SCN)2} (Figure S4).18
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.1c01161.
1
Experimental procedures, characterization data, and H
and 13C NMR of new compounds (PDF)
AUTHOR INFORMATION
Corresponding Authors
■
Cheng-Tao Feng − School of Pharmacy, Anhui University of
Chinese Medicine, Hefei 230012, China; School of Chemical
Engineering, Anhui University of Science and Technology,
Huainan 232001, China; Email: fengct@mail.ustc.edu.cn
Kun Xu − Faculty of Environment and Life, Beijing University
of Technology, Beijing 100124, China; orcid.org/0000-
0002-0419-8822; Email: kunxu@bjut.edu.cn
On the basis of the control experiments and CV studies, a
plausible mechanism was proposed, as shown in Scheme 5.
Scheme 5. Tentative Mechanistic Pathway
Authors
Ze-Yin Meng − School of Pharmacy, Anhui University of
Chinese Medicine, Hefei 230012, China; School of Chemical
Engineering, Anhui University of Science and Technology,
Huainan 232001, China
Ling Zhang − School of Chemical Engineering, Anhui
University of Science and Technology, Huainan 232001,
China
Qing Yang − School of Chemical Engineering, Anhui
University of Science and Technology, Huainan 232001,
China
De-Xiang Chen − School of Chemical Engineering, Anhui
University of Science and Technology, Huainan 232001,
China
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.1c01161
Initially, imidazo[1,5-a]pyridine (1a) undergoes electrooxida-
tion to give radical cation C, which is attacked by −SCN to give
radical D. Then, radical D has a further electrooxidation to
afford carbocation E. Alternatively, −SCN could be oxidized at
the anode and then undergo dimerization to produce the
electrophilic intermediate (SCN)2, which would then trapped
by imidazo[1,5-a]pyridine (1a) to give carbocation E. Because
substrates having higher oxidation potentials failed in this
reaction (Scheme 3, 6j−6l), the reaction sequence involving
intermediate C should be the major reaction pathway. The
resulting intermediate E subsequently undergoes deprotona-
tion to produce the thiocyanated intermediate A, which is
attacked by the nucleophilic phosphite 3a to yield product 4aa
(path I). Meanwhile, intermediate A could also be transformed
into disulfide B,19 which would react with nucleophilic
phosphite 3a to produce product 4aa (path II).
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by Anhui Provincial Natural Science
Foundation (2008085MB50), Graduate Innovation Founda-
tion of Anhui University of Science and Technology (grant
2019CX2057), Program for Science and Technology Innova-
tion Talents in Universities of Henan Province (19HAS-
TIT033), and Beijing Municipal Commission of Education
Project (KM202110005006).
REFERENCES
■
(1) Recent reviews: (a) Jiang, Y. Y.; Xu, K.; Zeng, C. C. Use of
Electrochemistry in the Synthesis of Heterocyclic Structures. Chem.
Rev. 2018, 118, 4485−4540. (b) Xiong, P.; Xu, H.-C. Chemistry with
Electrochemically Generated N-Centered Radicals. Acc. Chem. Res.
2019, 52, 3339−3350. (c) Siu, J. C.; Fu, N.; Lin, S. Catalyzing
Electrosynthesis: A Homogeneous Electrocatalytic Approach to
Reaction Discovery. Acc. Chem. Res. 2020, 53, 547−560. (d) Wang,
F.; Stahl, S. S. Electrochemical Oxidation of Organic Molecules at
Lower Overpotential: Accessing Broader Functional Group Compat-
In summary, we have developed a green synthesis of S-
(hetero)aryl phosphorothioates enabled by the synergy of
electrooxidation and ultrasonic irradiation. The synergistic
cooperation of electrooxidation and ultrasonication markedly
accelerated the C−H phosphorothiolation reaction. This three-
component oxidative cross-coupling strategy employs the
4217
https://doi.org/10.1021/acs.orglett.1c01161
Org. Lett. 2021, 23, 4214−4218

Organic Letters
pubs.acs.org/OrgLett
Letter
ibility with Electron−Proton Transfer Mediators. Acc. Chem. Res.
2020, 53, 561−574. (e) Ackermann, L. Metalla-electrocatalyzed C−H
Activation by Earth-Abundant 3d Metals and Beyond. Acc. Chem. Res.
2020, 53, 84−104. (f) Jiao, K.-J.; Xing, Y.-K.; Yang, Q.-L.; Qiu, H.;
Mei, T.-S. Site-Selective C−H Functionalization via Synergistic Use of
Electrochemistry and Transition Metal Catalysis. Acc. Chem. Res.
2020, 53, 300−310.
Zhang, S.; Xu, K. Electrochemical Synthesis of trans-2,3-Disubstituted
Aziridines via Oxidative Dehydrogenative Intramolecular C(sp3)−H
Amination. Org. Lett. 2019, 21, 9430−9433. (c) Zhang, S.; Li, L.; Li,
J.; Shi, J.; Xu, K.; Gao, W.; Zong, L.; Li, G.; Findlater, M.
Electrochemical Arylation of Aldehydes, Ketones, and Alcohols: from
Cathodic Reduction to Convergent Paired Electrolysis. Angew. Chem.,
Int. Ed. 2021, 60, 7275−7282.
(16) (a) Fauber, B. P.; Gobbi, A.; Robarge, K.; Zhou, A.; Barnard,
A.; Cao, J.; Deng, Y.; Eidenschenk, C.; Everett, C.; Ganguli, A.;
Hawkins, J.; Johnson, A. R.; La, H.; Norman, M.; Salmon, G.;
Summerhill, S.; Ouyang, W.; Tang, W.; Wong, H. Discovery of
imidazo[1,5-a]pyridines and -pyrimidines as potent and selective
RORc inverse agonists. Bioorg. Med. Chem. Lett. 2015, 25, 2907−
2912. (b) Fuse, S.; Ohuchi, T.; Asawa, Y.; Sato, S.; Nakamura, H.
Development of 1-aryl-3-furanyl/thienyl-imidazopyridine templates
for inhibitors against hypoxia inducible factor (HIF)-1 transcriptional
activity. Bioorg. Med. Chem. Lett. 2016, 26, 5887−5890.
(2) Pletcher, D.; Green, R. A.; Brown, R. C. D. Flow Electrolysis
Cells for the Synthetic Organic Chemistry Laboratory. Chem. Rev.
2018, 118, 4573−4591.
(3) Elsherbini, M.; Wirth, T. Electroorganic Synthesis under Flow
Conditions. Acc. Chem. Res. 2019, 52, 3287−3296 and references
cited therein.
(4) Cravotto, G.; Cintas, P. Power ultrasound in organic synthesis:
moving cavitational chemistry from academia to innovative and large-
scale applications. Chem. Soc. Rev. 2006, 35, 180−196.
(5) Puri, S.; Kaur, B.; Parmar, A.; Kumar, H. Applications of
Ultrasound in Organic Synthesis - A Green Approach. Curr. Org.
Chem. 2013, 17, 1790−1828 and references cited therein..
(6) (a) Atobe, M.; Sasahira, M.; Nonaka, T. Ultrasonic effects on
electroorganic processes: Part 17. Product selectivity control in
cathodic reduction of acrylonitrile. Ultrason. Sonochem. 2000, 7, 103−
107. (b) Shen, Y.; Atobe, M.; Fuchigami, T. Electroorganic Synthesis
Using a Fluoride Ion Mediator under Ultrasonic Irradiation:1
Synthesis of Oxindole and 3-Oxotetrahydroisoquinoline Derivatives.
Org. Lett. 2004, 6, 2441−2444. (c) Sunaga, T.; Atobe, M.; Inagi, S.;
Fuchigami, T. Highly efficient and selective electrochemical
fluorination of organosulfur compounds in Et3N·3HF ionic liquid
under ultrasonication. Chem. Commun. 2009, 8, 956−958.
(7) Kazuo, H.; Katsuki, H.; Mitsuo, H.; Masaru, N.; Kenji, T.;
Masaaki, Y. Phenyl Thiophosphate Fungicides. Jpn. Kokai Tokkyo
Koho JP 48018461 B 19730606, 1973.
(8) Reddy, E. P.; Reddy, M. V. R.; Bell, S. C. Substituted Phenoxy-
And Phenylthio- Derivatives for Treating Proliferative Disorders. PCT
Int. Appl. WO 2005089269 A2, 2005.
(9) Lee, A.-h.; Metcalf, R. L. In vitro inhibition of acetylcholinester-
ase by O,O-dimethyl S-aryl phosphorothioates. Pestic. Biochem.
Physiol. 1973, 2, 408−417.
(10) Murdock, L.; Hopkins, T. Insecticidal, anticholinesterase, and
hydrolytic properties of O,O-dialkyl S-aryl phosphorothiolates in
relation to structure. J. Agric. Food Chem. 1968, 16, 954−958.
(11) Qiu, Y.; Worch, J. C.; Chirdon, D. N.; Kaur, A.; Maurer, A. B.;
Amsterdam, S.; Collins, C. R.; Pintauer, T.; Yaron, D.; Bernhard, S.;
Noonan, K. J. T. Tuning Thiophene with Phosphorus: Synthesis and
Electronic Properties of Benzobisthiaphospholes. Chem. - Eur. J. 2014,
20, 7746−7751.
(17) (a) Wang, H. Q.; Xu, W. T.; Wang, Z. Q.; Yu, L. T.; Xu, K.
Copper-Catalyzed Oxidative Amination of sp3 C−H Bonds under
Air: Synthesis of 1,3-Diarylated Imidazo[1,5-a]pyridines. J. Org. Chem.
2015, 80, 2431−2435. (b) Wang, H. Q.; Xu, W. T.; Xin, L. L.; Liu, W.
M.; Wang, Z. Q.; Xu, K. Synthesis of 1,3-Disubstituted Imidazo[1,5-
a]pyridines from Amino Acids via Catalytic Decarboxylative Intra-
molecular Cyclization. J. Org. Chem. 2016, 81, 3681−3687. (c) Feng,
C. T.; Wei, H. J.; Li, J.; Peng, Y.; Xu, K. Synthesis of Cyanide-
Functionalized Imidazo[1,5-a]quinolines via Copper-Mediated Aero-
bic Three-Component Cyclizations. Adv. Synth. Catal. 2018, 360,
4726−4730.
(18) A similar CV behavior of pseudohalide SeCN− can be found in:
Solangi, A.; Bond, A. M.; Burgar, L.; Hollenkamp, A. F.; Horne, M.
D.; Ru
Electrochemical and NMR Investigations of the SeCN/(SeCN) /
̈
ther, T.; Zhao, C. Comparison of Diffusivity Data Derived from
̅
2
(SeCN)3
6852.
̅
System in Ionic Liquids. J. Phys. Chem. B 2011, 115, 6843−
(19) This hypothesis was evidenced by the control experiment
(Scheme 4b). A similar process can be found in: Yang, L.; Tian, Z.-Y.;
Zhang, C.-P. Transition-Metal-Free Selective Synthesis of (Z)-1,2-
Diarylthio-1-arylalkenes, (2-Arylethene-1,1,2-triyl)tris(arylsulfane)s
and Alkynyl Sulfides from Thiocyanates and Terminal Arylalkynes.
ChemistrySelect 2019, 4, 311−315.
(12) (a) Ouyang, Y.-J.; Li, Y.-Y.; Li, N.-B.; Xu, X.-H. A simple and
convenient method for the synthesis of S-aryl phosphorothioates
catalyzed by cesium hydroxide. Chin. Chem. Lett. 2013, 24, 1103−
1105. (b) Bai, J.; Cui, X.; Wang, H.; Wu, Y. Copper-catalyzed
reductive coupling of aryl sulfonyl chlorides with H-phosphonates
leading to S-aryl phosphorothioates. Chem. Commun. 2014, 50,
8860−8863. (c) Moon, Y.; Moon, Y.; Choi, H.; Hong, S. Metal- and
oxidant-free S−P(O) bond construction via direct coupling of P(O)H
with sulfinic acids. Green Chem. 2017, 19, 1005−1013.
(13) Li, C.-Y.; Liu, Y.-C.; Li, Y.-X.; Reddy, D. M.; Lee, C.-F.
Electrochemical Dehydrogenative Phosphorylation of Thiols. Org.
Lett. 2019, 21, 7833−7836 and references cited therein.
(14) (a) Xu, J.; Zhang, L.; Li, X.; Gao, Y.; Tang, G.; Zhao, Y.
Phosphorothiolation of Aryl Boronic Acids Using P(O)H Com-
pounds and Elemental Sulfur. Org. Lett. 2016, 18, 1266−1269.
(b) Shi, H.; Chen, J.; Zhuo, S.; Wu, Z.; Fang, M.; Tang, G.; Zhao, Y.
Iodide-Catalyzed Phosphorothiolation of Heteroarenes Using P(O)H
Compounds and Elemental Sulfur. Adv. Synth. Catal. 2019, 361,
3210−3216.
(15) Selected examples: (a) Zhang, S.; Li, L. J.; Zhang, J. J.; Zhang, J.
Q.; Xue, M. Y.; Xu, K. Electrochemical fluoromethylation triggered
lactonizations of alkenes under semi-aqueous conditions. Chem. Sci.
2019, 10, 3181−3185. (b) Wang, H. Q.; Shi, J.; Tan, J. J.; Xu, W.;
4218
https://doi.org/10.1021/acs.orglett.1c01161
Org. Lett. 2021, 23, 4214−4218