Functionalization of primary ch bonds in picolines toward pyridylthioamides

Article abstract of DOI:10.1246/BCSJ.20200004

We report a method for coupling of nitroarenes, 2- or 4-methylazaarenes, and elemental sulfur to afford (2-pyridyl)aryl thioamides. Good tolerance of functionalities was observed, including primary and secondary amines, bromo, iodo, ester, and boronic est

Full text of DOI:10.1246/BCSJ.20200004

Document type: Article
Functionalization of Primary C-H Bonds in Picolines toward
Pyridylthioamides
Tuan H. Ho,1,2 Ha H. K. Le,1,2 Tuong A. To,1,2 Tung T. Nguyen,*1,2 and Nam T. S. Phan*1,2
1Faculty of Chemical Engineering, Ho Chi Minh City University of Technology (HCMUT),
268 Ly Thuong Kiet, District 10, Ho Chi Minh City, Vietnam
2Vietnam National University Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam
E-mail: ptsnam@hcmut.edu.vn (N. T. S. Phan), tungtn@hcmut.edu.vn (T. T. Nguyen)
Received: January 7, 2020; Accepted: March 27, 2020; Web Released: June 5, 2020
Nam T. S. Phan
Nam T. S. Phan did his PhD with Dr Peter Styring at The University of Sheffield (UK), and conducted his
postdoctoral research with Dr Christopher W. Jones at Georgia Institute of Technology (USA). His current
research focuses on new methods for organic synthesis.
Tung T. Nguyen
Tung T. Nguyen did his PhD with Dr. Olafs Daugulis at University of Houston where he developed synthetic
methodologies for palladium and cobalt-catalyzed, directed functionalization of sp2 and sp3 C–H bonds. He
is currently an associate researcher at HCMC University of Technology, VNU-HCM, working with Prof. Nam
T. S. Phan in the development of new methods for S-heterocycle syntheses.
Abstract
Synthesis of (2-pyridyl)aryl methanes via palladium-catalyzed
decarboxylation or C-C cleavage was feasible.1c,1d The suc-
cesses were dependent on the use of palladium catalysis and
monodentate phosphine ligands. Xia and Huang reported a rare
method for addition of C-H bonds in 2-methyl azaarenes to
imines.1e One example of palladium-catalyzed, pyridine-
directed coupling of methylene C-H bonds with aryl bromides
was also presented.1f It should be noted that most of the known
methods have suffered from the use of relatively scarce second-
row transition metals. Only a couple of examples that allow for
the metal-free, base-promoted activation of sp3 C-H bonds in
methylpyridines have been reported.2 In 2011, Knochel devel-
oped a method for zincation of picolines with TMPZnCl.LiCl
(TMP = 2,2,6,6-tetramethylpiperidyl).2a The benzylzinc inter-
mediates were then used for coupling with aryl bromides. If
electron-deficient nitroarenes were treated with strong bases
such as tBuOK, arylation of activated methyl and methylene
C-H bonds in substituted quinoxalines, quinolines, and azoles
was obtained regioselectively.2b Yet those transformations are
still far from practicality, since they often require extremely
hygroscopic conditions.
We report a method for coupling of nitroarenes, 2- or 4-
methylazaarenes, and elemental sulfur to afford (2-pyridyl)aryl
thioamides. Good tolerance of functionalities was observed,
including primary and secondary amines, bromo, iodo, ester,
and boronic ester groups. Thioamides derived from pyrazole,
thiazole, quinoline, quinoxalines, and azoles were obtained in
good yields, showing the compatibility of heterocycles. This
appears to be a general method to obtain pyridyl thioamides in
one step from commercial, simple substrates.
Keywords: Pyridylthioamide
j
Elemental sulfur
j
Picolines
1. Introduction
Activation of sp3 C-H bonds in alkylazaarenes has been
targeted over the last decades, since it is an atom-economical
scheme to obtain complex heterocycles. Since a seminal report
of Fagnou for directed C-H arylation of 2-methyl picoline N-
oxides,1a many attempts have been devoted to broadening the
substrate scope with regard to functionalization of primary C-
H bonds. Charette described an N-pyridinium ylide-directed
arylation of activated methyl groups with aryl chlorides.1b
The use of elemental sulfur as a metal-free representative
in organic syntheses is emerging.3a In comparison with other
Bull. Chem. Soc. Jpn. 2020, 93, 783–789 | doi:10.1246/bcsj.20200004
© 2020 The Chemical Society of Japan | 783

methods using strong bases, those promoted by elemental
sulfur are much easier to handle under air. Nguyen reported
early examples for sulfur-mediated synthesis of 2-heteroaryl
benzothiazoles via functionalization of primary C-H bonds in
picolines.3b,3c Using elemental sulfur in functionalization of
activated sp3 C-H bonds adjacent to ketone,3d carboxylic
acid,3e and alcohol3f groups was known. Herein we report our
attempts to afford (2-pyridyl)arylthioamides by coupling nitro-
arenes, 2-/4-picolines, and elemental sulfur. Although synthe-
sis of N-arylthioamides is feasible,4 the scope of the reactants
has not been well established with heterocycles. Three exam-
ples of thiopicolinanilides were prepared by reactions of pico-
lines, anilines, and elemental sulfur at elevated temperatures.4a
Aromatic aldehydes, phenylacetic acids, and styrenes were also
competent substrates to couple with anilines.4b-4d Pace and co-
workers described a rare addition of aryllithium compounds to
isothiocyanates to afford hindered thioamides.4e Given that N-
arylpicolinamides are extensively used to stabilize high-valent
metal complexes,5 developing a method to obtain pyridylthio-
amides should be of interest. More importantly, uses of com-
mercial, simple substrates such as nitroarenes, picolines, and
elemental sulfur would increase the practicality of the method.
rich (3ad, 3ae, 3af) and electron-poor (3ag, 3ah) nitro com-
pounds were all reactive. Hindered nitroarenes successfully
yielded the pyridylthioamides (3ab, 3ac), proving that steric
effect somewhat does not affect the transformation. Function-
alities such as primary amine (3ae), secondary amine (3af),
ester (3ag), bromo (3ah), iodo (3ai), and boronic ester (3aj)
groups were compatible with reaction conditions. Coupling of
nitro-substituted heteroarenes such as that containing pyrazole
(3ak), pyridine (3al), and benzothiazole (3am) afforded the
thioamides in moderate to good yields.
In some nitroarenes, 2-phenylbenzothiazoles were obtained,
presumably after a sequence of thioamidation/cyclization
(Scheme 2). It should be noted that such a sulfur-mediated
cyclization often suffered from the use of prefunctionalized
ortho-halo nitroarenes.6 In our condition, the reaction of 3-
methoxy nitrobenzene afforded a 2:1 ratio of the desired
thioamide (3am) and a related 2-pyridyl benzothiazole (4am).
Replacing the methoxy group with a more electron-donating
group such as Me2N gave selective cyclization products (4an,
4a¤n). Piperazine-derived nitrobenzene was also compatible
with the conditions (4ao). The use of 6-nitroquinoline to couple
with 2-picoline gave products (3ap, 4ap) in low yields.
2. Results and Discussion
N
H
N
sulfur (2 equiv)
NO2
N
+
We firstly focused our attention on the reaction of nitro-
benzene 1a, 2-picoline 2a, and elemental sulfur to afford
picolinethioamide 3aa. A few control experiments are shown in
Table 1. An 87% yield of the product was obtained if DABCO
base was used (Entry 1). The reaction was tolerant of other
tertiary amines, albeit giving lower yields (Entries 2 and 3).
Inorganic bases were inert to the transformation (Entry 4).
Omitting DABCO caused the reaction yield to plummet, show-
ing the crucial role of the amine (Entry 5). The transformation
required the use of excess 2-picoline 2a (Entry 6). Running the
reaction at a temperature lower than 120 °C was not sufficient
to obtain an affordable yield (Entry 7). Lastly, if the reaction
was carried out under air, 3aa was obtained in 68% yield
(Entry 8).
Ar
Ar
DABCO (0.75 equiv)
under argon, 120 °C
S
N
N
N
H
N
H
H
H
N
F3C
N
N
N
S
S
S
H2N
S
3ae, 36%
3ac, 62%
3ad, 71%
3ab, 73%
N
N
N
H
N
H
H
Br
N
N
S
S
S
N
EtOOC
O
3ah, 68%
3af, 63%
3ag, 54%
N
H
N
H
N
H
N
N
I
N
S
O
B
S
N
S
O
3ak, 72%
3aj, 57%
3ai, 59%
N
Scope of the reaction with respect to nitroarenes is next
investigated and presented in Scheme 1. In general, electron-
N
H
H
N
S
N
N
S
3am, 61%
S
3al, 58%
N
Table 1. Control experimentsa
N
Scheme 1. Scope of nitroarenes.
H
NO2
N
N
sulfur (2 equiv)
+
R
N
R
N
S
NO2
+
DABCO (0.75 equiv)
under argon, 120 °C
S
sulfur (2 equiv)
1a
2a
2 equiv
3aa
X
Y
and/or
N
DABCO (0.75 equiv)
under argon, 120 °C
H
N
X = N, Y = CH
or
X = CH, Y = N
S
Entry
variation from standard conditions
yield of 3aa, %
R
1
2
3
4
5
6
7
8
none
87, 85b
28
49
<5
18
35
37
68
N
H
Me2N
X
N
S
MeO
1-methylmorpholine instead of DABCO
1,4-dimethylpiperazine instead of DABCO
K2CO3 instead of DABCO
no DABCO
N
N
S
MeO
N
Y
+
S
X = N, Y = CH, 4ao, 88%
X = CH, Y = N, 4a'o, 81%
4an, 21%
3an, 40%
MeN
N
H
N
N
1 equivalent of 2a was used
100 °C instead of 120 °C
under air instead argon
N
N
N
N
S
+
N
S
S
N
4ap, 71%
3aq, 11%
4aq, 29%
aNitrobenzene (0.5 mmol), under argon for 16 h. Yields are GC
b
yields using diphenyl ether internal standard. Isolated yield.
Scheme 2. Thioamidation/cyclization of nitroarenes.
784 | Bull. Chem. Soc. Jpn. 2020, 93, 783–789 | doi:10.1246/bcsj.20200004
© 2020 The Chemical Society of Japan

N
N
X
Y
R
H
N
H
N
H
X
Y
N
sulfur (2 equiv)
N
sulfur (2 equiv)
+
NO2
+
N
NO2
+
+
Ph
Ph
R
Ph
Ph
Ph
DABCO (0.75 equiv)
under argon, 120 °C
S
S
DABCO (0.75 equiv)
under argon, 120 °C
S
N
2a'
X = N, Y = CH
or X = CH, Y = N
1a
2a
3aa, 37% yield
3aa', 16% yield
2a/2a' = 1:1
NH2
N
H
N
without TEMPO: 78% yield
0.5 equiv TEMPO: 55% yield
N
sulfur (2 equiv)
N
N
NO2
H
+
Ph
H
H
N
Ph
N
N
DABCO (0.75 equiv)
under argon, 120 °C
S
Ph
Ph
3ca
Ph
1a
2c
2a
S
S
S
N
H
N
3da, 67%
3ca, 78%
3ba, 35%
N
sulfur (2 equiv)
NO2
Ph
+
F
Ph
no DABCO
under argon, 120 °C
S
1a
3aa, 48% yield
N
H
N
N
H
H
3 equiv
N
N
N
N
N
H
Ph
Ph
Ph
Ph
Ph
N
N
sulfur (2 equiv)
S
S
NO2
Ph
S
+
Ph
DABCO (0.75 equiv)
under argon, 120 °C
S
3ga, 66%
3ea, 86%
3fa, 46%
3aa, not observed
O
1a
4a
N
H
N
H
N
H
N
NO2
N
R3N Sn-1
S
N
N
N
Ph
N
S
Ph
N
N
N
O
-Sn
H
S
S
S
S
n
R3N = DABCO
R3N Sn-1
3ja,b 44%
3ia,a 56%
3ha,a 25%
N
H
N
O
N
N
reduction
then quenching
N
S
O
O
N
Ph
H
Ph
N
N
N
H
S
H
N
Ph
H
S
N
Ar
N
N
Sn-1 H2O
+
Ph
Ph
Ph
S
S
S
Ar = 4-CH3C6H4
S
Scheme 4. Mechanistic considerations.
3ac',c 44%
3da', 42%
3aa', 50%
3ab', 52%
Scheme 3. Scope of methylazaarenes. a4 equivalents of
b
sulfur, 0.5 equivalent of pyridine. CH3CN (0.5 mL) was
a simple reduction of nitrobenzene 1a to afford aniline under
the standard condition was not detected. Based on these results
and that of previous reports,3c,3g a plausible mechanism was
proposed (Scheme 4). Bis-pyridyl polysulfide was forged via
the reaction of 2-picoline and the DABCO-sulfur adduct.
Decomposition of the sulfide, possibly as a trisulfide radical
anion, afforded the (2-pyridyl)methyl radical followed by its
addition to nitrobenzene. The ensuing sequence of sulfuration,
reduction, and quenching furnished the thioamide.
c
added. CH3CN (0.25 mL) was added.
Isosteres of 2-picolines successfully coupled with nitroben-
zene. The scope of the reactants is presented in Scheme 3. An
amino-substituted picoline afforded the thioamide in 35% yield
(3ba). Only mono-functionalization of sp3 C-H bonds occurred
when 2,6-lutidine was used (3ca). The reaction of 2,3-lutidine
gave a 67% yield of single regioisomer (3da). Activated
primary C-H bonds in quinolines (3ea, 3fa) and quinoxalines
(3ga) were active, yielding synthetically useful bidentate
ligands. 5,6-Bicyclic compounds could be used, affording the
pyridylthioamides in low to moderate yields (3ha, 3ia, 3ja).
It should be noted that such heterocycles were incompetent
substrates in the presence of strong base.3g Methyl groups at
C4 positions of pyridines were also compatible with reaction
conditions, albeit giving the pyridylthioamides in much lower
yields compared to those of 2-picolines (3aa¤, 3ab¤, 3ac¤, 3da¤).
Some mechanistic experiments were next carried out. Some
results are presented in Scheme 4. If a mixture of 2-picoline/4-
picoline 2a/2a¤ at a 1:1 molar ratio was used to couple with
nitrobenzene 1a, a 7:3 ratio of two pyridylthioamides 3aa/3aa¤
were obtained in a combined 53% yield. Our result was con-
sistent with that observed by Deng and co-workers, as 2-
picoline was more reactive than 4-picoline in competitive reac-
tions.3g The transformation was somewhat involved the forma-
tion of an active, unstable radical species, since the yield of the
picoline thioamide was slightly decreased in the presence of the
radical quencher TEMPO. Indeed, an EPR signal was detected
when nitrobenzene 1a reacted with 4-picoline 2a¤ under stan-
dard conditions, presumably due to the formation of a trisulfide
radical anion.7,8 Picolines could be used to replace DABCO in
the complexation step with elemental sulfur. Since reaction of
2-pyridinecarboxaldehyde 4a failed to give the desired thio-
amide 3aa, a simple oxidation of primary sp3 C-H bonds into
aldehyde was not likely involved in the mechanism. Similarly,
3. Conclusion
In conclusion, we have developed a method for coupling
of nitroarenes, 2-/4-methylazaarenes, and elemental sulfur to
afford (2-pyridyl)arylthioamides. Reactions proceeded in the
presence of DABCO base. Functionalities such as primary and
secondary amines, ester, bromo, iodo, and boronic ester groups
were compatible with reaction conditions. The scope of 2-
methylazaarenes included the feasible use of heterocycles
including quinoline, quinoxaline, and azoles. Our method
would offer a synthetically useful route to obtain pyridyl
thioamides in one step.
4. Experimental
General. All reagents and starting materials were obtained
from Sigma-Aldrich, Acros and Alfa, and were used as received
without any further purification unless otherwise noted. Gas
chromatographic (GC) analyses were performed using a
Shimadzu GC 2010-Plus equipped with a flame ionization
detector (FID) and an SPB-5 column (length = 30 m, inner
diameter = 0.25 mm, and film thickness = 0.25 ¯m). The GC
yield was calculated using diphenyl ether as the internal stan-
dard. GC-MS analyses were performed on a Shimadzu GCMS-
QP2010Ultra with a ZB-5MS column (length = 30 m, inner
diameter = 0.25 mm, and film thickness = 0.25 ¯m). MS spec-
tra were compared with the spectra gathered in the NIST library.
1
The H NMR and 13C NMR were recorded on Bruker AV 500
Bull. Chem. Soc. Jpn. 2020, 93, 783–789 | doi:10.1246/bcsj.20200004
© 2020 The Chemical Society of Japan | 785

spectrometers using residual solvent peak as a reference. Unless
otherwise noted, chemical shifts are reported in ppm and
referenced to the residual peak for CDCl3 (δ = 7.26 ppm for
1H NMR and δ = 77.2 ppm for 13C NMR) or DMSO-d6 (δ =
1H), 7.96 (dd, J = 8.8, 2.0 Hz, 1H), 7.68 (dd, J = 7.5, 4.7 Hz,
1H). 13C NMR (126 MHz, DMSO-d6) δ 186.6, 153.3, 147.9,
147.7, 138.2, 128.4, 126.4, 125.0, 124.8, 113.6. This com-
pound is known.10
N-(4-Morpholinophenyl)pyridine-2-carbothioamide (3af):
1H NMR (500 MHz, DMSO-d6) δ 12.13 (s, 1H), 8.68-8.65 (m,
1H), 8.53 (d, J = 8.0 Hz, 1H), 8.03 (td, J = 7.8, 1.7 Hz, 1H),
7.90 (d, J = 9.0 Hz, 2H), 7.63 (ddd, J = 7.5, 4.7, 1.0 Hz, 1H),
7.02-6.97 (m, 2H), 3.78-3.72 (m, 4H), 3.18-3.13 (m, 4H).
13C NMR (126 MHz, DMSO-d6) δ 187.6, 152.7, 149.2, 147.2,
137.7, 130.8, 126.1, 124.45, 124.38, 114.3, 66.0, 48.1. This
compound is known.11
1
2.50 ppm for H NMR and δ = 39.5 ppm for 13C NMR). Split-
ting is reported with the following symbols: s = singlet, bs =
broad singlet, d = doublet, t = triplet, q = quartet, td = triplet
of doublets, dd = doublet of doublets, ddd = doublet of dou-
blets of doublets, and m = multiplet. Coupling constants (J) are
reported in hertz. HR-MS spectra were recorded by an Agilent
HPLC 1200 Series coupled to Bruker micrOTOF-QII.
General Procedure.
In a typical experiment, a vial
equipped with a magnetic stir bar was charged with nitroarene
(0.5 mmol), 2- or 4-methylazaarene (1.0 mmol), sulfur (32 mg,
1.0 mmol, 32 mg/mmol), and DABCO (42 mg, 0.375 mmol).
The vial was purged with argon for 1 min, placed on a pre-
heated oil bath (120 °C), then stirred for 16 h. Upon the com-
pletion of the reaction, ethyl acetate (15 mL) was added to
dilute the reaction mixture. The organic phase was washed
with brine (3 © 5 mL) before being dried over anhydrous
Na2SO4, filtered, and concentrated using a rotary evaporator.
The resulting residue was purified by silica gel column chro-
matography using an appropriate ratio of hexanes/EtOAc
mixture as eluent.
Ethyl 4-(pyridine-2-carbothioamido)benzoate (3ag):
1H NMR (500 MHz, CDCl3) δ 12.25 (s, 1H), 8.78 (d, J = 8.0
Hz, 1H), 8.56 (d, J = 4.1 Hz, 1H), 8.25 (d, J = 8.7 Hz, 2H),
8.14 (d, J = 8.7 Hz, 2H), 7.90 (td, J = 7.9, 1.7 Hz, 1H), 7.49
(ddd, J = 7.4, 4.7, 0.9 Hz, 1H), 4.39 (q, J = 7.1 Hz, 2H), 1.41
(t, J = 7.1 Hz, 3H). 13C NMR (126 MHz, CDCl3) δ 188.5,
166.0, 151.4, 146.7, 142.7, 137.8, 130.7, 128.1, 126.4, 125.0,
121.8, 61.2, 14.5. HR-MS (ESI) calcd. for C15H14N2O2SNa+
[M + Na]+: 309.0668; found 309.0671.
N-(3-Bromophenyl)pyridine-2-carbothioamide
(3ah):
1H NMR (500 MHz, CDCl3) δ 12.07 (s, 1H), 8.78 (d, J = 8.0
Hz, 1H), 8.55 (dd, J = 4.7, 0.6 Hz, 1H), 8.36 (t, J = 1.9 Hz,
1H), 8.03 (dd, J = 8.0, 1.4 Hz, 1H), 7.90 (td, J = 7.8, 1.7 Hz,
1H), 7.49 (ddd, J = 7.5, 4.7, 1.0 Hz, 1H), 7.44-7.40 (m, 1H),
7.32 (t, J = 8.1 Hz, 1H). 13C NMR (126 MHz, CDCl3) δ 188.5,
151.4, 146.7, 140.1, 137.8, 130.3, 129.6, 126.4, 125.5, 125.0,
122.5, 121.3. HR-MS (ESI) calcd. for C12H979BrN2SNa+
[M + Na]+: 316.1712; found 316.1713.
N-Phenylpyridine-2-carbothioamide (3aa):
1H NMR
(500 MHz, CDCl3) δ 12.06 (s, 1H), 8.81 (dt, J = 8.0, 1.0 Hz,
1H), 8.56 (ddd, J = 4.7, 1.7, 0.9 Hz, 1H), 8.10-8.07 (m, 2H),
7.89 (td, J = 7.8, 1.7 Hz, 1H), 7.49-7.45 (m, 3H), 7.32-7.28
(m, 1H). 13C NMR (126 MHz, CDCl3) δ 188.0, 151.6, 146.7,
138.9, 137.6, 129.1, 126.7, 126.2, 125.0, 122.9. This com-
pound is known.4a
N-(3-Iodophenyl)pyridine-2-carbothioamide
(3ai):
N-(o-Tolyl)pyridine-2-carbothioamide (3ab): 1H NMR
(500 MHz, DMSO-d6) δ 12.14 (s, 1H), 8.68 (d, J = 4.7 Hz,
1H), 8.56 (d, J = 8.0 Hz, 1H), 8.03 (td, J = 7.8, 1.6 Hz, 1H),
7.68-7.63 (m, 1H), 7.49-7.44 (m, 1H), 7.33 (dd, J = 6.6,
1.9 Hz, 1H), 7.27 (ddd, J = 12.2, 5.9, 3.9 Hz, 2H), 2.23 (s, 3H).
13C NMR (126 MHz, DMSO-d6) δ 191.4, 152.2, 147.5, 138.4,
137.7, 134.1, 130.5, 127.3, 126.7, 126.5, 126.3, 124.7, 17.6.
This compound is known.9
1H NMR (500 MHz, CDCl3) δ 12.04 (s, 1H), 8.77 (d, J = 8.0
Hz, 1H), 8.54 (d, J = 4.6 Hz, 1H), 8.46 (s, 1H), 8.11 (dd, J =
8.1, 1.4 Hz, 1H), 7.90 (td, J = 7.8, 1.6 Hz, 1H), 7.61 (d, J =
7.9 Hz, 1H), 7.49 (dd, J = 7.4, 4.8 Hz, 1H), 7.18 (t, J = 8.0
Hz, 1H). 13C NMR (126 MHz, CDCl3) δ 188.4, 151.3, 146.6,
140.0, 137.8, 135.6, 131.3, 130.4, 126.4, 125.0, 122.0, 93.8.
HR-MS (ESI) calcd. for C12H9IN2SNa+ [M + Na]+: 362.9423;
found 362.9429.
N-(2-Methyl-3-(trifluoromethyl)phenyl)pyridine-2-carbo-
thioamide (3ac): 1H NMR (500 MHz, CDCl3) δ 11.80 (s,
1H), 8.80 (d, J = 8.0 Hz, 1H), 8.58 (d, J = 4.5 Hz, 1H), 8.08 (d,
J = 8.0 Hz, 1H), 7.92 (td, J = 7.8, 1.5 Hz, 1H), 7.65 (d, J =
7.8 Hz, 1H), 7.53 (dd, J = 7.4, 4.8 Hz, 1H), 7.41 (t, J = 7.9 Hz,
1H), 2.45 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 190.6, 151.0,
146.7, 138.8, 137.7, 132.6, 129.8, 126.4, 126.2, 125.2, 125.0
(d, J = 5.8 Hz), 13.8 (d, J = 2.3 Hz). HR-MS (ESI) calcd. for
C14H12F3N2S+ [M + H]+: 297.0668; found 297.0671.
N-( p-Tolyl)pyridine-2-carbothioamide (3ad): 1H NMR
(500 MHz, DMSO-d6) δ 12.22 (s, 1H), 8.67 (d, J = 4.4 Hz,
1H), 8.53 (d, J = 8.0 Hz, 1H), 8.04 (t, J = 7.7 Hz, 1H), 7.84 (d,
J = 8.3 Hz, 2H), 7.65 (dd, J = 6.8, 5.3 Hz, 1H), 7.26 (d, J =
8.1 Hz, 2H), 2.33 (s, 3H). 13C NMR (126 MHz, DMSO-d6) δ
189.3, 152.7, 147.3, 137.8, 136.7, 135.8, 128.9, 126.3, 124.6,
123.8, 20.7. This compound is known.9
N-(4-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)phen-
yl)pyridine-2-carbothioamide (3aj):
1H NMR (500 MHz,
CDCl3) δ 12.14 (s, 1H), 8.79 (d, J = 8.0 Hz, 1H), 8.55 (d, J =
4.7 Hz, 1H), 8.13 (d, J = 8.4 Hz, 2H), 7.92-7.87 (m, 3H), 7.49-
7.46 (m, 1H), 1.36 (s, 12H). 13C NMR (126 MHz, CDCl3) δ
187.9, 151.6, 146.5, 141.3, 137.8, 135.7, 126.2, 125.0, 121.6,
84.0, 25.0. HR-MS (ESI) calcd. for C18H22BN2O2S [M + H]+:
341.1490; found 341.1523.
N-(4-(1H-Pyrrol-1-yl)phenyl)pyridine-2-carbothioamide
(3ak): 1H NMR (500 MHz, CDCl3) δ 12.12 (s, 1H), 8.81 (d,
J = 8.0 Hz, 1H), 8.57 (d, J = 4.3 Hz, 1H), 8.17 (d, J = 8.8 Hz,
2H), 7.91 (td, J = 7.8, 1.6 Hz, 1H), 7.51-7.46 (m, 3H), 7.12 (t,
J = 2.1 Hz, 2H), 6.37 (t, J = 2.1 Hz, 2H). 13C NMR (126 MHz,
CDCl3) δ 187.8, 151.4, 146.6, 138.8, 137.9, 136.4, 126.3,
125.1, 124.0, 120.7, 119.4, 110.8. HR-MS (ESI) calcd. for
C16H14N3S+ [M + H]+: 280.0903; found 280.0938.
N-(4-Aminophenyl)pyridine-2-carbothioamide
(3ae):
N-(Pyridin-3-yl)pyridine-2-carbothioamide
(3al):
1H NMR (500 MHz, DMSO-d6) δ 12.49 (s, 1H), 9.43 (s, 1H),
8.84 (d, J = 2.0 Hz, 1H), 8.71 (d, J = 4.6 Hz, 1H), 8.56 (d, J =
8.0 Hz, 1H), 8.15 (d, J = 8.7 Hz, 1H), 8.07 (td, J = 7.7, 1.6 Hz,
1H NMR (500 MHz, DMSO-d6) δ 12.44 (s, 1H), 8.96 (d, J =
2.4 Hz, 1H), 8.71 (d, J = 4.6 Hz, 1H), 8.54 (d, J = 8.0 Hz, 1H),
8.48 (dd, J = 4.7, 1.3 Hz, 1H), 8.36-8.31 (m, 1H), 8.06 (td, J =
786 | Bull. Chem. Soc. Jpn. 2020, 93, 783–789 | doi:10.1246/bcsj.20200004
© 2020 The Chemical Society of Japan

7.8, 1.7 Hz, 1H), 7.71-7.67 (m, 1H), 7.50 (dd, J = 8.2, 4.7 Hz,
1H). 13C NMR (126 MHz, DMSO-d6) δ 191.8, 152.3, 147.5,
147.1, 146.0, 137.8, 136.0, 132.0, 126.7, 124.9, 123.3. HR-MS
(ESI) calcd. for C11H10N3S+ [M + H]+: 216.0590; found
216.0591.
N-(Benzo[d]thiazol-6-yl)pyridine-2-carbothioamide (3am):
1H NMR (500 MHz, DMSO-d6) δ 12.49 (s, 1H), 9.43 (s, 1H),
8.84 (d, J = 2.0 Hz, 1H), 8.71 (d, J = 4.6 Hz, 1H), 8.56 (d, J =
8.0 Hz, 1H), 8.15 (d, J = 8.7 Hz, 1H), 8.07 (td, J = 7.7, 1.6
Hz, 1H), 7.96 (dd, J = 8.8, 2.0 Hz, 1H), 7.68 (dd, J = 7.5, 4.7
Hz, 1H). 13C NMR (126 MHz, DMSO-d6) δ 190.6, 156.8,
152.6, 151.2, 147.4, 137.8, 136.7, 133.6, 126.5, 124.8, 123.6,
122.7, 117.7. HR-MS (ESI) calcd. for C13H9N3S2+ [M + H]+:
272.0311; found 272.0307.
N-(3-Methoxyphenyl)pyridine-2-carbothioamide (3an):
1H NMR (500 MHz, DMSO-d6) δ 12.25 (s, 1H), 8.68 (d, J =
4.7 Hz, 1H), 8.52 (d, J = 8.0 Hz, 1H), 8.08-8.02 (m, 1H), 7.73
(s, 1H), 7.66 (dd, J = 7.4, 4.8 Hz, 1H), 7.59 (d, J = 7.9 Hz,
1H), 7.36 (t, J = 8.1 Hz, 1H), 6.88 (dd, J = 8.3, 2.4 Hz, 1H),
3.79 (s, 3H). 13C NMR (126 MHz, DMSO-d6) δ 189.6, 159.2,
152.7, 147.3, 140.2, 137.8, 129.3, 126.4, 124.6, 115.9, 112.1,
109.3, 55.2. HR-MS (ESI) calcd. for C13H13N2OS+ [M + H]+:
245.0743; found 245.0739.
Hz, 1H), 8.91 (d, J = 3.0 Hz, 1H), 8.81 (d, J = 8.0 Hz, 1H),
8.59 (d, J = 4.5 Hz, 1H), 8.27 (d, J = 8.2 Hz, 1H), 8.23 (d, J =
9.0 Hz, 1H), 8.03 (dd, J = 9.0, 2.3 Hz, 1H), 7.92 (td, J =
7.8, 1.5 Hz, 1H), 7.51 (dd, J = 7.2, 4.9 Hz, 1H), 7.47 (dd, J =
8.3, 4.3 Hz, 1H). 13C NMR (126 MHz, CDCl3) δ 188.3, 151.5,
149.9, 146.8, 146.0, 137.8, 137.03, 136.97, 130.0, 128.6,
126.4, 126.0, 124.9, 121.9, 119.1. One carbon signal could not
be located. HR-MS (ESI) calcd. for C15H12N3S [M + H]+:
266.0746; found 266.0754.
2-(Pyridin-2-yl)thiazolo[5,4-f]quinoline (4aq): 1H NMR
(500 MHz, CDCl3) δ 8.95 (s, 1H), 8.67 (s, 1H), 8.37 (dd, J =
15.3, 8.0 Hz, 2H), 8.30 (d, J = 9.0 Hz, 1H), 8.14 (d, J = 9.0
Hz, 1H), 7.85 (t, J = 7.6 Hz, 1H), 7.51 (dd, J = 7.9, 3.9 Hz,
1H), 7.44-7.33 (m, 1H). 13C NMR (126 MHz, CDCl3) δ 169.7,
152.6, 151.2, 150.0, 149.8, 146.7, 137.3, 133.6, 133.3, 129.0,
125.55, 125.46, 123.8, 121.7, 120.7. HR-MS (ESI) calcd. for
C15H10N3S+ [M + H]+: 266.0590; found 264.0607.
6-Amino-N-phenylpyridine-2-carbothioamide
(3ba):
1H NMR (500 MHz, DMSO-d6) δ 12.17 (s, 1H), 8.03 (d, J =
7.7 Hz, 2H), 7.68 (d, J = 7.1 Hz, 1H), 7.60 (t, J = 7.8 Hz, 1H),
7.47 (t, J = 7.9 Hz, 2H), 7.29 (t, J = 7.4 Hz, 1H), 6.72 (d,
J = 8.0 Hz, 1H), 6.34 (bs, 2H). 13C NMR (126 MHz, DMSO-
d6) δ 189.2, 157.5, 150.1, 138.9, 138.4, 128.7, 126.2, 122.8,
112.6, 111.6. HR-MS (ESI) calcd. for C12H12N3S+ [M + H]+:
230.0746; found 230.0759.
5-Methoxy-2-(pyridin-2-yl)benzo[d]thiazole
(4an):
1H NMR (500 MHz, CDCl3) δ 8.68 (d, J = 3.0 Hz, 1H), 8.37
(d, J = 7.9 Hz, 1H), 7.85 (td, J = 7.8, 1.5 Hz, 1H), 7.81 (d, J =
8.8 Hz, 1H), 7.59 (d, J = 2.4 Hz, 1H), 7.39 (dd, J = 7.0, 5.2 Hz,
1H), 7.08 (dd, J = 8.8, 2.4 Hz, 1H), 3.92 (s, 3H). 13C NMR
(126 MHz, CDCl3) δ 170.6, 159.3, 155.5, 151.5, 149.8, 137.2,
128.2, 125.4, 122.4, 120.8, 116.4, 105.7, 55.8. HR-MS (ESI)
calcd. for C13H11N2OS+ [M + H]+: 243.0587; found 243.0586.
N,N-Dimethyl-2-(pyridin-2-yl)benzo[d]thiazol-5-amine
(4ao): 1H NMR (500 MHz, DMSO-d6) δ 8.69 (d, J = 4.5 Hz,
1H), 8.27 (d, J = 7.9 Hz, 1H), 8.01 (td, J = 7.7, 1.6 Hz, 1H),
7.89 (d, J = 8.9 Hz, 1H), 7.60-7.51 (m, 1H), 7.31 (d, J = 2.4
Hz, 1H), 7.04 (dd, J = 8.9, 2.5 Hz, 1H), 2.99 (s, 6H). 13C NMR
(126 MHz, DMSO-d6) δ 168.9, 155.5, 150.7, 150.0, 149.8,
137.7, 125.7, 123.2, 122.1, 120.0, 113.9, 105.0, 40.5. HR-MS
(ESI) calcd. for C14H14N3S+ [M + H]+: 256.0903; found
256.0908.
6-Methyl-N-phenylpyridine-2-carbothioamide
(3ca):
1H NMR (500 MHz, CDCl3) δ 12.13 (s, 1H), 8.61 (d, J = 7.8
Hz, 1H), 8.06 (d, J = 7.7 Hz, 2H), 7.76 (t, J = 7.8 Hz, 1H),
7.47 (t, J = 7.9, 2H), 7.33 (d, J = 7.6 Hz, 1H), 7.29 (t, J =
7.4 Hz, 1H), 2.64 (s, 3H). 13C NMR (126 MHz, CDCl3) δ
188.4, 155.8, 150.9, 138.9, 137.8, 129.0, 126.7, 125.9, 123.0,
122.1, 24.4. HR-MS (ESI) calcd. for C13H13N2S+ [M + H]+:
229.0794; found 229.0795.
3-Methyl-N-phenylpyridine-2-carbothioamide
(3da):
1H NMR (500 MHz, DMSO-d6) δ 12.09 (s, 1H), 8.40 (d, J =
4.3 Hz, 1H), 7.97 (d, J = 7.8 Hz, 2H), 7.73 (d, J = 7.6 Hz, 1H),
7.46 (t, J = 7.9 Hz, 2H), 7.35 (dd, J = 7.7, 4.8 Hz, 1H), 7.30 (t,
J = 7.4 Hz, 1H), 2.37 (s, 3H). 13C NMR (126 MHz, DMSO-d6)
δ 196.2, 158.8, 145.9, 139.2, 138.7, 128.6, 128.5, 126.4, 123.5,
122.9, 18.0. HR-MS (ESI) calcd. for C13H13N2S+ [M + H]+:
229.0794; found 229.0807.
N,N-Dimethyl-2-(pyridin-4-yl)benzo[d]thiazol-5-amine
(4a¤o): 1H NMR (500 MHz, CDCl3) δ 8.74 (d, J = 3.8 Hz,
2H), 7.91 (d, J = 5.8 Hz, 2H), 7.72 (d, J = 8.9 Hz, 1H), 7.39 (d,
J = 2.4 Hz, 1H), 6.99 (dd, J = 8.9, 2.4 Hz, 1H), 3.04 (s, 6H).
13C NMR (126 MHz, CDCl3) δ 165.5, 155.9, 150.59, 150.53,
141.1, 123.5, 121.8, 121.2, 114.4, 105.8, 41.1. HR-MS (ESI)
calcd. for C14H14N3S+ [M + H]+: 256.0903; found 256.0924.
5-(4-Methylpiperazin-1-yl)-2-(pyridin-2-yl)benzo[d]thia-
zole (4ap): 1H NMR (500 MHz, DMSO-d6) δ 8.70 (d, J =
4.3 Hz, 1H), 8.27 (d, J = 7.9 Hz, 1H), 8.02 (td, J = 7.7, 1.6 Hz,
1H), 7.93 (d, J = 8.9 Hz, 1H), 7.58-7.54 (m, 1H), 7.52 (d, J =
2.2 Hz, 1H), 7.24 (dd, J = 8.9, 2.3 Hz, 1H), 3.25-3.20 (m, 4H),
2.52-2.46 (m, 4H, overlapping with solvent peaks), 2.24 (s,
3H). 13C NMR (126 MHz, DMSO-d6) δ 169.2, 155.3, 150.7,
150.6, 149.9, 137.8, 125.8, 125.8, 122.2, 120.0, 116.9, 108.1,
54.6, 48.6, 45.7. HR-MS (ESI) calcd. for C17H19N4S+
[M + H]: 311.1325; found 311.1351.
N-Phenylquinoline-2-carbothioamide (3ea):
1H NMR
(500 MHz, DMSO-d6) δ 12.47 (s, 1H), 8.59 (q, J = 8.6 Hz,
2H), 8.23 (d, J = 8.4 Hz, 1H), 8.09 (d, J = 8.1 Hz, 1H), 8.03
(d, J = 7.8 Hz, 2H), 7.90 (t, J = 7.5 Hz, 1H), 7.74 (t, J = 7.4
Hz, 1H), 7.50 (t, J = 7.5 Hz, 2H), 7.33 (t, J = 7.2 Hz, 1H).
13C NMR (126 MHz, DMSO-d6) δ 190.5, 152.5, 145.0, 139.2,
137.4, 130.7, 129.5, 128.6, 128.5, 128.3, 128.0, 126.6, 123.8,
121.0. This compound is known.12
6-Fluoro-N-phenylquinoline-2-carbothioamide
(3fa):
1H NMR (500 MHz, DMSO-d6) δ 12.44 (s, 1H), 8.58 (dd, J =
33.4, 8.7 Hz, 2H), 8.29 (dd, J = 9.2, 5.5 Hz, 1H), 8.02 (d, J =
7.7 Hz, 2H), 7.92 (dd, J = 9.3, 2.7 Hz, 1H), 7.82 (td, J = 8.9,
2.8 Hz, 1H), 7.50 (t, J = 7.8 Hz, 2H), 7.33 (t, J = 7.4 Hz, 1H).
13C NMR (126 MHz, DMSO-d6) δ 190.3, 161.7, 159.7, 152.3,
152.2, 142.2, 139.2, 136.9, 136.9, 132.5, 132.5, 129.4, 129.3,
128.6, 126.6, 123.8, 121.8, 121.1, 120.9, 111.2, 111.1. HR-MS
(ESI) calcd. for C16H12FN2S+ [M + H]+: 283.0700; found
283.0699.
N-(Quinolin-6-yl)pyridine-2-carbothioamide
(3aq):
1H NMR (500 MHz, CDCl3) δ 12.36 (s, 1H), 9.24 (d, J = 2.0
Bull. Chem. Soc. Jpn. 2020, 93, 783–789 | doi:10.1246/bcsj.20200004
© 2020 The Chemical Society of Japan | 787

N-Phenylquinoxaline-2-carbothioamide (3ga): 1H NMR
(500 MHz, DMSO-d6) δ 12.50 (s, 1H), 9.77 (s, 1H), 8.26 (dd,
J = 6.2, 3.5 Hz, 1H), 8.19 (dd, J = 6.3, 3.4 Hz, 1H), 8.03-7.94
(m, 4H), 7.51 (t, J = 7.8 Hz, 2H), 7.35 (t, J = 7.4 Hz, 1H).
13C NMR (126 MHz, DMSO-d6) δ 189.55, 148.0, 145.5, 142.1,
139.1, 138.7, 131.8, 131.5, 129.7, 128.9, 128.7, 126.8, 123.9.
HR-MS (ESI) calcd. for C15H12N3S+ [M + H]+: 266.0746;
found 266.0744.
(s, 3H). 13C NMR (126 MHz, CDCl3) δ 195.4, 150.5, 149.8,
137.7, 129.9, 123.7, 120.7, 21.4. HR-MS (ESI) calcd. for
C13H13N2S+ [M + H]+: 229.0794; found 229.0796.
We are grateful to The Vietnam National University Ho Chi
Minh City (VNUHCM) for financial support (project No.
NCM2019-20-01). We also thank Vu T. Nguyen (The Univer-
sity of Texas at San Antonio, USA) for the invaluable help in
the EPR study.
N-Phenylbenzo[d]oxazole-2-carbothioamide
(3ha):
1H NMR (500 MHz, DMSO-d6) δ 12.61 (s, 1H), 7.96 (d, J =
7.8 Hz, 1H), 7.91 (dd, J = 12.5, 4.9 Hz, 3H), 7.63-7.57 (m,
1H), 7.56-7.51 (m, 1H), 7.50-7.45 (m, 2H), 7.33 (dd, J = 10.6,
4.2 Hz, 1H). 13C NMR (126 MHz, DMSO-d6) δ 178.0, 158.0,
150.7, 140.1, 138.6, 128.6, 127.5, 126.9, 125.8, 124.0, 121.2,
111.7. HR-MS (ESI) calcd. for C14H11N2OS+ [M + H]+:
255.0587; found 255.0595.
Supporting Information
This material is available on https://doi.org/10.1246/bcsj.
20200004.
References
1
a) L.-C. Campeau, D. J. Schipper, K. Fagnou, J. Am. Chem.
N-Phenylbenzo[d]thiazole-2-carbothioamide
(3ia):
Soc. 2008, 130, 3266. b) J. J. Mousseau, A. Larivée, A. B.
Charette, Org. Lett. 2008, 10, 1641. c) T. Niwa, H. Yorimitsu, K.
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ACS Catal. 2016, 6, 7652.
1H NMR (500 MHz, DMSO-d6) δ 12.48 (s, 1H), 8.19 (dd, J =
8.5, 1.2 Hz, 2H), 7.92-7.90 (m, 2H), 7.63 (td, J = 7.8, 1.5 Hz,
1H), 7.58 (td, J = 7.8, 1.5 Hz, 1H), 7.47 (tt, J = 8, 2 Hz, 2H),
7.33 (tt, J = 7.5, 1 Hz, 1H). 13C NMR (126 MHz, DMSO-d6)
δ 182.8, 169.9, 152.9, 138.7, 138.5, 128.5, 127.2, 126.8,
124.6, 124.4, 122.4. One carbon signal could not be located.
+
HR-MS (ESI) calcd. for C14H11N2S2 [M + H]+: 271.0358;
found 271.0344.
2
a) S. Duez, A. K. Steib, S. M. Manolikakes, P. Knochel,
N-Phenyl-1H-benzo[d]imidazole-2-carbothioamide (3ja):
1H NMR (500 MHz, DMSO-d6) δ 13.02 (s, 1H), 12.30 (s, 1H),
7.96 (dd, J = 8.5, 1 Hz, 2H), 7.80 (d, J = 8 Hz, 1H), 7.63 (d,
J = 8 Hz, 1H), 7.458 (t, J = 7.5 Hz, 2H), 7.38-7.29 (m, 3H).
13C NMR (126 MHz, DMSO-d6) δ 181.3, 149.1, 142.1, 138.8,
135.5, 128.4, 126.5, 124.5, 124.2, 123.0, 120.3, 112.8. HR-MS
(ESI) calcd. for C14H12N3S+ [M + H]+: 254.0746; found
254.0747.
Angew. Chem., Int. Ed. 2011, 50, 7686. b) S.-S. Li, S. Fu, L. Wang,
L. Xu, J. Xiao, J. Org. Chem. 2017, 82, 8703.
3
For reviews: a) T. B. Nguyen, Adv. Synth. Catal. 2017, 359,
1066. Examples: b) T. B. Nguyen, L. Ermolenko, A. Al-Mourabit,
J. Am. Chem. Soc. 2013, 135, 118. c) T. B. Nguyen, L. Ermolenko,
A. Al-Mourabit, Org. Lett. 2013, 15, 4218. d) H. Huang, Z. Xu, X.
Ji, B. Li, G.-J. Deng, Org. Lett. 2018, 20, 4917. e) N. T. Do, K. M.
Tran, H. T. Phan, T. A. To, T. T. Nguyen, N. T. S. Phan, Org.
Biomol. Chem. 2019, 17, 8987. f) Q. Xing, Y. Ma, H. Xie, F. Xiao,
F. Zhang, G.-J. Deng, J. Org. Chem. 2019, 84, 1238. g) H. Huang,
Q. Wang, Z. Xu, G.-J. Deng, Adv. Synth. Catal. 2019, 361, 591.
N-Phenylpyridine-4-carbothioamide (3aa¤):
1H NMR
(500 MHz, CDCl3) δ 9.91 (s, 1H), 8.59 (s, 2H), 7.79 (d, J =
7.8 Hz, 2H), 7.63 (d, J = 4.8 Hz, 2H), 7.46 (t, J = 7.7 Hz, 2H),
7.33 (t, J = 7.4 Hz, 1H). 13C NMR (126 MHz, CDCl3) δ 195.5,
150.2, 138.9, 129.3, 127.5, 123.6, 120.9. This compound is
known.4a
4
a) H. D. Porter, J. Am. Chem. Soc. 1954, 76, 127. b) K.
Okamoto, T. Yamamoto, T. Kanbara, Synlett 2007, 17, 2687. c) T.
Guntreddi, R. Vanjari, K. N. Singh, Org. Lett. 2014, 16, 3624. d) P.
Zhang, W. Chen, M. Liu, H. Wu, J. Org. Chem. 2018, 83, 14269.
e) V. Pace, L. Castoldi, S. Monticelli, S. Safranek, A. Roller, T.
Langer, W. Holzer, Chem.®Eur. J. 2015, 21, 18966.
3-Methyl-N-phenylpyridine-4-carbothioamide
(3ab¤):
1H NMR (500 MHz, CDCl3) δ 11.08 (s, 1H), 8.20 (d, J = 4.7
Hz, 1H), 8.16 (s, 1H), 7.89 (d, J = 7.6 Hz, 2H), 7.44 (t, J = 7.9
Hz, 2H), 7.31 (t, J = 7.4 Hz, 1H), 7.23 (d, J = 5.0 Hz, 1H),
2.40 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 195.7, 151.8,
150.7, 146.7, 138.8, 129.2, 127.3, 122.9, 120.8, 16.2. HR-MS
(ESI) calcd. for C13H13N2S+ [M + H]+: 229.0794; found
229.0828.
5
Selected examples: a) E. T. Nadres, O. Daugulis, J. Am.
Chem. Soc. 2012, 134, 7. b) R. Odani, K. Hirano, T. Satoh, M.
Miura, J. Org. Chem. 2013, 78, 11045. c) S. Rej, N. Chatani, ACS
Catal. 2018, 8, 6699. d) Q. Li, S.-Y. Zhang, G. He, Z. Ai, W. A.
Nack, G. Chen, Org. Lett. 2014, 16, 1764. e) S. Roy, S. Pradhan, T.
Punniyamurthy, Chem. Commun. 2018, 54, 3899.
N-Phenylquinoline-4-carbothioamide (3ac¤):
1H NMR
6
Selected examples: a) J. Jiang, G. Li, F. Zhang, H. Xie,
(500 MHz, DMSO-d6) δ 12.40 (s, 1H), 8.97 (d, J = 4.4 Hz,
1H), 8.10 (d, J = 8.3 Hz, 1H), 8.07 (d, J = 7.9 Hz, 1H), 8.01 (d,
J = 7.6 Hz, 2H), 7.85-7.80 (m, 1H), 7.70-7.66 (m, 1H), 7.53
(d, J = 4.4 Hz, 1H), 7.50 (t, J = 7.9 Hz, 2H), 7.34 (t, J = 7.4
Hz, 1H). 13C NMR (126 MHz, DMSO-d6) δ 194.2, 150.3,
149.1, 147.9, 139.1, 129.8, 129.3, 128.8, 127.4, 126.7, 124.9,
123.4, 123.1, 117.7. HR-MS (ESI) calcd. for C16H13N2S+
[M + H]+: 265.0794; found 265.0799.
N-( p-Tolyl)pyridine-4-carbothioamide (3da¤): 1H NMR
(500 MHz, CDCl3) δ 9.28 (s, 1H), 8.60 (d, J = 5.9 Hz, 2H),
7.57 (dd, J = 5.0, 3.4 Hz, 4H), 7.19 (d, J = 8.1 Hz, 2H), 2.32
G.-J. Deng, Adv. Synth. Catal. 2018, 360, 1622. b) X. Zhu, Y.
Yang, G. Xiao, J. Song, Y. Liang, G. Deng, Chem. Commun. 2017,
53, 11917.
7
8
Please see the Supporting Information for details.
Selected examples for detection of trisulfur radical anion:
a) T. Chivers, P. J. W. Elder, Chem. Soc. Rev. 2013, 42, 5996. b) G.
Zhang, H. Yi, H. Chen, C. Bian, C. Liu, A. Lei, Org. Lett. 2014,
16, 6156.
9
R. R. Kumar, M. K. M. Subarkhan, R. Ramesh, RSC Adv.
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