Regioselective deoxygenative C[sbnd]H trifluoromethylthiolation of heteroaryl N-oxides with AgSCF3

Article abstract of DOI:10.1016/j.jfluchem.2019.109367

A mild and efficient method for the regioselective deoxygenative C[sbnd]H trifluoromethylthiolation of heteroaryl N-oxides with AgSCF₃ is presented, employing p-toluenesulfonic anhydride and tetra-n-butylammonium iodide as the activators. This reaction delivers a series of C2-trifluoromethylthiolated heteroaromatic compounds in moderate to excellent yields. It provides a complementary method for C[sbnd]H trifluoromethylthiolation reactions.

Full text of DOI:10.1016/j.jfluchem.2019.109367

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Regioselective deoxygenative C<ce:glyph name="sbnd"/>H
trifluoromethylthiolation of heteroaryl N-oxides with AgSCF3
Shi-Bo Zhang, Xiu-Hua Xu, Feng-Ling Qing
PII:
S0022-1139(19)30259-3
DOI:
https://doi.org/10.1016/j.jfluchem.2019.109367
FLUOR 109367
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Please cite this article as: Zhang S-Bo, Xu X-Hua, Qing F-Ling, Regioselective deoxygenative
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C<ce:glyph name=sbnd/>H trifluoromethylthiolation of heteroaryl N-oxides with AgSCF3,
Journal of Fluorine Chemistry (2019), doi: https://doi.org/10.1016/j.jfluchem.2019.109367
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Regioselective deoxygenative C─H trifluoromethylthiolation of heteroaryl N-oxides
with AgSCF3
Shi-Bo Zhanga, Xiu-Hua Xub, Feng-Ling Qinga,b
aKey Laboratory of Science and Technology of Eco-Textiles, Ministry of Education, College of
Chemistry, Chemical Engineering and Biotechnology, Donghua University, 2999 North Renmin Lu,
Shanghai 201620, China
bKey Laboratory of Organofluorine Chemistry, Center for Excellence in Molecular Synthesis, Shanghai
Institute of Organic Chemistry, University of Chinese Academy of Science, Chinese Academy of Science,
345 Lingling Lu, Shanghai 200032, China
Tel.: 86-21-54925187; Fax: 86-21-64166128; E-mail: flq@mail.sioc.ac.cn
 Corresponding author. Tel.: +86 21 54925187; fax: +86 21 64166128.
E-mail address: flq@mail.sioc.ac.cn (F.-L. Qing).
Graphical Abstract
Highlights
 C─H trifluoromethylthiolation of heteroaryl N-oxides.
 Broad functional group compatibility and excellent regioselectivity.
1

 Facile synthesis of C2-trifluoromethylthiolated heteroaromatic compounds.
Abstract
A mild and efficient method for the regioselective deoxygenative C─H trifluoromethylthiolation of
heteroaryl N-oxides with AgSCF3 is presented, employing p-toluenesulfonic anhydride and tetra-n-
butylammonium iodide as the activators. This reaction delivers a series of C2-trifluoromethylthiolated
heteroaromatic compounds in moderate to excellent yields. It provides a complementary method for C─H
trifluoromethylthiolation reactions.
Keywords:
Trifluoromethylthiolation;
Regioselective;
Heteroaromatics;
N-oxide;
Silver
trifluoromethanethiolate.
1. Introduction
The trifluoromethylthio (SCF3) group has received growing interest in pharmaceuticals, agrochemicals,
and functional materials due to its unique properties such as extremely high lipophilicity, strong electron-
withdrawing power, transmembrane permeability, and metabolic stability [1]. Recently, extensive
research efforts have been devoted to the development of methods for the incorporation of SCF3 group
into diverse skeletal structures [2]. In this regard, a series of new trifluoromethylthiolating reagents [3]
and various novel trifluoromethylthiolation reactions, such as transition metal-mediated/catalyzed
trifluoromethylthiolation of prefunctionalized (hetero)aromatics [4] and radical trifluoromethylthiolation
of unsaturated substrates [5], have been reported.
C─H bond functionalization has recently gained prominence as a valuable approach in organic
synthesis due to its inherent economic and environmentally benign nature [6]. Over the past several years,
various Csp─H [7], Csp2─H [8-10], and Csp3─H [11] trifluoromethylthiolation methods have been
developed as alternative approaches towards CF3S-substituted compounds. Among them, Csp2─H
2

trifluoromethylthiolation has received more attention because of the widespread biological activities of
CF3S-substituted (hetero)aromatic compounds. However, the reported Csp2─H trifluoromethylthiolation
reactions suffer from limited substrate scope, which mainly focused on two types of substrates, electron-
rich (hetero)arenes and (hetero)arenes bearing a directing group. Electron-rich arenes [8] and heteroarenes
[9] reacted with electrophilic trifluoromethylthiolating reagents via electrophilic aromatic substitution
(SEAr) to afford the C─H trifluoromethylthiolated products (Scheme 1a), whereas the directing group-
assisted, transition-metal-promoted trifluoromethylthiolation of aryl C─H bonds normally furnished
ortho-trifluoromethylthiolated products (Scheme 1b). Despite these progresses, the development of robust
and operationally simple Csp2─H trifluoromethylthiolation reactions remains largely underexplored.
Scheme 1 Csp2─H trifluoromethylthiolation
3

In 2015, our group reported a copper-mediated oxidative C─H trifluoromethylthiolation of quinones
with easily prepared and stable AgSCF3 using K2S2O8 as the oxidant (Scheme 1c) [12]. As an extension
of this work and in continuation of our recent research interest in C─H fluoroalkylation reactions
[9b,11a,13], herein we disclose a direct C─H trifluoromethylthiolation of heteroaryl N-oxides with
AgSCF3 in the presence of Ts2O and n-Bu4NI (Scheme 1d). Being different from the previously reported
electrophilic (Scheme 1a), transition-metal-mediated/catalyzed (Scheme 1a), and radical (Scheme 1c)
trifluoromethylthiolation reactions, a nucleophilic process is involved in this reaction. Notably, during the
preparation of this manuscript, Kuninobu and co-workers reported a similar 2-position-selective
trifluoromethylthiolation of six-membered heteroaromatic N-oxides with AgSCF3 using 2,4-
dinitrobenzenesulfonyl chloride as the activator [14].
2. Results and Discussion
Heterocyclic N-oxides are important and readily available synthetic intermediates, which have
emerged as attractive substrates for the preparation of various N-heterocycles bearing different
substituents in the C2 position [15]. Recently, the C─H fluoroalkylation and fluoroalkenylation of
heteroaryl N-oxides have been reported for the regioselective incorporation of fluoroalkyl and
fluoroalkenyl groups into heteroarenes [16]. Very recently, Hartwig disclosed a novel C─H
trifluoromethoxylation of heteroaryl N-oxides with CF3OTf as both of the activator and OCF3 source [17].
Inspired by these works, we became interested in exploring the C─H trifluoromethylthiolation of
heteroaryl N-oxides.
We initiated our investigation by choosing 4-bromoquinoline 1-oxide (1a) as the model substrate for
screening of the reaction parameters (Table 1). The reaction of 1a and AgSCF3 in MeCN did not occur
when Tf2O was used as an activator (entry 1). Further examination of the activators (entries 2-6) revealed
that the reaction worked efficiently in the presence of Ts2O, giving the desired product 2a in 46% yield
4

(entry 4). We envisioned that the addition of another activator for promoting the generation of
nucleophilic SCF3 anion from AgSCF3 might accelerate this reaction. Thus, different additives, including
CuI, KI, n-Bu4NI, and n-Bu4NBr were investigated (entries 7-10). Among them, n-Bu4NI was superior to
other additives, affording 2a in 63% yield (entry 9). Further screening of the solvents led to the discovery
that THF was the best choice among those tested solvents (entries 9 and 11-16), and the yield of 2a
reached up to 85% (entry 13). When an organic or inorganic base was added to the reaction mixture,
slightly lower yields were observed (entries 17 and 18). Finally, the reaction under N2 atmosphere gave
the same yield of 2a (entry 19 vs 13). Notably, during the optimization process, 2a was formed as the
19
major product. Other CF3S-substituted isomer was hardly detected by F NMR analysis of the crude
reaction mixture (see the Supporting Information).
Table 1. Optimization of reaction conditions.a
Entry
Activator
Additive
Solvent
Yield (%)b
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeNO2
1
Tf2O
BzCl
TsCl
―
0
2
―
5
3
―
33
46
34
11
58
44
63
60
73
4
Ts2O
Ms2O
TMSCl
Ts2O
Ts2O
Ts2O
Ts2O
Ts2O
―
5
―
6
―
7
CuI
8
KI
9
n-Bu4NI
n-Bu4NBr
n-Bu4NI
10
11
5

Ts2O
Ts2O
Ts2O
Ts2O
Ts2O
Ts2O
Ts2O
Ts2O
12
13
14
15
16
17
18
19c
n-Bu4NI
DCM
THF
62
85
50
59
0
n-Bu4NI
n-Bu4NI
Toluene
DMF
n-Bu4NI
n-Bu4NI
DMSO
THF
n-Bu4NI/NEt3
78
73
85
n-Bu4NI/Na2CO3 THF
n-Bu4NI THF
aReaction conditions: 1a (0.1 mmol), AgSCF3 (0.2 mmol), activator (0.15 mmol), additive (0.2 mmol), solvent (1.0 mL), rt, under air,
4 h.
bYields were determined by 19F NMR spectroscopy using trifluoromethylbenzene as an internal standard.
cUnder N2.
With the optimized reaction conditions in hand (Table 1, entry 13), the substrate scope of this
transformation was investigated (Table 2). A wide range of quinoline N-oxides (1a-r) were firstly
evaluated. Quinoline N-oxides bearing electron-donating groups (Me, OMe, Ph) or electron-withdrawing
groups (Cl, Br, NO2) reacted smoothly, affording the corresponding products in moderate to excellent
yields. Notably, the effect of the substituents on the phenyl ring of the quinoline N-oxides was not apparent.
Mono-substituted (1h-o), di-substituted (1p), and tri-substituted (1q) quinoline N-oxides as well as
benzo[h]quinoline N-oxide (1r) were all compatible with the reaction conditions. In addition, the reaction
of 1a could be scaled up to 5.0 mmol, affording 2a in 67% yield.
Table 2. Scope of quinoline N-oxides.a
6

aReaction conditions: 1 (0.4 mmol), AgSCF3 (0.8 mmol), Ts2O(0.6 mmol), n-Bu4NI (0.8 mmol), THF (4.0 mL), rt,, 4 h, isolated yields.
bReaction was performed on a 5.0 mmol scale.
This reaction system was easily extended to other heteroaryl N-oxides including isoquinoline N-
oxides (1s-u), phenanthridine N-oxide (1v), and 1,5-naphthyridine N-oxide (1w) (Table 3). Finally,
several pyridine N-oxides including 4-methylpyridine N-oxide, 4-cyanopyridine N-oxide, and 4-
phenylpyridine N-oxide were subjected to the standard reaction conditions. Consistent with the previous
studies [15-17], pyridine N-oxides were generally less reactive than bi- and tricyclic heterocyclic N-oxides.
Among them, 4-phenylpyridine N-oxide (1x) delivered the trifluoromethylthiolated product 2x in highest
yield (26%). Switching the activator from Ts2O to 4-NO2C6H4SO2Cl led to a lower yield of 2x (20%).
Table 3. Scope of other heteroaryl N-oxides.a
7

aReaction conditions: 1 (0.4 mmol), AgSCF3 (0.8 mmol), Ts2O(0.6 mmol), n-Bu4NI (0.8 mmol), THF (4.0 mL), rt,, 4 h, isolated yields.
On the basis of the previous reports [15-17], a plausible mechanism for this C─H
trifluoromethylthiolation reaction is depicted in Scheme 2. Initially, the reaction of quinoline N-oxides 1
and Ts2O gives intermediate A. On the other hand, the activation of AgSCF3 with n-Bu4NI generates a
nucleophilic source of SCF3 anion [18]. Subsequently, the regioselective nucleophilic attack of SCF3
anion at α-carbon of quinolines affords the dearomatized intermediate B. Finally, the resulting
intermediate B undergoes deprotonation/aromatization to furnish the C2-trifluoromethylthiolated
products 2.
Scheme 2 Proposed reaction mechanism.
8

3. Conclusion
In conclusion, we have presented a practical C─H trifluoromethylthiolation of heteroaryl N-oxides
with AgSCF3 as the trifluoromethylthio source using Ts2O and n-Bu4NI as the activators. This method
proves applicable to a variety of heterocycles, such as quinolines, benzo[h]quinolines, isoquinolines,
phenanthridines, and 1,5-naphthyridines, possessing a variety of substitution patterns. Efforts are in
progress towards further exploration of other C─H fluoroalkylation and fluoroalkylthiolation reactions.
4. Experimental Section
4.1. General information
1H NMR (TMS as the internal standard), 13C NMR and 19F NMR spectra (CFCl3 as the outside standard
and low field is positive) were recorded on a 400 MHz spectrometer. Chemical shifts (δ) are reported in
ppm, and coupling constants (J) are in Hertz (Hz). The following abbreviations were used to explain the
multiplicities: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet. HRMS data using ESI were
obtained on a Thermo Fisher Scientific LTQ FTICR-MS. All reagents were used as received from
commercial sources without further purification or prepared as described in references. Substrates 1e, 1f,
1l, and 1s were purchased and used directly from commercial sources. Substrates 1a-d, 1g-k, 1m-r, and
1t-x were prepared in accordance with methods described in the references [15a,16a].
4.2. General procedure for the synthesis of quinoline N-oxides
To a solution of quinolone (5.0 mmol) in CH2Cl2 (10.0 mL) was added m-CPBA (1.73 g, 10 mmol) at
0 °C. The reaction mixture was then stirred at room temperature overnight. The reaction mixture was
diluted with CH2Cl2 and washed with aq. KOH. The organic layer was dried over Na2SO4 and the solvent
was evaporated under reduced pressure. The resulting residue was purified by silica gel flash column
chromatography (EA/MeOH = 20: 1) to give the product.
9

4.2.1. 6-Bromo-4-chloroquinoline 1-oxide (1p). Compound 1p was obtained as a white solid (770.8 mg,
60%), mp 220-222 oC. 1H NMR (400 MHz, CDCl3) δ 8.54 (d, J = 9.2 Hz, 1H), 8.34 (d, J = 6.6 Hz, 1H),
13
8.26 (s, 1H), 7.80 (d, J = 9.2 Hz, 1H), 7.31 (d, J = 6.5 Hz, 1H). C NMR (101 MHz, CDCl3) δ 140.8,
135.2, 134.4, 129.0, 128.2, 127.3, 124.6, 122.2, 122.1. IR (thin film) ν 3059, 1548, 1491, 1337, 1288,
1216, 868, 814 cm-1; MS (ESI): m/z 258 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for
C9H5BrClNO+: 257.9316; Found: 257.9315.
4.2.2. 4-Chloro-6,7-dimethoxyquinoline 1-oxide (1q). Compound 1q was obtained as a white solid (780.1
mg, 65%), mp 182-184 oC. 1H NMR (400 MHz, CDCl3) δ 8.26 (d, J = 6.5 Hz, 1H), 8.00 (s, 1H), 7.26 (s,
1H), 7.17 (d, J = 6.6 Hz, 1H), 4.03 (s, 3H), 4.00 (s, 3H). 13C NMR (101 MHz, CDCl3) δ 153.9, 151.9,
138.1, 133.9, 128.4, 123.4, 119.2, 102.7, 99.5, 56.7, 56.4. IR (thin film) ν 1618, 1506, 1749, 1418, 1340,
1267, 1246, 850 cm-1; MS (ESI): m/z 240 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for
+
C11H10ClNO3 : 240.0422; Found: 240.0442.
4.3. General procedure for C─H trifluoromethylthiolation of heteroaryl N-oxides
A mixture of heteroaryl N-oxide (0.4 mmol), AgSCF3 (166.3 mg, 0.8 mmol), Ts2O (195.8 mg, 0.6
mmol), and n-Bu4NI (295.5 mg, 0.8 mmol) was added in a 25 mL Schlenk tube, and then THF (4.0 mL)
was added. The mixture was stirred at room temperature for 4 h. After the reaction was complete, saturated
NH4Cl solution was added. The resulting mixture was extracted with EtOAc for three times. The
combined organic layer was dried over anhydrous Na2SO4 and concentrated under reduced pressure. The
residue was purified by silica gel column chromatography (PE/EA= 100:1) to give the desired product
(2a-2w).
4.3.1. 4-Bromo-2-(trifluoromethylthio)quinoline (2a). Compound 2a was obtained as a colorless oil (93.3
mg, 76%). 1H NMR (400 MHz, CDCl3) δ 8.21 (d, J = 8.4, 1H), 8.11 (d, J = 8.4, 1H), 7.90 (s, 1H), 7.86-
13
8.82 (m, 1H), 7.75-7.69 (m, 1H). 19F NMR (376 MHz, CDCl3) δ -39.17 (s, 3F). C NMR (101 MHz,
CDCl3) δ 149.6 (q, J = 2.7 Hz), 148.6, 135.2, 131.5, 129.7, 129.1 (q, J = 310.1 Hz), 128.9, 126.8, 126.6
10

(q, J = 2.2 Hz). IR (thin film) ν 1566, 1485, 1394, 1107, 1077, 814, 756, 687 cm-1; MS (ESI): m/z 308
(M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C10H6BrF3NS+: 307.9351; Found: 307.9350.
4.3.2. 4-Chloro-2-(trifluoromethylthio)quinoline (2b). Compound 2b was obtained as a colorless oil (82.1
mg, 78%). 1H NMR (400 MHz, CDCl3) δ 8.21 (d, J = 8.4, 1H), 8.11 (d, J = 8.5, 1H), 7.86-7.82 (m, 1H),
7.74-7.63 (m, 2H). 19F NMR (376 MHz, CDCl3) δ -39.19 (s, 3F). 13C NMR (101 MHz, CDCl3) δ149.6
(q, J = 2.7 Hz), 148.8, 143.9, 131.5, 129.6, 129.1 (q, J = 310.1 Hz), 128.6, 125.4, 124.1, 122.9 (d, J = 2.3
Hz). IR (thin film) ν 1627, 1551, 1494, 1376, 1291, 1222, 1083, 916, 874 cm-1; MS (ESI): m/z 264
(M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C10H6ClF3NS+: 263.9856; Found: 263.9856.
4.3.3. 4-Methyl-2-(trifluoromethylthio)quinoline (2c). Compound 2c was obtained as a white solid (62.2
1
mg, 64%), mp 74-75 oC. H NMR (400 MHz, CDCl3) δ 8.11 (d, J = 8.5 Hz, 1H), 8.00 (dd, J = 8.4 Hz,
1H), 7.78-7.74 (m, 1H), 7.64-7.60 (m, 1H), 7.45 (s, 1H), 2.73 (s, 3H). 19F NMR (376 MHz, CDCl3) δ -
39.33 (s, 3F). 13C NMR (101 MHz, CDCl3) δ 148.6, 147.1, 145.4, 129.2, 128.9, 128.4 (q, J = 310.1 Hz),
126.4, 126.2, 122.9 (d, J = 2.1 Hz), 122.7, 17.7. IR (thin film) ν 1593, 1557, 1382, 1294, 1090, 904, 844,
560 cm-1; MS (ESI): m/z 244 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C11H9F3NS+: 244.0402;
Found: 244.0402.
4.3.4. 4-Phenyl-2-(trifluoromethylthio)quinoline (2d). Compound 2d was obtained as a white solid (102.5
1
mg, 84%), mp 94-95 oC. H NMR (400 MHz, CDCl3) δ 8.17 (d, J = 8.4 Hz, 1H), 7.92 (d, J = 8.5, 1H),
7.79-7.75 (m, 1H), 7.59-7.45 (m, 7H).19F NMR (376 MHz, CDCl3) δ -39.17 (s, 3F). 13C NMR (101 MHz,
CDCl3) δ 150.4, 149.5 (q, J = 2.6 Hz), 148.9, 136.9, 130.4, 129.7, 129.4 (q, J = 310.1 Hz), 129.4, 128.9,
128.7, 127.7, 125.92, 125.85, 123.4 (q, J = 2.1 Hz). IR (thin film) ν 1599, 1536, 1488, 1409, 1161, 1086,
768 cm-1; MS (ESI): m/z 306 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C16H11F3NS+: 306.0559;
Found: 306.0559.
4.3.5. 4-Nitro-2-(trifluoromethylthio)quinoline (2e). Compound 2e was obtained as a yellow solid (89.8
mg, 82%), mp 52-53 °C. 1H NMR (400 MHz, CDCl3) δ 8.41 (d, J = 8.7, 1H), 8.23 (d, J = 8.5, 1H), 8.06
11

13
(s, 1H), 7.95-7.91 (m, 1H), 7.84-7.80 (m, 1H). 19F NMR (376 MHz, CDCl3) δ -39.09 (s, 3F). C NMR
(101 MHz, CDCl3) δ 153.0, 150.4, 150.3 (d, J = 2.8 Hz), 132.1, 130.6, 129.9, 128.7 (q, J = 310.1 Hz),
122.8, 117.6, 117.0 (q, J = 2.4 Hz). IR (thin film) ν 1603, 1518, 1494, 1346, 1152, 1080, 853, 693 cm-1;
MS (ESI): m/z 275 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C10H6F3N2O2S+: 275.0097; Found:
275.0097.
4.3.6. 2-(Trifluoromethylthio)quinoline (2f). Compound 2f was obtained as a colorless oil (48.6 mg, 53%).
1H NMR (400 MHz, CDCl3) δ 8.10 (d, J = 8.6 Hz, 1H), 8.03 (d, J = 8.5, 1H), 7.77 (d, J = 8.2, 1H), 7.70-
13
7.68 (m, 1H), 7.56-7.49 (m, 2H). 19F NMR (376 MHz, CDCl3) δ -39.34 (s, 3F). C NMR (101 MHz,
CDCl3) δ 148.9 (d, J = 2.8 Hz), 147.4, 136.6, 129.5, 128.4 (q, J = 309.1 Hz), 128.3, 126.7, 126.6, 126.0,
122.3 (d, J = 2.2 Hz). IR (thin film) ν 1618, 1497, 1234, 1131, 1080, 919, 868, 835 cm-1; MS (ESI): m/z
230 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C10H7F3NS+: 230.0246; Found: 230.0245.
4.3.7. 3-Bromo-2-(trifluoromethylthio)quinoline (2g). Compound 2g was obtained as a white solid (82.3
mg, 67%), mp 80-81 °C. 1H NMR (400 MHz, CDCl3) δ 8.27 (s, 1H), 8.02 (d, J = 8.6, 1H), 7.77-7.67 (m,
13
2H), 7.57-7.53 (m, 1H). 19F NMR (376 MHz, CDCl3) δ -39.33 (s, 3F). C NMR (101 MHz, CDCl3) δ
151.3, 146.6, 138.8, 130.6, 129.1, 128.7 (q, J = 310.1 Hz), 127.6, 127.5, 126.6, 115.1 (q, J = 2.9 Hz). IR
(thin film) ν 1548, 1488, 1324, 1086, 956,904, 874, 771 cm-1; MS (ESI): m/z 308 (M+H)+; HRMS (ESI)
m/z: [M+H]+ Calculated for C10H6BrF3NS+: 307.9351; Found: 307.9351.
4.3.8. 5-Methoxy-2-(trifluoromethylthio)quinoline (2h). Compound 2h was obtained as a white solid (72.5
mg, 70%), mp 70-71°C. 1H NMR (400 MHz, CDCl3) δ 8.56 (d, J = 8.7 Hz, 1H), 7.67-7.63 (m, 2H), 7.55
(d, J = 8.7 Hz, 1H), 6.89 (d, J = 5.9, 1H), 4.00 (s, 3H). 19F NMR (376 MHz, CDCl3) δ -39.34 (s, 3F). 13C
NMR (101 MHz, CDCl3) δ 155.2, 155.0, 149.1, 139.9, 131.8, 129.2 (q, J = 310.1 Hz), 121.3, 120.4, 117.2
(d, J = 2.1 Hz), 105.4, 56.0. IR (thin film) ν 1615, 1569, 1470, 1355, 1267, 1088, 753, 629 cm-1; MS
(ESI): m/z 260 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C11H9F3NOS+: 260.0351; Found:
260.0352.
12

4.3.9. 5-Bromo-2-(trifluoromethylthio)quinoline (2i). Compound 2i was obtained as a white solid (94.5
mg, 77%), mp 48-49 °C. 1H NMR (400 MHz, CDCl3) δ 8.53 (d, J = 8.8, 1H), 8.05 (d, J = 8.5, 1H), 7.85
(d, J = 7.5, 1H), 7.70-7.56 (m, 2H). 19F NMR (376 MHz, CDCl3) δ -39.17 (s, 3F). 13C NMR (101 MHz,
CDCl3) δ 151.3, 148.8, 137.2, 131.2, 130.7 (d, J = 12.7 Hz), 129.2 (q, J = 310.1 Hz), 129.1, 126.5, 123.8
(q, J = 2.3 Hz), 121.8. IR (thin film) ν 1578, 1548, 1285, 1116, 1080, 944, 805, 744 cm-1; MS (ESI): m/z
308 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C10H6BrF3NS+: 307.9351; Found: 307.9351.
4.3.10. 6-Fluoro-2-(trifluoromethylthio)quinoline (2j). Compound 2j was obtained as a white solid (62.2
mg, 67%), mp 58-59 °C. 1H NMR (400 MHz, CDCl3) δ 8.17-8.07 (m, 2H), 7.61 (d, J = 8.6 Hz, 1H), 7.54
(d, J = 8.7 Hz, 1H), 7.45 (d, J = 8.6 Hz, 1H). 19F NMR (376 MHz, CDCl3) δ -39.38 (s, 3F), -110.83 to -
110.89 (m, 1F). 13C NMR (101 MHz, CDCl3) δ 161.1 (d, J = 251.5 Hz), 149.4, 145.4, 137.0 (d, J = 5.5
Hz), 131.9 (d, J = 9.2 Hz), 129.3 (q, J = 310.1 Hz), 127.9 (d, J = 10.3 Hz), 124.3 (d, J = 2.5 Hz), 121.0
(d, J = 25.9 Hz), 110.8 (d, J = 22.0 Hz). IR (thin film) ν 1627, 1494, 1291, 1222, 1083, 916, 874, 823 cm-
1; MS (ESI): m/z 248 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C10H6F4NS+: 248.0152; Found:
248.0151.
4.3.11. 6-Chloro-2-(trifluoromethylthio)quinoline (2k). Compound 2k was obtained as a white solid (65.5
mg, 62%), mp 88-90 °C. 1H NMR (400 MHz, CDCl3) δ 8.09 (d, J = 8.6 Hz, 1H), 8.03 (d, J = 9.0 Hz, 1H),
7.82 (d, J = 2.3 Hz, 1H), 7.70 (d, J = 9.0 Hz, 1H), 7.59 (d, J = 8.6 Hz, 1H). 19F NMR (376 MHz, CDCl3)
13
δ -39.27 (s, 3F). C NMR (101 MHz, CDCl3) δ 150.5 (d, J = 2.6 Hz), 146.7, 136.7, 133.7 (d, J = 28.1
Hz), 131.6, 130.8 (d, J = 5.4 Hz), 129.3 (q, J = 310.1 Hz), 127.6, 126.3, 123.9 (d, J = 2.2 Hz). IR (thin
film) ν 1581, 1551, 1479, 1288, 1137, 895, 826, 756 cm-1; MS (ESI): m/z 264 (M+H)+; HRMS (ESI) m/z:
[M+H]+ Calculated for C10H6ClF3NS+: 263.9856; Found: 263.9856.
4.3.12. 6-Methoxy-2-(trifluoromethylthio)quinoline (2l). Compound 2l was obtained as a white solid (56.0
mg, 54%), mp 88-90 °C. 1H NMR (400 MHz, CDCl3) δ 8.07 (d, J = 8.5 Hz, 1H), 8.01 (d, J = 9.2 Hz, 1H),
7.59 (d, J = 8.5 Hz, 1H), 7.41 (d, J = 9.2, 1H), 7.07 (d, J = 2.8 Hz, 1H), 3.94 (s, 3H).19F NMR (376 MHz,
13

CDCl3) δ -39.69 (s, 3F). 13C NMR (101 MHz, CDCl3) δ 157.8, 144.9 (q, J = 2.6 Hz), 143.6, 135.3, 129.8,
128.5 (q, J = 310.1 Hz), 127.6, 123.9 (d, J = 2.0 Hz), 122.5, 103.8, 54.6. IR (thin film) ν 1618, 1497,
1376, 1234, 1131, 1080, 1019, 835 cm-1; MS (ESI): m/z 260 (M+H)+; HRMS (ESI) m/z: [M+H]+
Calculated for C11H9F3NOS+: 260.0351; Found: 260.0351.
4.3.13. 7-Bromo-2-(trifluoromethylthio)quinoline (2m). Compound 2m was obtained as a white solid
(71.2 mg, 58%), mp 64-65 °C. 1H NMR (400 MHz, CDCl3) δ 8.86 (d, J = 4.5 Hz, 1H), 8.28 (s, 1H), 8.17
(d, J = 9.0 Hz, 1H), 7.78-7.59 (m, 2H).19F NMR (376 MHz, CDCl3) δ -39.93 (s, 3F). 13C NMR (101 MHz,
CDCl3) δ 149.6, 148.3, 132.2 (d, J = 2.2 Hz), 131.4, 130.6, 128.0, 127.8 (q, J = 311.1 Hz), 126.9, 125.5,
123.8. IR (thin film) ν 1600, 1545, 1485, 1340, 1152, 1092, 820, 774 cm-1; MS (ESI): m/z 308 (M+H)+;
HRMS (ESI) m/z: [M+H]+ Calculated for C10H6BrF3NS+: 307.9351; Found: 307.9348.
4.3.14. 8-Methyl-2-(trifluoromethylthio)quinoline (2n). Compound 2n was obtained as a colorless oil
(68.0 mg, 70%). 1H NMR (400 MHz, CDCl3) δ 7.90 (d, J = 8.5 Hz, 1H), 7.48-7.39 (m, 2H), 7.32-7.27
(m, 2H), 2.64 (s, 3H).19F NMR (376 MHz, CDCl3) δ -39.45 (s, 3F). 13C NMR (101 MHz, CDCl3) δ 149.1
(d, J = 2.3 Hz), 147.5, 137.6, 137.3, 130.5, 129.4 (q, J = 308.0 Hz), 127.2, 126.8, 125.4, 121.9 (d, J = 2.4
Hz), 17.6. IR (thin film) ν 1569, 1494, 1418, 1373, 1297, 1092, 874, 826 cm-1; MS (ESI): m/z 244 (M+H)+;
HRMS (ESI) m/z: [M+H]+ Calculated for C11H9F3NS+: 244.0402; Found: 244.0403.
4.3.15. 8-Methoxy-2-(trifluoromethylthio)quinoline (2o). Compound 2o was obtained as a white solid
1
(81.1 mg, 78%), mp 66-67 °C. H NMR (400 MHz, CDCl3) δ 8.16 (d, J = 8.5 Hz, 1H), 7.68 (d, J = 8.5
Hz, 1H), 7.53 (t, J = 8.0 Hz, 1H), 7.41 (d, J = 8.2 Hz, 1H), 7.12 (d, J = 7.8 Hz, 1H), 4.09 (s, 3H).19F NMR
(376 MHz, CDCl3) δ -39.41 (s, 3F). 13C NMR (101 MHz, CDCl3) δ 155.1, 148.9 (q, J = 2.9 Hz), 140.2,
137.7, 129.6 (q, J = 309.1 Hz), 128.3, 128.1, 124.2 (q, J = 2.2 Hz), 119.2, 109.0, 56.2. IR (thin film) ν
1612, 1551, 1463, 1373, 1086, 986, 829, 753 cm-1; MS (ESI): m/z 260 (M+H)+; HRMS (ESI) m/z: [M+H]+
Calculated for C11H9F3NOS+: 260.0351; Found: 260.0351.
14

4.3.16. 6-Bromo-4-chloro-2-(trifluoromethylthio)quinoline (2p). Compound 2p was obtained as a white
1
solid (118.6 mg, 87%), mp 66-68 °C. H NMR (400 MHz, CDCl3) δ 8.37 (s, 1H), 7.96 (d, J = 8.9 Hz,
1H), 7.88 (d, J = 8.9 Hz, 1H), 7.66 (s, 1H). 19F NMR (376 MHz, CDCl3) δ -39.10 (s, 3F). 13C NMR (101
MHz, CDCl3) δ 150.4 (d, J = 2.7 Hz), 147.4, 142.6, 135.1, 131.2, 128.9 (q, J = 310.1 Hz), 126.5, 126.4,
123.3 (q, J = 2.3 Hz), 123.1. IR (thin film) ν 1557, 1536, 1470, 1370, 1258, 1113, 871, 838 cm-1; MS
(ESI): m/z 342 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C10H5BrClF3NS+: 341.8961; Found:
341.8963.
4.3.17. 4-Chloro-6,7-dimethoxy-2-(trifluoromethylthio)quinoline (2q). Compound 2q was obtained as a
white solid (116.3 mg, 90%), mp 112-113 °C. 1H NMR (400 MHz, CDCl3) δ 7.63 (s, 1H), 7.50 (s, 1H),
13
7.39 (s, 1H), 4.08 (s, 3H), 4.06 (s, 3H). 19F NMR (376 MHz, CDCl3) δ -39.61 (s, 3F). C NMR (101
MHz, CDCl3) δ 154.0, 151.8, 146.2, 145.6 (d, J = 2.9 Hz), 141.4, 129.3 (q, J = 310.1 Hz), 122.8 (d, J =
2.0 Hz), 121.6, 108.1, 101.4, 56.4, 56.3. IR (thin film) ν 1621, 1566, 1427, 1249, 1080, 998, 844, 756 cm-
1; MS (ESI): m/z 308 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C12H10ClF3NO2S+: 324.0067;
Found: 324.0067.
4.3.18. 2-(Trifluoromethylthio)benzo[h]quinoline (2r). Compound 2r was obtained as a white solid (70.3
mg, 63%), mp 33-34 °C. 1H NMR (400 MHz, CDCl3) δ 9.25 (d, J = 7.8 Hz, 1H), 8.13 (d, J = 8.2 Hz, 1H),
7.90 (d, J = 7.4 Hz, 1H), 7.83 (d, J = 8.8 Hz, 1H), 7.74 (d, J = 7.2 Hz, 2H), 7.67-7.58 (m, 2H).19F NMR
(376 MHz, CDCl3) δ -39.51 (s, 3F). 13C NMR (101 MHz, CDCl3) δ 148.7 (d, J = 3.1 Hz), 147.0, 137.1,
133.8, 130.8, 129.7 (q, J = 309.1 Hz), 128.9, 128.8, 127.7, 127.5, 125.3, 124.7, 124.5, 123.5 (d, J = 2.2
Hz). IR (thin film) ν 1624, 1584, 1491, 1400, 838, 756, 644 cm-1; MS (ESI): m/z 280 (M+H)+; HRMS
(ESI) m/z: [M+H]+ Calculated for C14H9F3NS+: 280.0402; Found: 280.0402.
4.3.19. 1-(Trifluoromethylthio)isoquinoline (2s). Compound 2s was obtained as a colorless oil (42.1 mg,
46%). 1H NMR (400 MHz, CDCl3) δ 8.56 (d, J = 5.6 Hz, 1H), 8.32 (d, J = 7.9 Hz, 1H), 7.88 (d, J = 9.0
Hz, 1H), 7.78-7.75 (m, 1H), 7.72-7.67 (m, 2H). 19F NMR (376 MHz, CDCl3) δ -38.93 (s, 3F). 13C NMR
15

(101 MHz, CDCl3) δ 149.9 (d, J = 2.3 Hz), 142.6, 136.8, 131.1, 129.8 (d, J = 1.7 Hz), 129.1 (q, J = 310.1
Hz), 128.5, 127.3, 125.8, 121.9. IR (thin film) ν 1581, 1551, 1488, 1318, 1092, 974, 823, 744 cm-1; MS
(ESI): m/z 230 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C10H7F3NS+: 230.0246; Found:
230.0245.
4.3.20. 4-Bromo-1-(trifluoromethylthio)isoquinoline (2t). Compound 2t was obtained as a white solid
(87.2 mg, 71%), mp 52-53 °C. 1H NMR (400 MHz, CDCl3) δ 8.75 (s, 1H), 8.32 (d, J = 8.5 Hz, 1H), 8.23
(d, J = 8.6 Hz, 1H), 7.90-7.86 (m, 1H), 7.78-7.84 (m, 1H). 19F NMR (376 MHz, CDCl3) δ -39.17 (s, 3F).
13C NMR (101 MHz, CDCl3) δ 149.4 (d, J = 2.3 Hz), 144.3, 135.5, 132.3, 130.6, 129.4, 128.8 (q, J =
310.1 Hz), 126.9, 126.2, 121.2. IR (thin film) ν 1615, 1560, 1545, 1191, 1122, 1089, 980 cm-1; MS (ESI):
m/z 308 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C10H6BrF3NS+: 307.9351; Found: 307.9353.
4.3.21. 5-Bromo-1-(trifluoromethylthio)isoquinoline (2u). Compound 2u was obtained as a white solid
1
(76.1 mg, 62%), mp 49-50 °C. H NMR (400 MHz, CDCl3) δ 8.65 (d, J = 5.8 Hz, 1H), 8.30 (d, J = 8.5
Hz, 1H), 8.7-8.03 (m, 2H), 7.56-7.52 (m, 1H). 19F NMR (376 MHz, CDCl3) δ -38.97 (s, 3F). 13C NMR
(101 MHz, CDCl3) δ 150.7 (d, J = 4.7 Hz), 143.8, 135.9, 134.8, 130.4 (d, J = 1.6 Hz), 128.6, 128.9 (q, J
= 310.1 Hz), 125.4, 122.3, 120.7. IR (thin film) ν 1569, 1476, 1394, 1318, 1095, 829, 802 cm-1; MS (ESI):
m/z 308 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C10H6BrF3NS+: 307.9351; Found: 307.9350.
4.3.22. 6-(Trifluoromethylthio)phenanthridine (2v). Compound 2v was obtained as a white solid (82.6
mg, 74%), mp 89-90 °C. 1H NMR (400 MHz, CDCl3) δ 8.64 (d, J = 8.4 Hz, 1H), 8.55 (d, J = 9.5 Hz, 1H),
8.34 (d, J = 7.6 Hz, 1H), 8.21 (d, J = 7.9 Hz, 1H), 7.93-7.88 (m, 1H), 7.79-7.69 (m, 3H). 19F NMR (376
MHz, CDCl3) δ -38.56 (s, 3F). 13C NMR (101 MHz, CDCl3) δ 151.0 (d, J = 2.4 Hz), 143.8, 133.3, 131.5,
130.2, 129.2, 129.1 (q, J = 310.1 Hz), 128.0, 127.9, 126.4, 126.3 (q, J = 2.0 Hz), 123.8, 122.5, 122.0. IR
(thin film) ν 1612, 1563, 1451, 1340, 1107, 1083, 950, 753 cm-1; MS (ESI): m/z 280 (M+H)+; HRMS
(ESI) m/z: [M+H]+ Calculated for C14H9F3NS+: 280.0402; Found: 280.0401.
16

4.3.23. 2-(Trifluoromethylthio)-1,5-naphthyridine (2w). Compound 2w was obtained as a white solid
1
(68.1 mg, 74%), mp 61-62 °C. H NMR (400 MHz, CDCl3) δ 8.87 (d, J = 4.2 Hz, 1H), 8.81 (d, J = 4.7
Hz, 1H), 8.34 (d, J = 6.9 Hz, 1H), 7.72-7.70 (m, 1H), 7.67-7.64 (m, 1H). 19F NMR (376 MHz, CDCl3) δ
13
-40.55 (s, 3F). C NMR (101 MHz, CDCl3) δ 149.5, 149.1, 142.1, 140.4 (d, J = 2.1 Hz), 139.4, 136.8,
128.3 (q, J = 310.1 Hz), 124.5, 120.0 (q, J = 2.4 Hz). IR (thin film) ν 1575, 1488, 1470, 1288, 1107, 1025,
838, 783 cm-1; MS (ESI): m/z 231 (M+H)+; HRMS (ESI) m/z: [M+H]+ Calculated for C9H6F3N2S+:
231.0198; Found: 231.0196.
4.3.24. 4-Phenyl-2-(trifluoromethylthio)pyridine (2x). Compound 2x was obtained as a colorless oil (26.5
mg, 26%). 1H NMR (400 MHz, CDCl3) δ 8.58 (d, J = 5.2 Hz, 1H), 7.72 (s, 1H), 7.58-7.51 (m, 2H), 7.48-
7.36 (m, 4H). 19F NMR (376 MHz, CDCl3) δ -39.97 (s, 3F). 13C NMR (101 MHz, CDCl3) δ 149.9, 149.4,
148.8 (q, J = 2.6 Hz), 135.8, 128.7, 128.4 (q, J = 310.1 Hz), 128.3, 126.0, 125.0 (q, J = 1.9 Hz), 120.8. IR
(thin film) ν 1587, 1536, 1457, 1376, 1131, 1104, 1077, 690 cm-1; MS (ESI): m/z 256 (M+H)+; HRMS
(ESI) m/z: [M+H]+ Calculated for C12H9F3NS+: 256.0402; Found: 256.0401.
4.4. Procedure for gram-scale reaction
A mixture of 4-bromoquinoline 1-oxide 1a (1.11 g, 5.0 mmol), AgSCF3 (2.08 g, 10.0 mmol), Ts2O
(2.45 g, 7.5 mmol), and n-Bu4NI (3.69 g, 10.0 mmol) was added in a 100 mL Schlenk tube, and then THF
(50.0 mL) was added. The mixture was stirred at room temperature for 4 h. After the reaction was
complete, saturated NH4Cl solution was added. The resulting mixture was extracted with EtOAc for three
times. The combined organic layer was dried over anhydrous Na2SO4 and concentrated under reduced
pressure. The residue was purified by silica gel column chromatography (PE/EA= 100:1) to afford 2a in
67% yield (1.03 g).
Acknowledgement
17

We thank National Natural Science Foundation of China (21332010, 21421002), Strategic Priority
Research Program of the Chinese Academy of Sciences (XDB20000000), and Youth Innovation
Promotion Association CAS (No. 2016234) for funding this work.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j. jfluchem.xxxx.xx.xxx.
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