A green and transition-metal-free light-mediated trifluoromethylation reaction of coumarins

Article abstract of DOI:10.1016/j.jfluchem.2018.08.003

A simple, metal- and oxidant-free photo catalysis strategy for the direct trifluoromethylation of coumarins with inexpensive sodium triflinate (Langlois reagent, CF₃SO₂Na) as the CF₃ source under xenon lamp irradiation is described. The reaction proceeds under ambient conditions and affords the corresponding products in moderate yields. The acetone can be used as low-cost radical initiator to generate CF₃ radicals from sodium triflinate efficiently.

Full text of DOI:10.1016/j.jfluchem.2018.08.003

Accepted Manuscript
Title: A Green and Transition-Metal-Free Light-mediated
Trifluoromethylation Reaction of Coumarins
Authors: Na Lin, Yaming Li, Xinyu Hao, Kun Jin, Rong
Zhang, Chunying Duan
PII:
S0022-1139(18)30192-1
DOI:
Reference:
https://doi.org/10.1016/j.jfluchem.2018.08.003
FLUOR 9207
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Revised date:
Accepted date:
10-5-2018
3-8-2018
3-8-2018
Please cite this article as: Lin N, Li Y, Hao X, Jin K, Zhang R, Duan C, A Green and
Transition-Metal-Free Light-mediated Trifluoromethylation Reaction of Coumarins,
Journal of Fluorine Chemistry (2018), https://doi.org/10.1016/j.jfluchem.2018.08.003
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A Green and Transition-Metal-Free Light-mediated
Trifluoromethylation Reaction of Coumarins
Na Lin, Yaming Li*, Xinyu Hao, Kun Jin, Rong Zhang and Chunying Duan
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, China.
Tel./fax: +86-411-84986295; E-mail: ymli@dlut.edu.cn (Y. Li)
Grapgical abstract
An efficient and practical approach to the photoinduced trifluoromethylation of coumarins in
the absence of additional metal photocatalyst was developed with easily handled CF3SO2Na.
Significantly, this photochemical strategy employed acetone, one of the most widely used and
cheapest organic solvents, instead of expensive metal catalyst or dangerous peroxides to
generate CF3 radical, which provides a green route to cost-effective large-scale synthesis of
trifluoromethylated chemicals.
Highlights

Coumarin is a common motif in a variety of natural products and/or synthetic molecules with
interesting biological activities and technological applications and the trifluoromethyl coumarins are
great attractive in the pharmaceutical and agrochemical fields.


Visible light photoredox synthesis, employing photosensitizers have unrivaled advantages in terms
the potential green chemistry.
The combination of green visible light photocatalysis and cost-effective CF3SO2Na (Langlois reagent)
has considerable interest in both academic and industry.
Abstract
A simple, metal- and oxidant-free photo catalysis strategy for the direct trifluoromethylation
of coumarins with inexpensive sodium triflinate (Langlois reagent, CF3SO2Na) as the CF3
source under xenon lamp irradiation is described. The reaction proceeds under ambient
conditions and affords the corresponding products in moderate yields. The acetone can be used
as low-cost radical initiator to generate CF3 radicals from sodium triflinate efficiently.
Key words: Trifluoromethylation; Coumarins; Photo-Catalyzed; Transition-Metal-Free; Acetone;
Langlois reagent

1. Introduction
Coumarin is a common motif in a variety of natural products and/or synthetic molecules with
interesting biological activities and technological applications [1]. In addition, owing to their
remarkable fluorescent properties, coumarins also have been widely utilized in photosensitive
polymeric materials [2], Lasers [3], and fluorescent probes for metal ions [4].
The trifluoromethyl compounds are great interest in the pharmaceutical and agrochemical
fields due to their excellent performance in regulating the physical, chemical, and biological
properties of potential drug candidates [5]. It is therefore greatly desirable to develop new
practical and efficient methods for incorporating the CF3 substituent into organic substrates [6].
During the past decade, a wide range of trifluoromethylation approaches of arenes and
heteroarenes have been disclosed based on transition-metal catalyzed coupling strategies [7] and
photoredox induced radical trifluoromethylation protocols [8]. α,β-Unsaturated carbonyls that
contain an electron-deficient carbon–carbon double bond are not only versatile synthetic
intermediates but also a structural motif in biologically active molecules [9]. Coumarin
compounds contain the α,β-unsaturated carbonyl subunit. However, 3-trifluoromethyl coumarins
were not easily accessible since 4-trifluoromethyl coumarins [10]. Recently
Piasecka-Maciejewska [11] reported the preparation of 3-trifluoromethylcoumarins using
3-carboxylic acid coumarins and sulfur tetrafluoride. Wang [12] developed a copper-catalyzed
trifluoromethylation of quinone with expensive Togni`s reagent. Nadia O. Ilchenko [13] found
that quinones undergo copper-mediated C–H trifluoromethylation reactions using a hypervalent
iodine reagent. In 2014, Zou [14] reported a general straightforward method for
trifluoromethylation of coumarins with CF3SO2Na mediated by Mn(OAc)3. Also, in 2015, Our
group [15] reported a mild and fast method for Cu(I)-catalyzed trifluoromethylation of
coumarins by using CF3SO2Na–TBHP partners in a continuous-flow system. Also, some
reactions on the trifluoromethylation of coumarin derivatives were reported [16][17].
A variety of trifluoromethylations in the presence of a suitable photosensitizer, including the
precious Ru and Ir complexes [18] under visible-light irradiation have been disclosed. There are
particular advantages for the combination of green visible light photocatalysis and cost-effective
CF3SO2Na (Langlois reagent) [19] as trifluoromethylating reagents, offering a mild route to
construct a C-CF3 bond. In order to preserve expensive Ru- and Ir- photocatalysts, organic
transformations under visible light irradiation without additional photocatalysts have received
considerable attention. Recently, Li`s group reported a simple, metal and oxidant-free

photochemical strategy for the direct trifluoromethylation of arenes from CF3SO2Na, in which
photoexcited aliphatic ketones act as promising radical initiators under light irradiation [20].
And in 2018, they just applied their method to the synthesis of 6-trifluoromethylphenanthridines
from isocyanides [21].
The trifluoromethylation of coumarins under visible light irradiation in the absence of
additional metal photocatalyst is a more challenging access to coumarin scaffolds in an efficient
and atom-economical manner. Herein, we report a simple, transition-metal and oxidant free
photochemical strategy for the direct trifluoromethylation of coumarins under xenon lamp
irradiation using the inexpensive CF3SO2Na as the CF3 source.
2. Results and discussion
Our investigation commenced with the trifluoromethylation of coumarin using CF3SO2Na
(4.0 equiv) as a CF3 source, and acetone (2.0 mL) as a solvent at the room temperature under an
argon atmosphere (Table 1). After 24 h reaction, the desired trifluoromethylation product was
obtained in 65% yield (Table 1, entry 1). Encouraged by this result, we then reduced the reaction
time to 12h and found that the yield remains without change. When further cutting down the
reaction time to 6 h, the yield of trifluoromethylation product was significant decreased to 41%
(Table 1, entries 2-3). It should be noted that replacing K2HPO4 with other bases including
K3PO4, K2CO3, Cs2CO3 and KOH leads to lower yields (Table 1, entry 2, entries 4-7). By
slightly reducing the amount of the CF3SO2Na also resulted in a lower yield of 41% (Table 1,
entry 8). Various solvents were then screened, acetone was the most suitable one (Table 1, entry
2, entries 9-12). Especially, No further increment of the yield was found with dried acetone as
solvent (water free, Table 1, entry 9). Finally, when the reaction was carried out without
irradiation, no desired product was obtained (Table 1, entry 13). The optimized conditions for
this process were defined as the use of 1a (0.2 mmol) with CF3SO2Na (4 equiv), and K2HPO4 (2
equiv) in acetone (2 mL) at the room temperature under argon atmosphere with the irradiation of
a Xenon lamp for 12 h.
With optimized condition in hand, the scope of substrates was explored and the results are
summarized in Scheme 2. A wide variety of coumarins bearing either electron-withdrawing or
electron-donating groups at the aryl ring could be transformed into the corresponding
trifluoromethylation products in moderate to good yields. The halogens (Cl, Br), nitro, methyl,
methoxy and ester groups were tolerated in this system owing to the mildness of the reaction

conditions. The trifluoromethylation of coumarins bearing methyl and t-butyl at the 6-position
were effective and resulted in moderate to good yields ( 2b, 2c, 2d ). Good yields could also be
obtained with a 7-methoxyl substituted derivative, giving 67% yield (2e). In the case of a weak
electron-withdrawing group, such as acetoxyl, chlorine and bromo at the 6-position, moderate
yields of 62%, 54% and 56% were obtained respectively ( 2f, 2g, 2h ). However, the strong
electron-withdrawing group nitro at the 6-position afforded a poor yield of 41% ( 2i ). For
4-phenyl-coumarins, the family members of coumarin derivatives, their corresponding
trifluoromethyl products were obtained in moderate yields ( 2k-2o, 55-67% ). Notably, the
trifluoromethylation product of quinolinone afforded a good yield of 65% ( 2p ).
Based on our experiment and previous work[15][20], a reaction mechanism was proposed
(Scheme 3), which included a radical initial, followed by a radical addition, and the loss of
hydrogen atom to aromatization. First, under the irradiation of the xenon lamp, acetone, acted as
a photosensitizer, absorbs resonant photons, a lone pair electron transits from oxygen to the
carbonyl carbon. Next the resulting electron-deficient oxygen atom of the carbonyl may abstract
one electron from CF3SO2Na to generate a CF3 radical, which is called the photoreduction of
ketone. Then the CF3 radical attacked the α-position of coumarin (1), the more stable free radical
intermediate (A) was formed. Afterwards the radical intermediate (A) interacted with the
reduction product of acetone, the reduction product of acetone captured the hydrogen radical and
absorbed SO2 to the salt. At last the radical intermediate lost the hydrogen radical and formed a
double bond to obtain 3-trifluoromethyl coumarin (2).
3. Conclusion
In summary, an efficient and practical approach to the photoinduced trifluoromethylation of
coumarins in the absence of additional metal photocatalyst was developed with easily handled
CF3SO2Na. Significantly, this photochemical strategy employed acetone, one of the most widely
used and cheapest organic solvents, instead of expensive metal catalyst or dangerous peroxides
to generate CF3 radical, which provides a green route to cost-effective large-scale synthesis of
trifluoromethylated chemicals.
4. Experimental
4.1 General
All reagents unless otherwise noted were obtained from commercial sources and used without
further purification. Sodium Trifluoromethanesulfinate (>95.0%) was used without any

purification. Reactions were monitored by thin-layer chromatography (TLC) on silica gel plates
and visualization of the plates was performed under UV light (254 nm and 365nm). Further flash
1
19
column chromatography was performed on silica gel (200-300 mesh). H NMR and F NMR
spectra were recorded on a Bruker-500 or 400 NMR spectrometer using TMS as an internal
13
standard and the external standard of 19F NMR uses trifluoroacetic acid. C NMR spectra were
1
recorded on a Bruker NMR(126M). Chemical shifts for H NMR were reported in ppm relative
13
to TMS. All C NMR spectra were reported in ppm relative to deuterated chloroform (77.00
ppm). The following abbreviations are used to set multiplicities: s = singlet, d = doublet, t =
triplet, dd = doublet of doublets, q = quartet, tq = triplet of quartets, qt = quartet of triplets, and
m = multiplet. Coupling constants (J) were reported in Hertz (Hz). GC-MS data were also
recorded. High-resolution mass spectrometry data were recorded on a high-resolution mass
spectrometer in the ESI mode.
To a tube were added 1a (1.0 equiv), CF3SO2Na(4.0 equiv), K2HPO4, Acetone (2 mL) . Then
the tube was evacuated and backfilled with argon for three times. The tube around condensate
water was stirred at room temperature in argon with the irradiation of Xenon lamp for 12 h.
After the reaction was finished, the mixture was washed with saturated sodium chloride solution
and then extracted with ethyl acetate for three times. The combined organic layers were dried
over Na2SO4 and concentrated under reduced pressure, then purified by chromatography on
silica gel.
4.2 Characterization of compounds
3-(trifluoromethyl)-2H-1-Benzopyran-2-one (2a).
White powder, 27.4 mg, 64%; mp 130-1310C;
1H NMR (500 MHz, CDCl3): δ 8.17 (s, 1H), 7.69 (t, J = 7.9 Hz, 1H), 7.64 (d, J = 6.7 Hz, 1H),
7.44 – 7.34 (m, 2H). 13C NMR (126 MHz, CDCl3): δ 155.85 (s), 154.62 (s), 143.32 (q, J = 4.8
Hz), 134.42 (s), 129.47 (s), 125.26 (s), 121.33 (q, J = 272.0 Hz), 117.68 (q, J = 33.4 Hz), 116.96
(s), 116.76 (s).19F NMR (470 MHz, CDCl3): δ -66.18 (s). GC-MS (EI, m/z): 214(M+, 100),
186(57), 136(52), 63(34). IR (KBr), ν 3120 (C=C-H), 1755 (C=O), 1628 (C=C) cm−1.
6-Methyl-3-(trifluoromethyl)-2H-1-Benzopyran-2-one (2b).

White powder, 26 mg, 57%; mp 141-1420C;
1H NMR (500 MHz, CDCl3): δ 8.10 (s, 1H), 7.48 (dd, J = 8.5, 1.8 Hz, 1H), 7.40 (s, 1H), 7.29
13
(d, J = 8.5 Hz, 1H), 2.44 (s, 3H). C NMR (126 MHz, CDCl3): δ 156.12 (s), 152.83 (s), 143.26
(q, J = 4.9 Hz), 135.53 (s), 135.19 (s), 129.11 (s), 121.44 (q, J = 272.0 Hz), 117.58 (q, J = 33.1
19
Hz), 116.73 (s), 116.55 (s), 20.70 (s). F NMR (470 MHz, CDCl3) δ: -66.14 (s). GC–MS (EI,
m/z): 228(M+, 100), 200(48), 199(43), 131(43). IR (KBr), ν 3125 (C=C-H), 1750 (C=O), 1623
(C=C) cm−1
.
6, 8-Dimethyl-3-(trifluoromethyl)-2H-1-Benzopyran-2-one (2c).
White powder, 29 mg, 60%; mp 126-1270C;
1H NMR (500 MHz, CDCl3): δ 8.07 (s, 1H), 7.34 (s, 1H), 7.22 (s, 1H), 2.43 (s, 3H), 2.40 (s,
3H). 13C NMR (126 MHz, CDCl3): δ 156.30 (s), 151.22 (s), 143.60 (q, J = 4.8 Hz), 136.92 (s),
134.62 (s), 126.78 (s), 126.29 (s), 121.56 (q, J = 271.9 Hz), 117.14 (q, J = 33.0 Hz), 116.36 (s),
20.61 (s), 15.26 (s). 19F NMR (470 MHz, CDCl3): δ -66.05 (s). HRMS (ESI) m/z: [M + Na] +
Calcd For C12H9F3O2Na 265.0452; found 265.0446. IR (KBr), ν 3118 (C=C-H), 1753 (C=O),
1626 (C=C) cm−1
.
6-t-Butyl-3-(trifluoromethyl)-2H-1-Benzopyran-2-one (2d).
White powder, 37.8 mg, 70%; mp 162-1630C;
1H NMR (500 MHz, CDCl3): δ 8.17 (s, 1H), 7.73 (d, J = 8.8 Hz, 1H), 7.58 (s, 1H), 7.33 (d, J
= 8.8 Hz, 1H), 1.37 (s, 9H). 13C NMR (126 MHz, CDCl3): δ 156.24 (s), 152.72 (s), 148.61 (s),
143.81 (q, J = 4.9 Hz), 132.26 (s), 125.68 (s), 121.49 (q, J = 271.9 Hz), 117.38 (q, J = 33.3 Hz),
116.27 (s), 113.80 (s), 34.65 (s), 31.22 (s). 19F NMR (470 MHz, CDCl3): δ -66.11 (s). HRMS
(ESI) m/z: [M+Na]+ Calcd. For C14H13F3O2Na 293.0765; found 293.0733. IR (KBr), ν 3116
(C=C-H), 1752 (C=O), 1625 (C=C) cm−1
.
7-Methoxyl-3-(trifluoromethyl)-2H-1-Benzopyran-2-one (2e).

White powder, 32.7 mg, 67%; mp 124-1250C;
1H NMR (500 MHz, CDCl3): δ 8.09 (s, 1H), 7.52 (d, J = 8.7 Hz, 1H), 6.93 (dd, J = 8.7, 2.3 Hz,
1H), 6.84 (d, J = 2.3 Hz, 1H), 3.92 (s, 3H). 13C NMR (126 MHz, CDCl3): δ 165.01 (s), 156.84
(s), 156.38 (s), 143.26 (q, J = 4.8 Hz), 130.59 (s), 121.77 (q, J = 271.5 Hz), 113.77 (q, J = 33.3
Hz), 113.76 (s), 110.38 (s), 100.74 (s), 56.04 (s). 19F NMR (470 MHz, CDCl3): δ -65.68 (s).
GC-MS (EI, m/z): 244(M+, 78), 216(73), 201 (100), 69(40). IR (KBr), ν 3118 (C=C-H), 1750
(C=O), 1630 (C=C) cm−1
.
7-Acetyloxy-3-(trifluoromethyl)-2H-1-Benzopyran-2-one (2f).
White powder, 33.6 mg, 62%; mp 146-1470C;
1H NMR (500 MHz, CDCl3): δ 8.14 (s, 1H), 7.63 (d, J = 8.5 Hz, 1H), 7.20 (d, J = 2.2 Hz, 1H),
13
7.16 (dd, J = 8.5, 2.2 Hz, 1H), 2.36 (s, 3H). C NMR (126 MHz, CDCl3): δ 168.30 (s), 155.51
(s), 155.39 (s), 155.22 (s), 142.72 (q, J = 4.9 Hz), 130.31 (s), 121.32 (q, J = 272.0 Hz), 119.36
19
(s), 117.04 (q, J = 33.4 Hz), 114.47 (s), 110.52 (s), 21.11 (s). F NMR (470 MHz, CDCl3): δ
-66.14 (s). GC-MS (EI, m/z): 230(M+, 26), 202(27), 43(100), 32(38). IR (KBr), ν 3123 (C=C-H),
1769, 1762 (C=O), 1621 (C=C) cm−1
.
6-Chloro-3-(trifluoromethyl)-2H-1-Benzopyran-2-one (2g).
White powder, 26.7 mg, 54%; mp 161-1620C;
1H NMR (500 MHz, CDCl3): δ 8.09 (s, 1H), 7.63 (d, J = 11.8 Hz, 2H), 7.36 (d, J = 8.7 Hz,
1H). 13C NMR (126 MHz, CDCl3): δ 155.18 (s), 153.04 (s), 142.07 (q, J = 4.9 Hz), 134.36 (s),
130.68 (s), 128.54 (s), 121.06 (q, J = 272.4 Hz), 118.98 (q, J = 33.5 Hz), 118.53 (s), 117.75 (s).
19F NMR (470 MHz, CDCl3): δ -66.35 (s). HRMS (ESI) m/z: [M+Na]+ Calcd. For
C10H4ClF3O2Na 270.9758; found 270.9750. IR (KBr), ν 3113 (C=C-H), 1743 (C=O), 1625 (C=C)
cm−1
.
6-Bromo-3-(trifluoromethyl)-2H-1-Benzopyran-2-one (2h).

White powder, 32.6 mg, 56%; mp 162-1630C;
1H NMR (500 MHz, CDCl3): δ 8.09 (s, 1H), 7.76 (dd, J = 7.0, 2.2 Hz, 2H), 7.30 (d, J = 9.5 Hz,
13
1H). C NMR (126 MHz, CDCl3): δ 155.11 (s), 153.49 (s), 142.01 (q, J = 4.9 Hz), 137.16 (s),
131.63 (s), 121.04 (q, J = 272.4 Hz), 118.90 (q, J = 33.4 Hz), 118.75 (s), 118.25 (s), 117.84 (s).
19F NMR (470 MHz, CDCl3): δ -66.34 (s). GC-MS (EI, m/z): 292(M+, 71), 294(70), 157(89),
87(100). IR (KBr), ν 3115 (C=C-H), 1740 (C=O), 1627 (C=C) cm−1
.
6-Nitro-3-(trifluoromethyl)-2H-1-Benzopyran-2-one (2i).
White powder, 21.2 mg, 41%; mp 188-1890C;
1H NMR (500 MHz, CDCl3): δ 8.58 (d, J = 2.0 Hz, 1H), 8.54 (dd, J = 9.1, 2.3 Hz, 1H), 8.25 (s,
1H), 7.56 (d, J = 9.1 Hz, 1H). 13C NMR (126 MHz, CDCl3): δ 157.85 (s), 154.11 (s), 144.50 (s),
142.02 (q, J = 5.0 Hz), 128.86 (s), 125.24 (s), δ 120.70 (q, J = 272.7 Hz), 120.14 (q, J = 34.1
19
Hz), 118.41 (s), 116.81 (s). F NMR (470 MHz, CDCl3): δ -66.51 (s). GC-MS (EI, m/z):
256(M+, 59), 157(100), 87(83), 62(55). IR (KBr), ν 3135 (C=C-H), 1734 (C=O), 1646 (C=C)
cm−1
.
7-Methoxy-4-Methyl-3-(trifluoromethyl)-2H-1-Benzopyran-2-one (2j).
White powder, 35.6 mg, 69%; mp 140-1410C;
1H NMR (500 MHz, CDCl3) δ 7.70 (d, J = 9.1 Hz, 1H), 6.92 (dd, J = 9.1, 2.5 Hz, 1H), 6.78 (d,
13
J = 2.5 Hz, 1H), 3.91 (s, 3H), 2.63 (dd, J = 4.2, 2.0 Hz, 3H). C NMR (126 MHz, CDCl3) δ
164.40 (s), 156.32 (s), 155.13 (s), 155.10 (d, J = 1.2 Hz), 127.16 (s), 123.15 (q, J = 274.7 Hz),
113.37 (s), 112.47 (s), 112.00 (q, J = 30.3 Hz), 100.43 (s), 55.96 (s), 15.65 (q, J = 4.1 Hz).19F
NMR (470 MHz, CDCl3) δ -56.33 (q, J = 1.9 Hz). GC-MS (EI, m/z): 258(M+, 68), 230(99),
215(100), 32(17). IR (KBr), ν 3105 (C=C-H), 1755 (C=O), 1621 (C=C) cm−1
.
4-Phenyl-3-(trifluoromethyl)-2H-1-benzopyran-2-one (2k).

White powder, 34.8 mg, 60%; mp 132-1330C;
1H NMR (500 MHz, CDCl3) δ 7.63 (t, J = 7.7 Hz, 1H), 7.53 (s, 3H), 7.41 (d, J = 8.3 Hz, 1H),
13
7.26 (s, 2H), 7.20 (t, J = 7.6 Hz, 1H), 7.01 (d, J = 8.0 Hz, 1H). C NMR (126 MHz, CDCl3) δ
156.86 (d J = 2.0 Hz), 156.32 (s), 153.46 (s), 134.09 (s), 132.86 (s), 129.31 (s), 129.26 (s),
128.49 (s), 127.30 (d, J = 1.5 Hz), 124.77 (s), 121.87 (q, J = 275.4 Hz), 119.49 (s), 116.84 (s),
114.98 (q, J = 30.3 Hz). 19F NMR (377 MHz, CDCl3) δ -57.90 (s). GC–MS (EI, m/z): 290.06. IR
(KBr), ν 1753 (C=O), 1620 (C=C) cm−1
.
6-Methyl-4-Phenyl-3-(trifluoromethyl)-2H-1-benzopyran-2-one (2l).
White powder, 34 mg, 56%; mp 121-1220C;
1H NMR (500 MHz, CDCl3) δ 7.56 – 7.49 (m, 3H), 7.43 (dd, J = 8.4, 1.7 Hz, 1H), 7.30 (d, J =
8.4 Hz, 1H), 7.25 (dd, J = 6.5, 2.9 Hz, 2H), 6.75 (s, 1H), 2.27 (s, 3H). 13C NMR (126 MHz,
CDCl3) δ 156.84 (d, J = 2.0 Hz), 156.55 (s), 151.64 (s), 135.19 (s), 134.63 (s), 132.98 (s), 129.24
(s), 128.78 (s), 128.46 (s), 127.29 (d, J = 1.6 Hz), 121.95 (q, J = 275.1 Hz), 119.15 (s), 116.61 (s),
114.92 (q, J = 29.9 Hz), 20.91 (s). 19F NMR (377 MHz, CDCl3) δ -57.82 (s). GC–MS (EI, m/z):
304.07. IR (KBr), ν 1752 (C=O), 1623 (C=C) cm−1
.
6-t-Butyl-4-Phenyl-3-(trifluoromethyl)-2H-1-benzopyran-2-one (2m).
White powder, 46.4 mg, 67%; mp 98-990C;
1H NMR (500 MHz, CDCl3) δ 7.54 – 7.47 (m, 3H), 7.40 (d, J = 1.3 Hz, 1H), 7.26 – 7.21 (m,
3H), 6.93 (d, J = 8.5 Hz, 1H), 1.34 (s, 9H). 13C NMR (126 MHz, CDCl3) δ 159.11 (s), 156.74 (s),
153.53 (s), 133.12 (s), 129.17 (s), 128.79 (s), 128.40 (s), 127.27 (s), 122.40 (s), 122.04 (q, J =
274.9 Hz), 116.99 (s), 114.02 (q, J = 29.9 Hz), 113.59 (s), 35.43 (s), 30.87 (s).19F NMR (377
MHz, CDCl3) δ -57.77 (s). GC–MS (EI, m/z): 346.12. IR (KBr), ν 1750 (C=O), 1618 (C=C)
cm−1
.
6-Chloro-4-Phenyl-3-(trifluoromethyl)-2H-1-benzopyran-2-one (2n).

White powder, 35.6 mg, 55%; mp 137-1380C;
1H NMR (500 MHz, CDCl3) δ 7.59 – 7.51 (m, 1H), 7.41 (d, J = 1.9 Hz, 1H), 7.24 (dd, J = 6.5,
2.9 Hz, 1H), 7.17 (dd, J = 8.7, 1.9 Hz, 1H), 6.95 (d, J = 8.7 Hz, 1H). 13C NMR (126 MHz,
CDCl3) δ 156.27 (d, J = 2.0 Hz), 155.71 (s), 153.61 (s), 140.38 (s), 132.44 (s), 130.22 (s), 129.56
(s), 128.66 (s), 127.21 (d, J = 1.5 Hz), 125.47 (s), 121.71 (q, J = 275.3 Hz), 118.14 (s), 117.06 (s),
114.93 (q, J = 30.4 Hz). 19F NMR (377 MHz, CDCl3) δ -57.95 (s). GC–MS (EI, m/z): 324.02. IR
(KBr), ν 1749 (C=O), 1625 (C=C) cm−1
.
6- Bromo-4-Phenyl-3-(trifluoromethyl)-2H-1-benzopyran-2-one (2o).
White powder, 39.7 mg, 54%; mp 131-1320C;
1H NMR (500 MHz, CDCl3) δ 7.71 (dd, J = 8.8, 2.3 Hz, 1H), 7.56 (dd, J = 4.9, 1.8 Hz, 3H),
13
7.30 (d, J = 8.8 Hz, 1H), 7.25 (dd, J = 6.4, 3.1 Hz, 2H), 7.10 (d, J = 2.2 Hz, 1H). C NMR (126
MHz, CDCl3) δ 155.75 (d, J = 2.2 Hz), 155.61 (s), 152.30 (s), 136.91 (s), 132.04 (s), 131.40 (s),
129.72 (s), 128.76 (s), 127.22 (s), 121.57 (q, J = 276.1 Hz), 121.08 (s), 118.63 (s), 117.65 (s),
19
116.04 (q, J = 30.8 Hz). F NMR (377 MHz, CDCl3) δ -58.08 (s). GC–MS (EI, m/z): 367.96,
369.96. IR (KBr), ν 1755 (C=O), 1624 (C=C) cm−1
.
1-Methyl-3-(trifluoromethyl)-2(1H)-Quinolinone (2p).
White powder, 29.5 mg, 65%; mp 63-640C;
1H NMR (500 MHz, CDCl3) δ 8.12 (s, 1H), 7.77 – 7.60 (m, 2H), 7.41 (d, J = 8.6 Hz, 1H),
7.32 (t, J = 7.8 Hz, 1H), 3.75 (s, 3H). 13C NMR (126 MHz, CDCl3) δ 158.00 (s), 141.00 (s),
138.86 (q, J = 5.2 Hz), 133.15 (s), 130.44 (s), 122.92 (s), 122.40 (q, J = 271.7 Hz), 121.13 (q, J
19
= 30.3 Hz), 118.06 (s), 114.40 (s), 29.52 (s). F NMR (470 MHz, CDCl3) δ -66.16 (s). GC-MS
(EI, m/z): 227(M+, 69), 179(78), 176(100), 121(68). IR (KBr), ν 3119 (C=C-H), 1720 (C=O),
1627 (C=C) cm−1
.

Acknowledgements
This work was supported by the National Natural Science Foundation of China (NSFC)
(Project Nos. 21176039 and 20923006).
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Scheme captions
Scheme 1. Methods for the trifluoromethylation of α,β-unsaturated carbonyl subunit and our strategy

Scheme 2. Scope of Coumarinsa
aUnless stated otherwise all reactions were performed in a tube around condensate water with 1 (1.0 equiv, 0.2
mmol), CF3SO2Na(4 equiv), K2HPO4(2 equiv) in acetone(2 mL) at room temperature under argon atmosphere
with the irradiation of a Xenon lamp for 12 h. All listed yields are isolated yields.

Scheme 3. Proposed Mechanism
Proposed mechanism for trifluoromethylation of Coumarins

Table
Table 1. Optimization of the Reaction Conditionsa
Reagent
(equiv)
Base
(equiv)
Entry
Solvent
Time (h)
Yield(%)b
1
2
Acetone
Acetone
Acetone
Acetone
Acetone
Acetone
Acetone
Acetone
Acetone(dry)
CH3CN
4
4
4
4
4
4
4
3
4
4
4
4
4
K2HPO4
K2HPO4
K2HPO4
K3PO4
24
12
6
65
64
3
41
4
12
12
12
12
12
12
12
12
12
12
32
5
K2CO3
27
6
Cs2CO3
KOH
34
7
19
8
K2HPO4
K2HPO4
K2HPO4
K2HPO4
K2HPO4
K2HPO4
41
9
60
10
11
12
13c
27
CH2Cl2
trace
N.R
N.R
DMA
Acetone
aUnless stated otherwise all reactions were performed in a tube around condensate water with 1a (1.0 equiv,
0.2 mmol), base(2 equiv) in solvent (2 mL) at room temperature under argon atmosphere with the irradiation
of a Xenon lamp for 12 h. bIsolated yields. cWithout irradiation.