Recyclable alkylated fac-Ir(ppy)3 complex as a visible-light photoredox catalyst for the synthesis of 3-trifluoromethylated and 3-difluoroacetylated coumarins

Article abstract of DOI:10.1016/j.tet.2018.10.075

A recyclable fac-tris(heptadecanyl-2-phenylpyridine) iridium [fac-Ir(hdppy)₃] photocatalyst was synthesized. The hexane-phase-selective solubility of fac-Ir(hdppy)₃ in a thermomorphic multicomponent solvent (TMS) allowed its easy recycling by automatic liquid/liquid separation at room temperature. The excellent catalytic and recoverable activities of fac-Ir(hdppy)₃ were demonstrated via trifuoromethylation and difluoroacetylation reactions of phenyl 3-phenylpropiolate under visible-light irradiation in a TMS system.

Full text of DOI:10.1016/j.tet.2018.10.075

Accepted Manuscript
Recyclable alkylated fac-Ir(ppy) complex as a visible-light photoredox catalyst for the
3
synthesis of 3-trifluoromethylated and 3-difluoroacetylated coumarins
Xiaodan Zhang, Yaming Li, Xinyu Hao, Kun Jin, Rong Zhang, Chunying Duan
PII:
S0040-4020(18)31312-7
https://doi.org/10.1016/j.tet.2018.10.075
TET 29908
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 5 September 2018
Revised Date: 18 October 2018
Accepted Date: 29 October 2018
Please cite this article as: Zhang X, Li Y, Hao X, Jin K, Zhang R, Duan C, Recyclable alkylated fac-
Ir(ppy) complex as a visible-light photoredox catalyst for the synthesis of 3-trifluoromethylated and 3-
3
difluoroacetylated coumarins, Tetrahedron (2018), doi: https://doi.org/10.1016/j.tet.2018.10.075.
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Recyclable alkylated fac-Ir(ppy)3 complex as a visible-
light photoredox catalyst for the synthesis of
Leave this area blank for abstract info.
3-trifluoromethylated and 3-difluoroacetylated coumarins
Xiaodan Zhang, Yaming Li , Xinyu Hao, Kun Jin, Rong Zhang and Chunying Duan
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, China
PC
1. thermomorphic photocatalyst
2. easy phase separation and catalyst reuse
Recyclable
T
3. mild reaction condition
4. broad reaction types
nC17H35
R2
R2
Rf
N
R1
Ir
PC
PC
R1
O
O
70 °C
N
N
O
O
homogeneous
Rf=CF3, CF2COOEt
nC17H35
nC17H35
reaction
substrate
product
photocatalyst (PC): fac-Ir(hdppy)3
preparation
separation
progression of process

3
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Recyclable alkylated fac-Ir(ppy)3 complex as a visible-light photoredox catalyst for
the synthesis of 3-trifluoromethylated and 3-difluoroacetylated coumarins
Xiaodan Zhang, Yaming Li , Xinyu Hao, Kun Jin, Rong Zhang and Chunying Duan*
State Key Laboratory of Fine Chemicals, Dalian University of Technology,
Dalian 116024, China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A recyclable fac-tris(heptadecanyl-2-phenylpyridine) iridium [fac-Ir(hdppy)3] photocatalyst
was synthesized. The hexane-phase-selective solubility of fac-Ir(hdppy)3 in
a
thermomorphic multicomponent solvent (TMS) allowed its easy recycling by automatic
liquid/liquid separation at room temperature. The excellent catalytic and recoverable
activities of fac-Ir(hdppy)3 were demonstrated via trifuoromethylation and
difluoroacetylation reactions of phenyl 3-phenylpropiolate under visible-light irradiation
in a TMS system.
Available online
Keywords:
photocatalysis
thermomorphic multicomponent solvent
catalyst recycle
trifluoromethylation
difluroacetylation
2015 Elsevier Ltd. All rights reserved.
1. Introduction
tagged) fac-Ir(ppy)3 complex PC, which catalyzed deiodation,
Photocatalysts (PCs) based on Ru and Ir complexes have been
commonly used as efficient catalysts for organic transformations
driven by visible light1. However, despite their emergence as
efficient catalysts for a wide application, the relative high cost
still limits their practical uses in large scale2. In addition,
organometallic PCs have a notable impact on the environment
because of slow degradation and tendency to act as fluorescent
pollutants.
deiodation/cyclization, and E/Z isomerization; the catalyst
showed high activity due to its homogeneous nature in solution,
while the installed tether allowed for its convenient separation
from the reaction products through a TMS system. However,
since the molecular weight distribution of (PIB-polymer-tagged)
fac-Ir(ppy)3, there are still solubility limitations and catalyst
leaching problems. We aimed to develop a recyclable and
homogeneous Ir complex PC with an accurate structure. Our
initial strategy was to design a long alkyl-chain-bound 2-
Recycling and reuse of PCs are receiving new attention as
critical components of emerging chemical technologies due to
both environmental concerns and economic benefits3. The
present academic and industrial chemical processes are favoring
heterogeneous catalysts, which leads to efficient recycling and
reuse4. However, most heterogeneous catalysts not only require
multiple synthetic steps in catalyst preparation, but also need an
additional filtration or a workup of the final reaction mixture to
recovery the catalyst2,5. In most instances, homogeneous catalysts
have more advantages in terms of reaction activity, selectivity,
and ease of handing for recycling over heterogeneous catalysts6.
phenylpyridine Ir complex as
a phase-selectively soluble
homogeneous PC that could be applied in a TMS system.
With particular interest in photochemistry and fluorine
chemistry, we describe herein an alkyl-bound 2-phenylprydine Ir
complex PC, which serves as a homogeneous, recoverable PC,
and is compatible with TMS such that the alkyl support is soluble
in a nonpolar solvent while the products remain in a polar solvent.
This PC shows good catalytic activity and can be easily
recovered and reused for the trifluoromethylation and
difluoroacetylation of phenyl 3-phenylpropiolates.
One way of realizing the desired homogenous catalysis
involves use of a thermomorphic multicomponent solvent
(TMS)7. In this TMS system, the catalyst is soluble in one solvent,
while the reactants/products are soluble in the other solvent that
is immiscible with the catalyst solvent8. The solvents comprising
these thermomorphic systems form a homogeneous one-phasic
mixture in a heating reactor, and the mixture can be separated
into two liquid phases at lower temperatures after the reaction.
Specifically, in 2016, Reiser9 developed a hexa (PIB-polymer-
2. Results and discussion
As shown in Scheme 1, the substrates for the photochemical
reaction were first dissolved in DMF (Scheme 1, step 1). Hexane
containing the fac-Ir(hdppy)3 PC and DMF containing the
substrates were immiscible at room temperature (step 2). When
heated to 70 °C in hot water bath, the two immiscible solvents
Corresponding author. Tel./fax: +86 411 84986295;
E-mail address: ymli@dlut.edu.cn (Y. Li); cyduan@dlut.edu.cn (C. Duan).

4
Tetrahedron
ACCEPTED MANUSCRIPT
hexane and DMF formed homogeneous phase (step 3). After
in this case (entry 4). Screening of organic and inorganic bases
completion of the reaction, the reaction tube was inserted in an
ice bath. After sufficient cooling, the mixed solvent automatically
separated into hexane and DMF phases again (step 4). Hexane
which contained fac-Ir(hdppy)3 was conveniently recovered and
used for the next reaction, while purification of the DMF layer
gave the desired product by silica gel column chromatography.
revealed that K2HPO4 was the most efficient base for this
reaction (entries 5−8). Finally, even after increasing the
reaction time to 24 h, the product yield remained at
approximately 54% (entry 9).
Table 1. Optimization for the trifluoromethylation condition of phenyl 3-
phenylpropiolatea
Entry
Base
Solvent
Temp.
70°C
70°C
25°C
70°C
70°C
70°C
70°C
70°C
70°C
Time
12h
12h
12h
12h
12h
12h
12h
12h
24h
Yield
11%
53%
15%
9%
1
2
K2HPO4
K2HPO4
K2HPO4
K2HPO4
K3PO4
CH3CN/hexane
DMF/hexane
DMF/hexane
DMF/hexane
DMF/hexane
DMF/hexane
DMF/hexane
DMF/hexane
DMF/hexane
3
4b
Scheme 1. Recoverable alkyl-bound Ir complexes PC and recovery progress.
5
35%
29%
37%
15%
54%
6
K2CO3
Based on this strategy, we synthesized fac-Ir(hdppy)3 for
application to the TMS system as a homogeneous PC (Scheme
2). Initially, we synthesized fac-Ir(mppy)3 using 2-phenyl-4-
methyl pyridine instead of 2-phenyl pyridine, based on the
reported synthetic method for fac-Ir(ppy)310. Then, fac-Ir(mppy)3
reacted with 1-bromohexadecane and was converted into
hexadecane-bound fac-Ir(heptadecanyl-ppy)3 [abbreviated to fac-
Ir(hdppy)3]. Finally, purified fac-Ir(hdppy)3 was obtained by
silica gel column chromatography (for detailed synthetic
procedures, see the Experimental Section and Supporting
Information).
7
Cs2CO3
8
i
Pr2NEt
9
K2HPO4
aReaction conditions: phenyl 3-phenylpropiolate (0.2 mmol), fac-Ir(hdppy)3
(1 mol%), Togni’s reagent (0.4 mmol), base (0.4 mmol), DMF (1 mL),
CH3CN (1 mL) or hexane (1 mL), irradiation with 15 W blue LED at 70°C in
hot water bath; isolated yields. bdark.
With the optimized conditions catalyzed by the recyclable fac-
Ir(hdppy)3 in hand, the recyclability and catalytic activity were
then evaluated. The PC fac-Ir(hdppy)3 recovered from the 1st run
was reused without any treatment in the subsequent recycling
run, and a new trifluoromethylation reaction (2nd run) was then
performed with fresh reactants under the same conditions. As
shown in Table 2, the recycled fac-Ir(hdppy)3 was collected and
reused without significant loss of catalytic activity (product yield
53%). Even after the 5th run, no significant decrease in the yield
(51%) of 6a was observed. In addition, the recovered upper layer
of the Ir species from the initial catalyst into the reaction medium
was investigated. After the 1st run and 5th run, the yields of the
recovered fac-Ir(hdppy)3 PC were 95% and 76%, respectively
(measured by UV-vis spectroscopy). Inductively coupled plasma
mass spectrometry (ICP-MS) analysis showed that the recovered
yield of the Ir species was 79% after the 5th run.
Scheme 2. Synthesis of the fac-Ir(hdppy)3
Our group have long focused on the development in the new
synthetic method for the trifluoromethylation of aromatic and
heterocyclic compounds11. To test the catalytic activity and
recyclability of fac-Ir(hdppy)3, it was used to catalyze the
trifluoromethylation of phenyl 3-phenylpropiolate under visible
light as a model reaction, based on a similar reaction that a
copper catalyzed cyclization and direct trifluoromethylation of
internal phenyl 3-phenylpropiolate with Togni’s reagent reported
by Ding12. The reaction conditions were optimized for
trifluoromethylation with Togni’s reagent, K2HPO4, and 1
mol% of fac-Ir(hdppy)3 under irradiation by a blue LED for
12h. First, CH3CN and DMF which are commonly used in
reaction catalyzed by visible light were mixed with hexane;
the DMF/hexane mixed solvents was found to be suitable
for this reaction (Table 1, entries 1 and 2). The DMF and
hexane layers could not merge into a homogeneous phase at
25°C, leading to a poor yield of 15% (entry 3). The reaction
proceeded in the dark, confirming that blue light was necessary
Table 2. Recyclability studies of the [fac-Ir(hdppy)3] catalyzed cyclization to
3-trifluoromethyl-4-phenyl-coumarina
Run
1
2
3
4
5
Yield (%)
53
53
54
51
51
aReaction conditions: phenyl 3-phenylpropiolate (0.2 mmol), fac-Ir(hdppy)3
(1 mol%), Togni’s reagent (0.4 mmol), K2HPO4 (0.4 mmol), DMF (1 mL)
and hexane (1 mL), irradiation with 15 W blue LED at 70°C in hot water
bath; isolated yields.

5
Encouraged by the good recyclability and catalytic activity of
fac-Ir(hdppy)3 in the photoredox trifluoromethylation of phenyl
3-phenylpropiolate, we further investigated the substrates scope
of this reaction. The electron-donating group substituted
substrates afforded the corresponding products in moderate to
good yields (Table 3, 6b-6d). However, substrates bearing
chlorine or bromine atom on the aromatic ring resulted in slightly
lower yields (6e and 6f). Additionally, a para-methyl and a para-
chlorine substituted phenyl linked to the alkynyl moiety could
also be used to construct 3-trifluoromethyl-4-phenyl-coumarin
derivatives in moderate yields (6g and 6h).
With the test results for the recyclability and catalytic
ACCEPTED MANUSCRIPT
activities in hand, we proceeded to explore the substrate
scope of the fac-Ir(hdppy)3-catalyzed difluoroacetylation. As
shown in Table 5, both moderately electron-withdrawing
groups and electron-donating groups located on the phenyl
ring linked to the propiolate or alkynyl proceeded well to
afford the desired coumarins (7a-7e) in good yields. The
exception was the substrate bearing bromine at the para
position of phenyl propiolate, which gave the product in a
moderate yield of 61% (7f).
Table 5. Substrate scope of 3-difluoroacetyl-4-phenyl coumarina
Table 3. Substrate scope of 3-trifluoromethyl-4-phenyl coumarina
aReaction conditions: phenyl 3-phenylpropiolate (0.2 mmol), fac-Ir(hdppy)3
(1 mol%), BrCF2COOEt (0.4 mmol), K2CO3 (0.4 mmol), DMF (1 mL) and
hexane (1 mL), irradiation with 15 W blue LED at 70°C in hot water bath;
isolated yields.
aReaction conditions: phenyl 3-phenylpropiolate (0.2 mmol), fac-Ir(hdppy)3
(1 mol%), Togni’s reagent (0.4 mmol), K2HPO4 (0.4 mmol), DMF (1 mL)
and hexane (1 mL), irradiation with 15 W blue LED at 70°C in hot water
bath; isolated yields.
On the basis of the experimental results and reported
literatures12-14, a plausible mechanism is proposed in Scheme 3.
Initially, Ir(III) is excited to *Ir(III) under irradiation by a blue
LED. Then, *Ir(III) is oxidatively quenched by Togni’s reagent
or BrCF2COOEt to generate a CF3 or CF2COOEt radical, along
with the generation of Ir(IV). Subsequently, the CF3 or
CF2COOEt radical attacks phenyl 3-phenylpropiolate (5a) and
undergoes selective radical addition of the triple bond, leading to
The difluoromethylene group (CF2) is also an intriguing
structural motif, similar to the trifluoromethyl group (CF3)
that has drawn the attention of many chemists. Fu13 reported
a mild and efficient method for the synthesis of 3-
difluoroacetylated coumarins through visible-light promoted
difluoroacetylation of phenyl 3-phenylpropiolate with
BrCF2COOEt, which also followed a radical procedure,
similar to the trifluoromethylation reaction reported by
Ding12. Therefore, we further investigated the recyclability
and catalytic feasibility of fac-Ir(hdppy)3 by using it to
catalyze this difluoroacetylation at 70 °C, without changing
the other condition reported by Fu13. This reaction gave the
difluoroacetylated product in similar yield as the observed
radical intermediate 8. Compound
8
further undergoes
intramolecular homolytic aromatic substitution to give the radical
intermediate 9. Intermediate 9 is then oxidized by Ir(IV) to form
phenyl cation 10 via a single electron transfer, and Ir(III) is
regenerated.
Ultimately,
3-trifluoromethylated
or
3-
difluoroacetylated product 6a or 7a is produced in a progress of
deprotonation of 10 assisted by base, respectively.
with fac-Ir(ppy)3 at room temperature. In addtion, fac
Ir(hdppy)3 could be still recovered in high yield of 97% from
the upper layer. Until the 5th run, the recovered yield of fac
-
-
Ir(hdppy)3 was 83%, and the products remained at 68% yield
(Table 4).
Table 4. Recyclability studies of the [fac-Ir(hdppy)3] catalyzed cyclization
to 3-difluoroacetyl-4-phenyl coumarina
Run
1
2
3
4
5
Yield(%)
72
70
70
71
68
aReaction conditions: phenyl 3-phenylpropiolate (0.2 mmol), fac-Ir(hdppy)3
(1 mol%), BrCF2COOEt (0.4 mmol), K2CO3 (0.4 mmol), DMF (1 mL) and
hexane (1 mL), irradiation with 15 W blue LED at 70°C in hot water bath;
isolated yields.
Scheme 3. Proposed reaction mechanism
3. Conclusion

6
Tetrahedron
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In summary, fac-Ir(hdppy)3, a recoverable n-heptadecanyl-
1369.9591; found 1369.9601.
bound fac-Ir(ppy)3 PC is successfully synthesized. This catalyst
shows excellent catalytic performance as well as recyclability for
trifluoromethylation or difluoroacetylation of phenyl 3-
phenylpropiolate to generate 3-trifluoromethylated and 3-
difluoroacetylated coumarins under visible light, and could
4.3.
Procedure
for
trifluoromethylation
and
difluoroacetylation catalyzed by fac-Ir(hdppy)3
A flame-dried reaction vessel with a magnetic stirring bar was
sequentially charged with phenyl 3-phenylpropiolate (0.2 mmol),
PC (0.002 mmol), Togni’s reagent (0.4 mmol, 124 mg), K2HPO4
(0.4 mmol, 89 mg), DMF (1 mL) and hexane (1 mL). The
mixture was stirred and heated in the 70°C hot water bath with
irradiation by a blue LED, whereupon the two solvent phases
merged into a homogeneous solvent. After the reaction was
completed, the reaction vessel was placed in an ice-water bath for
30 min, and hexane and DMF separated into two phases again.
Hexane, which contained fac-Ir(hdppy)3 was suctioned gently for
use in the next reaction. The DMF layer containing the product
was charged with 10 mL of water and extracted with ethyl
acetate (5×3 mL). The combined ethyl acetate layer was dried
over Na2SO4 and concentrated under vacuum. After evaporation,
the obtained residue was purified by column chromatography on
silica gel with EtOAc/petroleum ether as the eluent to give the
desired product.
be easily separated from reaction products through
a
thermomorphic solvent (TMS) system based on the high phase-
selective solubility of the long alkyl chain bound species. The PC
could be reused up to five times without significant loss of
activity. These features suggest this recyclable fac-Ir(hdppy)3
would be generally useful for other photoredox reaction.
4. Experiment
4.1. General information
All reagents unless otherwise noted were obtained from
commercial sources and used without further purification.
BrCF2COOEt (>99.0%) were used without any purification. All
these reactions were monitored by TLC with silica gel GF254
precoated plates. The products were isolated by column
chromatography on silica gel (200–300 mesh size). 1H NMR, 13
C
NMR and 19F NMR spectra were recorded on INOVA 500
instruments with operating frequencies of 500, 126 and 377
MHz, respectively. Chemical shifts for 1H NMR were reported in
ppm relative to TMS. All 13C 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.
4-Phenyl-3-(trifluoromethyl)-2H-chromen-2-one (6a, CAS:
1
1562426-68-9)12,15. White solid (31.3 mg, 53%). H 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), 7.26 (s, 2H), 7.20 (t, J = 7.6 Hz, 1H), 7.01 (d, J =
8.0 Hz, 1H). 13C NMR (126 MHz, CDCl3) δ 156.86 (q, 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):
290.23.
6-Methyl-4-phenyl-3-(trifluoromethyl)-2H-chromen-2-one
1
(6b, CAS: 1621190-85-9)12. White solid (34.8 mg, 56%). H
NMR (500 MHz, CDCl3) δ 7.56 – 7.49 (m, 3H), 7.43 (q, J =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.
4.2. Synthesis of fac-Ir(hdppy)3 complex
The synthetic method of fac-Ir(mppy)3 was based on the report
by K.R. Mann10 in 2007. The detailed method could be found in
SI.
A round-bottomed flask was charged with fac-Ir(mppy)3 (348
mg, 0.5 mmol) and 40 mL of anhydrous tetrahydrofuran (THF)
and cooled to -78 °C in a liquid nitrogen/ethyl acetate bath for 10
min. A solution of LDA, prepared in situ by treating a solution of
182 mg of iPr2NH (1.8 mmol, 1.2 equiv.) in 10 mL of THF with
nBuLi 660 ꢀL (1.65 mmol, 1.1 equiv.), was added dropwise to
the flask by means of a syringe. The solution was stirred for 30
min at -78 °C during which time it turned brown in colour. A
solution of 1-bromoheptadacane (460 ꢀL, 1.5 mmol) in 5 mL of
THF was added dropwise using a syringe, and the solution was
allowed to warm to room temperature, followed by stirring for 2
h. After the completion of the reaction, THF was removed under
reduced pressure. The obtained yellow residue was dissolved in
ethyl acetate and concentrated under vacuum. Then, the residue
was purified by column chromatography on silica with
EtOAc/petroleum ether (1/100) as the eluent to give the desired
6-(tert-Butyl)-4-phenyl-3-(trifluoromethyl)-2H-chromen-2-
one (6c, CAS: 2242965-74-6) 11(e). White solid (42.6 mg, 60%).
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
(d, J = 1.6 Hz), 122.40 (s), 122.04 (q, J = 274.9 Hz), 118.65 (s),
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). HRMS (ESI) m/z:
[M+Na]+ Calcd. For C20H17F3O2Na 369.1078; found 369.1086.
7-Methoxy-4-(4-methoxyphenyl)-3-(trifluoromethyl)-2H-
chromen-2-one (6d). White solid (44.4 mg, 65%). 1H NMR (500
MHz, CDCl3) δ 7.57 – 7.49 (m, 3H), 7.33 (d, J = 9.1 Hz, 1H),
7.26 (dd, J = 6.7, 2.8 Hz, 2H), 7.20 (dd, J = 9.1, 3.0 Hz, 1H),
6.41 (d, J = 2.9 Hz, 1H), 3.64 (s, 3H). 13C NMR (126 MHz,
CDCl3) δ 156.58 (s), 156.50 (s), 156.16 (s), 147.87 (s), 132.91 (s),
129.36 (s), 128.52 (s), 127.21 (d, J = 1.6 Hz), 121.93 (q, J =
275.2 Hz), 121.40 (s), 119.93 (s), 117.81 (s), 115.25 (q, J = 30.1
Hz), 111.77 (s), 55.67 (s). 19F NMR (377 MHz, CDCl3) δ -57.90
(s). IR (cm-1): ν 2929, 1723, 1618, 1397, 1090. HRMS (ESI) m/z:
[M+Na]+ Calcd. For C17H11F3O3Na 343.0558; found 343.0547.
1
product fac-Ir(hdppy)3 (362 mg, 0.265 mmol, 53%). H NMR
(500 MHz, CDCl3) δ 8.57 (d, J = 5.1 Hz, 1H), 7.66 (dd, J = 8.0,
0.9 Hz, 1H), 7.53 (dd, J = 7.6, 1.7 Hz, 1H), 7.41 (s, 1H), 7.38 (td,
J = 7.5, 1.0 Hz, 1H), 7.23 (td, J = 7.8, 1.7 Hz, 1H), 7.10 (dd, J =
5.1, 1.3 Hz, 1H), 2.64 (t, J = 7.7 Hz, 2H), 1.71 – 1.60 (m, 2H),
1.26 (s, 28H), 0.88 (t, J = 6.9 Hz, 3H). 13C NMR (126 MHz,
CDCl3) δ 158.15 (s), 151.56 (s), 149.20 (s), 141.50 (s), 133.23 (s),
131.45 (s), 129.51 (s), 127.43 (s), 124.90 (s), 122.68 (s), 121.85
(s), 35.33 (s), 31.95 (s), 30.28 (s), 29.18-29.73 (m), 22.71 (s),
14.14 (s). HRMS (ESI) m/z: [M]+ Calcd. For C84H126IrN3

7
6-Chloro-4-phenyl-3-(trifluoromethyl)-2H-chromen-2-one
(s), 116.83 (t, J = 22.9 Hz), 111.93 (t, J = 252.8 Hz), 63.17 (s),
ACCEPTED MANUSCRIPT
(6e, CAS: 2242965-75-7) 11(e). White solid (33.0 mg, 48%). H
21.72 (s), 13.81 (s). 19F NMR (377 MHz, CDCl3) δ -98.04 (s).
1
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).
HRMS (ESI) m/z: [M+Na]+ Calcd. For C16H8ClF3O2Na 347.0063;
found 347.0056.
GC–MS (EI, m/z): 358.10.
Ethyl
2-(6-tert-butyl-2-oxo-4-phenyl-2H-chromen-3-yl)-
2,2-difluoroacetate (7c, CAS: 1699735-62-0)13. White solid
1
(68.1 mg, 82%). H NMR (500 MHz, CDCl3) δ 7.52 – 7.46 (m,
3H), 7.41 (d, J = 1.8 Hz, 1H), 7.31 (dd, J = 6.6, 3.0 Hz, 2H), 7.25
(dd, J = 8.6, 1.9 Hz, 1H), 7.00 (d, J = 8.5 Hz, 1H), 4.34 (q, J =
7.1 Hz, 2H), 1.34 (s, 9H), 1.33 (t, J = 7.1 Hz, 3H). 13C NMR (126
MHz, CDCl3) δ 162.81 (t, J = 32.3 Hz), 159.36 (t, J = 4.5 Hz),
158.38 (s), 156.01 (s), 153.22 (s), 133.12 (s), 128.95 (s), 128.41
(s), 128.19 (s), 127.59 (t, J = 2.2 Hz), 122.43 (s), 117.71 (s),
117.04 (t, J = 23.0 Hz), 113.65 (s), 111.93 (t, J = 252.7 Hz),
63.15 (s), 35.37 (s), 30.91 (s), 13.82 (s). 19F NMR (377 MHz,
CDCl3) δ -98.12 (s). GC–MS (EI, m/z): 400.15.
6-Bromo-4-phenyl-3-(trifluoromethyl)-2H-chromen-2-one
1
(6f, CAS: 2242965-76-8)11(e). White solid (33.8 mg, 43%). H
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), 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). 13C 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),
116.04 (q, J = 30.8 Hz). 19F NMR (377 MHz, CDCl3) δ -58.08 (s).
HRMS (ESI) m/z: [M+Na]+ Calcd. For C16H8BrF3O2Na 390.9557;
found 390.9563.
Ethyl
2,2-difluoro-2-(7-methoxy-2-oxo-4-phenyl-2H-
chromen-3-yl)acetate (7d). White solid (60.8 mg, 80%).1H
NMR (500 MHz, CDCl3) δ 7.51 (dd, J = 5.0, 1.7 Hz, 3H), 7.35
(d, J = 9.0 Hz, 1H), 7.32 (dd, J = 6.5, 3.1 Hz, 2H), 7.18 (dd, J =
9.0, 3.0 Hz, 1H), 6.47 (d, J = 2.9 Hz, 1H), 4.35 (q, J = 7.1 Hz,
2H), 3.65 (s, 3H), 1.33 (t, J = 7.1 Hz, 3H). 13C NMR (126 MHz,
CDCl3) δ 162.77 (t, J = 32.2 Hz), 159.15 (t, J = 4.5 Hz), 156.21
(s), 155.79 (s), 147.58 (s), 132.90 (s), 129.10 (s), 128.30 (s),
127.53 (t, J = 2.3 Hz), 120.70 (s), 120.65 (s), 118.30 (t, J = 22.9
Hz), 117.87 (s), 111.83 (t, J = 253.1 Hz), 111.42 (s), 63.23 (s),
55.69 (s), 13.82 (s). IR (cm-1): ν 2937, 1793, 1741, 1627, 1371,
1160, 1090. 19F NMR (377 MHz, CDCl3) δ -98.36 (s). HRMS
(ESI) m/z: [M+Na]+ Calcd. For C20H19F2O5Na 397.0863; found
397.0876.
4-(4-Methoxyphenyl)-3-(trifluoromethyl)-2H-chromen-2-
one (6g, CAS: 1621190-90-6)12,15. White solid (34.4 mg, 51%).
1H NMR (500 MHz, CDCl3) δ 7.65 – 7.55 (m, 1H), 7.39 (dd, J =
8.3, 0.6 Hz, 1H), 7.23 – 7.16 (m, 3H), 7.11 (dd, J = 8.1, 1.3 Hz,
1H), 7.05 (d, J = 8.7 Hz, 2H), 3.90 (s, 3H). 13C NMR (126 MHz,
CDCl3) δ 160.38 (s), 157.04 (d, J = 2.1 Hz), 156.47 (s), 153.43
(s), 133.98 (s), 129.29 (s), 128.89 (s), 124.79 (s), 124.70 (s),
121.97 (q, J = 275.2 Hz), 119.79 (s), 116.83 (s), 115.14 (q, J =
30.7 Hz), 113.98 (s), 55.38 (s).19F NMR (377 MHz, CDCl3) δ -
57.79 (s). GC–MS (EI, m/z): 320.07.
Ethyl 2-(6-chloro-2-oxo-4-phenyl-2H-chromen-3-yl)-2,2-
difluoro-acetate (7e, CAS: 1699735-64-2)13. White solid (57.1
mg, 73%).1H NMR (500 MHz, CDCl3) δ 7.42 (d, J = 1.9 Hz,
1H), 7.30 (dd, J = 6.6, 2.9 Hz, 2H), 7.18 (dd, J = 8.7, 2.0 Hz,
1H), 7.00 (d, J = 8.7 Hz, 1H), 4.35 (q, J = 7.1 Hz, 2H), 1.34 (t, J
= 7.1 Hz, 3H). 13C NMR (126 MHz, CDCl3) δ 162.58 (t, J = 31.1
Hz), 158.40 (t, J = 4.5 Hz), 155.48 (s), 153.32 (s), 139.65 (s),
132.48 (s), 129.73 (s), 129.28 (s), 128.41 (s), 127.53 (s), 125.44
(s), 118.87 (s), 117.99 (t, J = 23.1 Hz), 117.14 (s), 111.68 (t, J =
253.8 Hz), 63.33 (s), 13.80 (s).19F NMR (377 MHz, CDCl3) δ -
98.38 (s). GC–MS (EI, m/z): 378.05.
4-(4-Chlorophenyl)-3-(trifluoromethyl)-2H-chromen-2-one
1
(6h, CAS: 1621190-89-3)12,15. White solid (39.0 mg, 58%). H
NMR (500 MHz, CDCl3) δ 7.68 – 7.61 (m, 1H), 7.53 (d, J = 8.5
Hz, 2H), 7.42 (dd, J = 8.3, 0.9 Hz, 1H), 7.25 – 7.19 (m, 3H), 7.00
(dd, J = 8.1, 1.4 Hz, 1H). 13C NMR (126 MHz, CDCl3) δ 156.02
(s), 155.62 (d, J = 2.0 Hz), 153.47 (s), 135.67 (s), 134.34 (s),
131.20 (s), 128.95 (s), 128.77 (s), 128.76 (s), 124.91 (s), 121.75
(q, J = 275.3 Hz), 119.13 (s), 117.00 (s), 115.38 (q, J = 30.1
Hz).19F NMR (377 MHz, CDCl3) δ -57.82 (s). GC–MS (EI, m/z):
324.02.
Ethyl 2-(6-bromo-2-oxo-4-phenyl-2H-chromen-3-yl)-2,2-
difluoroacetate (7f, CAS: 1699735-65-3)13. (54.5 mg, 61%). 1H
NMR (500 MHz, CDCl3) δ 7.58 (d, J = 1.7 Hz, 1H), 7.54 – 7.48
(m, 3H), 7.33 (dd, J = 8.6, 1.8 Hz, 1H), 7.30 (dd, J = 6.5, 2.8 Hz,
2H), 6.92 (d, J = 8.6 Hz, 1H), 4.34 (q, J = 7.1 Hz, 2H), 1.33 (t, J
= 7.1 Hz, 3H). 13C NMR (126 MHz, CDCl3) δ 162.55 (t, J = 32.1
Hz), 158.30 (t, J = 4.4 Hz), 155.56 (s), 153.19 (s), 132.42 (s),
129.80 (s), 129.29 (s), 128.42 (s), 128.31 (s), 127.79 (s), 127.54
(t, J = 2.2 Hz), 120.10 (s), 119.24 (s), 118.19 (t, J = 23.0 Hz),
111.69 (t, J = 253.7 Hz), 63.33 (s), 13.81 (s). 19F NMR (377
MHz, CDCl3) δ -98.42 (s). GC–MS (EI, m/z): 421.99, 423.99.
Ethyl
2,2-difluoro-2-(2-oxo-4-phenyl-2H-chromen-3-
yl)acetate (7a, CAS: 1699735-60-8)13. White solid (51.0 mg,
1
72%). H NMR (500 MHz, CDCl3) δ 7.61 (t, J = 7.8 Hz, 1H),
7.54 – 7.48 (m, 3H), 7.41 (d, J = 8.3 Hz, 1H), 7.41 (d, J = 8.3 Hz,
1H), 7.32 (dd, J = 6.4, 2.7 Hz, 2H), 7.21 (t, J = 7.7 Hz, 1H), 7.06
(d, J = 8.0 Hz, 1H), 4.35 (q, J = 7.1 Hz, 2H), 1.34 (t, J = 7.1 Hz,
3H). 13C NMR (126 MHz, CDCl3) δ 162.73 (t, J = 32.2 Hz),
158.98 (t, J = 4.4 Hz), 156.09 (s), 153.15 (s), 133.46 (s), 132.88
(s), 129.05 (s), 128.79 (s), 128.27 (s), 127.62 (t, J = 2.3 Hz),
124.81 (s), 120.20 (s), 118.05 (t, J = 22.9 Hz), 116.90 (s), 111.81
(t, J = 253.2 Hz), 63.24 (s), 13.82 (s). 19F NMR (377 MHz,
CDCl3) δ -98.34 (s). GC–MS (EI, m/z): 344.09.
Ethyl 2,2-difluoro-2-(4-(4-methoxyphenyl)-6-methyl-2-oxo-
2H-chromen-3-yl)acetate (7g). White solid (54.8 mg, 70%). 1H
NMR (500 MHz, CDCl3) δ 7.60 (t, J = 8.5 Hz, 1H), 7.40 (dd, J =
8.3, 0.7 Hz, 1H), 7.25 (d, J = 8.8 Hz, 2H), 7.24 – 7.20 (m, 1H),
7.16 (dd, J = 8.1, 1.5 Hz, 1H), 7.03 (d, J = 8.7 Hz, 2H), 4.35 (q, J
= 7.1 Hz, 2H), 3.89 (s, 3H), 1.33 (t, J = 7.1 Hz, 3H). 13C NMR
(126 MHz, CDCl3) δ 162.83 (t, J = 32.2 Hz), 160.24 (s), 159.12
(t, J = 4.3 Hz), 156.28 (s), 153.15 (s), 133.34 (s), 129.22 (s),
128.82 (s), 124.82 (s), 124.73 (s), 120.48 (s), 118.08 (t, J = 22.6
Hz), 116.90 (s), 113.75 (s), 111.86 (t, J = 253.1 Hz), 63.20 (s),
55.35 (s), 13.82 (s). 19F NMR (377 MHz, CDCl3) δ -98.13 (s). IR
Ethyl
2,2-difluoro-2-(6-methyl-2-oxo-4-phenyl-2H-
chromen-3-yl)acetate (7b, CAS:1699735-61-9)13. White solid
1
(58.1 mg, 78%). H NMR (500 MHz, CDCl3) δ 7.52 – 7.48 (m,
3H), 7.31 (dd, J = 6.6, 2.9 Hz, 2H), 7.21 (s, 1H), 7.02 (dd, J =
8.2, 0.7 Hz, 1H), 6.93 (d, J = 8.2 Hz, 1H), 4.34 (q, J = 7.1 Hz,
2H), 2.46 (s, 3H), 1.33 (t, J = 7.1 Hz, 3H). 13C NMR (126 MHz,
CDCl3) δ 162.85 (t, J = 32.3 Hz), 159.26 (t, J = 4.5 Hz), 156.19
(s), 153.24 (s), 145.23 (s), 133.09 (s), 128.96 (s), 128.48 (s),
128.20 (s), 127.61 (t, J = 2.2 Hz), 126.06 (s), 117.80 (s), 116.98

8
Tetrahedron
(cm-1): ν 2933, 1791, 1744, 1624, 1163, 1072. HRMS (ESI) m/z:
134 (2012) 7211-7214;
ACCEPTED MANUSCRIPT
[M+Na]+ Calcd. For C20H16F2O5Na 397.0863; found 397.0857.
(c) J. Wang, C. Wang, K. E. deKrafft, W. Lin, ACS Catal.
2 (2012) 417-421;
(d) C. Wang, Z. Xie, K. E. deKrafft, W. Lin, J. Am. Chem.
Soc. 133 (2011) 13445-13454;
Ethyl 2,2-difluoro-2-(4-(4-chlorophenyl)-6-methyl-2-oxo-
2H-chromen-3-yl)acetate (7h). White solid (62.0 mg, 76%). H
1
NMR (500 MHz, CDCl3) δ 7.63 (t, J = 7.8 Hz, 1H), 7.50 (d, J =
8.4 Hz, 2H), 7.42 (d, J = 8.3 Hz, 1H), 7.28 (d, J = 8.5 Hz, 2H),
7.24 (t, J = 7.7 Hz, 1H), 7.05 (dd, J = 8.1, 1.3 Hz, 1H), 4.36 (q, J
= 7.1 Hz, 2H), 1.34 (t, J = 7.1 Hz, 3H). 13C NMR (126 MHz,
CDCl3) δ 162.59 (t, J = 32.1 Hz), 158.71 (t, J = 4.5 Hz), 154.84
(s), 153.15 (s), 135.35 (s), 133.69 (s), 131.25 (s), 129.10 (s),
128.70 (s), 128.46 (s), 124.95 (s), 119.83 (s), 118.40 (t, J = 22.9
Hz), 117.05 (s), 111.74 (t, J = 253.4 Hz), 63.35 (s), 13.81 (s).19F
NMR (377 MHz, CDCl3) δ -98.21 (s). IR (cm-1): ν 2927, 1791,
1740, 1625, 1090, 1054. HRMS (ESI) m/z: [M+Na]+ Calcd. For
C19H13ClF2O4Na 401.0368; found 401.0362.
(e) H. Shimakoshi, M. Nishi, A. Tanaka, K. Chikama, Y.
Hisaeda, Chem. Commun. 47 (2011) 6548-6550.
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(b) Z. Zhou, C. He, J. Xiu, L. Yang, C. Duan, J. Am.
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(b) I. Romanenko, S. Norsic, L. Veyre, R. Sayah, F.
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Acknowledgements
(e) A. Behr, A. Kämper, R. Kuhlmann, A. J. Vorholta, R.
Franke, Catal. Sci. Technol. 6 (2016) 208-214.
(f) X. Zhang, Y. Li, X. Hao, K. Jin, R. Zhang, C. Duan,
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This work was supported by the National Natural Science
Foundation of China (NSFC) (Project Nos. 21176039 and
20923006).
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