Photochemical Synthesis of 1,4-Dicarbonyl Bifluorene Compounds via Oxidative Radical Coupling Using TEMPO as the Oxygen Atom Donor

Article abstract of DOI:10.1021/acs.joc.0c02781

A visible-light-induced metal-free synthesis of 1,4-dicarbonyl compounds from alkyne-containing aryl iodides via photochemical C-I bond cleavage, intramolecular cyclization, oxidation, and intermolecular radical coupling sequence is reported. TEMPO was employed as the oxygen atom donor in this transformation. This protocol provided a new strategy for the synthesis of 1,4-dicarbonyl bifluorene compounds.

Full text of DOI:10.1021/acs.joc.0c02781

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Note
Photochemical Synthesis of 1,4-Dicarbonyl Bifluorene Compounds
via Oxidative Radical Coupling Using TEMPO as the Oxygen Atom
Donor
Jincheng Xu, Aishun Ding, Yanbin Zhang, and Hao Guo*
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ABSTRACT: A visible-light-induced metal-free synthesis of 1,4-dicarbonyl compounds from alkyne-containing aryl iodides via
photochemical C−I bond cleavage, intramolecular cyclization, oxidation, and intermolecular radical coupling sequence is reported.
TEMPO was employed as the oxygen atom donor in this transformation. This protocol provided a new strategy for the synthesis of
1,4-dicarbonyl bifluorene compounds.
there have been few reports7 on radical coupling targeting the
The 1,4-dicarbonyl motif widely exists in various bioactive
natural products and pharmaceuticals.1,2 As a versatile building
formation of 1,4-dicarbonyl compounds so far. In general,
block, it is also quite useful in organic synthesis.3,4 Thus, the
radical coupling reaction needs a highly functional group
tolerant and mild synthetic strategy to access various organic
molecules.11,12 Therefore, it is promising to develop a new
method for the synthesis of 1,4-dicarbonyl compounds via a
radical coupling process, which provides more choice for
synthesizing these compounds.
syntheses of 1,4-dicarbonyl compounds have attracted
attention of chemists widely. Several strategies have been
developed in this field (Scheme 1A), including (i) Stetter
reaction of aldehydes with Michael acceptors,5 (ii) nucleophilic
substitution of enolates with α-haloketones,6 (iii) oxidative
coupling of enolates,7 (iv) chain extension of 1,3-diketones,8
(v) acylation of homoenolate equivalents with acyl chlorides,9
and (vi) radical conjugate addition of acyl radicals with
Michael acceptors.10 However, to the best of our knowledge,
Recently, we developed an intramolecular iodine-atom
transfer radical addition of alkyne under visible light
irradiation.13 This method showed precise control of the
Caryl−I bond cleavage and Calkenyl−I bond formation tuned by a
photosensitizer. It also provided a convenient and atom-
economic way to synthesize vinyl iodide compounds. During
the mechanistic studies, the observation indicated that
TEMPO could significantly inhibit this transformation. As a
result, conversion and yield decreased dramatically. However,
side products formed under such conditions received less
attention. With our continuous interest in this reaction, further
investigation revealed that the main byproduct in the presence
of TEMPO was a dimeric 1,4-dicarbonyl bifluorene com-
pound, which showed several applications in the field of
functional materials14 and potential photosensitizer (vide
infra). On the basis of this discovery, more explorations in
this field were carried out. Herein, we wish to report a new
Scheme 1. Synthesis of 1,4-Dicarbonyl Compounds
Received: November 20, 2020
Published: January 29, 2021
https://dx.doi.org/10.1021/acs.joc.0c02781
© 2021 American Chemical Society
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Note
synthetic protocol for 1,4-dicarbonyl bifluorene compounds via
a radical coupling process (Scheme 1B).
detailed screening, see Table S1 in the Supporting
Information). Control experiments indicated that light was
essential for the formation of 3a (Table 1, entry 2). Without
photoirradiation, even though the reaction mixture was heated
at 60 °C, no reaction occurred (Table 1, entry 3), which meant
that the reaction was not thermally initiated. Finally, no
products 2a and 3a were formed in the absence of 4d, which
revealed that 4d was necessary for this transformation (Table
1, entry 4). Thus, Condition A (4d (10 mol %), TEMPO (2
equiv), acetone/DCM = 1:1, PLED, and rt) was applied as the
optimized condition for further studies.
Initially, we used 2-iodo-2′-[(4-methoxyphenyl)ethynyl]-
1,1′-biphenyl (1a) as the model substrate and TEMPO as
the oxygen atom donor.15 The reaction was irradiated by a
purple light-emitting diode (PLED) at room temperature. A
series of reaction parameters were tested, and the optimized
reaction condition was obtained (Table 1, entry 1) (for
Table 1. Investigation of Reaction Parameters
With the optimized reaction condition in hand, the substrate
scope was then investigated. As shown in Scheme 2, a variety
of alkyne-containing aryl iodides reacted under our established
condition. Reactants with a strong electron donating group
(1a−c), a weak electron donating group (1d−h), a weak
electron withdrawing group (1j−k), or no substitution (1i) in
Ar3 were converted into the desired products in good to
excellent yields. Strong electron withdrawing groups (1l−p)
had a negative influence on this reaction. The yields were a
little lower. Notably, for acetyl (1n) or methoxycarbonyl (1o)
substituted substrates, longer reaction time was required, while,
for a substrate with a cyano group (1p), higher temperature
was necessary. Next, some trisubstituted reactants were
investigated under the optimized reaction conditions (1q−v).
All the tested substrates showed decent reactivity. The desired
products were generated in good to excellent yields,
b
NMR yield (%)
a
entry
variation from Condition A
none
without light
1a
2a
3a
c
1
2
3
4
0
99
99
99
0
0
0
0
86 (84)
0
0
0
without light, 60 °C instead of rt
without 4d
a
1a (0.1 mmol), 4d (10 mol %), and TEMPO (2 equiv) in anhydrous
acetone/DCM = 1:1 (50 mL) was irradiated by PLED for 48 h at rt
b
under an argon atmosphere. Yield was determined by 1H NMR
analysis of the crude reaction mixture using CH2Br2 (0.1 mmol) as
c
internal standard. Isolated yield.
a
Scheme 2. Substrate Scope
a
All reactions were carried out using 1 (0.1 mmol), 4d (10 mol %), and TEMPO (2 equiv) in anhydrous acetone/DCM = 1:1 (50 mL) irradiated
b
c
d
by PLED for 48 h at rt under an argon atmosphere. Isolated yield was reported. Gram-scale reaction. The reaction was carried out for 72 h. The
reaction was carried out for 120 h. The reaction was carried out at 60 °C. The reaction was carried out using 1a (0.1 mmol), 1d (0.1 mmol), 4d
(20 mol %), and TEMPO (4 equiv) in anhydrous acetone/DCM = 1:1 (50 mL).
e
f
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respectively. Importantly, a variety of functional groups, such
as alkoxy (1a−b, 1q−v), acetylamino (1c), alkyl (1d, 1e, 1r),
hydroxy (1f), cyano (1g, 1p, 1s), trimethylsilyl (1h), halogen
atom (1j−k, 1u−v), dimethylcarbamoyl (1l), methylsulfonyl
(1m), acetyl (1n), and methoxycarbonyl (1o), were all
tolerated in this reaction, which showed very good functional
group tolerance. A hetero-coupled product 3ad was success-
fully prepared in a 36% isolated yield when the same amount of
1a and 1d was applied (Scheme 2). Meanwhile, two homo-
coupled products 3a and 3d were produced inevitably, and the
ratio of 3a:3ad:3d was 1:2.1:1.2. To explore the synthetic
utility of this method, a gram-scale reaction using 1a (2.5
mmol, 1.028 g) was carried out under the standard conditions,
and the desired product 3a was obtained in an 83% isolated
yield.
Then, the practical utility of these 1,4-dicarbonyl bifluorenes
was further explored. According to the structure analysis, these
compounds may have the potential to be a photosensitizer. We
tried to use these compounds as the photosensitizers in the
photo-oxidation of thioether. Excitingly, the selective oxidation
of thioether into sulfoxide proceeded smoothly under the
catalysis of 3d under 365−375 nm UV light irradiation at room
temperature under an air atmosphere (Scheme 3). Sulfoxide
was generated in a 70% isolated yield. No sulfone product was
found in the reaction.
photo-irradiation, 3a was not formed and 2a was stoichio-
metrically recovered (Table 2, entry 3), which suggested that
light was necessary for this step.
As shown in Figure S3 (see Supporting Information),
intermediate 2a has a wide and strong absorption band below
440 nm in the UV−vis absorption spectra, which indicates that
light (λ < 440 nm) might directly activate 2a. 1a has no
obvious absorption in this wavelength range of light (350−500
nm). Thus, 1a needs to gain energy from the excited 4d to
reach its excited state to accomplish the following trans-
formation. Next, calculations of triplet energies of 1a and 4d
were conducted. The triplet energy of 4d (267 kJ/mol) is
higher than that of 1a (252 kJ/mol), which indicates that the
energy transfer process occurring between 4d (T1) and
substrate 1a (S0) might be possible.
To diagnose the oxygen atom source of the target product 3,
H218O was subjected into the reaction mixture (Scheme 4).
Scheme 4. 18O Labeling Experiment
Scheme 3. Selective Oxidation of Thioether 5 Using 3d as
the Photosensitizer
Moreover, to avoid possible interference of the oxygen atom
from acetone, DCM was used as the solvent instead of mixed
solvent. The result showed that no 18O incorporation was
observed in 3a, which indicated that the oxygen atom should
not stem from the trace amount of water in the reaction
mixture.
HRMS analysis of the crude reaction mixture confirmed the
formation of 2,2,6,6-tetramethylpiperidine (Figure S4), which
indicated that TEMPO might be the oxygen source of product
3 in this transformation. On the basis of the experimental
results and previous reports, a plausible mechanism is
proposed (Scheme 5). Under visible light irradiation, the
photosensitizer 4d is converted to a long-lived excited state
4d* which sensitizes substrate 1 into its triplet state 1*. The
ground state 4d is regenerated for another catalytic cycle.
Reversible homolytic cleavage13,16,17 of the aryl C−I bond of
1* and the subsequent intramolecular radical cyclization afford
alkenyl radical intermediate 8. Then, the radical intermediate 8
is trapped by an iodine radical to form vinyl iodide
intermediate 2. Meanwhile, reversible heterolytic cleavage of
the aryl C−I bond of 1* and the following intramolecular
carbo-iodination also yield vinyl iodide 2 which can be
converted into 8 by photoinduced reversible homolytic
cleavage of the alkenyl C−I bond in the absence of
photosensitizer. UV−vis absorption spectra of 2a (Figure S3)
indicated that vinyl iodide might be directly excited under
PLED irradiation. Then, 8 is trapped by TEMPO to form the
TEMPO adduct 1118 which can be excited under PLED
irradiation. A single-electron transfer from excited 11* to the
iodine atom occurs to form N radical cation 12 and an iodine
anion.
To investigate the mechanism of the reaction, some control
experiments were carried out (Table 2). Since alkenyl iodide
Table 2. Control Experiments
a
b
entry
variation from Condition A
NMR yield (%)
1
2
3
none
without 4d
without light
92
93
0 (99)
c
a
2a (0.1 mmol), 4d (10 mol %), and TEMPO (2 equiv) in anhydrous
acetone/DCM = 1:1 (50 mL) was irradiated by PLED for 48 h at rt
b
under argon atmosphere. Yield was determined by 1H NMR analysis
of the crude reaction mixture using CH2Br2 (0.1 mmol) as internal
c
standard. Recovery yield of 2a.
2a was observed in the process of this reaction, we
hypothesized that it might be an intermediate of this
transformation. Thus, 2a was employed under Condition A.
Indeed, 3a was generated in 92% NMR yield (Table 2, entry
1). Then the reaction was carried out in the absence of catalyst
4d (Table 2, entry 2); 3a was also formed in 93% NMR yield,
which meant that 4d was not essential for the transformation
from 2a to 3a. When the reaction was conducted without
An intermolecular nucleophilic attack of iodine anion to 12
leads to the N−O bond cleavage,15c,f affording an amino
radical which can be quenched by the hydrogen atom from the
solvent molecules. The resulting benzyl iodide 13 is excited by
PLED irradiation to provide an α-acyl radical species 14 via
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Scheme 5. Plausible Mechanism
spectrometer (TOF analyzer). Melting points were determined on a
WRS-2 apparatus. X-ray crystallographic structure determination was
carried out on a Bruker SMART CCD. Anhydrous DCM was distilled
with CaH2. Anhydrous acetone was distilled with CaSO4. 2,2′-Diiodo-
5,5′-dimethoxy-1,1′-biphenyl,20 2,2′-diiodo-1,1′-biphenyl,21 1a,17
1d,17 1i,17 1j,17 1k,13 1o,13 1p,17 1q,17 1r,17 1t,17 1u,17 and 1v13
were synthesized according to literature procedures.
Procedure I for the Synthesis of 4-(Dimethylcarbamoyl)-
phenylacetylene (1l′). To a stirred suspension of 4-ethynylbenzoic
acid (2.926 g, 20 mmol) in dry DCM (40 mL) was added thionyl
chloride (2.2 mL, 30 mmol) at 0 °C. Then the ice bath was removed
and the reaction mixture was stirred at room temperature. After 5 h,
Et3N (8.3 mL, 60 mmol) and Me2NH (2 M in THF) (12 mL, 24
mmol) were added dropwise into the reaction mixture subsequently.
The reaction was stirred for another 5 h at room temperature. Then,
the reaction mixture was washed with H2O and extracted with ethyl
acetate. The organic layer was dried over MgSO4 and concentrated in
vacuo. Further purification by flash chromatography on silica gel
(eluent: petroleum ether/ethyl acetate = 3:1) afforded 1l′ as a solid
(2.340 g, 68%); mp 118.5−118.6 °C (petroleum ether/ethyl acetate);
1H NMR (400 MHz, CDCl3) δ 7.52 (d, J = 8.4 Hz, 2 H), 7.38 (d, J =
C−I bond homolysis. Ultimately, two C-central radicals 14
undergo an intermolecular radical-radical coupling reaction to
yield the final product 3.
On the basis of the above reaction mechanism (Scheme 5),
TEMPO might serve a dual function. First, TEMPO coupled
with alkenyl radical 8 and then provided an oxygen atom by
N−O bond cleavage. Second, TEMPO quenched the in situ
generated iodine radical,19 which promoted the reaction.
Therefore, 2 equiv of TEMPO was consumed in the reaction
process. The C−X bond cleavage types of haloarenes depend
on the electronegativity of the halogen atom, electronic
properties of the substituent groups in the haloarene, and
solvent.16 Although homolysis and heterolysis may occur at the
same time, homolysis is favored in iodoarenes due to the lower
electronegativity of the iodine atom. In our previous reports,13
the transformation from 1a to 2a was evidently inhibited when
5 equiv of TEMPO was applied. Such a result should be due to
the fact that the remaining excess TEMPO in the reaction
mixture inhibited the radical reaction, even though some
TEMPO was consumed in the reaction process. These two
results could be complemented mutually.
8.8 Hz, 2 H), 3.14 (s, 1 H), 3.11 (s, 3 H), 2.97 (s, 1 H); 13C{1H}
NMR (100 MHz, CDCl3) δ 170.8, 136.5, 132.1, 127.1, 123.4, 82.9,
78.5, 39.4, 35.3; IR (neat) 1614, 1512, 1482, 1453, 1394 cm−1;
HRMS (ESI) m/z: [M + H]+ calcd for C11H12NO: 174.0913, found:
174.0917.
Typical Procedure II for the Synthesis of ((4-(Trifluoro-
methoxy)phenyl)ethynyl) Copper and Its Derivatives. ((4-
(Trifluoromethoxy)phenyl)ethynyl)copper. A solution of cuprous
iodide (1.908 g, 10 mmol) in aqueous ammoniacal (28 mL) was
poured into a solution of 4-(trifluoromethoxy)penylacetylene (1.5
mL, 10 mmol) in ethanol (80 mL). The reaction mixture was allowed
to stir at room temperature overnight. The bright chartreuse
precipitate was filtered off and washed three times with water,
ethanol, and ethyl acetate. The bright canary green solid was dried at
60 °C under reduced pressure with oil pump. The crude product was
used without further purification.
In conclusion, we have developed a visible-light-induced
synthetic method of 1,4-dicarbonyl bifluorene compounds
under metal-free and mild conditions. In this transformation,
TEMPO was used as the oxygen atom donor. Further studies
in this field are being carried out in our group.
EXPERIMENTAL SECTION
■
General Information. All the photoreactions were carried out
using PLED (2 × 1 m strip, Greethink 5050, 12 V/m) at a distance of
8−10 cm at rt unless stated otherwise. Pyrex flasks were used for all
1
photoreactions without any filters. H (400 MHz), 13C (100 MHz),
and 19F (376 MHz) NMR spectra of samples in CDCl3 or DMSO-d6
were recorded on an AVANCE III 400 spectrometer. IR spectra were
recorded on an Avatar 360 FT-IR spectrometer. HRMS (ESI)
determinations were performed on a Bruker micrOTOF II
The Following Compounds Were Prepared According to
Typical Procedure II. ((4-(Acetylamino)phenyl)ethynyl)copper.
The reaction of 4-(acetylamino)phenylacetylene (1.593 g, 10
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mmol), cuprous iodide (1.917 g, 10 mmol), aqueous ammoniacal (28
mL), and ethanol (80 mL) afforded ((4-(acetylamino)phenyl)-
ethynyl)copper as a bright canary yellow solid. The crude product
was used without further purification.
removed under reduced pressure. Purification by flash chromatog-
raphy on silica gel (eluent: petroleum ether:ethyl acetate = 2:1)
afforded 1c as an oil (0.566 g, 43%); 1H NMR (400 MHz, CDCl3) δ
7.97 (dd, J = 8.0, 0.8 Hz, 1 H), 7.61−7.57 (m, 1 H), 7.44−7.32 (m, 6
H), 7.28−7.24 (m, 1 H), 7.12−7.05 (m, 3 H), 2.15 (s, 3 H); 13C{1H}
NMR (100 MHz, CDCl3) δ 168.2, 146.7, 145.8, 138.8, 137.7, 132.1,
131.5, 130.3, 129.4, 129.0, 127.9, 127.8, 127.7, 122.8, 119.2, 118.9,
99.5, 92.8, 88.1, 24.7; IR (neat) 1668, 1592, 1530, 1514, 1460, 1447,
1404 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for C22H17INO:
438.0349, found: 438.0348.
2-((4-(tert-Butyl)phenyl)ethynyl)-2′-iodo-1,1′-biphenyl (1e). The
reaction of ((4-(tert-butyl)phenyl)ethynyl)copper (0.985 g, 4.4
mmol) and 2,2′-diiodo-1,1′-biphenyl (1.627 g, 4.0 mmol) in
triethylamine (10 mL) and butyl acetate (20 mL) was stirred in an
oil bath at 140 °C for 48 h under an argon atmosphere. The solvent
was removed under reduced pressure. Purification by flash
chromatography on silica gel (eluent: petroleum ether) afforded 1e
as an oil (0.729 g, 42%); 1H NMR (400 MHz, CDCl3) δ 7.97 (d, J =
8.0 Hz, 1 H), 7.64−7.58 (m, 1 H), 7.44−7.32 (m, 4 H), 7.28−7.23
(m, 3 H), 7.11−7.05 (m, 3 H), 1.27 (s, 9 H); 13C{1H} NMR (100
MHz, CDCl3) δ 151.3, 146.8, 145.9, 138.8, 131.6, 131.1, 130.4, 129.4,
128.9, 127.8, 127.7, 125.2, 123.1, 120.2, 99.5, 93.3, 87.8, 34.7, 31.1; IR
(neat) 1516, 1460, 1442, 1430, 1365 cm−1; HRMS (ESI) m/z: [M +
H]+ calcd for C24H22I: 437.0761, found: 437.0762.
((4-(tert-Butyl)phenyl)ethynyl)copper. The reaction of 4-(tert-
butyl)phenylacetylene (3.6 mL, 20 mmol), cuprous iodide (3.826 g,
20 mmol), aqueous ammoniacal (56 mL), and ethanol (160 mL)
afforded ((4-(tert-butyl)phenyl)ethynyl)copper as a bright canary
yellow solid. The crude product was used without further purification.
((4-(Hydroxymethyl)phenyl)ethynyl)copper. The reaction of 4-
(hydroxymethyl)phenylacetylene (1.326 g, 10 mmol), cuprous iodide
(1.917 g, 10 mmol), aqueous ammoniacal (28 mL), and ethanol (80
mL) afforded ((4-(hydroxymethyl)phenyl)ethynyl)copper as a bright
canary yellow solid. The crude product was used without further
purification.
((4-(Cyanomethyl)phenyl)ethynyl)copper. The reaction of 4-
(cyanomethyl)phenylacetylene (2.7 mL, 20 mmol), cuprous iodide
(3.823 g, 20 mmol), aqueous ammoniacal (56 mL), and ethanol (160
mL) afforded ((4-(cyanomethyl)phenyl)ethynyl)copper as a bright
canary yellow solid. The crude product was used without further
purification.
((4-(Trimethylsilyl)phenyl)ethynyl)copper. The reaction of 4-
(trimethylsilyl)phenylacetylene (1.201 g, 7 mmol), cuprous iodide
(1.342 g, 7 mmol), aqueous ammoniacal (20 mL), and ethanol (56
mL) afforded ((4-(trimethylsilyl)phenyl)ethynyl)copper as a bright
canary yellow solid. The crude product was used without further
purification.
((4-(Dimethylcarbamoyl)phenyl)ethynyl)copper. The reaction of
4-(dimethylcarbamoyl)phenylacetylene (1.735 g, 10 mmol), cuprous
iodide (1.921 g, 10 mmol), aqueous ammoniacal (28 mL), and
ethanol (80 mL) afforded ((4-(dimethylcarbamoyl)phenyl)ethynyl)
copper as a dark green solid. The crude product was used without
further purification.
((4-(Methylsulfonyl)phenyl)ethynyl)copper. The reaction of 4-
(methylsulfonyl)phenylacetylene (1.069 g, 6 mmol), cuprous iodide
(1.151 g, 6 mmol), aqueous ammoniacal (17 mL), and ethanol (48
mL) afforded ((4-(methylsulfonyl)phenyl)ethynyl)copper as a bright
canary yellow solid. The crude product was used without further
purification.
((4-Acetylphenyl)ethynyl)copper. The reaction of 4-acetylpheny-
lacetylene (871 mg, 6 mmol), cuprous iodide (1.159 g, 6 mmol),
aqueous ammoniacal (17 mL), and ethanol (48 mL) afforded ((4-
acetylphenyl)ethynyl)copper as a bright canary yellow solid. The
crude product was used without further purification.
Typical Procedure III for the Synthesis of 2-((4-(Trifluoro-
methoxy)phenyl)ethynyl)-2′-iodo-1,1′-biphenyl (1b) and Its
Derivatives. 2-((4-(Trifluoromethoxy)phenyl)ethynyl)-2′-iodo-1,1′-
biphenyl (1b). To a 120 mL of dry Pyrex sealed tube was added 2,2′-
diiodo-1,1′-biphenyl (1.223 g, 3.0 mmol), ((4-(trifluoromethoxy)-
phenyl)ethynyl)copper (0.830 g, 3.3 mmol), triethylamine (7.5 mL),
and butyl acetate (15 mL). The mixture was stirred in an oil bath at
140 °C for 36 h under an argon atmosphere. The solvent was
removed under reduced pressure. Purification by flash chromatog-
raphy on silica gel (eluent: petroleum ether) afforded 1b as an oil
(0.488 g, 35%); 1H NMR (400 MHz, CDCl3) δ 7.98 (dd, J = 8.0, 1.2
Hz, 1 H), 7.65−7.58 (m, 1 H), 7.45−7.37 (m, 3 H), 7.36−7.32 (m, 1
H), 7.29−7.26 (m, 1 H), 7.18−7.13 (m, 2 H), 7.12−7.05 (m, 3 H);
13C{1H} NMR (100 MHz, CDCl3) δ 148.70, 148.68, 146.9, 145.7,
2-((4-(Hydroxymethyl)phenyl)ethynyl)-2′-iodo-1,1′-biphenyl (1f).
The reaction of ((4-(hydroxymethyl)phenyl)ethynyl)copper (0.641 g,
3.3 mmol) and 2,2′-diiodo-1,1′-biphenyl (1.220 g, 3.0 mmol) in
triethylamine (7.5 mL) and butyl acetate (15 mL) was stirred in an oil
bath at 140 °C for 60 h under an argon atmosphere. The solvent was
removed under reduced pressure. Purification by flash chromatog-
raphy on silica gel (eluent: petroleum ether:ethyl acetate = 5:1)
1
afforded 1f as an oil (0.357 g, 29%); H NMR (400 MHz, CDCl3) δ
7.98 (dd, J = 8.0, 0.8 Hz, 1 H), 7.65−7.59 (m, 1 H), 7.45−7.33 (m, 4
H), 7.30−7.26 (m, 1 H), 7.25−7.21 (m, 2 H), 7.16−7.12 (m, 2 H),
7.11−7.06 (m, 1 H), 4.64 (s, 2 H); 13C{1H} NMR (100 MHz,
CDCl3) δ 146.8, 145.8, 140.8, 138.8, 131.6, 131.5, 130.3, 129.4, 129.0,
128.0, 127.8, 127.7, 126.7, 122.7, 122.5, 99.5, 92.9, 88.5, 64.9; IR
(neat) 3355, 1582, 1556, 1511, 1460, 1438, 1427, 1413 cm−1; HRMS
(ESI) m/z: [M + Na]+ calcd for C21H15INaO: 433.0060, found:
433.0063.
2-((4-(Cyanomethyl)phenyl)ethynyl)-2′-iodo-1,1′-biphenyl (1g).
The reaction of ((4-(cyanomethyl)phenyl)ethynyl)copper (0.905 g,
4.4 mmol) and 2,2′-diiodo-1,1′-biphenyl (1.626 g, 4.0 mmol) in
triethylamine (10 mL) and butyl acetate (20 mL) was stirred in an oil
bath at 140 °C for 64 h under an argon atmosphere. The solvent was
removed under reduced pressure. Purification by flash chromatog-
raphy on silica gel (eluent: petroleum ether:ethyl acetate = 5:1)
afforded 1g as a solid (0.561 g, 33%); mp 99.7−99.9 °C (petroleum
ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 7.98 (d, J = 8.0
Hz, 1 H), 7.62 (d, J = 6.8 Hz, 1 H), 7.46−7.37 (m, 3 H), 7.35 (d, J =
7.6 Hz, 1 H), 7.28 (d, J = 7.2 Hz, 1 H), 7.20 (d, J = 8.0 Hz, 2 H), 7.14
(d, J = 8.0 Hz, 2 H), 7.09 (t, J = 7.6 Hz, 1 H), 3.70 (s, 2 H); 13C{1H}
NMR (100 MHz, CDCl3) δ 146.9, 145.8, 138.8, 132.0, 131.7, 130.3,
129.6, 129.5, 129.0, 128.3, 127.85, 127.78, 127.7, 123.3, 122.5, 117.4,
99.4, 92.1, 89.3, 23.5; IR (neat) 1511, 1460, 1442, 1414 cm−1; HRMS
(ESI) m/z: [M + NH4]+ calcd for C22H18IN2: 437.0509, found:
437.0511.
2-((4-(Trimethylsilyl)phenyl)ethynyl)-2′-iodo-1,1′-biphenyl (1h).
The reaction of ((4-(trimethylsilyl)phenyl)ethynyl)copper (0.780 g,
3.3 mmol) and 2,2′-diiodo-1,1′-biphenyl (1.219 g, 3.0 mmol) in
triethylamine (7.5 mL) and butyl acetate (15 mL) was stirred in an oil
bath at 140 °C for 36 h under an argon atmosphere. The solvent was
removed under reduced pressure. Purification by flash chromatog-
raphy on silica gel (eluent: petroleum ether) afforded 1h as an oil
(0.652 g, 48%); 1H NMR (400 MHz, CDCl3) δ 7.97 (dd, J = 8.0, 1.2
Hz, 1 H), 7.65−7.59 (m, 1 H), 7.44−7.33 (m, 6 H), 7.29−7.25 (m, 1
H), 7.14−7.05 (m, 3 H), 0.23 (s, 9 H); 13C{1H} NMR (100 MHz,
CDCl3) δ 146.9, 145.8, 140.8, 138.8, 133.0, 131.6, 130.4, 130.3, 129.4,
128.9, 128.0, 127.8, 127.7, 123.5, 122.8, 99.5, 93.3, 88.8, −1.3; IR
138.8, 132.8, 131.6, 130.3, 129.5, 129.0, 128.3, 127.9, 127.7, 124.2 (C-
F, JC‑F = 256.1 Hz), 122.4, 122.0, 121.6 (C-F, JC‑F = 256.1 Hz), 120.7,
119.1 (C-F, JC‑F = 256.1 Hz), 116.5 (C-F, JC‑F = 256.1 Hz), 99.4, 91.6,
89.2; 19F NMR (376 MHz, CDCl3) δ −57.8; IR (neat) 1581, 1508,
1460, 1440, 1430 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for
C21H13F3IO: 464.9958, found: 464.9962.
The Following Compounds Were Prepared According to
Typical Procedure III. 2-((4-(Acetylamino)phenyl)ethynyl)-2′-
iodo-1,1′-biphenyl (1c). The reaction of ((4-(acetylamino)phenyl)-
ethynyl)copper (0.745 g, 3.3 mmol) and 2,2′-diiodo-1,1′-biphenyl
(1.223 g, 3.0 mmol) in pyridine (20 mL) was stirred in an oil bath at
130 °C for 48 h under an argon atmosphere. The solvent was
3660
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Note
(neat) 1602, 1505, 1459, 1443, 1429, 1392 cm−1; HRMS (ESI) m/z:
[M + Na]+ calcd for C23H21INaSi: 475.0349, found: 475.0347.
2-((4-(Dimethylcarbamoyl)phenyl)ethynyl)-2′-iodo-1,1′-biphenyl
(1l). The reaction of ((4-(dimethylcarbamoyl)phenyl)ethynyl)copper
(0.781 g, 3.3 mmol) and 2,2′-diiodo-1,1′-biphenyl (1.219 g, 3.0
mmol) in triethylamine (7.5 mL) and butyl acetate (15 mL) was
stirred in an oil bath at 140 °C for 42 h under an argon atmosphere.
The solvent was removed under reduced pressure. Purification by
flash chromatography on silica gel (eluent: petroleum ether:ethyl
(32 mg, 0.2 mmol), anhydrous acetone (25 mL), and anhydrous
DCM (25 mL) were added subsequently into a 120 mL dry Pyrex
sealed tube. The reaction mixture was degassed with three freeze-
pump-thaw cycles (15 min per cycle). Then, the reaction mixture was
irradiated by PLED at rt under an argon atmosphere. The reaction
was completed after 48 h as monitored by TLC (eluent: petroleum
ether:ethyl acetate = 20:1). The solvent was removed, and the residue
was purified by flash chromatography on silica gel (eluent: petroleum
ether:ethyl acetate = 10:1) to afford 3a as a solid (25 mg, 84%); mp
219.6−220.1 °C (petroleum ether/ethyl acetate); 1H NMR (400
MHz, CDCl3) δ 8.18 (d, J = 8.0 Hz, 2 H), 7.46 (d, J = 7.6 Hz, 2 H),
7.35 (t, J = 7.4 Hz, 2 H), 7.28−7.21 (m, 4 H), 7.06−6.97 (m, 6 H),
6.56 (t, J = 7.6 Hz, 2 H), 6.46 (d, J = 8.0 Hz, 4 H), 5.92 (d, J = 7.6 Hz,
2 H), 3.64 (s, 6 H); 13C{1H} NMR (100 MHz, CDCl3) δ 198.6,
161.7, 147.4, 143.2, 142.7, 141.1, 131.05, 130.95, 130.6, 128.3, 127.8,
126.7, 126.4, 125.6, 119.3, 118.6, 112.6, 73.8, 55.1; IR (neat) 1667,
1601, 1574, 1510, 1448 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for
C42H31O4: 599.2217, found: 599.2222. Supplementary crystallo-
graphic data have been deposited at the Cambridge Crystallographic
Data Center. CCDC: 2004217; see Supporting Information.
The Following Compounds Were Prepared According to
Typical Procedure IV. 9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-
(trifluoromethoxy)phenyl)methanone) (3b). The reaction of 1b
(46 mg, 0.1 mmol), 4-methoxythioxanthone (2 mg, 0.01 mmol),
TEMPO (32 mg, 0.2 mmol), anhydrous acetone (25 mL), and
anhydrous DCM (25 mL) afforded 3b as a solid (32 mg, 91%); mp
197.3−198.1 °C (petroleum ether/ethyl acetate); 1H NMR (400
MHz, CDCl3) δ 8.05 (d, J = 8.0 Hz, 2 H), 7.50 (d, J = 7.6 Hz, 2 H),
7.39 (t, J = 7.2 Hz, 2 H), 7.32−7.22 (m, 4 H), 7.12−7.00 (m, 6 H),
6.81 (d, J = 8.0 Hz, 4 H), 6.59 (t, J = 7.4 Hz, 2 H), 5.91 (d, J = 7.6 Hz,
2 H); 13C{1H} NMR (100 MHz, CDCl3) δ 199.4, 150.9, 146.1,
143.2, 141.6, 141.1, 136.8, 130.7, 130.0, 128.8, 128.3, 126.9, 126.3,
126.0, 124.0 (C-F, JC‑F = 256.7 Hz), 121.4 (C-F, JC‑F = 256.7 Hz),
119.6, 119.3, 118.9, 116.3 (C-F, JC‑F = 256.7 Hz), 73.6; 19F NMR
(376 MHz, CDCl3) δ −57.7; IR (neat) 1676, 1601, 1502, 1476, 1447
cm−1; HRMS (ESI) m/z: [M + H]+ calcd for C42H25F6O4: 707.1652,
found: 707.1657.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-(acetylamino)phenyl)-
methanone) (3c). The reaction of 1c (44 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (33 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
afforded 3c as a solid (22 mg, 67%); mp 238.3−238.6 °C (petroleum
ether/ethyl acetate); 1H NMR (400 MHz, DMSO-d6) δ 9.97 (s, 2 H),
8.02 (d, J = 8.0 Hz, 2 H), 7.69 (d, J = 7.6 Hz, 2 H), 7.52−7.39 (m, 4
H), 7.30 (t, J = 7.6 Hz, 2 H), 7.19 (d, J = 8.4 Hz, 4 H), 7.08 (t, J = 7.6
Hz, 2 H), 6.83 (d, J = 8.4 Hz, 4 H), 6.58 (t, J = 7.6 Hz, 2 H), 5.80 (d,
J = 7.6 Hz, 2 H), 1.96 (s, 6 H); 13C{1H} NMR (100 MHz, DMSO-
d6) δ 202.6, 173.1, 150.8, 147.3, 146.4, 146.3, 145.4, 136.8, 134.6,
133.3, 133.2, 132.7, 131.1, 130.1, 130.0, 124.5, 123.9, 121.7, 77.5,
28.5; IR (neat) 1666, 1593, 1523, 1445, 1403, 1370 cm−1; HRMS
(ESI) m/z: [M + H]+ calcd for C44H33N2O4: 653.2435, found:
653.2424.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis(p-tolylmethanone) (3d).
The reaction of 1d (40 mg, 0.1 mmol), 4-methoxythioxanthone (2
mg, 0.01 mmol), TEMPO (32 mg, 0.2 mmol), anhydrous acetone (25
mL), and anhydrous DCM (25 mL) afforded 3d as a solid (26 mg,
90%); mp 231.5−231.8 °C (petroleum ether/ethyl acetate); 1H NMR
(400 MHz, CDCl3) δ 8.11 (d, J = 8.0 Hz, 2 H), 7.47 (d, J = 7.6 Hz, 2
H), 7.36 (t, J = 7.4 Hz, 2 H), 7.29−7.20 (m, 4 H), 7.03 (t, J = 7.4 Hz,
2 H), 6.92 (d, J = 7.6 Hz, 4 H), 6.77 (d, J = 7.6 Hz, 4 H), 6.56 (t, J =
7.4 Hz, 2 H), 5.91 (d, J = 7.6 Hz, 2 H), 2.15 (s, 6 H); 13C{1H} NMR
(100 MHz, CDCl3) δ 200.1, 146.9, 143.3, 142.4, 141.3, 141.2, 135.9,
130.9, 128.3, 128.1, 127.8, 126.6, 126.4, 125.7, 119.3, 118.6, 73.8,
21.3; IR (neat) 1735, 1671, 1607, 1448 cm−1; HRMS (ESI) m/z: [M
+ H]+ calcd for C42H31O2: 567.2319, found: 567.2325.
1
acetate = 2:1) afforded 1l as an oil (0.627 g, 46%); H NMR (400
MHz, CDCl3) δ 7.98 (dd, J = 8.0, 0.8 Hz, 1 H), 7.66−7.59 (m, 1 H),
7.45−7.33 (m, 4 H), 7.31−7.26 (m, 3 H), 7.19−7.14 (m, 2 H), 7.12−
7.06 (m, 1 H), 3.08 (s, 3 H), 2.93 (s, 3 H); 13C{1H} NMR (100
MHz, CDCl3) δ 170.9, 146.9, 145.7, 138.8, 135.6, 131.7, 131.2, 130.3,
129.4, 129.0, 128.3, 127.8, 127.7, 127.0, 124.5, 122.4, 99.4, 92.3, 89.7,
39.5, 35.3; IR (neat) 1633, 1609, 1561, 1493, 1462, 1442, 1393 cm−1;
HRMS (ESI) m/z: [M + H]+ calcd for C23H19INO: 452.0506, found:
452.0517.
2-((4-(Methylsulfonyl)phenyl)ethynyl)-2′-iodo-1,1′-biphenyl
(1m). The reaction of ((4-(methylsulfonyl)phenyl)ethynyl)copper
(0.796 g, 3.3 mmol) and 2,2′-diiodo-1,1′-biphenyl (1.217 g, 3.0
mmol) in triethylamine (7.5 mL) and butyl acetate (15 mL) was
stirred in an oil bath at 140 °C for 60 h under an argon atmosphere.
The solvent was removed under reduced pressure. Purification by
flash chromatography on silica gel (eluent: petroleum ether:ethyl
acetate = 5:1) afforded 1m as a solid (0.466 g, 35%); mp 169.9−170.1
1
°C (petroleum ether/ethyl acetate); H NMR (400 MHz, CDCl3) δ
7.99 (dd, J = 8.0, 1.2 Hz, 1 H), 7.81 (d, J = 8.4 Hz, 2 H), 7.67−7.62
(m, 1 H), 7.50−7.40 (m, 3 H), 7.36−7.26 (m, 4 H), 7.14−7.08 (m, 1
H), 3.02 (s, 3 H); 13C{1H} NMR (100 MHz, CDCl3) δ 147.3, 145.5,
139.3, 138.8, 131.9, 131.8, 130.3, 129.5, 129.2, 129.1, 128.9, 127.9,
127.8, 127.2, 121.8, 99.3, 92.5, 91.2, 44.4; IR (neat) 1592, 1499, 1462,
1439 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for C21H16IO2S:
458.9910, found: 458.9904.
2-((4-Acetylphenyl)ethynyl)-2′-iodo-1,1′-biphenyl (1n). The re-
action of ((4-acetylphenyl)ethynyl)copper (0.468 g, 2.2 mmol) and
2,2′-diiodo-1,1′-biphenyl (0.819 g, 2.0 mmol) in pyridine (10 mL)
was stirred in an oil bath at 115 °C for 60 h under an argon
atmosphere. The solvent was removed under reduced pressure.
Purification by flash chromatography on silica gel (eluent: petroleum
ether:ethyl acetate = 20:1) afforded 1n as a solid (0.228 g, 27%); mp
117.5−117.8 °C (petroleum ether/ethyl acetate); 1H NMR (400
MHz, CDCl3) δ 7.99 (d, J = 8.0 Hz, 1 H), 7.82 (d, J = 7.6 Hz, 2 H),
7.64 (d, J = 6.8 Hz, 1 H), 7.48−7.38 (m, 3 H), 7.35 (d, J = 7.6 Hz, 1
H), 7.29 (d, J = 7.2 Hz, 1 H), 7.21 (d, J = 8.0 Hz, 2 H), 7.10 (t, J = 7.6
Hz, 1 H), 2.56 (s, 3 H); 13C{1H} NMR (100 MHz, CDCl3) δ 197.2,
147.1, 145.6, 138.9, 136.0, 131.8, 131.4, 130.3, 129.5, 129.1, 128.6,
128.1, 127.9, 127.7, 122.2, 99.4, 92.2, 91.8, 26.5; IR (neat) 1682,
1600, 1558, 1459, 1427, 1402 cm−1; HRMS (ESI) m/z: [M + H]+
calcd for C22H16IO: 423.0240, found: 423.0247.
2-((4-(Cyanomethyl)phenyl)ethynyl)-2′-iodo-5,5′-dimethoxy-
1,1′-biphenyl (1s). The reaction of ((4-(cyanomethyl)phenyl)-
ethynyl)copper (0.681 g, 3.3 mmol) and 2,2′-diiodo-5,5′-dime-
thoxy-1,1′-biphenyl (1.399 g, 3.0 mmol) in triethylamine (7.5 mL)
and butyl acetate (15 mL) was stirred in an oil bath at 140 °C for 72 h
under an argon atmosphere. The solvent was removed under reduced
pressure. Purification by flash chromatography on silica gel (eluent:
petroleum ether:ethyl acetate = 5:1) afforded 1s as a solid (0.455 g,
32%); mp 177.1−177.2 °C (petroleum ether/ethyl acetate); 1H NMR
(400 MHz, CDCl3) δ 7.81 (d, J = 8.4 Hz, 1 H), 7.54 (d, J = 8.8 Hz, 1
H), 7.22−7.14 (m, 4 H), 6.96−6.90 (m, 2 H), 6.81 (d, J = 2.4 Hz, 1
H), 6.70 (dd, J = 8.8, 3.2 Hz, 1 H), 3.86 (s, 3 H), 3.79 (s, 3 H), 3.70
(s, 2 H); 13C{1H} NMR (100 MHz, CDCl3) δ 159.5, 159.4, 148.2,
146.4, 139.4, 133.1, 131.8, 129.2, 127.8, 123.6, 117.4, 115.9, 115.7,
115.0, 114.7, 113.8, 90.7, 89.4, 87.7, 55.5, 55.4, 23.5; IR (neat) 1601,
1561, 1513, 1464, 1415 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for
C24H19INO2: 480.0455, found: 480.0449.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-(tert-butyl)phenyl)-
methanone) (3e). The reaction of 1e (44 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
afforded 3e as a solid (29 mg, 88%); mp 200.1−200.5 °C (petroleum
Typical Procedure IV for the Photoreactions. 9H,9′H-[9,9′-
Bifluorene]-9,9′-diylbis((4-methoxyphenyl)methanone) (3a). 1a (41
mg, 0.1 mmol), 4-methoxythioxanthone (2 mg, 0.01 mmol), TEMPO
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Note
ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 8.12 (d, J = 7.6
Hz, 2 H), 7.48 (d, J = 7.2 Hz, 2 H), 7.36 (t, J = 7.2 Hz, 2 H), 7.29−
7.20 (m, 4 H), 7.07−6.94 (m, 10 H), 6.56 (t, J = 7.4 Hz, 2 H), 5.92
(d, J = 8.0 Hz, 2 H), 1.14 (s, 18 H); 13C{1H} NMR (100 MHz,
CDCl3) δ 199.8, 154.3, 147.0, 143.2, 142.5, 141.2, 135.7, 131.0, 128.3,
127.8, 126.6, 126.5, 125.6, 124.3, 119.2, 118.5, 73.8, 34.7, 30.9; IR
(neat) 1671, 1605, 1448 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for
C48H43O2: 651.3258, found: 651.3244.
CDCl3) δ 199.6, 146.2, 143.2, 141.7, 141.2, 137.2, 136.9, 130.7, 129.5,
128.7, 128.2, 127.8, 126.9, 126.3, 125.9, 119.6, 118.8, 73.6; IR (neat)
1680, 1590, 1485, 1451 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for
C40H25Cl2O2: 607.1226, found: 607.1217.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-fluorophenyl)-
methanone) (3k). The reaction of 1k (40 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
afforded 3k as a solid (27 mg, 94%); mp 202.7−202.8 °C (petroleum
ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 8.09 (d, J = 8.0
Hz, 2 H), 7.48 (d, J = 7.6 Hz, 2 H), 7.38 (t, J = 7.4 Hz, 2 H), 7.30−
7.22 (m, 4 H), 7.08−6.99 (m, 6 H), 6.65 (t, J = 8.2 Hz, 4 H), 6.58 (t,
J = 7.6 Hz, 2 H), 5.91 (d, J = 7.6 Hz, 2 H); 13C{1H} NMR (100 MHz,
CDCl3) δ 199.3, 165.4, 162.9, 146.5, 143.2, 141.9, 141.1, 134.8, 130.8,
130.7, 130.6, 128.6, 128.1, 126.8, 126.3, 125.9, 119.6, 118.8, 114.6,
114.4, 73.7; 19F NMR (376 MHz, CDCl3) δ −107.9; IR (neat) 1676,
1601, 1507, 1447 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for
C40H25F2O2: 575.1817, found: 575.1810.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-(dimethylcarbamoyl)-
phenyl)methanone) (3l). The reaction of 1l (45 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
afforded 3l as a solid (30 mg, 88%); mp 180.1−180.7 °C (petroleum
ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 8.04 (d, J = 7.6
Hz, 2 H), 7.49 (d, J = 7.6 Hz, 2 H), 7.37 (t, J = 7.4 Hz, 2 H), 7.31−
7.20 (m, 4 H), 7.10−6.99 (m, 10 H), 6.58 (t, J = 7.4 Hz, 2 H), 5.90
(d, J = 8.0 Hz, 2 H), 3.00 (s, 6 H), 2.76 (s, 6 H); 13C{1H} NMR (100
MHz, CDCl3) δ 200.5, 170.6, 145.8, 143.2, 141.6, 141.2, 139.7, 138.3,
130.6, 128.7, 128.1, 128.0, 126.8, 126.3, 126.2, 125.9, 119.5, 118.8,
73.6, 39.2, 35.2; IR (neat) 1673, 1633, 1510, 1490, 1447, 1397 cm−1;
HRMS (ESI) m/z: [M + H]+ calcd for C46H37N2O4: 681.2748,
found: 681.2734.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-(methylsulfonyl)phenyl)-
methanone) (3m). The reaction of 1m (46 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
afforded 3m as a solid (22 mg, 63%); mp 247.7−248.2 °C (petroleum
ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 8.00 (d, J = 7.6
Hz, 2 H), 7.58 (d, J = 8.8 Hz, 4 H), 7.53 (d, J = 7.6 Hz, 2 H), 7.42 (t,
J = 7.4 Hz, 2 H), 7.34−7.26 (m, 4 H), 7.15 (d, J = 8.4 Hz, 4 H), 7.09
(t, J = 7.4 Hz, 2 H), 6.62 (t, J = 7.4 Hz, 2 H), 5.90 (d, J = 8.0 Hz, 2
H), 2.90 (s, 6 H); 13C{1H} NMR (100 MHz, CDCl3) δ 200.2, 145.0,
143.4, 143.3, 142.0, 141.2, 140.8, 130.4, 129.3, 128.6, 127.1, 126.7,
126.26, 126.24, 119.9, 119.1, 73.5. 44.2; IR (neat) 1679, 1481, 1447,
1393 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for C42H31O6S2:
695.1557, found: 695.1547.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-acetylphenyl)-
methanone) (3n). The reaction of 1n (42 mg, 0.1 mmol), 4-
methoxythioxanthone (3 mg, 0.01 mmol), TEMPO (33 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
was completed after 72 h to afford 3n as a solid (15 mg, 48%); mp
239.3−240.1 °C (petroleum ether/ethyl acetate); 1H NMR (400
MHz, CDCl3) δ 8.04 (d, J = 7.6 Hz, 2 H), 7.60−7.54 (m, 4 H), 7.51
(d, J = 7.6 Hz, 2 H), 7.39 (t, J = 7.4 Hz, 2 H), 7.32−7.22 (m, 4 H),
7.10−7.03 (m, 6 H), 6.60 (t, J = 7.4 Hz, 2 H), 5.91 (d, J = 7.6 Hz, 2
H), 2.45 (s, 6 H); 13C{1H} NMR (100 MHz, CDCl3) δ 200.8, 197.4,
145.5, 143.3, 142.7, 141.31, 141.28, 138.2, 130.5, 128.9, 128.3, 128.0,
127.5, 126.9, 126.3, 126.0, 119.7, 118.9, 73.6, 26.6; IR (neat) 1687,
1604, 1445, 1400, 1356 cm−1; HRMS (ESI) m/z: [M + Na]+ calcd for
C44H30NaO4: 645.2036, found: 645.2025.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-(hydroxymethyl)phenyl)-
methanone) (3f). The reaction of 1f (41 mg, 0.1 mmol), 4-
methoxythioxanthone (3 mg, 0.01 mmol), TEMPO (32 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
afforded 3f as a solid (20 mg, 67%); mp 185.3−186.0 °C (petroleum
ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 8.08 (d, J = 8.0
Hz, 2 H), 7.48 (d, J = 7.2 Hz, 2 H), 7.36 (t, J = 7.2 Hz, 2 H), 7.29−
7.18 (m, 4 H), 7.07−6.92 (m, 10 H), 6.56 (t, J = 7.4 Hz, 2 H), 5.91
(d, J = 8.0 Hz, 2 H), 4.49 (s, 4 H); 13C{1H} NMR (100 MHz,
CDCl3) δ 200.4, 146.5, 143.7, 143.2, 142.1, 141.2, 137.9, 130.8, 128.5,
128.4, 128.0, 126.7, 126.4, 125.8, 125.6, 119.4, 118.7, 73.7, 64.6; IR
(neat) 3397, 1667, 1610, 1572, 1476, 1450, 1413 cm−1; HRMS (ESI)
m/z: [M + H]+ calcd for C42H31O4: 599.2217, found: 599.2218.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-(cyanomethyl)phenyl)-
methanone) (3g). The reaction of 1g (43 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
afforded 3g as a solid (27 mg, 85%); mp 203.5−204.0 °C (petroleum
ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 8.06 (d, J = 7.6
Hz, 2 H), 7.50 (d, J = 7.2 Hz, 2 H), 7.39 (t, J = 7.2 Hz, 2 H), 7.31−
7.22 (m, 4 H), 7.09−6.99 (m, 6 H), 6.97−6.93 (m, 4 H), 6.59 (t, J =
7.4 Hz, 2 H), 5.91 (d, J = 7.6 Hz, 2 H), 3.57 (s, 4 H); 13C{1H} NMR
(100 MHz, CDCl3) δ 200.1, 146.1, 143.2, 141.7, 141.2, 138.4, 132.5,
130.7, 128.8, 128.7, 128.2, 127.0, 126.8, 126.3, 125.9, 119.6, 118.8,
117.1, 73.6, 23.3; IR (neat) 1677, 1607, 1448, 1417 cm−1; HRMS
(ESI) m/z: [M + H]+ calcd for C44H29N2O2: 617.2224, found:
617.2249.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-(trimethylsilyl)phenyl)-
methanone) (3h). The reaction of 1h (46 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
afforded 3h as a solid (29 mg, 84%); mp 189.4−190.1 °C (petroleum
ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 8.08 (d, J = 7.6
Hz, 2 H), 7.49 (d, J = 7.6 Hz, 2 H), 7.37 (t, J = 7.4 Hz, 2 H), 7.29−
7.20 (m, 4 H), 7.16−7.09 (m, 4 H), 7.07−6.95 (m, 6 H), 6.56 (t, J =
7.6 Hz, 2 H), 5.91 (d, J = 8.0 Hz, 2 H), 0.11 (s, 18 H); 13C{1H} NMR
(100 MHz, CDCl3) δ 200.6, 146.6, 144.3, 143.2, 142.2, 141.2, 138.7,
132.4, 130.8, 128.4, 127.9, 127.1, 126.7, 126.4, 125.7, 119.3, 118.6,
73.8, −1.4; IR (neat) 1673, 1594, 1446, 1384 cm−1; HRMS (ESI) m/
z: [M + H]+ calcd for C46H43O2Si2: 683.2796, found: 683.2794.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis(phenylmethanone) (3i). The
reaction of 1i (38 mg, 0.1 mmol), 4-methoxythioxanthone (2 mg, 0.01
mmol), TEMPO (33 mg, 0.2 mmol), anhydrous acetone (25 mL),
and anhydrous DCM (25 mL) afforded 3i as a solid (25 mg, 93%);
1
mp 172.0−172.5 °C (petroleum ether/ethyl acetate); H NMR (400
MHz, CDCl3) δ 8.08 (d, J = 7.6 Hz, 2 H), 7.48 (d, J = 7.2 Hz, 2 H),
7.36 (t, J = 7.4 Hz, 2 H), 7.29−7.20 (m, 4 H), 7.16 (t, J = 7.0 Hz, 2
H), 7.07−6.94 (m, 10 H), 6.57 (t, J = 7.4 Hz, 2 H), 5.93 (d, J = 7.6
Hz, 2 H); 13C{1H} NMR (100 MHz, CDCl3) δ 201.0, 146.5, 143.3,
142.1, 141.3, 138.9, 130.8, 128.5, 128.0, 127.4, 126.7, 126.4, 125.8,
119.4, 118.7, 73.8; IR (neat) 1675, 1599, 1580, 1448 cm−1; HRMS
(ESI) m/z: [M + H]+ calcd for C40H27O2: 539.2006, found:
539.2007.
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-methoxycarbonylphen-
yl)methanone) (3o). The reaction of 1o (44 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
was completed after 120 h to afford 3o as a solid (19 mg, 58%); mp
222.3−222.9 °C (petroleum ether/ethyl acetate); 1H NMR (400
MHz, CDCl3) δ 8.03 (d, J = 7.6 Hz, 2 H), 7.65 (d, J = 8.0 Hz, 4 H),
7.50 (d, J = 7.6 Hz, 2 H), 7.38 (t, J = 7.2 Hz, 2 H), 7.31−7.20 (m, 4
H), 7.09−7.01 (m, 6 H), 6.59 (t, J = 7.6 Hz, 2 H), 5.91 (d, J = 7.6 Hz,
2 H), 3.80 (s, 6 H); 13C{1H} NMR (100 MHz, CDCl3) δ 201.0,
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-chlorophenyl)-
methanone) (3j). The reaction of 1j (41 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
afforded 3j as a solid (28 mg, 92%); mp 227.4−227.7 °C (petroleum
ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 8.06 (d, J = 7.6
Hz, 2 H), 7.49 (d, J = 7.2 Hz, 2 H), 7.39 (t, J = 7.2 Hz, 2 H), 7.30−
7.22 (m, 4 H), 7.05 (t, J = 7.4 Hz, 2 H), 6.99−6.90 (m, 8 H), 6.58 (t,
J = 7.4 Hz, 2 H), 5.90 (d, J = 7.6 Hz, 2 H); 13C{1H} NMR (100 MHz,
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Note
166.3, 145.6, 143.3, 142.8, 141.3, 131.7, 130.6, 128.9, 128.8, 128.3,
127.7, 126.9, 126.3, 126.0, 119.6, 118.9, 73.6, 52.1; IR (neat) 1729,
1679, 1450, 1437 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for
C44H31O6: 655.2115, found: 655.2111.
1609, 1578, 1495, 1466 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for
C44H35O6: 659.2428, found: 659.2424.
(3,3′,6,6′-Tetramethoxy-9H,9′H-[9,9′-bifluorene]-9,9′-diyl)bis((4-
chlorophenyl)methanone) (3u). The reaction of 1u (48 mg, 0.1
mmol), 4-methoxythioxanthone (3 mg, 0.01 mmol), TEMPO (33 mg,
0.2 mmol), anhydrous acetone (25 mL), and anhydrous DCM (25
mL) afforded 3u as a solid (33 mg, 90%); mp 230.4−230.7 °C
(petroleum ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 7.94
(d, J = 8.4 Hz, 2 H), 7.00−6.89 (m, 10 H), 6.81−6.75 (m, 4 H), 6.19
(d, J = 8.4 Hz, 2 H), 5.87 (d, J = 8.4 Hz, 2 H), 3.89 (s, 6 H), 3.71 (s, 6
H); 13C{1H} NMR (100 MHz, CDCl3) δ 200.3, 160.2, 159.9, 144.5,
142.6, 139.5, 137.2, 136.9, 134.9, 131.4, 129.4, 127.8, 127.1, 112.8,
112.3, 104.7, 104.1, 72.5, 55.5, 55.3; IR (neat) 1675, 1611, 1580,
1495, 1468, 1433 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for
C44H33Cl2O6: 727.1649, found: 727.1627.
(3,3′,6,6′-Tetramethoxy-9H,9′H-[9,9′-bifluorene]-9,9′-diyl)bis((4-
fluorophenyl)methanone) (3v). The reaction of 1v (46 mg, 0.1
mmol), 4-methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32 mg,
0.2 mmol), anhydrous acetone (25 mL), and anhydrous DCM (25
mL) afforded 3v as a solid (31 mg, 89%); mp 220.8−221.0 °C
(petroleum ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 7.96
(d, J = 8.4 Hz, 2 H), 7.04−6.96 (m, 6 H), 6.82−6.75 (m, 4 H), 6.66
(t, J = 8.6 Hz, 4 H), 6.19 (d, J = 8.4 Hz, 2 H), 5.88 (d, J = 8.8 Hz, 2
H), 3.89 (s, 6 H), 3.71 (s, 6 H); 13C{1H} NMR (100 MHz, CDCl3) δ
199.9, 165.2, 162.7, 160.2, 159.8, 144.5, 142.6, 139.9, 135.14, 135.06,
131.4, 130.6, 130.5, 127.1, 114.6, 114.4, 112.7, 112.3, 104.6, 104.0,
72.6, 55.5, 55.2; 19F NMR (376 MHz, CDCl3) δ −108.5; IR (neat)
1671, 1599, 1578, 1495, 1468, 1435 cm−1; HRMS (ESI) m/z: [M +
H]+ calcd for C44H33F2O6: 695.2240, found: 695.2228.
Gram-Scale Synthesis of 9H,9′H-[9,9′-Bifluorene]-9,9′-
diylbis((4-methoxyphenyl)methanone) (3a). 1a (1.028 g, 2.5
mmol), 4-methoxythioxanthone (61 mg, 0.25 mmol), TEMPO (784
mg, 5 mmol), anhydrous acetone (625 mL), and anhydrous DCM
(625 mL) were added subsequently into a 2 L dry Pyrex flask. The
reaction mixture was bubbled with argon for 30 min. Then, the
reaction mixture was irradiated by PLED at rt under an argon
atmosphere. The reaction was completed after 48 h as monitored by
TLC (eluent: petroleum ether:ethyl acetate = 20:1). The solvent was
removed, and the residue was purified by flash chromatography on
silica gel (eluent: petroleum ether:ethyl acetate = 10:1) to afford 3a as
a solid (0.622 g, 83%).
9H,9′H-[9,9′-Bifluorene]-9,9′-diylbis((4-cyanophenyl)-
methanone) (3p). The reaction of 1p (41 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (33 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
was carried out in an oil bath at 60 °C to afford 3p as a solid (23 mg,
77%); mp 206.2−206.8 °C (petroleum ether/ethyl acetate); 1H NMR
(400 MHz, CDCl3) δ 7.99 (d, J = 7.6 Hz, 2 H), 7.52 (d, J = 7.2 Hz, 2
H), 7.42 (t, J = 7.2 Hz, 2 H), 7.33−7.23 (m, 8 H), 7.12−7.02 (m, 6
H), 6.61 (t, J = 7.2 Hz, 2 H), 5.89 (d, J = 7.6 Hz, 2 H); 13C{1H}
NMR (100 MHz, CDCl3) δ 200.1, 145.1, 143.3, 142.4, 141.2, 140.8,
131.4, 130.4, 129.2, 128.6, 128.2, 127.1, 126.2, 119.9, 119.1, 118.0,
114.3, 73.4; IR (neat) 1684, 1607, 1474, 1450, 1400 cm−1; HRMS
(ESI) m/z: [M + H]+ calcd for C42H25N2O2: 589.1911, found:
589.1900.
(3,3′,6,6′-Tetramethoxy-9H,9′H-[9,9′-bifluorene]-9,9′-diyl)bis((4-
methoxyphenyl)methanone) (3q). The reaction of 1q (47 mg, 0.1
mmol), 4-methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (33 mg,
0.2 mmol), anhydrous acetone (25 mL), and anhydrous DCM (25
mL) afforded 3q as a solid (33 mg, 92%); mp 219.2−219.7 °C
(petroleum ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 8.04
(d, J = 8.4 Hz, 2 H), 7.01 (d, J = 8.8 Hz, 4 H), 6.97 (d, J = 2.0 Hz, 2
H), 6.80−6.74 (m, 4 H), 6.47 (d, J = 8.4 Hz, 4 H), 6.17 (dd, J = 8.4,
2.0 Hz, 2 H), 5.88 (d, J = 8.4 Hz, 2 H), 3.88 (s, 6 H), 3.71 (s, 6 H),
3.66 (s, 6 H); 13C{1H} NMR (100 MHz, CDCl3) δ 199.3, 161.5,
160.0, 159.6, 144.5, 142.5, 140.9, 136.0, 131.7, 131.3, 130.5, 127.2,
112.63, 112.58, 112.0, 104.5, 103.9, 72.7, 55.5, 55.3, 55.1; IR (neat)
1601, 1578, 1512, 1495, 1466, 1431 cm−1; HRMS (ESI) m/z: [M +
H]+ calcd for C46H39O8: 719.2639, found: 719.2632.
(3,3′,6,6′-Tetramethoxy-9H,9′H-[9,9′-bifluorene]-9,9′-diyl)bis(p-
tolylmethanone) (3r). The reaction of 1r (46 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
afforded 3r as a solid (32 mg, 93%); mp 228.8−229.4 °C (petroleum
ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 7.98 (d, J = 8.8
Hz, 2 H), 6.97 (d, J = 2.0 Hz, 2 H), 6.91 (d, J = 8.0 Hz, 4 H), 6.81−
6.74 (m, 8 H), 6.17 (dd, J = 8.8, 2.0 Hz, 2 H), 5.88 (d, J = 8.8 Hz, 2
H), 3.88 (s, 6 H), 3.71 (s, 6 H), 2.16 (s, 6 H); 13C{1H} NMR (100
MHz, CDCl3) δ 200.8, 160.0, 159.7, 144.5, 142.6, 141.0, 140.4, 136.2,
135.7, 131.6, 128.2, 128.1, 127.2, 112.6, 112.1, 104.4, 103.9, 72.7,
55.5, 55.2, 21.3; IR (neat) 1669, 1609, 1578, 1495, 1468, 1435 cm−1;
HRMS (ESI) m/z: [M + H]+ calcd for C46H39O6: 687.2741, found:
687.2745.
(3,3′,6,6′-Tetramethoxy-9H,9′H-[9,9′-bifluorene]-9,9′-diyl)bis((4-
(cyanomethyl)phenyl)methanone) (3s). The reaction of 1s (48 mg,
0.1 mmol), 4-methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32
mg, 0.2 mmol), anhydrous acetone (25 mL), and anhydrous DCM
(25 mL) afforded 3s as a solid (30 mg, 81%); mp 132.9−133.6 °C
(petroleum ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 7.95
(d, J = 8.8 Hz, 2 H), 7.06−6.93 (m, 10 H), 6.83−6.74 (m, 4 H), 6.20
(d, J = 8.4 Hz, 2 H), 5.88 (d, J = 8.4 Hz, 2 H), 3.89 (s, 6 H), 3.72 (s, 6
H), 3.58 (s, 4 H); 13C{1H} NMR (100 MHz, CDCl3) δ 200.7, 160.2,
159.8, 144.6, 142.7, 139.5, 138.7, 134.9, 132.2, 131.3, 128.7, 127.1,
127.0, 117.2, 112.8, 112.4, 104.6, 104.0, 72.5, 55.5, 55.2, 23.3; IR
(neat) 1673, 1611, 1580, 1493, 1469, 1432 cm−1; HRMS (ESI) m/z:
[M + H]+ calcd for C48H37N2O6: 737.2646, found: 737.2631.
(3,3′,6,6′-Tetramethoxy-9H,9′H-[9,9′-bifluorene]-9,9′-diyl)bis-
(phenylmethanone) (3t). The reaction of 1t (44 mg, 0.1 mmol), 4-
methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (33 mg, 0.2
mmol), anhydrous acetone (25 mL), and anhydrous DCM (25 mL)
afforded 3t as a solid (29 mg, 88%); mp 191.5−191.7 °C (petroleum
ether/ethyl acetate); 1H NMR (400 MHz, CDCl3) δ 7.96 (d, J = 8.4
Hz, 2 H), 7.19−7.11 (m, 2 H), 7.03−6.93 (m, 10 H), 6.82−6.73 (m,
4 H), 6.19 (d, J = 8.4 Hz, 2 H), 5.90 (d, J = 8.8 Hz, 2 H), 3.88 (s, 6
H), 3.71 (s, 6 H); 13C{1H} NMR (100 MHz, CDCl3) δ 201.6, 160.1,
159.7, 144.5, 142.7, 139.9, 139.2, 135.4, 131.5, 130.6, 127.9, 127.4,
127.2, 112.6, 112.2, 104.5, 103.9, 72.6, 55.5, 55.2; IR (neat) 1671,
Synthesis of Ethyl Phenyl Sulfoxide (6). 5 (69 mg, 0.5 mmol),
3d (12 mg, 0.025 mmol), and CH3CN (5 mL) were added
subsequently into a 25 mL dry Pyrex flask. The reaction mixture
was irradiated by 365−375 nm UV light at rt under an air atmosphere.
The reaction was completed after 16 h as monitored by TLC (eluent:
petroleum ether:ethyl acetate = 2:1). The solvent was removed, and
the residue was purified by flash chromatography on silica gel (eluent:
petroleum ether:ethyl acetate = 1:1) to afford 622 as an oil (54 mg,
1
70%); H NMR (400 MHz, CDCl3) δ 7.66−7.57 (m, 2 H), 7.56−
7.46 (m, 3 H), 2.97−2.71 (dm, 2 H), 1.20 (t, J = 7.4 Hz, 3 H).
Detection of the Fragment Tetramethylpiperidine. Aryl
iodide 1a (41 mg, 0.1 mmol), 4-methoxythioxanthone (2 mg, 0.01
mmol), TEMPO (32 mg, 0.2 mmol), anhydrous acetone (25 mL),
and anhydrous DCM (25 mL) were added subsequently into a 120
mL dry Pyrex sealed tube. The reaction mixture was degassed with
three freeze-pump-thaw cycles (15 min per cycle). Then, the reaction
mixture was irradiated by PLED for 48 h at rt under an argon
atmosphere. The fragment tetramethylpiperidine was detected by
HRMS analysis of the crude reaction mixture (see Figure S3 in
Supporting Information). HRMS (ESI) m/z: [M + H]+ calcd for
C9H20N: 142.1590, found: 142.1595.
Oxygen Labeling Experiment. Aryl iodide 1a (41 mg, 0.1
mmol), 4-methoxythioxanthone (2 mg, 0.01 mmol), TEMPO (32 mg,
0.2 mmol), H218O (36 μL, 2 mmol), and anhydrous DCM (50 mL)
were added subsequently into a 120 mL dry Pyrex sealed tube. The
reaction mixture was degassed with three freeze-pump-thaw cycles
(15 min per cycle). Then, the reaction mixture was irradiated by
PLED at rt under an argon atmosphere. The reaction was completed
after 48 h as monitored by TLC (eluent: petroleum ether:ethyl
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Note
acetate = 20:1). The solvent was removed, and the residue was
purified by flash chromatography on silica gel (eluent: petroleum
ether:ethyl acetate = 10:1) to afford 3a as a solid (24 mg, 80%).
HRMS analysis indicated that no 18O atom was transferred into the
product 3a.
https://pubs.acs.org/10.1021/acs.joc.0c02781
Notes
The authors declare no competing financial interest.
Crossover Experiment. 1a (41 mg, 0.1 mmol), 1d (39 mg, 0.1
mmol), 4-methoxythioxanthone (5 mg, 0.02 mmol), TEMPO (64 mg,
0.4 mmol), anhydrous acetone (25 mL), and anhydrous DCM (25
mL) were added subsequently into a 120 mL dry Pyrex sealed tube.
The reaction mixture was degassed with three freeze-pump-thaw
cycles (15 min per cycle). Then, the reaction mixture was irradiated
by PLED at rt under an argon atmosphere. The reaction was
completed after 48 h as monitored by TLC (eluent: petroleum
ether:ethyl acetate = 5:1). The ratio of 3a:3ad:3d was determined by
1H NMR analysis of the crude reaction mixture using CH2Br2 (0.1
mmol) as internal standard. The solvent was removed, and the residue
was purified by flash chromatography on silica gel (eluent: petroleum
ether:ethyl acetate = 10:1) to afford (9′-(4-methoxybenzoyl)-9H,9′H-
[9,9′-bifluoren]-9-yl)(p-tolyl)methanone 3ad as a solid (21 mg,
36%); mp 225.7−226.5 °C (petroleum ether/ethyl acetate); 1H NMR
(400 MHz, CDCl3) δ 8.22 (d, J = 8.0 Hz, 1 H), 8.07 (d, J = 8.0 Hz, 1
H), 7.49−7.43 (m, 2 H), 7.39−7.30 (m, 2 H), 7.29−7.16 (m, 4 H),
7.07−6.97 (m, 4 H), 6.91 (d, J = 8.0 Hz, 2 H), 6.77 (d, J = 8.0 Hz, 2
H), 6.59 (t, J = 7.4 Hz, 1 H), 6.52 (t, J = 7.4 Hz, 1 H), 6.45 (d, J = 8.8
Hz, 2 H), 5.98 (d, J = 7.6 Hz, 1 H), 5.85 (d, J = 7.6 Hz, 1 H), 3.62 (s,
3 H), 2.15 (s, 3 H); 13C{1H} NMR (100 MHz, CDCl3) δ 200.4,
198.3, 161.9, 147.3, 147.0, 143.3, 143.1, 142.9, 142.1, 141.2, 141.1,
141.0, 136.5, 131.1, 130.84, 130.79, 130.4, 128.4, 128.2, 128.1, 128.0,
127.8, 127.7, 126.7, 126.6, 126.4, 125.7, 125.6, 119.31, 119.27, 118.6,
112.7, 74.5, 73.1, 55.1, 21.3; IR (neat) 1667, 1600, 1573, 1508, 1473,
1446 cm−1; HRMS (ESI) m/z: [M + H]+ calcd for C42H31O3:
583.2268, found: 583.2278.
ACKNOWLEDGMENTS
■
We greatly acknowledge the financial support from the
Shanghai Science and Technology Committee (18DZ1-
201605).
REFERENCES
■
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.joc.0c02781.
■
sı
Figures S1−S5, Tables S1−S2, copies of NMR spectra
data of all compounds, and crystal information for
compound 3a (PDF)
Accession Codes
CCDC 2004217 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Author
Hao Guo − Department of Chemistry, Fudan University,
Shanghai 200438, People’s Republic of China; orcid.org/
0000-0003-3314-4564; Phone: +86-21-31249190;
Email: Hao_Guo@fudan.edu.cn; Fax: +86-21-31249190
■
Authors
Jincheng Xu − Department of Chemistry, Fudan University,
Shanghai 200438, People’s Republic of China; orcid.org/
0000-0002-4579-7784
Aishun Ding − Department of Chemistry, Fudan University,
Shanghai 200438, People’s Republic of China
Yanbin Zhang − Department of Chemistry, Fudan University,
Shanghai 200438, People’s Republic of China; orcid.org/
0000-0002-4087-420X
Complete contact information is available at:
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