Reaction of arynes with trifluoroacetylated β-diketones: Novel formation of isocoumarins and phenanthrenes

Article abstract of DOI:10.1002/hc.21444

Polysubstituted isocoumarins were synthesized by the reaction of substituted 2-(trimethylsilyl)aryl triflates with trifluoromethylated β-diketones in the presence of CsF. The reaction proceeded through carbon-carbon bond insertion of aryne and intramolecular cyclization to form intermediates of alcohol anions, which extruded trifluoromethyl anion to afford isocoumarins. By using CuBr as a catalyst, 2 eq. of aryne reacted with β-diketones to afford phenanthrenes and 1,2-diarylethanones. Although reaction of 2-(trimethylsilyl)phenyl triflate with 1,1,1-trifluoro-4′-methylbenzoylacetone in the presence of CsF gave 3-(4′-methylphenyl)isocoumarin in 67% yield, addition of 0.2 eq. of CuCN resulted in the formation of 9-(4-methylbenzoyl)-10-trifluoromethylphenanthrene in 35% yield.

Full text of DOI:10.1002/hc.21444

Received: 9 August 2018
DOI: 10.1002/hc.21444
Revised: 4 October 2018
|
R E S E A R C H A R T I C L E
Reaction of arynes with trifluoroacetylated β-diketones: Novel
formation of isocoumarins and phenanthrenes
Kentaro Okuma
|
Yukiko Tanabe
|
Takuto Fukami
|
Yuto Ishibashi
Department of Chemistry, Fukuoka
University, Jonan-ku, Fukuoka, Japan
Abstract
Polysubstituted isocoumarins were synthesized by the reaction of substituted
Correspondence
2
-(trimethylsilyl)aryl triflates with trifluoromethylated β-diketones in the presence
Kentaro Okuma, Department of Chemistry,
Fukuoka University, Jonan-ku, Fukuoka,
Japan.
of CsF. The reaction proceeded through carbon-carbon bond insertion of aryne and
intramolecular cyclization to form intermediates of alcohol anions, which extruded
trifluoromethyl anion to afford isocoumarins. By using CuBr as a catalyst, 2 eq. of
aryne reacted with β-diketones to afford phenanthrenes and 1,2-diarylethanones.
Although reaction of 2-(trimethylsilyl)phenyl triflate with 1,1,1-trifluoro-4′-methylb
enzoylacetone in the presence of CsF gave 3-(4′-methylphenyl)isocoumarin in 67%
yield, addition of 0.2 eq. of CuCN resulted in the formation of 9-(4-methylbenzoyl)-
Email: kokuma@fukuoka-u.ac.jp
1
0-trifluoromethylphenanthrene in 35% yield.
1
|
INTRODUCTION
β-diketones were used as substrates, isocoumarin derivatives
would be synthesized in a one-pot operation by intramolecu-
[8]
Synthesis of aromatic compounds is a central issue in funda-
lar cyclization of the formed enolate. Recently, Neog et al
reported the synthesis of isocoumarins by the reaction of
[1]
mental synthetic chemistry and material science. Arynes
are super-electrophilic reaction intermediates with numerous
synthetic applications, primarily attributed to their versatil-
ity in the concomitant incorporation of various functional
[9]
4-hydroxycoumarins with benzyne. In this paper, we will
discuss full details of the synthesis of polysubstituted isocou-
marins, 1.2-diarylethanones, and phenanthrene derivative by
using trifluoromethylated β-diketones and arynes (Figure 1).
[2]
groups on the vicinal positions of arene ring. It is well
known that benzyne generated from (2-trimethylsilyl)phenyl
triflate (1a) and fluoride anion reacted with β-diketones to
give C–C insertion products, which further proceeded in-
2
RESULTS AND DISCUSSION
|
[3]
tramolecular aldol reaction to afford 1- and 2-naphthols.
Isocoumarins are valuable intermediates for the synthesis of
several natural products and important hetero- and carbocy-
clic molecules, including isocarbostyrils, isoquinolines, and
We first tried the reaction of 2-trimethylsilylphenyl triflate
1a with trifluoroacetylacetone (2a) in refluxing acetonitrile,
which resulted in the formation of 3-methylisocoumarin 3a
in 68% yield. When trifluorobenzoylacetone 2b was used as a
substrate, 3-(4′-methylphenyl)isocoumarin 3b was obtained
in 71% yield. However, Langer et al. have reported that only
ethyl 2-(2,2,2-trifluoroacetyl)phenyacetate 5 was obtained in
90% yield when ethyl 4,4,4-trifluoroacetoacetate 4 was used
[
4]
isochromenes. Recent syntheses of these heterocycles in-
clude the copper-catalyzed reaction of acetyl chloride with
[5]
2
-halobenzoic acid and Wittig reagents, microwave ac-
celerated and Rh/Cu catalyzed C–H/O–H bond functional-
[
6]
ization, and iron (III)/PhSeSePh-mediated cyclization of
[7]
[10]
2
-alkynylaryl esters. By using trifluoroacetyl group in-
as a substrate (Scheme 1).
corporated β-diketones, we have developed a new synthetic
method of isocoumarins. When trifluoromethyl substituted
Yoshida et al and Stoltz et al have reported that the
reaction of trifluoromethyl ketones with aryne gave C-C
bond insertion products along with [2 + 2] cycloaddition
[
3,11]
Dedicated to Professor Naomichi Furukawa on the occasion of his 82nd
birthday.
and O-arylation products,
which was quite different
from ours. To confirm the leaving ability of trifluoroacetyl
Heteroatom Chemistry. 2018;e21444.
https://doi.org/10.1002/hc.21444
wileyonlinelibrary.com/journal/hc
© 2018 Wiley Periodicals, Inc.
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2
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OKUMA et Al.
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O
O
Me
O
TMS
OTf
O
TMS
OTf
O
O
CsF
R
CH3
CsF
rt
CH3
O
+
F3C
MeCN
rt, 12h
CH3
HO
CF
12%
3
R
2
a
1
a
6
1
R
Yoshida et al. 2006
R
reflux
CsF
CD CN
3
o
7
0 C
OH
Me
+
HCF3
Okuma et al. 2012
O
O
Ar
3
a
O
O
SCHEME 2 Reaction of alcohol with CsF
O
O
CuBr
+
O
Ar
CF3
O
O
O
2
Ar
CF3
CF3
CF
R
3
O
CF3
Ar
O
CuCN
R
O
This work
O
a
R
FIGURE 1 Reaction of arynes with beta-diketones
O
CF3
O
TMS
R
3
O
O
CsF
+
R
O
OTf
MeCN
reflux
6h
F3C
R
O
SCHEME 3 Reaction mechanism
1a
2a R = Me
b R = 4-MeC H
3
a 68%
b 71%
2
6
4
3
to give hemiacetal anion, which extruded CF anion to afford
3
O
isocoumarin 3 (Scheme 3).
CsF
O
O
CF3
OEt
Jablonski et al reported that the reaction of trifluoroace-
tophenone with potassium tert-butoxide gave trifluoromethyl
anion, which further reacted with benzophenones to give tri-
+
1a
MeCN
rt, 14h
F3C
OEt
4
5
O
[12]
fluoromethylated diaryl alcohols. Trifluoroacetophenones
[13]
also reacted with alkoxide or hydroxide to give benzoates.
SCHEME 1 Reaction of triflate 1a with 4,4,4-trifluorobutane-
,3-diones 2 and ester 4
Recently, Prakash et al reported the nucleophilic trifluoro-
methylation of carbon centers, in which trifluoromethane
1
[14]
was used as trifluoromethyl anion source. However, to our
knowledge, there is no report on the intramolecular nucleop-
hilic cyclization of trifluoroacetophenone derivatives.
group under the reaction conditions, we performed the re-
action of triflate 1a with trifluoroacetylacetone 2a and CsF
at rt. The reaction gave 3a (32%) and 1-trifluoromethyl-3
Since substituted benzyne precursors were easily synthe-
sized by using substituted phenols, the present method would
provide a general synthesis of 3,6,7,8-substituted isocouma-
rins in a one-pot operation. Treatment of triflate 1a with tri-
fluorobenzoylacetone 2c in the presence of CsF in refluxing
acetonitrile gave isocoumarin 3c in 70% yield. Other reac-
tions were carried out in a similar manner. Additionally, to
investigate the utility of the developed isocoumarin chemis-
try, we have tried the synthesis of naturally occurring iso-
-
methyl-1H-isochromen-1-ol 6 (12%), which would be the
intermediate of isocoumarin 3a. Treatment of alcohol 6
with CsF in CD CN at 70°C for 6 hours afforded isocou-
3
marin and fluoroform in solution, which clearly suggested
that trifluoromethyl anion was formed at this temperature
(
Scheme 2).
Thus, the reaction might proceed as follows: initially pro-
coumarins, xyridine A 3f[ and thunberginol A 3h . The
15]
[16]
ducedC–Cinsertionproductanionacyclizedintramolecularly

OKUMA et Al.
3 of 10
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reported biological activity of these compounds (antimicro-
bial, antiallergic, antidiabetic, and anticancer) has resulted in
as a substrate, 1-(4′-methylphenyl)-2-phenylethanone 8a was
obtained in 62% yield, whereas 1,1,1-trifluoro-(4′-nitro)ben-
zoylacetone resulted in the formation of 4-nitrobenzil 9e in
49% yield (Scheme 4).
[
17]
a number of successful syntheses. Reaction of triflate 1c
with 1,1,1-trifluoroheptane-2,4-dione 2d in the presence of
CsF gave xyridine A 3f in 69% yield. The precursor of thum-
berginol A 3h’ was also synthesized in 53% yield, which was
+
In the presence of Cu ion, initially formed aromatic anion
+
b was protonated to give phenylbenzoyltrifluoroacetone Cu
easily demethylated by using BBr to give thumberginol A
complex c. Halide anion attacked trifluoroacetyl carbonyl to
give 1,2-diarylethanones and trifluoroacetic acid (Scheme 5).
To confirm the formation of benzil 9 by oxidation of ben-
zoin, we then tried the reaction of triflate 1a with 2c and 0.2
eq. of CuBr in refluxing acetonitrile for 6 hours followed by
stirring in the air for 24 hours, which formed benzil 9b in
60% yield. Thus, CuBr was easily oxidized in the air to give
3
3
h (Figure 2).
Yung et al have reported that reaction of benzyne with
benzoylacetone in the presence of catalytic amount of CuBr
gave diphenylbenzoylacetone 7, which suggested that ex-
[18]
cess amount of benzyne gave phenylated product.
Thus,
we then tried the reaction of triflate 1a with trifluorometh-
ylated β-diketones in the presence of catalytic amount of
CuBr, whether the corresponding diphenylbenzoyl acetone
would be formed. Since equal amount of CuBr resulted in
the formation of stable copper complex, 0.2 eq. of CuBr was
used. Treatment of triflate 1a with diketone 2c and CsF in
the presence of 0.2 eq. of CuBr gave 1,2-diphenylethanone
CuBr , which catalyzed oxidation of 1,2-diphenylethanone
2
to give benzil 9b (Scheme 6). Actually, Yu and cowork-
ers reported the cupric acetate catalyzed oxidation of
1,2-diphenylethanone (benzoin) to give benzil 9b.[
19]
8
b in 49% yield. When 4-methylbenzoylacetone 2b was used
O
O
N2+
O
O
CuBr
+
O
H C
3
Ph
CO -
2
H C
2
Ph
TMS
OTf
O
O
Ph Ph
CsF
O
+
F3C
R' CH CN
3
R'
R
Yung et al.
7
R
reflux
6h
1
2
Isocoumarin 3
Yield / %
TMS
OTf
O
O
TMS
OTf
O
O
O
O
CuBr (0.2 eq.)
F3C
70
1a
O
1a
MeCN
reflux, 6 h
2
c
3c
R
O
8
O
+
TMS
OTf
O
O
O
F3C
O
Ar
+
2
b
67
O
2
Me
1
b
O
9
3d
+
CsF
R
O
O
O
O
2
c
51
69
8
9
3
e
8
a
R = Me
R = H
62%
49
52
45
0
0%
O
O
8b
8c
8d
9e
0
O
O
O
R = OMe
R = Cl
0
O
F3C
0
R = NO
49
2
2d
3
f
SCHEME 4 Synthesis of 1,2-diarylethanones from 1a and 2
OMe
OMeO
TMS
O
2c
53
OTf
Ar
1c
3g
Cu
-
O
CF COX
3
O
O
OMeO
O
8
Cu
O
F3C
OMe
OMe
O
5
3
Ar
OMe
OMe
F3C
F3C
O
X
2e
3h'
b
c
FIGURE 2 Synthesis of substituted isocoumarins 3
SCHEME 5 Reaction mechanism

4
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OKUMA et Al.
|
TMS
O
O
CuBr (0.2 eq.)
O
+
OTf
F3C
MeCN
R
reflux, 6 h
1
a
2c
CsF
8
a: R = 4-MeC H 10%
6
4
8
b: R = 4-ClC H
4%
5%
6
4
+
8
c: R = COOEt
O
TMS
OTf
O
CF3
MeCN
0 C, 24 h
R
o
O
5
+
1
a
CuCN
9
b 40%
(
0.2 eq.)
O
O
+
SCHEME 6 Reaction of triflate 1a with benzoylacetone 2c in
MeCN
reflux, 6 h
1
0a:R= 4-MeC H 35%
6 4
F3C
the presence of CuBr
R
1
0b: R = 4-ClC H 22%
6
4
2
or 4
10c: R = COOEt
5%
O
Uchiyama et al have recently reported the synthesis of
poly(ortho-arylene)s by CuCN catalyzed aryne polymeriza-
+ CsF
OH
CF3
EtO
+
[20]
tion, which prompted us to investigate the reaction of ben-
zyne with trifluorobenzoylacetones 2 in the presence of CuCN.
When 0.1 eq. of CuCN was treated with refluxing CH CN
3
1
1 28%
solution of triflate 1a, CsF, and benzoylacetone 2b for 3 hours,
ethanone 8a and phenanthrene 10a were obtained in 3% and 6%
yields along with insoluble pale yellow poly(ortho-phenylene)
s (20%). Structure of the product 10a was determined by spec-
troscopic and HRMS analysis. The IR spectrum of obtained
poly(ortho-phenylene)s is similar to that of Uchiyama et al.
When 0.2 eq. of CuCN was used as a catalyst, phenanthrene
+
poly(ortho-phenylene)s
SCHEME 7 Reaction of triflate 1a with diketone 2 by using
catalytic CuCN
TMS
OTf
1
0a was obtained as a major product (32%) along with benzoin
a (10%) and poly(ortho-phenylene)s (10%). When ester 4 was
8
1a
CuCN
0.2 eq.)
Ph
used as a substrate, ethyl 10-hydroxy-10-(trifluoromethyl)-9,1
Ph
(
O
O
+
0
-dihydrophenanthrene-9-carboxylate 11 was obtained in 28%
+
MeCN
reflux, 6 h
OH
yield along with ethyl phenylacetate (5%) and phenanthrene
H C
Ph
3
OH
12b 12%
1
0c (Scheme 7). Prolonged heating of compound 11 and CsF
1
2a: 32%
:
in refluxing acetonitrile for 6 hours resulted in the formation
of 10c in 70% yield.
+
CsF
Trifluoromethyl group would play a crucial role for the for-
mation of phenanthrene derivative 10. When benzoylacetone
was used as starting dione under these reaction conditions,
SCHEME 8 Reaction of triflate 1a with benzoylacetone by
using catalytic CuCN
4
-phenyl-2-naphthol (12a: 30%) and 3-phenyl-1-naphthol
(
12b: 10%) were obtained, the result of which was quite dif-
with CuCN in refluxing acetonitrile. While equal amount of
CuCN was used, only benzonitrile was obtained in 30% yield.
When 0.3 eq. of CuCN was used, N-phenyl-9H-fluoren-9-imine
(13) was obtained in 18% yield along with small amount of other
oligomers. Insoluble pale yellow poly(ortho-phenylene)s (10%)
was also produced, which clearly showed that cyanide anion ini-
tially attacked benzyne to give 2-cyanophenyl anion d. Another
benzyne reacted this anion to give 2-cyanobiphenyl anion e
which intramolecularly attacked cyano group followed by the ad-
dition of benzyne to give imine 13. Anion e further added another
molar of benzyne to give oligomers and poly(ortho-phenylne)s
(Scheme 9).
[18]
ferent from that of Yung et al. Mild formation of benzyne
under these conditions might prevent the double arylation of
benzoylacetone (Scheme 8).
Thus, the formation of phenanthrene 10 might be formed as
follows: initially formed benzyne adduct anion d was partially
stabilized by cuprous ion, which further reacted with another
molar of benzyne to give anion e. Intramolecular nucleophilic
addition gave alcohol 11, which was dehydrated to give phenan-
threne 10 (Scheme 9). Cuprous ion plays a crucial role for the
formation of 10 and 11. Two molar of benzyne reacted with tri-
flurobenzoylacetone 2 to give phenanthrene derivatives.
As Uchiyama reported, catalytic amount of CuCN (0.01
eq.) would be important catalyst for the synthesis of poly(ortho-
In summary, polysubstituted isocoumarins 3 were synthe-
sized by the reaction of triflate 1 with trifluoromethylated
β-diketones 2 in moderate to good yields. In the presence
[20]
phenylene)s. Thus, we have tried the reaction of triflate 1a

OKUMA et Al.
5 of 10
|
H
and chemical shifts are expressed in ppm relative to in-
ternal TMS for H- and C-NMR. Melting points were
uncorrected.
O
O
R
O
1
13
H
O
CF3
R
CF3
Cu
Cu
3
.2
Reaction of 2-trimethylsilylphenyl
|
triflate 1a with trifluoroacetylacetone 2a in the
presence of CsF
d
e
To a solution of 1,1,1-trifluoroacetylacetone (77 mg,
Cu
H
0
.50 mmol) and CsF (228 mg, 1.5 mmol) in acetonitrile
O
O
O
CF3
CF3
(
6.0 mL) was added triflate 1a (179 mg, 0.60 mmol) in ace-
-OH
R
R
tonitrile (3.0 mL). After refluxing for 6 hours, the reaction
mixture was washed with water, dried over MgSO , fil-
4
tered, and evaporated to give a pale yellow oil, which was
chromatographed over silica gel by elution with hexane-
dichloromethane (1:1) to afford 3-methylisocoumarin 3a
anion of 11
10
(56 mg, 0.35 mmol).
SCHEME 9 Formation mechanism of phenanthrene 10
O
O
Me
N
3a
TMS
CsF
C
+
CuCN
.3 eq.
3
-Methylisocoumarin 3a: colorless crystals: mp 68–69°C
MeCN
reflux, 3 h
0
OTf
[21]
1
(lit.
mp 72–73°C); H NMR (CDCl ) δ = 2.28 (s, 3H,
3
1a
1
3
Me), 6.24 (s, 1H, =CH), 7.34 (d, 1H, J = 8 Hz, Ar), 7.45 (t,
1
H, J = 8 Hz, Ar), 7.65 (t, 1H, J = 8 Hz, Ar), 8.25 (d, 1H,
+
J = 8 Hz, Ar). MS (GC): m/z Found 160.1 (M ). Calcd. for
+
C H O ; 160.1 (M ).
1
0
18
2
N
N
C
CN
C
O
Cu
Cu
O
d
e
3
b
Me
SCHEME 10 Reaction of triflate 1a with CsF and 0.3 eq. of
CuCN
3-p-Tolylisocoumalin 3b: colorless crystals: mp 116–118°C
[22] 1
(
lit. mp 109°C). H NMR (CDCl ) δ = 2.39 (s, 3H, CH ),
3 3
of catalytic amount of CuX, 1,2-diarylethanones, benzils,
and phenanthrene derivatives 10 were obtained in moderate
yields. The most interesting feature of this reaction includes
intramolecular cyclization of enolate to trifluoroacetyl moi-
ety. This method provides a versatile synthesis of polysubsti-
tuted isocoumarins in a one-pot operation.
6.88 (s, 1H, CH), 7.24 (d, J = 8 Hz, 2H, Ar), 7.43–7.47 (m,
2H), 7.68 (t, J = 8 Hz, 1H, Ar), 7.75 (d, J = 8 Hz, 1H, Ar),
8.28 (d, J = 8 Hz, 1H, Ar).
3
.3
Reaction of 4,4,4-trifluoro-1-p-
|
tolylbutan-1,3-dione with triflate 1a at rt
To a solution of 1,1,1-trifluoroacetylacetone (78 mg,
3
3
EXPERIMENTAL
General
|
0
.50 mmol) and CsF (228 mg, 1.5 mmol) in acetonitrile
(
6.0 mL) was added triflate 1a (179 mg, 0.60 mmol) in ace-
.1
|
tonitrile (3.0 mL). After standing at rt for 16 hours, the re-
All chemicals were obtained from commercial suppli-
ers and were used without further purification. Analytical
TLC was carried out on precoated plates (Merck silica gel
action mixture was washed with water, dried over MgSO ,
4
filtered, and evaporated to give a pale yellow oil, which was
chromatographed over silica gel by elution with hexane-
dichloromethane (1:1) to afford 3-methylisocoumarin 3a
(28 mg, 0.18 mmol) and 1-trifluoromethyl-3-methyl-1H-iso
chromen-1-ol 6 (14 mg, 0.06 mmol).
6
0, F254), and flash column chromatography was per-
formed with silica (Merck, 70–230 mesh). NMR spectra
1
13
(
H at 400 MHz; C at 100 MHz) were recorded in CDCl ,
3

6
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OKUMA et Al.
|
Me
(
m, 5H, Ar), 7.73 (t, J = 9 Hz, 1H, Ar), 7.90 (d, J = 8 Hz, 2H,
13
O
Ar), 8.33 (d, J = 8 Hz, 1H, Ar). C NMR (CDCl ) δ = 101.91
3
HO
CF
3
6
(=CH), 120.62, 125.32, 126.16, 128.21, 128.93, 129.70, 130.03,
1
32.05, 134.93, 137.67, 153.73 (Ar), 162.37 (C=O). MS (ESI)
+
+
Trifluoromethyl-3-methyl-1H-isochromen-1-ol 6: colorless
m/z: 223 (M + H). Calcd. for C H O : 223 (M + H).
15 11 2
1
oil. H NMR (CDCl ) δ = 2.02 (s, 3H, Me), 3.60 (s, 1H,
3
O
OH), 5.66 (s, 1H, =CH), 7.01 (d, 1H, J = 8 Hz, Ar), 7.24 (t,
O
O
O
6
7
1
H, J = 8 Hz, Ar), 7.36 (t, 1H, J = 8 Hz, Ar), 7.54 (d, 1H,
Me
1
3
3
d
J = 8 Hz, Ar). C NMR (CDCl ) δ = 19.62 (Me), 77.43
3
(
q-C), 99.83 (=CH), 122.72 (q, J =291 Hz, CF ), 123.84,
CF 3
1
9
1
26.32, 126.94, 127.57, 138.75, 150.53. F NMR (CDCl )
6,7-Methylenedioxy-3-methylisocoumarin 3i: colorless solid;
[25] 1
3
+
δ = −84.31. HRMS (m/z): Found: 230.0558 (M ). Calcd. for
C H F O : 230.0555.
mp 166–127°C (lit. mp 187–189°C). H NMR δ = 2.26 (s,
3H, CH ), 6.08 (s, 2H, OCH O), 6.15 (s, 1H, Ar), 6.71 (s, 1H,
1
1
9
3
2
3
2
Ar), 7.58 (s, 1H, Ar).
3
.4
Thermolysis of 6 in the presence of CsF
O
|
O
O
5
1
Alcohol 6 (5 mg, 0.015 mmol) and CsF (5 mg, 0.03 mmol)
O
3
e
were dissolved in CDCl (0.5 mL), and the mixture was
3
1
19
stirred for 2 hours at 60°C. By checking H NMR and
F
NMR, compound 6 was changed to 3a and HCF .
6,7-Methylenedioxy-3-phenylisocoumrin 3e: colorless solid; mp
[26] 1
3
1
88–190°C (lit. mp 189–191°C). H NMR (CDCl ) δ = 6.12
3
(
s, 2H, OCH O), 6.86 (d, J = 7 Hz, 1H, Ar), 6.87 (s, 1H, CH),
2
3
.5
Reaction of substituted triflate 1 with
|
7
.41–7.48 (m, 3H, Ar), 7.66 (s, 1H, Ar), 7.85 (d, J = 8 Hz, 2H,
trifluoroaroylacetone 2 in the presence of CsF
1
3
Ar). C NMR (CDCl ) δ = 102.06 (=CH), 102.48 (CH2),
3
To a solution of 1,1,1-trifluro-3′,4′-dimethoxybenzoylacetone
104.57, 107.74, 125.27 (Ph), 129.02 (Ph), 129.97 (Ph), 132.14,
135.33, 148.59, 152.98, 153.95 (Ar), 162.10 (C=O).
2
e (138 mg, 0.5 mmol) and CsF (242 mg, 1.6 mmol) in ace-
tonitrile (6 mL) was added with triflate 1c (262 mg, 0.8 mmol)
in acetonitrile (2 mL). After refluxing for 6 h, the reaction mix-
ture was washed with water, extracted with dichloromethane
O
O
O
6
9
O
Xyridin
A
3
f
(
10 mL) for three times, dried over magnesium sulfate, filtered,
and evaporated to give pale brawn oil, which was chromato-
graphed over silica gel by elution with hexane-dichloromethane
[
27]
Xyridine A 3f: colorless solid; mp 63–65°C (lit.
mp 64–
1
(3:1) to give isocoumarin 3h’ (82 mg, 0.26 mmol).
65°C) H NMR δ = 0.98 (t, J = 8 Hz, 3H, CH ), 1.72 (sext,
3
J = 8 Hz, 2H, CH ), 2.48 (t, J = 8 Hz, 2H, CH ), 6.08 (s, 2H,
2
2
OMeO
O
CH ), 6.15 (s, 1H, CH), 6.72 (s, 1H, Ar), 7.59 (s, 1H, Ar).
2
OMe
OMe
Ph
O
3h'
[
23]
OMe O
3
g
Compound 3h’: colorless solid: mp 140–142 °C (lit.
mp
1
1
42–144°C) H NMR (CDCl ) δ = 3.93 (s, 3H, OCH ), 3.98
3
3
(
s, 3H, OCH ), 4.01 (s, 3H, OCH ), 6.74 (s, 1H, CH), 6.89–6.93
8-Methoxyl-3-phenylisocoumarin 3g: colorless solid; mp
[28] 1
3
3
(
m. 2H, Ar), 6.99 (d, J = 8 Hz, 1H, Ar), 7.35 (s, 1H, Ar), 7.46
142–144°C (lit. mp 143–145°C). H NMR δ = 4.02 (s, 3H,
OMe), 6.85 (s, 1H, CH), 6.94 (d, J = 8 Hz, 1H, Ar), 7.03 (d,
J = 8 Hz, 1H, Ar), 7.41–7.47 (m, 3H, Ar), 7.61 (t, J = 8 Hz,
1H, Ar), 7.88 (d, J = 8 Hz, 2H, Ar). HRMS (m/z): Found:
13
(
d, J = 8 Hz, 1H, Ar), 7.60 (t, J = 8 Hz, 1H, Ar). C NMR
(
CDCl ) δ = 56.22 (OCH ), 56.41 (OCH ), 56.54 (OCH ),
3
3
3
3
1
00.82, 108.41, 109.11, 109.70, 111.27, 118.07, 118.81, 124.93,
+
+
1
35.99, 140.99, 149.34, 150.88, 154.17, 159.39, 161.88.
M : 253.0865. Calcd. for C H O : M +1: 253.0865.
1
6
14
3
O
O
70
3.6
Reaction of 1a with
|
trifluorobenzoylacetone 2c in the presence of
3c
CuBr (0.2 eq.)
[24]
3
8
-Phenylisocoumarin 3c: colorless solid; mp 88–90°C (lit. mp
To a solution of 1,1,1-trifluobenzoylacetone 2c (77 mg,
1
9–91°C). H NMR (CDCl ) δ = 6.98 (s, 1H, CH), 7.44–7.53
0.50 mmol), CuBr (14 mg, 0.10 mmol), and CsF (228 mg,
3

OKUMA et Al.
7 of 10
|
[
30]
1
.5 mmol) in acetonitrile (6.0 mL) was added triflate 1a
4-nitrobenzil 9e: Yellow solid: mp 129–131°C (lit.
138–
1
(
179 mg, 0.60 mmol) in acetonitrile (3.0 mL). After re-
139°C. H NMR (CDCl ) δ = 7.56 (t, 2H, J = 8 Hz, Ar), 7.72
3
fluxing for 6 hours, the reaction mixture was washed with
(t, 1H, J = 8 Hz, Ar), 7.99 (d, 2H, J = 8 Hz, Ar), 8.18 (d, 2H,
1
3
water, dried over MgSO , filtered, and evaporated to give
J = 8 Hz, Ar), 8.36 (d, 2H, J = 8 Hz, Ar). C NMR (CDCl )
4
3
a pale yellow oil, which was chromatographed over silica
gel by elution with hexane-dichloromethane (1:1) to afford
δ= 124.2, 129.3, 130.1, 131.0, 132.4, 135.6, 137.3, 151.2,
192.2 (C=O), 192.9 (C=O).
1
,2-diphenylethanone 8b (47 mg, 0.24 mmol).
3
1
.7
In situ oxidation of
|
O
,2-diphenylethanone by using CuBr
8
b
To a solution of 1,1,1-trifluobenzoylacetone 2c (77 mg,
0.50 mmol), CuBr (14 mg, 0.10 mmol), and CsF (230 mg,
29]
1
,2-diphenylethanone 8b: mp. 53–55°C (lit.[ mp 54–55°C).
1.5 mmol) in acetonitrile (6.0 mL) was added triflate 1a
(179 mg, 0.60 mmol) in acetonitrile (3.0 mL). After refluxing for
6 hours, the reaction mixture was stirred for additional 24 hours
at 50°C. the reaction mixture was washed with water, dried over
1
H NMR (CDCl ) δ = 4.29 (s, 2H, CH ), 7.21–7.31 (m, 5H,
3
2
Ar), 7.45 8t, 2H, J = 8 Hz, Ar), 7.53 (t, 1H, J = 8 Hz, Ar),
8
.01 (d, 2H, J = 8 Hz, Ar).
MgSO , filtered, and evaporated to give a pale yellow oil, which
4
O
was chromatographed over silica gel by elution with hexane-
dichloromethane (1:1) to afford benzil 9b (42 mg, 0.20 mmol).
8
a
CH
3
O
1
9
-(4-methylphenyl)-2-phenylethanone 8a: colorless solid mp
O
[
29]
1
9
b
8–99°C (lit.
mp. 95–96°C). H NMR (CDCl ) δ = 2.39
3
(
s, 3H, CH ), 4.25 (s, 2H, CH ), 7.23–7.33 (m, 7H, Ar), 7.91
3 2
1
3
[30]
(d, 2H, J = 8 Hz, Ar). C NMR (CDCl ) δ = 21.5 (CH ),
4
Benzil 9b: yellow crystals. mp 92–94°C (lit. mp 94–96°C).
3
3
1
5.2 (CH ), 126.7, 128.5, 128.6, 129.3, 129.3, 133.9, 134.7,
H NMR (CDCl ) δ = 7.52 (t, 4H, J = 8 Hz, Ar), 7.68 (t, 2H,
2
3
1
43.8, 197.1 (C=O).
J = 8 Hz, Ar), 7.99 (d, 4H, J = 8 Hz, Ar).
O
3
.8
Reaction of 1a with 1,1,1-trifluoro-
|
OMe
(
4-methyl)benzoylacetone 2b and CsF in the
8c
presence of CuBr (0.2 eq.)
1
-(4-methoxyphenyl)-2-phenylethanone 8c: colorless solid
To a solution of 1,1,1-trifluoro-(4-methyl)benzoylacetone 2b
(115 mg, 0.5 mmol), CuBr (14 mg, 0.1 mmol) and CsF (380 mg,
2.5 mmol) in acetonitrile (10 mL) was added with triflate 1a
(298 mg, 1.0 mmol) in acetonitrile (5 mL). After refluxing for
[
29]
1
mp 92–94°C (lit.
mp 93–94°C), H NMR (CDCl )
3
δ = 3.85 (s, 3H, OCH ), 4.15 (s, 2H, CH ), 6.90 (d, 2H,
3
2
J = 8 Hz), 7.20–7.33 (m, 7H, Ar), 7.87 (d, 2H, J = 8 Hz,
1
3
Ar). C NMR (CDCl ) δ = 45.3 (CH ), 126.9, 128.6,
6 h, the reaction mixture was washed with sat. aq. NH Cl, ex-
3
2
4
1
28.8, 129.3, 129.9, 134.1, 134.7, 139.3, 196.1 (C=O).
tracted with ethyl acetate (6 mL) for three times. The formed
colorless solid was filtered, the combined extract was dried over
sodium sulfate, filtered, and evaporated to give pale yellow solid,
which was chromatographed over silica gel by elution with
hexane:dichloromethane (3:1) to give ethyl 1-(4-methylphenyl
O
Cl
8
d
)
-2-phenylethanone 8a (11 mg, 0.05 mmol) and 9-(4-methylben
1
-(4-chlorophenyl)-2-phenylehanone 8d: colorless solid,
zonyl)-10-trifluoromethylphenathrene 10a (49 mg, 0.18 mmol).
[
29]
1
mp 127–129°C (lit.
mp 129–130°C). H NMR (CDCl )
Insoluble solid was found to be poly(ortho-phenylene)s by com-
paring its IR spectrum of with the reported one.
3
δ = 4.25 (s, 2H, CH2), 7.21–7.26 (m, 3H, Ar), 7.31 (dd,
O
2
H, J = 8 Hz, Ar), 7.42 (d, 2H, J = 8 Hz, Ar), 7.94 (d, 2H,
CF
3
J = 8 Hz, Ar).
H
3
C
O
10a
O
NO
2
9-(4-methylbenzonyl)-10-trifluoromethylphenathrene 10a:
1
9e
Colorless solid; H NMR (400 MHz, CDCl ): δ = 2.40 (s,
3

8
of 10
OKUMA et Al.
|
3
H, CH ), 7.23 (d, J = 8 Hz, 2H, ArH), 7.51 (ddd, J = 8, 7,
7.67–7.87 (m, 5H, ArH), 8.30 (br d, J = 8 Hz, 1H, ArH),
3
1
3
and 1 Hz, 1H, ArH), 7.67 (d, J = 8 Hz, 1H, ArH), 7.72–7.81
8.75–8.77 (m, 2H, ArH).; C NMR (101 MHz, CDCl ):
3
(
m, 5H, ArH), 8.31 (d, J = 8 Hz, 1H, ArH), 8.76 (d, J = 8 Hz,
δ = 14.0, 62.3, 121 (q, J = 29 Hz, CF ), 122.9, 123.0, 126.1,
3
1
3
1
H, ArH), 8.80 (d, J = 7 Hz, 1H, ArH).; C NMR (101 MHz,
126.2, 126.6, 126.9, 127.8, 127.9, 128.1, 129.4, 130.9, 131.6,
1
9
CDCl ): δ = 21.8 (CH ), 121.2, 121.5, 122.9, 123.1, 125.9,
168.2. F NMR (376 MHz, CDCl ): δ = −54.90 (CF ).
3 3
3
3
+
1
1
(
26.0, 126.1, 126.2, 126.3, 127.6, 127.7, 127.8, 127.9, 128.0,
29.3, 129.5, 129.6, 131.0, 131.7, 134.9, 137.3, 137.4, 145.1
HRMS: Calcd. for C H F O m/z = 318.0868 (M ), Found
18 13 3 2
m/z = 318.0869.
1
9
Ar), 196.4 (C=O). F NMR (376 MHz, CDCl ): δ = −52.39
3
O
+
HO CF3
(
CF ). HRMS: Calcd. for C H F O m/z = 364.1075 (M ),
3
22 13
3
EtO
Found m/z = 364.1076.
11
O
CF
3
Cl
1
Compound 11: Colorless crystals; mp 193–194°C H NMR
(
400 MHz, CDCl ): δ = 1.06 (t, J = 7 Hz, 3H, CH ), 3.931–
3
3
1
0b
4
(
.093 (m, 2H CH ), 4.24 (s, 1H, OH), 4.62 (s, 1H, CH), 7.28
2
dt, J = 8 and 1 Hz, 1H, ArH), 7.35–7.49 (m, 4H, ArH),
1
9
-(4-chlorobenzoyl)-10-trifluoromethylphenathrene 10b: H
7.74 (d, J = 8 Hz, 1H, ArH), 7.78 (dd, J = 8, 2 Hz), 7.86 (d,
1
3
NMR (400 MHz, CDCl ): δ = 7.42 (d, J = 9 Hz, 2H, ArH),
J = 8 Hz, 1H, ArH).; C NMR (101 MHz, CDCl ): δ = 13.7
3
3
7
1
.54 (ddd, J = 8, 7, and 1 Hz, 1H, ArH), 7.62 (d, J = 8 Hz,
H, ArH), 7.74–7.84 (m, 5H, ArH), 8.32 (d, J = 9 Hz, 1H,
(CH ), 50.3 (CH ), 62.0 (CH), 74.51 (q, J = 28 Hz, CF ),
3
2
3
120.3, 123.2, 123.6, 123.8, 126.0, 127.1, 128.2, 128.6, 128.9,
ArH), 8.79 (d, J = 8 Hz, 1H, ArH), 8.84 (d, J = 9 Hz, 1H,
129.0, 129.8, 129.9, 130.0, 132.3, 133.2, 134.2 (Ar), 171.1
1
3
19
ArH).; C NMR (101 MHz, CDCl ): δ = 121.2, 121.5, 121.8,
(COO). F NMR (376 MHz, CDCl ): δ = −79.79 (CF ).
3
3
3
+
1
1
1
22.1, 123.0, 123.1, 123.1, 125.8, 126.0, 126.1, 126.1, 126.1,
HRMS: Calcd. for C H F O m/z = 336.0973 (M ). Found
18 15 3 3
26.2, 127.4, 127.6, 127.9, 128.1, 128.3, 128.5, 129.4, 129.5,
m/z = 336.0973.
19
30.7, 131.0, 131.8, 135.6, 135.6, 136.4, 136.5.; F NMR
(
376 MHz, CDCl ): δ = −52.34 (CF ). HRMS: Calcd. for
3 3
3
.10
Reaction of triflate 1a
+
|
C H ClF O m/z = 384.0529 (M ), Found m/z = 384.0546.
2
2
13
3
with benzoylacetone and CsF in the
presence of CuCN
3
.9
Reaction of 1a with ethyl
|
To a solution of benzoylacetone (81 mg, 0.5 mmol), CuCN
trifluoroacetoacetate 4 in the presence of
(
9.0 mg, 0.1 mmol) and CsF (380 mg, 2.5 mmol) in acetoni-
CuCN (0.2 eq.)
trile (10 mL) was added with triflate 1a (298 mg, 1.0 mmol)
To a solution of ethyl trifluoroacetoacetate 4 (92 mg,
in acetonitrile (5 mL). After refluxing for 6 hours, the reaction
0
2
1
.5 mmol), CuCN (9 mg, 0.1 mmol) and CsF (379 mg,
.5 mmol) in acetonitrile (10 mL) were added with triflate
a (298 mg, 1.0 mmol) in acetonitrile (5 mL). After reflux-
mixture was washed with sat. aq. NH Cl, extracted with ethyl
4
acetate (6 mL) for three times. The formed colorless solid
was filtered, and the combined extract was dried over sodium
sulfate, filtered, and evaporated to give pale yellow solid,
which was chromatographed over silica gel by elution with
hexane:dichloromethane (3:1) to give 4-phenyl-2-naphthol
(33 mg, 0.15 mmol) and 3-phenyl-1-naphthol (11 mg,
0.05 mmol). These products were identical with the authentic
samples.[
ing for 3 hours, the reaction mixture was washed with sat.
aq. NH Cl, extracted with ethyl acetate (6 mL) for three
4
times. Colorless precipitate was filtered, and the combined
extract was dried over sodium sulfate, filtered, and evapo-
rated to give pale yellow solid, which was chromatographed
over silica gel by elution with hexane:dichloromethane (3:1)
to give 9-ethoxycarbonyl-10-trifluoromethylphenanthrene
3]
Ph
1
0c (20 mg, 0.06 mmol) and 9-ethoxycarbonyl-10-hydroxy
-
10-trifluoromethyl-9,10-dihydrophenanthrene 11 (47 mg,
OH
0
.14 mmol).
O
CF3
1
EtO
4
1
7
-phenyl-2-naphthol 12a: H NMR (CD CN) δ = 7.23 (s,
3
H, Ar), 7.26 (t, 1H, J = 15 Hz, Ar), 7.41–7.48 (m, 3H, Ar),
1
0c
.50 (d, 2H, J = 4 Hz, Ph), 7.53–7.54 (m, 1H, Ar), 7.71 (d,
1
13
Compound10c: Colorlesssolid; H NMR(400 MHz, CDCl ):
1H, J = 8 Hz, Ar), 7.77 (d, 1H, J = 8 Hz, Ar), C NMR
3
δ = 1.47 (t, J = 7 Hz, 3H, CH ), 4.59 (q, J = 7 Hz, 2H, CH ),
(101 MHz, CDCl ) δ = 109.9, 119.1, 124.3, 126.5, 127.0,
3
2
3

OKUMA et Al.
9 of 10
|
1
27.3, 127.8, 127.9, 128.7, 130.3, 135.6, 140.4, 142.9. 152.8
A. Kunai, Bull. Chem. Soc. Jpn. 2010, 83, 199;K. Okuma,
Heterocycles 2012, 85, 515;P. M. Tadross, B. M. Stoltz, Chem.
Rev. 2012, 112, 3550.
(
Ar).
Ph
[3] H. Yoshida, M. Watanabe, J. Ohshita, A. Kunai, Chem. Commun.
2
005, 26, 3292;K. Okuma, R. Itoyama, A. Sou, N. Nagahora, K.
Shioji, Chem. Commun. 2012, 48, 11145.
OH
[
4] For reviews, see E. Napolitano, New J. Org. Synth. 1997, 29,
6
31;R. D. Barry, Chem. Rev. 1969, 64, 229;R. A. Hill, Naturally
1
3
-phenyl-1-naphthol 12b: H NMR (CD CN) δ = 7.18 (s, 1H,
occurring isocoumarins. in Progress in the Chemistry of Natural
Compounds, Vol 49, (Eds: W. Hem, H. Griesebach, G. W. Kirby,
C. Tamm), Springer Verlag, Wien 1986, pp. 1–78;S. Pal, V.
Chatare, M. Pal, Cur. Org. Chem. 2011, 15, 782.
3
Ar), 7.38 (s, 1H, J = 15 Hz. Ar), 7.45–7.53 (m, 5H, Ar), 7.67
(
s, 1H, Ar), 7.74 (d, 2H, J = 8 Hz, Ar), 7.88 (d, 1H, J = 8 Hz,
13
Ar), 8.18 (d, 1H, J = 9 Hz, Ar). C NMR (101 MHz, CDCl )
3
[
[
5] X. Chen, Y. Liu, RSC Advances 2017, 7, 37839.
6] Q. Li, Y. Yan, X. Wang, B. Gong, X. Tang, J. Shi, H. E. Xu, W.
Yi, RSC Advances 2013, 3, 23402.
δ = 108.7, 119.1, 121.8, 123.8, 125.7, 127.2, 127.6, 127.8,
128.3, 129.1, 135.3, 139.2, 141.1, 151.9 (Ar).
[
7] A. Speranca, B. Godoi, S. Pinton, D. F. Back, P. H. Menezes, G.
Zeni, J. Org. Chem. 2011, 76, 6789.
3
0
.11
Reaction of triflate 1a with CsF and
|
[
8] K. Okuma, K. Hirano, Y. Tanabe, R. Itoyama, A. Miura, N.
Nagahora, K. Shioji, Chem. Lett. 2014, 43, 495.
.3 eq. of CuCN
To a suspension of CsF (453 mg, 3.0 mmol) and CuCN
[9] K. Neog, D. Dutta, B. Das, P. Gongoi, Org. Lett. 2017, 19, 730.
10] M. Zahid, M. F. Ibad, Z. A. Abilov, P. Langer, J. Fluorine Chem.
[
[
(
27 mg, 0.3 mmol) in acetonitrile (7.0 mL) was added a
2
013, 146, 80.
solution of triflate 1a (298 mg, 1.0 mmol). After refluxing
11] U. K. Tambar, B. M. Stoltz, J. Am. Chem. Soc. 2005, 127, 5340.
12] L. Jablonski, J. Joubert, T. Billard, B. R. Langlois, Synlett 2003, 2,
30;D. Inschauspe, J.-B. Sortais, T. Billard, B. R. Langlois, Synlett
003, 2, 233;L. Jablonski, T. Billard, B. R. Langlois, Tetrahedron Lett.
003, 44, 1055;B. R. Langlois, N. Roques, J. Fluorine Chem. 2007,
for 6 hours, the reaction mixture was washed with sat. aq.
NH Cl, extracted with ethyl acetate (6 mL) for three times.
[
4
2
Colorless precipitate was filtered, and the combined extract
was dried over sodium sulfate, filtered, and evaporated to
give pale yellow solid, which was chromatographed over sil-
ica gel by elution with hexane:dichloromethane (3:1) to give
2
2
128, 1318;T. Billard, S. Bruns, B. R. Langlois, Org. Lett. 2000, 2, 2101.
[13] A. Delgado, J. Clardy, Tetrahedron Lett. 1992, 33, 2789;J. P.
Guthrie, J. Cossar, Can. J. Chem. 1990, 68, 1640.
2
- N-phenyl-9H-fluoren-9-imine 13 (46 mg, 0.18 mmol).
[
14] G. K. S. Prakash, P. V. Jog, P. T. D. Batamack, G. A. Olah, Science
2
012, 338, 1324.
N
C
[15] M. Yoshikawa, E. Uchida, N. Chatani, N. Murakami, J. Yamahara,
Chem. Pharm. Bull. 1992, 40, 3121;M. Yoshikawa, E. Uchida,
N. Chatani, H. Kobayashi, Y. Naitoh, Y. Okuno, H. Matsuda, J.
Yamahara, N. Murakami, Chem. Pharm. Bull. 1992, 40, 3352.
13
[
16] N. Ruangrungsi, T. Sekine, T. Phadungcharoen, S. Suriyagan, I.
Murakoshi, Phytochemistry 1995, 38, 481;A. Saeed, J. Chin. Chem.
Soc. 2003, 50, 313;A. Saeed, J. Heterocyclic Chem. 2003, 40, 337.
N-phenyl-9H-fluoren-9-imine 13[ : Colorless solid:
31]
1
H
NMR (400 MHz, CDCl ): δ = 6.56 (d, 1H, J = 8 Hz, Ar),
3
[
17] A. C. Tadd, M. R. Fielding, M. C. Willis, Chem. Commun. 2009,
6
.92 (t, 1H, J = 8 Hz, Ar), 6.99 (d, 2H, J = 8 Hz, Ar), 7.21
t, 1H, J = 8 Hz, Ar), 7.35–7.49 (m, 5H, Ar), 7.60 (d, 2H,
J = 8 Hz, Ar), 7.92 (d, 1H, J = 8 Hz, Ar). HRMS: Calcd. for
4
5, 6744;A. Kurume, Y. Kamata, M. Yamashita, Q. Wang, H.
(
Matsuda, M. Yoshikawa, I. Kawasaki, S. Ohta, Chem. Pharm.
Bull. 2008, 56, 1264;M. Uchiyama, H. Ozawa, K. Takuma, Y.
Matsumoto, M. Yonehara, K. Hiroya, T. Sakamoto, Org. Lett.
+
+
C H N; m/z = 255.1048 (M ). Found m/z = 255.1046 (M ).
9
13
2
006, 8, 5517;R. Rossi, A. Carpita, F. Bellina, P. Stabile, L.
Mannina, Tetrahedron 2003, 59, 2067.
ORCID
[
18] Y.-Y. Yung, W.-G. Shou, Y.-G. Wang, Tetrahedron Lett. 2007, 48, 8163.
19] J. W. Yu, S. Mao, Y.-Q. Wang, Tetrahedron Lett. 2015, 56, 1575.
20] Y. Mizukoshi, K. Mikami, M. Uchiyama, J. Am. Chem. Soc. 2015,
[
[
Kentaro Okuma
https://orcid.org/0000-0001-9722-5705
1
37, 74.
[
[
21] S. Cai, F. Wang, C. Xi, J. Org. Chem. 2012, 77, 2331.
22] D. Nandi, D. Ghosh, S. Chen, B. Kuo, N. M. Wang, H. M. Lee, J.
Org. Chem. 2013, 78, 3445.
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Chem. 2012, 77, 5736.
How to cite this article: Okuma K, Tanabe Y,
[
[
[
[
27] A. Saeed, J. Heterocyclic Chem. 2003, 40, 337.
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