Improved synthesis of coumarins by iron(III)-catalyzed cascade reaction of propiolic acids and phenols

Article abstract of DOI:10.1055/s-0030-1258473

The reaction of propiolic acids with phenols in the presence of FeClAgOTf catalyst proceeded efficiently in a mixed solvent of trifluoroacetic acid and 1,2-dichloroethane, and provided coumarins in good to high yields. This iron-catalyzed reaction offers a much-improved synthesis of coumarins. Thieme Stuttgart New York.

Full text of DOI:10.1055/s-0030-1258473

PAPER
1283
Improved Synthesis of Coumarins by Iron(III)-Catalyzed Cascade Reaction of
Propiolic Acids and Phenols
I
M
ron(III)-Catalyzed
S
y
d
nthesis of Co
.
umarins Shahajahan Kutubi, Takuya Hashimoto, Tsugio Kitamura*
Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, 1 Honjo-machi,
Saga 840-8502, Japan
Fax +81(952)288548; E-mail: kitamura@cc.saga-u.ac.jp
Received 31 January 2011; revised 19 February 2011
workers reported the hydroarylation reaction of aryl-sub-
Abstract: The reaction of propiolic acids with phenols in the pres-
stituted alkynes with simple and substituted arenes in the
ence of FeCl /AgOTf catalyst proceeded efficiently in a mixed sol-
3
presence of iron(III) chloride in nitromethane without us-
vent of trifluoroacetic acid and 1,2-dichloroethane, and provided
ing additives under mild conditions.13 Aryl-substituted
coumarins in good to high yields. This iron-catalyzed reaction of-
fers a much-improved synthesis of coumarins.
alkynes undergo hydroarylation with electron-rich arenes
to afford 1,1-diarylalkenes. To conduct more efficiently
the hydroarylation reaction of an electron-deficient pro-
piolic acid, we decided to use iron(III) chloride activated
with silver(I) triflate and found that the hydroarylation of
propiolic acid with arenes proceeded intermolecularly to
give cinnamic acids under catalytic conditions.14
Key words: iron, hydroarylation, coumarins, propiolic acids, pro-
pynoic acids, phenols
Coumarin and its derivatives occur widely in nature and
1
most of them show biological activity. To date, many re-
1
actions for coumarin synthesis have been reported, in-
(1) iron-catalyzed intermolecular hydroarylation
cluding various named reactions such as the Perkin,
Knoevenagel, and Pechmann reactions. Recently, many
methods for coumarin synthesis using transition-metal
Ar
R1
Fe cat.
R1
R2
Ar
H
+
R2
2
–11
catalysts have also been developed.
However, most
synthetic methods require halogenated substrates such as
iodophenols and iodoarenes for the construction of the
coumarin skeleton. These synthetic reactions involve
bond cleavage of the carbon–halogen bonds by transition
metals and produce waste halides. Judging from the atom-
economy of the reaction, the use of halogenated substrates
is not desirable. If the direct construction of a C–C bond
from the C–H bond of a simple arene is possible, this strat-
egy would be a straightforward and efficient process.
(
2) iron-catalyzed intramolecular hydroarylation
X
X
Fe cat.
R
R
(3) iron-catalyzed cascade reactions involving hydroarylation
OH
OH
Fe cat.
CO2H
+
CO2H
Trost and Toste have developed an atom-economic syn-
thesis of coumarins from the reaction of propiolic acids
and phenols in the presence of Pd (dba) ·CHCl or
hydroarylation
2
3
3
esterification
cyclization
7
Pd(OAc) catalyst in formic acid. We have reported the
2
hydroarylation of alkynes with the aid of palladium or
O
O
O
O
1
0
Fe cat.
platinum catalysts in trifluoroacetic acid and expanded
this to the synthesis of coumarins by the reaction of propi-
intramolecular
hydroarylation
9
a–f
olates with phenols. Shi et al. also reported the synthe-
sis of coumarins by the intramolecular reaction of aryl Scheme 1
8
propiolates with AuCl /AgOTf catalyst.
3
Iron is an abundant, inexpensive, readily available, non- The intramolecular hydroarylation of alkynes occurs ef-
toxic, and environmentally friendly transition metal, and fectively [Scheme 1, (2)].15 Very recently, Komeyama
it shows increasing and promising catalytic ability in and Takaki demonstrated that iron(III) triflate catalyzes
1
2
many organic syntheses. Until now, however, little at- the intramolecular hydroarylation of aryl-substituted
tention has been paid to iron as a catalyst for hydroaryla- alkynes.1 Inspired by these successful iron-catalyzed in-
tion reactions of alkynes. Recently, as an example of termolecular and intramolecular reactions, we decided to
intermolecular hydroarylation [Scheme 1, (1)], Lu and co- explore further successive cascade pathways to obtain
coumarin derivatives directly from phenols and propiolic
5b
acids [Scheme 1, (3)], where there are two possible
routes: hydroarylation/cyclization and esterification/
intramolecular hydroarylation. Herein, we report for the
SYNTHESIS 2011, No. 8, pp 1283–1289
x
x
.
x
x
.2
0
1
1
Advanced online publication: 10.03.2011
DOI: 10.1055/s-0030-1258473; Art ID: F16111SS
Georg Thieme Verlag Stuttgart · New York
©

1
284
Md. S. Kutubi et al.
PAPER
Table 1 Iron-Catalyzed Reaction of 2a with 1a–j (Scheme 2)a
b
c
Entry
1
Phenol 1
DCE (mL) Coumarin 3
Yield (%) Yield (%) of Pd-catalyzed reaction
OH
O
O
0.5
33
85
–
1
1
a
3a
OH
OH
O
O
O
O
2
0.5
0.5
49
b
3b
3c
O
O
3d
88
–
1
1
c
OH
4
5
1
93
62
67
–
d
3
d
OH
O
O
O
O
0.5
t-Bu
t-Bu
3e
1
e
MeO
O
O
MeO
OH
OH
6e
0.5
84
25
OMe
1
f
3
(
f + 3g
3f/3g 79:21)f
MeO
MeO
O
O
7e
8e
9e
0.5
0.5
0.5
65
60
59
42
53
–
OMe
OMe
1
g
3h
OH
O
O
O
O
O
O
1
1
h
OH
3i
HO
O
O
O
O
OH
3
j
i
OH
HO
1
0e
0.5
95
–
HO
OH
OH
1
j
3k
a
b
c
d
e
f
Reaction conditions: FeCl (0.4 mmol), AgOTf (1.2 mmol), 1 (4 mmol), 2a (2 mmol), TFA (0.5 mL), DCE, 60 °C, 15 h.
Isolated yield.
Yield from the previous Pd-catalyzed reaction, see ref. 9d.
3
1c (2 mmol) was used.
The reaction was conducted at 30 °C.
1
The product ratio was determined by H NMR. Coumarins 3f and 3g were separated by column chromatography (silica gel).
Synthesis 2011, No. 8, 1283–1289 © Thieme Stuttgart · New York

PAPER
Iron(III)-Catalyzed Synthesis of Coumarins
1285
first time the iron-catalyzed cascade reaction of propiolic nols 1b and 1d, the corresponding 4-phenylcoumarins 4a
acids with phenols directed to the synthesis of coumarins. and 4b were obtained in 80 and 90% yields, respectively
(
entries 1 and 2). For 3-methoxyphenol (1f), the reaction
As we have already identified good conditions for the
iron-catalyzed hydroarylation of propiolic acids in previ-
proceeded regioselectively to give 7-methoxy-4-phenyl-
coumarin (4c) in 75% yield (entry 3). The reaction of 2b
with 1g gave the corresponding coumarin 4d in 62% yield
1
4
ous studies, the choice of similar conditions was also de-
sirable in this study. Thus, we examined the reaction of
phenols 1 and propiolic acid (2a) in the presence of FeCl3/
AgOTf catalyst in a mixed solvent of trifluoroacetic acid
and 1,2-dichloroethane (Scheme 2); the results are given
in Table 1.
(
entry 4). Aliphatic oct-2-ynoic acid (2c) underwent the
same reaction with 1d and 1g to give the corresponding
coumarins 5a and 5b in 87 and 68% yields, respectively
(
entries 5 and 6).
The iron-catalyzed reaction using substituted propiolic
acids similarly showed improved yields of coumarins
compared with the previous palladium-catalyzed exam-
ples.
First, we investigated the reaction of phenol (1a) and pro-
piolic acid (2a). When the reaction of 1a (4 mmol) with 2a
(
2 mmol) in trifluoroacetic acid (0.5 mL) and 1,2-dichlo-
roethane (0.5 mL) was conducted in the presence of
iron(III) chloride (0.4 mmol) and silver(I) triflate (1.2
mmol) at 60 °C for 15 hours, coumarin (3a) was obtained
in 33% yield (entry 1). The reaction of 2a with 3,5-di-
methylphenol (1b) and 3,4,5-trimethylphenol (1c) pro-
ceeded efficiently to give the corresponding coumarins 3b
and 3c in 85 and 88% yields, respectively (entries 2 and
OH
FeCl3 (20 mol%)
AgOTf (60 mol%)
O
O
R1
R1
+ R2
CO2H
TFA, DCE
2b R2 = Ph
2c R2 = n-C5H11
R2
R2 = Ph
1
4
5
3
). In the reaction with 2-naphthol (1d), coumarin 3d was
2
R
= n-C5H11
obtained in 93% yield (entry 4). A bulky 4-tert-butylphe-
nol (1e) afforded the corresponding coumarin 3e in 62%
yield (entry 5). In the case of alkoxyphenols, the reaction
Scheme 3
was carried out at 30 °C because these phenols were reac- Although the mechanism for the generation of coumarins
tive and did not give good yields of the products when the by the iron catalyst is not clear at present, two pathways
reaction was performed at 60 °C. The reaction with 3- may exist from propiolic acids and phenols: (1) intermo-
methoxyphenol (1f) afforded a mixture (79:21) of regioi- lecular hydroarylation followed by cyclization, and (2) es-
somers, 7-methoxycoumarin (3f) and 5-methoxycou- terification followed by intramolecular hydroarylation
14
marin (3g), in 84% yield (entry 6). The reaction with 3,5- (Scheme 1). As we have already reported, intermolecu-
dimethoxyphenol (1g) and 3,4-(methylenedioxy)phenol lar hydroarylation of propiolic acid with arenes occurs in
(
1h) yielded the corresponding coumarins 3h and 3i in 65 the presence of iron catalysts. However, although the
and 60% yields, respectively (entries 7 and 8). Similarly, yield was low, an aryl propiolate was formed. When the
,3-dihydroxybenzene (1i) and 1,3,5-trihydroxybenzene FeCl /AgOTf-catalyzed reaction of but-2-ynoic acid (2d)
1j) efficiently reacted with 2a to give the corresponding with 3,5-dimethylphenol (1b) was conducted in trifluoro-
coumarins 3j and 3k in 59 and 95% yields, respectively acetic acid and 1,2-dichloroethane at 60 °C for six hours,
1
3
(
(
entries 9 and 10).
3,5-dimethylphenyl but-2-ynoate (6) was obtained in 19%
yield, together with 4,5,7-trimethylcoumarin (7) in 22%
yield (Scheme 4). Although this result suggested the es-
terification/intramolecular hydroarylation process, it was
found that the esterification did not proceed efficiently un-
der these conditions because the reaction of propanoic
acid with 1b gave the corresponding 3,5-dimethylphenyl
OH
FeCl3 (20 mol%)
AgOTf (60 mol%)
O
O
+
CO2H
R
R
TFA, DCE
2a
1
3
propanoate only in 22% yield (FeCl /AgOTf, 60 °C, 15 h).
3
Scheme 2
In the FeCl /AgOTf-catalyzed reaction of propiolic acids
3
and phenols, therefore, we propose that the intermolecular
To understand the efficiency of iron-catalyzed coumarin hydroarylation/cyclization process occurs along with the
synthesis, we compared these results with those from the esterification/intramolecular hydroarylation process.
previous palladium-catalyzed reaction of 2a with 1 in tri-
In summary, we have demonstrated that iron-catalyzed
9
d
fluoroacetic acid. It is clearly understood that the present
iron-catalyzed reaction gives better yields of coumarins 2
than that catalyzed by palladium.
hydroarylation can be applied to the direct synthesis of
coumarin derivatives from phenols and propiolic acids.
The reaction of propiolic acids with phenols in the pres-
We next examined the reaction of substituted propiolic ence of FeCl /AgOTf catalyst proceeds efficiently in a
3
acids with phenols. Under the conditions described above, mixed solvent of trifluoroacetic acid and 1,2-dichloro-
phenylpropiolic acid (2b) and oct-2-ynoic acid (2c) were ethane and provides coumarins in good to high yields. The
subjected to reaction with phenols 1 in the presence of present iron-catalyzed coumarin synthesis is expected to
iron(III) chloride and silver(I) triflate (Scheme 3); the re- have a high degree of utility for a variety of coumarin de-
sults are given in Table 2. In the reaction of 2b with phe-
Synthesis 2011, No. 8, 1283–1289 © Thieme Stuttgart · New York

1
286
Md. S. Kutubi et al.
PAPER
Table 2 Iron-Catalyzed Reaction of 2b,c with 1b,d,f,g (Scheme 3)a
c
Entry
1
1
2
DCE (mL) Coumarin 3
Yield (%)b Yield (%) of Pd-catalyzed reaction
O
O
O
1b
2b
0.5
80
90
–
Ph
O
4
4
a
2
1d
2b
1
69
Ph
b
MeO
O
O
O
3
4
1f
2b
2b
0.5
0.5
75
62
65
44
Ph
O
4
c
MeO
1g
OMe Ph
4
d
O
O
5
1d
1g
2c
2c
1
87
68
–
n-C5H11
O
5
MeO
a
O
6
0.5
57
OMe n-C5H11
5
b
a
Reaction conditions: FeCl (0.4 mmol), AgOTf (1.2 mmol), 1 (4 mmol), 2 (2 mmol), TFA (0.5 mL), DCE, 60 °C, 15 h.
Isolated yield.
Yield from the previous Pd-catalyzed reaction, see ref. 9d.
3
b
c
OH
with a Yanaco micro melting point apparatus and are uncorrected.
Column chromatographic separation was carried out using Silica
Gel 60, spherical (Kanto Chemical Co.).
FeCl3 (20 mol%)
AgOTf (60 mol%)
+
CO2H
TFA, DCE
60 °C, 6 h
Coumarins by FeCl /AgOTf-Catalyzed Reaction of Propiolic
2d
3
1b
Acids with Phenols; General Procedure
O
O
O
O
A mixture of FeCl (0.4 mmol) and AgOTf (1.2 mmol) in TFA (0.5
3
mL) and DCE (0.5–1 mL) was stirred at r.t. for 10 min and then phe-
nol 1 (4 mmol) and propiolic acid 2 (2 mmol) were added and the
mixture was stirred at 60 °C or 30 °C for 15 h. The mixture was
poured into H O (20 mL), neutralized with NaHCO , and extracted
+
6
7
2
3
with CH Cl (3 × 20 mL). The organic layer was washed with 2 M
19%
22%
2
2
NaOH (10 mL), dried (anhyd Na SO ), and concentrated under re-
2
4
Scheme 4
duced pressure. The residue was purified by column chromatogra-
phy (silica gel, EtOAc–hexane) to give coumarins 3, 4a–d, or 5a,b
as solids, which were recrystallized from the solvents indicated.
rivatives because it is a highly efficient and economical
process.
Coumarin (3a)9e,16,17
Mp 66–67 °C (hexane).
1
All solvents and starting materials were commercially available and
H NMR (300 MHz, CDCl ): d = 6.43 (d, J = 9.6 Hz, 1 H, vinyl),
3
1
13
used as received without further purification. H and C NMR
spectra were recorded on a Jeol JNM-AL 300 FT-NMR spectrome-
ter (TMS as an internal standard). Melting points were measured
7.28–7.36 (m, 2 H, aryl), 7.47–7.57 (m, 2 H, aryl), 7.71 (d, J = 9.6
Hz, 1 H, vinyl).
Synthesis 2011, No. 8, 1283–1289 © Thieme Stuttgart · New York

PAPER
Iron(III)-Catalyzed Synthesis of Coumarins
1287
1
3
13
C NMR (75 MHz, CDCl ): d = 116.67, 116.85, 118.81, 124.38,
C NMR (75 MHz, CDCl ): d = 55.74, 55.89, 92.79, 94.75, 103.95,
3
3
1
27.83, 131.78, 143.38, 154.04, 160.71.
110.87, 138.66, 156.76, 156.94, 161.43, 163.67.
5
,7-Dimethylcoumarin (3b)9e,d,18,19
6,7-(Methylenedioxy)coumarin (3i)7b,9d,e
Mp 133–135 °C (CH Cl –hexane).
Mp 224–226 °C (CH Cl –hexane).
2
2
2
2
1
1
H NMR (300 MHz, CDCl ): d = 2.40 (s, 3 H, CH ), 2.48 (s, 3 H,
3
H NMR (300 MHz, acetone-d ): d = 6.16 (s, 2 H, OCH O), 6.24 (d,
6 2
3
3
CH ), 6.35 (d, J = 9.6 Hz, 1 H, vinyl), 6.92 (s, 1 H, aryl), 6.98 (s, 1
J = 9.6 Hz, 1 H, vinyl), 6.89 (s, 1 H, aryl), 7.10 (s, 1 H, aryl), 7.85
H, aryl), 7.87 (d, J = 9.6 Hz, 1 H, vinyl).
(d, J = 9.6 Hz, 1 H, vinyl).
1
3
13
C NMR (75 MHz, CDCl ): d = 18.06, 21.56, 114.57, 114.91,
C NMR (75 MHz, acetone-d ): d = 98.59, 103.52, 106.18, 113.66,
3
6
1
15.22, 126.90, 135.61, 140.30, 142.65, 154.64, 161.03.
113.83, 144.66, 145.77, 152.18, 152.22, 160.97.
5
,6,7-Trimethylcoumarin (3c)20
7-Hydroxycoumarin (3j)21
Mp 226.5–228 °C (EtOAc–hexane).
Mp 159–160 °C (CH Cl –hexane).
2
2
1
1
H NMR (300 MHz, CDCl ): d = 2.22 (s, 3 H, CH ), 2.36 (s, 3 H,
H NMR (300 MHz, acetone-d ): d = 6.16 (d, J = 9.5 Hz, 1 H, vi-
3
3
6
CH ), 2.41 (s, 3 H, CH ), 6.32 (d, J = 9.9 Hz, 1 H, vinyl), 6.97 (s, 1
nyl), 6.75 (d, J = 2.4 Hz, 1 H, aryl), 6.84 (dd, J = 2.4, 8.4 Hz, 1 H,
3
3
H, aryl), 7.95 (d, J = 9.9 Hz, 1 H, vinyl).
aryl), 7.51 (d, J = 8.4 Hz, 1 H, aryl), 7.85 (d, J = 9.5 Hz, 1 H, vinyl).
1
3
13
C NMR (75 MHz, CDCl ): d = 14.80, 15.42, 114.47, 115.31,
C NMR (75 MHz, acetone-d ): d = 103.28, 112.81, 112.89,
3
6
1
15.54, 131.45, 133.44, 140.92, 141.64, 152.42, 161.10.
113.75, 130.41, 144.68, 156.98, 161.05, 162.04.
3
H-Naphtho[2,1-b]pyran-3-one (3d)7b,9d,e,16
5,7-Dihydroxycoumarin (3k)22
Mp 275–278 °C (EtOAc–hexane).
Mp 117–118 °C (EtOAc–hexane).
1
1
H NMR (300 MHz, CDCl ): d = 6.59 (d, J = 9.6 Hz, 1 H, vinyl),
H NMR (300 MHz, acetone-d ): d = 6.04 (d, J = 9.6 Hz, 1 H, vi-
3
6
7
7
8
(
1
.47 (d, J = 9.0 Hz, 1 H, aryl), 7.58 (dd, J = 6.9, 8.1 Hz, 1 H, vinyl),
.70 (dd, J = 6.9, 8.4 Hz, 1 H, aryl), 7.92 (d, J = 8.1 Hz, 1 H, aryl),
.00 (d, J = 9.0 Hz, 1 H, aryl), 8.24 (d, J = 8.4 Hz, 1 H, aryl), 8.50
nyl), 6.28 (d, J = 2.0 Hz, 1 H, aryl), 6.36 (d, J = 2.0 Hz, 1 H, aryl),
8.01 (d, J = 9.6 Hz, 1 H, vinyl).
13
C NMR (75 MHz, acetone-d ): d = 95.46, 99.10, 103.12, 110.30,
6
d, J = 9.6 Hz, 1 H, vinyl).
1
39.73, 156.64, 157.92, 161.44, 162.80.
3
C NMR (75 MHz, CDCl ): d = 112.79, 115.44, 116.86, 121.20,
3
1
1
25.94, 128.16, 128.83, 128.87, 130.10, 132.95, 138.91, 153.67,
60.74.
5,7-Dimethyl-4-phenylcoumarin (4a)9a,c,e
Mp 94–95 °C (hexane).
1
H NMR (300 MHz, CDCl ): d = 1.79 (s, 3 H, CH ), 2.39 (s, 3 H,
3
.26–7.29 (m, 2 H, aryl), 7.43–7.45 (m, 3 H, aryl).
-tert-Butylcoumarin (3e)1b
3
3
6
CH ), 6.18 (s, 1 H, vinyl), 6.83 (s, 1 H, aryl), 7.08 (s, 1 H, aryl),
7
Mp 66–67 °C (CH Cl –hexane).
2
2
1
H NMR (300 MHz, CDCl ): d = 1.36 (s, 9 H, CH ), 6.41 (d, J = 9.6
13
3
3
C NMR (75 MHz, CDCl ): d = 21.26, 23.27, 115.45, 115.77,
3
Hz, 1 H, vinyl), 7.27 (d, J = 8.9 Hz, 1 H, aryl), 7.46 (d, J = 2.3 Hz,
1
1
16.08, 127.31, 128.51, 128.67, 129.46, 137.02, 139.55, 142.32,
55.15, 156.74, 160.49.
1
1
H, aryl), 7.58 (dd, J = 2.3, 8.9 Hz, 1 H, aryl), 7.72 (d, J = 9.6 Hz,
H, vinyl).
1
3
1-Phenyl-3H-naphtho[2,1-b]pyran-3-one (4b)9c–e
C NMR (75 MHz, CDCl ): d = 31.24, 34.43, 116.26, 116.31,
3
1
18.16, 124.08, 129.43, 143.89, 147.48, 151.93, 161.12.
Mp 160–161 °C (CH Cl –hexane).
2
2
1
H NMR (300 MHz, CDCl ): d = 6.39 (s, 1 H, vinyl), 7.15 (dd,
-Methoxycoumarin (3f)7b,9c–e
3
7
J = 6.6, 8.7 Hz, 1 H, aryl), 7.26 (d, J = 8.4 Hz, 1 H, aryl), 7.35–7.43
m, 3 H, aryl), 7.47–7.55 (m, 4 H, aryl), 7.85 (d, J = 8.1 Hz, 1 H, ar-
Mp 117–119 °C (CH Cl –hexane).
2
2
(
1
H NMR (300 MHz, CDCl ): d = 3.38 (s, 3 H, OCH ), 6.25 (d,
yl), 8.01 (d, J = 9.0 Hz, 1 H, aryl).
13
3
3
J = 9.6 Hz, 1 H, vinyl), 6.82–6.86 (m, 2 H, aryl), 7.37 (d, J = 8.1 Hz,
C NMR (75 MHz, CDCl ): d = 112.93, 116.71, 117.38, 125.31,
3
1
1
H, aryl), 7.63 (d, J = 9.6 Hz, 1 H, vinyl).
1
25.82, 126.65, 127.37, 128.93, 129.07, 129.15, 129.24, 131.21,
3
C NMR (75 MHz, CDCl ): d = 55.75, 100.86, 112.54, 112.57,
133.88, 139.47, 154.67, 156.39, 160.26.
3
1
13.14, 128.72, 143.35, 155.93, 161.14, 162.85.
7
-Methoxy-4-phenylcoumarin (4c)9c–e
5
-Methoxycoumarin (3g)7b,9d,e
Mp 111–112 °C (CH Cl –hexane).
2 2
Mp 81–82 °C (CH Cl –hexane).
1
2
2
H NMR (300 MHz, CDCl ): d = 3.88 (s, 3 H, OCH ), 6.21 (s, 1 H,
3
3
1
H NMR (300 MHz, CDCl ): d = 3.93 (s, 3 H, OCH ), 6.33 (d,
vinyl), 6.79 (dd, J = 2.4, 9.0 Hz, 1 H, aryl), 6.88 (d, J = 2.4 Hz, 1 H,
aryl), 7.38 (d, J = 9.0 Hz, 1 H, aryl), 7.41–7.45 (m, 2 H, aryl), 7.49–
7.52 (m, 3 H, aryl).
13
3
3
J = 9.6 Hz, 1 H, vinyl), 6.71 (d, J = 8.4 Hz, 1 H, aryl), 6.91 (d,
J = 8.4 Hz, 1 H, aryl), 7.44 (t, J = 8.4 Hz, 1 H, aryl), 8.10 (d, J = 9.6
Hz, 1 H, vinyl).
C NMR (75 MHz, CDCl ): d = 55.72, 101.02, 111.77, 112.22,
3
1
3
C NMR (75 MHz, CDCl ): d = 55.98, 105.12, 109.19, 109.62,
112.42, 127.91, 128.30, 128.75, 129.52, 135.49, 155.73, 155.94,
161.11, 162.72.
3
1
14.52, 132.31, 138.52, 155.11, 156.15, 160.96.
5
,7-Dimethoxycoumarin (3h)9c–e
5,7-Dimethoxy-4-phenylcoumarin (4d)7b,9c–e
Mp 146–148 °C (CH Cl –hexane).
Mp 169–171 °C (CH Cl –hexane).
2
2
2
2
1
1
H NMR (300 MHz, CDCl ): d = 3.85 (s, 3 H, OCH ), 3.89 (s, 3 H,
H NMR (300 MHz, CDCl ): d = 3.42 (s, 3 H, OCH ), 3.87 (s, 3 H,
3 3
3
3
OCH ), 6.15 (d, J = 9.6 Hz, 1 H, vinyl), 6.28 (d, J = 2.3 Hz, 1 H, ar-
OCH ), 6.00 (s, 1 H, vinyl), 6.23 (d, J = 2.4 Hz, 1 H, aryl), 6.53 (d,
3
3
yl), 6.41 (d, J = 2.3 Hz, 1 H, aryl), 7.96 (d, J = 9.6 Hz, 1 H, vinyl).
J = 2.4 Hz, 1 H, aryl), 7.24–7.27 (m, 2 H, aryl), 7.36–7.38 (m, 3 H,
aryl).
Synthesis 2011, No. 8, 1283–1289 © Thieme Stuttgart · New York

1
288
Md. S. Kutubi et al.
PAPER
Katritzky, A. R.; Rees, C. W.; Scriven, E. F. V., Eds.;
Pergamon Press: Oxford, 1996, Chap. 5.08, 351.
(d) Staunton, J. In Comprehensive Organic Chemistry, Vol.
1
3
C NMR (75 MHz, CDCl ): d = 55.33, 55.70, 93.52, 95.68, 103.46,
3
1
1
12.58, 127.04, 127.28, 127.83, 139.69, 155.62, 157.09, 158.16,
60.78, 163.31.
4
; Barton, D. H. R.; Ollis, W. D., Eds.; Pergamon Press:
1
-Pentyl-3H-naphtho[2,1-b]pyran-3-one (5a)9e
Oxford, 1979, Part 18.2, 629.
Mp 99–100 °C (CH Cl –hexane).
(2) Pd: (a) An, Z.; Catellani, M.; Chuisoli, G. P. J. Organomet.
Chem. 1989, 371, C51. (b) Deshpande, P. P.; Martin, O. R.
Tetrahedron Lett. 1990, 31, 6313. (c) Catellani, M.;
Chuisoli, G. P.; Fagnola, M. C.; Solari, G. Tetrahedron Lett.
2
2
1
H NMR (300 MHz, CDCl ): d = 0.94 (t, J = 7.2 Hz, 3 H, CH ),
3
3
1
.37–1.56 (m, 4 H, CH ), 1.77–1.87 (m, 2 H, CH ), 3.23 (t, J = 7.7
2
2
Hz, 2 H, CH ), 6.41 (s, 1 H, vinyl), 7.47 (d, J = 9.0 Hz, 1 H, aryl),
2
1
994, 35, 5919. (d) Catellani, M.; Chuisoli, G. P.; Fagnola,
M. C.; Solari, G. Tetrahedron Lett. 1994, 35, 5923.
e) Cacchi, S. Pure Appl. Chem. 1996, 68, 45. (f) Catellani,
7
1
2
.55 (dd, J = 6.9, 8.1 Hz, 1 H, aryl), 7.65 (ddd, J = 1.5, 6.9, 8.7 Hz,
H, aryl), 7.92 (dd, J = 1.5, 8.1 Hz, 1 H, aryl), 7.97 (d, J = 9.0 Hz,
H, aryl), 8.47 (d, J = 8.7 Hz, 1 H, aryl).
(
M.; Chuisoli, G. P.; Marzolini, G.; Rossi, E. J. Organomet.
Chem. 1996, 525, 65. (g) Arcadi, A.; Cacchi, S.; Fabrizi, G.;
Marinelli, F.; Pace, P. Synlett 1996, 568. (h) Cacchi, S.;
Fabrizi, G.; Moro, L.; Pace, P. Synlett 1997, 1367.
1
3
C NMR (75 MHz, CDCl ): d = 13.90, 22.33, 28.33, 31.51,.37.47,
13.91, 115.19, 117.90, 124.89, 125.26, 127.76, 129.64, 129.66,
31.30, 133.49, 154.78, 158.17, 160.51.
3
1
1
(
(
i) Kadnikov, D. V.; Larock, R. C. Org. Lett. 2000, 2, 3643.
j) Hesse, S.; Kirsch, G. Tetrahedron Lett. 2002, 43, 1213.
5
,7-Dimethoxy-4-pentylcoumarin (5b)9c–e
Mp 102–103 °C (CH Cl –hexane).
2
2
(k) Kadnikov, D. V.; Larock, R. C. J. Org. Chem. 2003, 68,
9423. (l) Kadnikov, D. V.; Larock, R. C. J. Organomet.
Chem. 2003, 687, 425. (m) Palencia, H.; Garcia-Jimenez,
F.; Takacs, J. M. Tetrahedron Lett. 2004, 45, 3849.
1
H NMR (300 MHz, CDCl ): d = 0.92 (t, J = 7.1 Hz, 3 H, CH ),
3
3
1
.34–1.42 (m, 4 H, CH ), 1.53–1.62 (m, 2 H, CH ), 2.87 (t, J = 7.6
2
2
Hz, 2 H, CH ), 3.85 (s, 3 H, OCH ), 3.87 (s, 3 H, OCH ), 5.97 (s, 1
H, vinyl), 6.31 (d, J = 2.4 Hz, 1 H, aryl), 6.46 (d, J = 2.4 Hz, 1 H,
aryl).
2
3
3
(
n) Battistuzzi, G.; Cacchi, S.; Salve, I. D.; Fabrizi, G.;
Parisi, L. M. Adv. Synth. Catal. 2005, 347, 308. (o) Aoki,
S.; Oyamada, J.; Kitamura, T. Bull. Chem. Soc. Jpn. 2005,
7
1
3
C NMR (75 MHz, CDCl ): d = 13.96, 22.42, 29.29, 31.78, 36.44,
3
8, 468.
5
1
5.61, 55.70, 93.57, 95.47, 104.21, 110.55, 157.27, 158.46, 158.59,
61.18, 162.56.
(
(
3) Ru: Chatterjee, A. K.; Toste, F. D.; Goldberg, S. D.; Grubbs,
R. H. Pure Appl. Chem. 2003, 75, 421.
4) Rh: (a) Yoneda, E.; Sugioka, T.; Hirao, K.; Zhang, S.-W.;
Takahashi, S. J. Chem. Soc., Perkin Trans. 1 1998, 477.
3
,5-Dimethylphenyl But-2-ynoate (6) and 4,5,7-Trimethylcou-
marin (7) by FeCl /AgOTf-Catalyzed Reaction of But-2-ynoic
3
(
b) Tollari, S.; Palmisano, G.; Cenini, S.; Cravotto, G.;
Acid (2d) with 3,5-Dimethylphenol (1b)
To a stirred mixture of FeCl (0.4 mmol) and AgOTf (1.2 mmol) in
TFA (0.5 mL) and DCE (0.5–1 mL) were added 1b (4 mmol) and
Giovenzana, G. B.; Penoni, A. Synthesis 2001, 735.
3
(
(
(
5) Rh and Co: Park, K. H.; Jung, I. G.; Chung, Y. K. Synlett
2
004, 2541.
6) Ni: Rayabarapu, D. K.; Shukla, P.; Cheng, C.-H. Org. Lett.
003, 5, 4903.
7) (a) Trost, B. M.; Toste, F. D. J. Am. Chem. Soc. 1996, 118,
305. (b) Trost, B. M.; Toste, F. D.; Greenman, K. J. Am.
2
d (2 mmol), and then the mixture was stirred at 60 °C for 6 h. The
mixture was poured into H O (20 mL), neutralized with NaHCO ,
2
3
2
and extracted with CH Cl (3 × 20 mL). The combined organic lay-
ers were washed with 2 M NaOH (10 mL), dried (anhyd Na SO ),
and concentrated under reduced pressure. The residue was purified
by column chromatography (silica gel, EtOAc–hexane) to give 6
2
2
2
4
6
Chem. Soc. 2003, 125, 4518.
(
(
8) Shi, Z.; He, C. J. Org. Chem. 2004, 69, 3669.
9) (a) Jia, C.; Piao, D.; Kitamura, T.; Fujiwara, Y. J. Org.
Chem. 2000, 65, 7516. (b) Oyamada, J.; Jia, C.; Fujiwara,
Y.; Kitamura, T. Chem. Lett. 2002, 380. (c) Kitamura, T.;
Yamamoto, K.; Kotani, M.; Oyamada, J.; Fujiwara, Y. Bull.
Chem. Soc. Jpn. 2003, 76, 1889. (d) Kotani, M.;
Yamamoto, K.; Oyamada, J.; Fujiwara, Y.; Kitamura, T.
Synthesis 2004, 1466. (e) Oyamada, J.; Kitamura, T.
Tetrahedron 2006, 62, 6918. (f) Kitamura, T.; Oyamada, J.;
Tsubota, T. Nature Protocols 2007, 2, 845. (g)Li, K.;Zeng,
Y.; Neuenswander, B.; Tunge, J. A. J. Org. Chem. 2005, 70,
6515.
(19%) and 7 (22%).
3
,5-Dimethylphenyl But-2-ynoate (6)23
1
H NMR (300 MHz, CDCl ): d = 2.06 (s, 3 H, CH ), 2.31 (s, 6 H,
CH ), 6.73 (s, 2 H, aryl), 6.87 (s, 1 H, aryl).
3
3
3
1
3
C NMR (75 MHz, CDCl ): d = 3.93, 21.20, 72.22, 87.67, 118.93,
3
1
28.00, 139.41, 149.96, 152.17.
4
,5,7-Trimethylcoumarin (7)23
Mp 170–172 °C (CH Cl –hexane).
2
2
1
H NMR (300 MHz, CDCl ): d = 2.37 (s, 3 H, CH ), 2.60 (d, J = 0.9
3
3
(
10) (a) Jia, C.; Piao, D.; Oyamada, J.; Lu, W.; Kitamura, T.;
Fujiwara, Y. Science 2000, 287, 1992. (b) Jia, C.; Lu, W.;
Oyamada, J.; Kitamura, T.; Matsuda, M.; Irie, M.; Fujiwara,
Y. J. Am. Chem. Soc. 2000, 122, 7252. (c) Jia, C.;
Hz, 3 H, CH ), 2.68 (s, 3 H, CH ), 6.16 (s, 1 H, vinyl), 6.88 (s, 1 H,
3
3
aryl), 7.01 (s, 1 H, aryl).
1
3
C NMR (75 MHz, CDCl ): d = 21.18, 24.31, 25.15, 115.46,
3
1
16.18, 116.79, 129.59, 136.39, 141.85, 154.27, 155.17, 160.76.
Kitamura, T.; Fujiwara, Y. Acc. Chem. Res. 2001, 34, 633.
(d) Oyamada, J.; Kitamura, T. Tetrahedron Lett. 2005, 46,
3
1
1
823. (e) Oyamada, J.; Kitamura, T. Chem. Lett. 2005, 34,
430. (f) Oyamada, J.; Kitamura, T. Tetrahedron 2007, 63,
2754. (g) Oyamada, J.; Hashimoto, T.; Kitamura, T.
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Synthesis 2011, No. 8, 1283–1289 © Thieme Stuttgart · New York

PAPER
Iron(III)-Catalyzed Synthesis of Coumarins
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Synthesis 2011, No. 8, 1283–1289 © Thieme Stuttgart · New York