Hydroarylation of acetylenes, acrylates, and isocyanates with heteroaromatic compounds under rhenium catalysis

Article abstract of DOI:10.1016/j.tet.2008.01.145

With the aid of a directing group, an imine moiety, heteroaromatic compounds add to acetylenes in the presence of a catalytic amount of [ReBr(CO)₃(THF)]₂ at the adjacent position of the directing group regioselectively to give hydroa

Full text of DOI:10.1016/j.tet.2008.01.145

Tetrahedron 64 (2008) 5974–5981
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Hydroarylation of acetylenes, acrylates, and isocyanates
with heteroaromatic compounds under rhenium catalysis
*
*
Yoichiro Kuninobu , Kou Kikuchi, Yukimi Tokunaga, Yuta Nishina, Kazuhiko Takai
Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University, Tsushima, Okayama 700-8530, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
With the aid of a directing group, an imine moiety, heteroaromatic compounds add to acetylenes in the
presence of a catalytic amount of [ReBr(CO)3(THF)]2 at the adjacent position of the directing group
regioselectively to give hydroarylation of the acetylenes in good to excellent yields. Similarly, hetero-
aromatic compounds react with acrylates and isocyanates to give the corresponding hydroarylation
products under rhenium catalysis.
Received 1 September 2007
Received in revised form 9 January 2008
Accepted 11 January 2008
Available online 12 March 2008
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
2. Results and discussion
Heteroaromatic compounds are important because many func-
tional materials and bioactive compounds contain heteroaromatic
skeletons as core structures.1 Various methods for functionalization
of heteroaromatic compounds have been developed, with electro-
philic, nucleophilic, and radical attack of substrates to hetero-
aromatic compounds being well known examples.2 In addition,
transition metal-catalyzed hydroarylation has a great potential to
obtain functionalized heteroaromatic compounds efficiently and
thus several trials have been investigated.3 For example, palladium-
catalyzed arylation of acrylates with furans4 and cationic zirco-
nium-catalyzed arylation of propene using a-picoline have been
reported.5 Recently, by using a directing group on heteroaromatic
rings, the functionalization can be achieved in high yields and
selectivities under ruthenium or rhodium catalysis: hydroarylation
of olefins,6 acetylenes,7 and isocyanates8 with heteroaromatic
compounds. We have also reported on rhenium-catalyzed hydro-
arylation of isocyanates by reactions with heteroaromatic
compounds.9 Intramolecular arylation of an olefin moiety with
heteroaromatic compounds has also been reported.10 Since the
direct hydroarylation of unsaturated molecules is atom economic
and the starting materials are available easily, this method is an
efficient and powerful tool to functionalize heteroaromatic com-
pounds. We report herein the hydroarylation of acetylenes,
acrylates, and isocyanates by treatment with heteroaromatic
compounds using a rhenium complex as a catalyst.11
2.1. Hydroarylation of acetylenes
Treatment of a furan derivative bearing an imino group at the
3-position, 1a, with diphenyl acetylene (2a) gave an alkenylated
furan. During column chromatography, hydrolysis resulted in the
formation of the corresponding furyl aldehyde 4a in 89% yield
(Table 1, entry 1).12–14 The reaction did not proceed in the presence
of catalysts such as Re2(CO)10, MnBr(CO)5, Mn2(CO)10, RhCl(PPh3)3,
Ir4(CO)12, SnCl4, and ZnCl2. Only a trace amount of 4a was formed
with
a catalytic amount of Ru3(CO)12 and RuH2(CO)(PPh3)3.
Acetylenes possessing alkyl groups, 2b and 2c, also provided the
corresponding alkenyl furans 4b and 4c in good yields and selec-
tivities (Table 1, entries 2 and 3). The mixture of alkenyl furans 4d
and 3a was produced by the reaction of imino furan 1a with acet-
ylene having an ester group, 2d (Table 1, entry 4). Although the
yield of 3a was low, the alkenylation reaction occurred not only at
the 2-position but also at the 4-position of the furan ring.15,16 Ter-
minal acetylenes such as ethynylbenzene and 1-dodecyne did not
react with 1a under the same conditions.
The hydroarylation reaction also proceeded with an imino
indole. For example, treatment of 3-imino indole 5a with acetylene
2a in the presence of a catalytic amount of [ReBr(CO)3(THF)]2 gave
2-alkenylated indole 6a in 72% yield regioselectively. In the case of
2-imino indole 5b, the reaction proceeded to give 3-alkenylated
product 6b in 26% yield (Scheme 1).
The proposed mechanism is described as follows (Scheme 2):17
(1) oxidative addition of a C–H bond of an aldimine to a rhenium
center (C–H bond activation); (2) insertion of an acetylene into
* Corresponding authors. Tel.: þ81 86 251 8095; fax: þ81 86 251 8094.
E-mail addresses: kuninobu@cc.okayama-u.ac.jp (Y. Kuninobu), ktakai@cc.
okayama-u.ac.jp (K. Takai).
a
rhenium–carbon bond;18 (3) reductive elimination, which
regenerates the rhenium catalyst.
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.01.145

Y. Kuninobu et al. / Tetrahedron 64 (2008) 5974–5981
5975
Table 1
H
H
t
Reactions between aldimine 1a and acetylenes 2a
Bu
t
Bu
N
N
H
H
N t
Bu
N t
Bu
X = O, NMe
R'
X
R
X
[ReBr(CO)3(thf)]2 (2.5 mol%)
+
R
R'
ReI
CH2ClCH2Cl, 115 °C, 24 h
R'
O
O
O
1a
2
3
R
R
H
N t
H
Bu
H
t
Bu
ReIII
H
O
N
H3O+
ReIII
X
R'
X
H
R'
R
4
R
R'
Entry
Acetylene
Product
Yield/%b
Scheme 2.
H
O
Ph
Ph
1c
89 [89:11]
73 [>99:<1]
80 [95:5]
2a
t
Bu
Ph
Ph
O
O
H
N
N t
4a
Bu
+
Ph
[ReBr(CO)3(thf)]2 (2.5 mol%)
24 h
H
+
H
Ph
Ph
O
O
1a
(1.0 equiv)
7
2a
Ph
Me
(1.0 equiv)
(1.0 equiv)
H
t
2b
t
2
3
4
Bu
Bu
HN
N
4b
Me
O
+
Ph
Ph
H
O
Ph
Ph
n
n
C5H11
C5H11
Temp
8
2c
Solvent
3a
n
C5H11
C5H11
O
n
4c
CH2ClCH2Cl
toluene
100 °C
115 °C
78%
74%
0%
4%
H
O
Me
CO2Me
Scheme 3.
2d
66 [>99:<1]
9 [>99:<1]
CO2Me
4d
O
Me
H
The reaction between furan having an imino group at the 2-posi-
tion, 1b, and acetylene 2a did not proceed at all. 3-Imino furan with
a substituent at the 2-position, 1c, and with substituents at the 2-
and 5-position, 1d, did not give the alkenylated products 3g and 3h.
(Scheme 4).
From the results of these experiments, the order of reactivities
for hydroarylation is as follows: the 3-position of the furyl group
ꢀphenyl group<the 2-position of the furyl group (Fig. 1).
When the 2-position was blocked with a methyl group, the
4-position of an imino thiophene could be functionalized.17 For
example, the hydroarylation of 2a with thiophene 9a at the
4-position was accomplished in the presence of a catalytic amount
of [ReBr(CO)3(THF)]2 (Scheme 5). Other thiophenes, such as
2-imino, 3-imino, and 2-methyl-3-imino thiophenes or imino
pyrroles, gave complex mixtures.
MeO2C
Me
t
Bu
N
CO2Me
O
3a
Me
a
Compounds 1a (1.0 equiv) and 2 (1.0 equiv).
b
The ratios of E and Z isomers are given in square brackets. However, the ste-
reochemistry could not be determined.
c
Temperature: 100 ꢁC.
To compare the reactivities of heteroaromatic and aromatic
compounds, the reaction of imino furan 1a and aromatic imino
benzene 7 with 2a was conducted in 1,2-dichloroethane or toluene
(Scheme 3). As a result, alkenyl furan 3a was obtained selectively
under both reaction conditions.
H
O
H
N t
Bu
[ReBr(CO)3(thf)]2
H3O+
(2.5 mol%)
+
Ph
Ph
CH2ClCH2Cl
135 °C, 24 h
Ph
N
Me
N
2a
Ph
Me
5a
6a 72%
Ph
[ReBr(CO)3(thf)]2
(2.5 mol%)
Ph
H3O+
N
+
Ph
Ph
t
Bu
N
Me
CH2ClCH2Cl
135 °C, 24 h
O
2a
N
Me
H
H
5b
6b 26%
Scheme 1.

5976
Y. Kuninobu et al. / Tetrahedron 64 (2008) 5974–5981
2.2. Hydroarylation of acrylates
H
H
H
H
N t
Bu
N t
Bu
H
H
N t
Bu
Ethyl acrylate (11a) also reacted with a heteroaromatic aldimine
9c by a catalytic amount of [ReBr(CO)3(THF)]2 to give the corre-
sponding adduct. After hydrolysis, 12a was obtained in 15% yield
(Scheme 6). In this case, the yield was improved with an Re2(CO)10
catalyst. In contrast to the reaction with 9c, reactions with imino
furans 1a and 1d or imino indoles 5a and 5b provided complex
mixtures.
<<
<
N
and
t
H
O
O
O
Bu
H
Figure 1. Order of the reactivities between furyl and phenyl groups.
Treatment of 2-imino thiophene 9d with 11a in the presence of
a catalytic amount of Re2(CO)10 gave the expected adduct 12b in
25% yield (Table 2, entry 1). In the case of substituted imino
thiophene 9b, which was protected by methyl groups at both 2- and
6-position, the reaction proceeded almost quantitatively to give 12c
and 13 in 48% and 50% yields, respectively (Table 2, entry 2). The
formation of 13 indicates that the intramolecular nucleophilic
attack occurred prior to the reductive elimination leading to
b-lactum. Imino pyrrole 14 reacted with 12a but resulted in a low
yield (Table 2, entry 3).
t
Ph
Bu
H
N
[ReBr(CO)3(thf)]2
(2.5 mol%)
CH2ClCH2Cl
135 °C, 24 h
Ph
O
H
H3O+
Ph
Ph
+
2a
R
S
10
S
9
R = H
CH3
10a 19%
R = H
CH3
9a
9b
10b
51%
Scheme 5.
Other a,b-unsaturated carbonyl compounds, such as vinyl
ketone 11b, reacted with 9c to give the corresponding alkylated
products 12e (Scheme 7). However, acrylamide and styrene gave
complex mixtures.
H
H
N t
Bu
2.3. Hydroarylation of isocyanates
O
H3O+
catalyst (3.0 mol%)
+
CO2Et
CO2Et
toluene, 150 °C, 24 h
Compared with the functionalization of heteroaromatic
compounds with non-polar unsaturated molecules, such as olefins
and acetylenes, the use of polar unsaturated molecules is still rare.
We have recently succeeded in the insertion of polar unsaturated
molecules using a rhenium catalyst.11b,d By using the rhenium
catalyst, [ReBr(CO)3(THF)]2, hydroarylation of isocyanates with
heteroaromatic compounds also occurred.
S
S
11a
(1.5 equiv)
9c
(1.0 equiv)
12a
12a
catalyst
[ReBr(CO)3(thf)]2 15%
Re2(CO)10
31%
Scheme 6.
Treatment of a thiophene bearing an aldimine moiety, 9c, with
phenyl isocyanate (15a) in the presence of a catalytic amount of
[ReBr(CO)3(THF)]2 in 1,2-dichloroethane at 90 ꢁC for 24 h promoted
the hydroarylation of 15a selectively at the 2-position of the thio-
phene ring. After hydrolysis, amide thiophene 16a was obtained in
92% yield (Table 3, entry 1).10,11 The 3-position of thiophene ring
could also be functionalized using 2-imino thiophene 9d and the
corresponding amidated product 16b was formed in 77% yield
(Table 3, entry 2). When 2-methyl-substituted thiophene 9a or
2,5-dimethyl-substituted thiophene 9b was employed, hydro-
arylation occurred at the 4-position selectively (Table 3, entries 3
and 4). During column chromatography, intramolecular cyclization
occurred to give the cyclic product 17a in 57% yield (Table 3, entry
4). The reactions of 3-imino furan 1a and 2-imino furan 1b with
isocyanate 15a gave furan-2-carboxamide 18a and furan-
3-carboxamide 18b in 63% and 36% yields, respectively (Table 3,
entries 5 and 6). When the 2-position was blocked with a methyl
group, the reaction proceeded at the 4-position (Table 3, entry 7).
Imino pyrrole 14 and indoles 5a and 5b afforded the corresponding
carboxamides 19, 20a, and 20b in high yields (Table 3, entries 8–10).
Aryl isocyanates with an electron-withdrawing or electron-
donating group, 15b and 15c, provided thiophene-2-carboxamides
16d and 16e in 72% and 81% yields, respectively (Table 4, entries 1
and 2). On the other hand, the yield of amide decreased when using
an isocyanate bearing a substituent at the ortho-position (Table 4,
entry 3). Thiophene-2-carboxamides 16g and 16h were also
produced with primary and secondary alkyl isocyanates 15e and
15f (Table 4, entries 4 and 5). In entry 4, cyclic compound 17b was
also formed in 19% yield. Although hydroarylation of alkyl
isocyanates by treatment with aromatic imines did not proceed,11b
hydroarylation of alkyl isocyanates with heteroaromatic com-
pounds occurred.
Ph
Ph
[ReBr(CO)3(thf)]2 (2.5 mol%)
CH2ClCH2Cl, 115 °C, 24 h
N
+
Ph
Ph
N
t
O
Bu
t
O
Bu
H
H
1b
2a
H
3f 0%
Ph
H
N t
N t
Bu
Ph
Bu
[ReBr(CO)3(thf)]2 (2.5 mol%)
CH2ClCH2Cl, 115 °C, 24 h
+
Ph
Ph
R
O
O
2a
0%
R = H : 3g
R = H : 1c
R = CH3: 1d
R = CH3: 3h 0%
Scheme 4.

Y. Kuninobu et al. / Tetrahedron 64 (2008) 5974–5981
5977
Table 2
Table 3
Reactions between heteroaromatic aldimines and ethyl acrylate 12aa
Reactions between heteroaromatic aldimines and phenyl isocyanate 15aa
Re2(CO)10
[ReBr(CO)3(thf)]2
amidated
heteroaromatic
aldehyde
16-20
alkylated
heteroaromatic
aldehyde
H3O+
(3.0 mol%)
H3O+
(2.5 mol%)
aldimine
+
+
Ph
aldimine
N
15a
C O
CO2Et
11a
toluene
150 °C, 24 h
CH2ClCH2Cl
reflux, 24 h
Entry
1
Aldimine
Product
Yield/%
25
Entry
Aldimine
Product
Yield/%
CO2Et
H
O
H
N
H
N t
t
Bu
S
Bu
O
H
S
N
9d
1
92
Ph
Ph
S
12b
H
9c
S
O
16a
EtO2C
H
O
O
N
H
t
Bu
N
12c
t
O
N
S
S
Bu
S
2
77
48
50
H
H
9d
O
H
2
t
H
Bu
16b
N
9b
S
H
O
H
Ph
HN
H
13
N t
S
Bu
O
3
38
S
16c
9a
S
CO2Et
N
t
N
Me
Bu
3
12
O
H
14
N
Ph
N
t
12d
Bu
Me
H
N
O
OH
H
a
Compound 12a (1.5 equiv).
4
57
S
17a
9b
S
H
H
N t
Bu
O
H
catalyst (3.0 mol%)
H3O+
H
+
COEt
COEt
O
N t
toluene, 150 °C, 24 h
Bu
S
H
S
N
9c
(1.0 equiv)
11b
5b
63
Ph
Ph
O
22%
12e
(1.5 equiv)
O
18a
O
1a
Scheme 7.
O
The proposed mechanism for the generation of amidated
heteroaromatic aldimines is described as follows (Scheme 8):17
(1) oxidative addition of a C–H bond of an aldimine to a rhenium
center (C–H bond activation); (2) insertion of an isocyanate into a
rhenium–carbon bond;18 (3) reductive elimination. As a result, an
N
H
N
t
O
O
Bu
6
7
36
38
O
H
1b
H
18b
Ph
HN
O H
t
H
Bu
H
H
O
t
N
Bu
t
N
Bu
N
H
N
O
18c
O
R
X
X
X
X
1c
X = S, O, NMe
O
ReI
H
O
H
t
Bu
ReIII
Ph
N
N
t
N
Bu
H
H
N
N
t
O
N
Me
Bu
ReIII
N
Me
8
80
H
H
R
O
14
H
19
R
N
C O
(continued on next page)
Scheme 8.

5978
Y. Kuninobu et al. / Tetrahedron 64 (2008) 5974–5981
Table 3 (continued)
H
N t
Bu
Entry
Aldimine
Product
Yield/%
[ReBr(CO)3(thf)]2 (2.5 mol%)
CH2ClCH2Cl, reflux, 24 h
N
+
+
t
Ph
N C O
S
Bu
t
H
O
Bu
H
7
15a
(1.0 equiv)
9d
H
N
(1.0 equiv)
(1.0 equiv)
HN Ph
O
t
9b
92
Bu
N
Me
20a
Ph
HN
O
N
H
5a
N
Me
+
N Ph
N
t
S
Bu
H
O
56%
16b 31%
21
Ph NH
H
N
O
Scheme 10.
H
O
t
N
Bu
10b
72
Me
N
5b
Me
20b
aldimine 7 with phenyl isocyanate 15a in the presence of a cat-
alytic amount of [ReBr(CO)3(THF)]2 promoted hydroarylation of
15a, and the corresponding thiophene derivative 16a and
phthalimidine derivative 21 were formed in 81% and 13% yields,
respectively (Scheme 9). On the other hand, thiophenyl aldimine
9d showed low reactivity compared with aromatic aldimine 7
(Scheme 10). The difference in the reactivities between 9c, 9d,
and 7 must reflect the electron density at the 2-positions of the
thiophene or the phenyl ring. From the results of these experi-
ments, the order of reactivities of C–H bonds is as follows: the 3-
position of thiophenyl group<phenyl group<the 2-position of
thiophenyl group (Fig. 2).
a
Compound 15a (1.0 equiv).
b
Temperature: 135 ꢁC.
Table 4
Reaction of thiophenyl aldimine 9b with several isocyanates 16a
H
H
t
Bu
[ReBr(CO)3(thf)]2
(2.5 mol%)
O
N
H3O+
H
+
R
N
C O
N
CH2ClCH2Cl
reflux, 24 h
R
S
S
9c
15
O
16
t
Bu
H
Entry
R
Yield/%
72
81
61
N
N t
Bu
H
1
2
3
(p-CF3)C6H4 (15b)
(p-MeO)C6H4 (15c)
(o-MeO)C6H4 (15d)
16d
16e
16f
H
N
<
<
t
Bu
S
H
S
H
H
OH
Ph
17b19
Figure 2. Order of the reactivities between thiophenyl and phenyl groups.
N
4
PhCH2CH2 (15e)
16g
16h
64
70
S
O
3. Conclusion
5b
We have succeeded in hydroarylation of acetylenes, acrylates,
and isocyanates with heteroaromatic compounds regioselectively
using a rhenium complex, [ReBr(CO)3(THF)]2, as a catalyst. In these
reactions, both 2- and 3-position of heteroaromatic compounds
could be functionalized selectively. In addition, hydroarylation of
an acetylene, acrylate, and isocyanate proceeded even at the
4-position of heteroaromatic compounds where it is usually diffi-
cult to be functionalized. We hope that these reactions can become
powerful tools to functionalize heteroaromatic compounds and
contribute to the development of transformations via hydro-
arylation of heteroaromatic compounds.
(15f)
a
Compounds 9b (1.0 equiv) and 15 (1.0 equiv).
Temperature: 135 ꢁC.
b
amide derivative is formed and the rhenium catalyst is
regenerated.
H
H
t
N t
Bu
Bu
[ReBr(CO)3(thf)]2 (2.5 mol%)
CH2ClCH2Cl, reflux, 24 h
N
+
+
Ph
N
C O
15a
(1.0 equiv)
S
9c
7
4. Experimental
4.1. General
(1.0 equiv)
(1.0 equiv)
H
t
t
Bu
Bu
HN
N
H
All reactions were carried out in a dry and degassed solvent
under an argon atmosphere. 1,2-Dichloroethane and toluene were
purchased from Wako Pure Chemical Industries and dried and
degassed before use. [ReBr(CO)3(THF)]2 was prepared by heating
a THF solution of ReBr(CO)5 at reflux temperature for 16 h and was
recrystalized from THF/hexane. Imines were prepared by conden-
sation of the corresponding aldehydes with the corresponding
amines in the presence of molecular sieves (4 Å) in hexane at 50 ꢁC
for 10 h, and were used after distillation. Aldehydes, acetylenes,
acrylates, and isocyanates were purchased from Wako Pure
+
N Ph
N
Ph
S
O
O
16a 81%
21 13%
Scheme 9.
To compare the reactivities of heteroaromatic and aromatic
compounds, the following reactions were conducted (Schemes 9
and 10). Treatment of thiophenyl aldimine 9c and aromatic

Y. Kuninobu et al. / Tetrahedron 64 (2008) 5974–5981
5979
Chemical Industries, Tokyo Kasei Kogyo Co., and Aldrich Co., and
used as-received. Silica gel (60N, spherical neutral) was purchased
from Kanto Chemical Co.
4.4.4. 2-(6-Dodec-6-enyl) furan-3-carbaldehyde (4c)
The isomers could not be isolated. 1H NMR (400 MHz, CDCl3)
d 0.87 (t, J¼6.9 Hz), 0.91 (t, J¼6.9 Hz), 1.21–1.45 (m), 1.47–1.62 (m),
2.03 (q, J¼7.5 Hz), 2.27 (q, J¼7.5 Hz), 2.39 (t, J¼7.5 Hz), 2.49 (t,
J¼7.6 Hz), 5.86 (t, J¼7.5 Hz), 5.92 (t, J¼7.5 Hz), 6.75–6.77 (m), 7.32
(d, J¼2.1 Hz), 7.41 (s), 9.74 (s), 9.87 (s); 13C NMR (100 MHz, CDCl3)
d 14.0, 22.4, 22.5, 28.1, 28.6, 29.1, 29.2, 29.6, 31.2, 31.2, 31.6, 36.9,
107.3, 108.3, 123.2, 128.8, 129.8, 136.8, 138.6, 141.5, 142.9, 166.4,
185.91; IR (Nujol, n/cmꢂ1) 1682, 1635, 1570, 1457, 1417, 1270, 1125,
756, 711; HRMS (ESI) calcd for C17H26O2Na ([MþNa]þ): 285.1830,
found: 285.1872.
1H (400 MHz) and 13C (100 MHz) NMR spectra were recorded
using a JEOL JNM-LA400 spectrometer. Proton chemical shifts are
reported relative to Me4Si (CDCl3) at d 0.00 ppm or residual solvent
peak (CDCl3 at d 7.26 ppm). Carbon chemical shifts are reported
relative to CDCl3 at d 77.00 ppm. IR spectra were recorded on
´
´
Nicolet Protege 460.
4.2. General procedure for the reaction of heteroaromatic
aldimines with acetylenes
4.4.5. 3-(3-Formylfuran-2-yl) but-2-enoic acid methyl ester (4d)
1H NMR (400 MHz, CDCl3) d 2.61 (d, J¼1.2 Hz, 3H), 3.79 (s, 3H),
6.39 (d, J¼1.2 Hz, 1H), 6.88 (d, J¼1.7 Hz, 1H), 7.45 (d, J¼1.7 Hz, 1H),
10.13 (s, 1H); 13C NMR (100 MHz, CDCl3) d 16.3, 51.6, 110.2, 121.3,
125.6, 142.1, 143.4, 160.4, 166.2, 184.9; IR (Nujol, n/cmꢂ1) 1709, 1659,
1619, 1556, 1457, 1415, 1376, 1261, 1179, 888, 789, 727; HRMS (ESI)
calcd for C10H10O4Na ([MþNa]þ): 217.0477, found: 217.0524.
A mixture of a heteroaromatic aldimine (0.25 mmol), an acety-
lene (0.25 mmol), and [ReBr(CO)3(THF)]2 (5.3 mg, 6.3 mmol) in
1,2-dichloroethane (0.50 mL) was heated for 24 h in sealed test
tube. The products were isolated by silica gel column chromatog-
raphy (AcOEt/hexane¼100:1).
4.4.6. 2-(1,2-Diphenylvinyl)-1-methyl-1H-indole-3-
carbaldehyde (6a)
4.3. General procedure for the reaction of heteroaromatic
aldimines with acrylates
1H NMR (400 MHz, CDCl3) d 3.48 (s, 3H), 6.93–6.96 (m, 2H),
7.12–7.17 (m, 3H), 7.31–7.36 (m, 5H), 7.37–7.39 (m, 3H), 7.54 (s, 1H),
8.38–8.41 (m 1H), 9.78 (s, 1H); 13C NMR (100 MHz, CDCl3) d 30.4,
109.0, 114.9, 122.2, 122.5, 123.2, 123.8, 125.3, 126.3, 128.3, 128.5,
128.8, 128.9, 129.7, 135.2, 135.4, 137.6, 140.4, 149.1, 185.9; IR (Nujol,
n/cmꢂ1) 1649, 1658, 1464, 1382, 759, 692; HRMS (ESI) calcd for
A mixture of a heteroaromatic aldimine (0.25 mmol), ethyl
acrylate (0.25 mmol), and Re2(CO)10 (4.9 mg, 7.5 mmol) in toluene
(0.50 mL) was heated for 24 h in sealed test tube. The products
were isolated by silica gel column chromatography (AcOEt/
hexane¼20:1).
C
24H19NONa ([MþNa]þ): 360.1364, found: 360.1437.
4.4. General procedure for the reaction of heteroaromatic
aldimines with isocyanates
4.4.7. 3-(1,2-Diphenyl-vinyl)-1-methyl-1H-indole-2-
carbaldehyde (6b)
1H NMR (400 MHz, CDCl3) d 3.48 (s, 3H), 6.93–6.96 (m, 2H),
7.12–7.17 (m, 3H), 7.31–7.36 (m, 5H), 7.37–7.39 (m, 3H), 7.54 (s, 1H),
8.38–8.41 (m 1H), 9.78 (s, 1H); 13C NMR (100 MHz, CDCl3) d 30.4,
109.0, 114.9, 122.2, 122.5, 123.2, 123.8, 125.3, 126.3, 128.3, 128.5,
128.8, 128.9, 129.7, 135.2, 135.4, 137.6, 140.4, 149.1, 185.9; IR (Nujol,
n/cmꢂ1) 1663, 1466, 1384, 1345, 748, 696; HRMS (ESI) calcd for
A
mixture of a heteroaromatic aldimine (0.25 mmol), an
isocyanate (0.25 mmol), and [ReBr(CO)3(THF)]2 (5.3 mg, 6.3 mmol)
in 1,2-dichloroethane (0.50 mL) was heated for 24 h in sealed test
tube. The products were isolated by silica gel column chromatog-
raphy (AcOEt/hexane¼10:1).
C
24H19NONa ([MþNa]þ): 360.1364, found: 360.1437.
4.4.1. 3-[3-(tert-Butylimino methyl)-4-(2-methoxycarbonyl-1-
methylvinyl)-furan-2-yl] but-2-enoic acid methyl ester (3a)
1H NMR (400 MHz, CDCl3) d 1.29 (s, 9H), 2.42 (s, 3H), 2.49 (d,
J¼0.9 Hz, 3H), 3.37 (s, 3H), 3.74 (s, 3H), 6.00 (s, 1H), 6.39 (s, 1H), 7.50
(s, 1H), 8.34 (s, 1H); 13C NMR (100 MHz, CDCl3) d 16.2, 19.3, 29.2,
51.1, 51,3, 58.5, 117.8, 122.1, 130.2, 141.2, 143.4, 147.5, 149.0, 166.9;
IR (Nujol, n/cmꢂ1) 1724, 1624, 1463, 1377, 1173, 1037, 877, 722;
HRMS (ESI) calcd for C19H25NO5Na ([MþNa]þ): 370.1631, found:
370.1599.
4.4.8. N-tert-Butyl-2,3-diphenyl-3H-inden-1-amine (8)
1H NMR (400 MHz, CDCl3) d 1.12 (s, 9H), 4.87 (s, 1H), 7.04 (d,
J¼7.6 Hz, 2H), 7.09–7.17 (m, 6H), 7.22 (t, J¼7.7 Hz, 2H), 7.28–7.31 (m,
1H), 7.34 (d, J¼8.4 Hz, 2H), 7.48 (d, J¼6.9 Hz, 1H); 13C NMR
(100 MHz, CDCl3) d 31.0, 54.9, 56.7, 119.9, 123.8, 125.4, 126.4, 126.5,
128.1, 128.2, 128.3, 128.5, 128.9, 136.7, 137.0, 140.4, 143.2, 144.3,
147.4; IR (Nujol, n/cmꢂ1) 3061, 3022, 1951, 1653, 1601, 1493, 1430,
1389, 1378, 1284, 1218, 1199, 1121, 1095, 1071, 1026, 938, 918, 815,
783, 759, 736, 696, 675, 666, 651, 621. Anal. Calcd for C25H25N: C,
88.45; H, 7.42; N, 4.13. Found: C, 88.57; H, 7.41; N, 4.03.
4.4.2. 2-(1,2-Diphenylvinyl) furan-3-carbaldehyde (4a)
1H NMR (400 MHz, CDCl3) d 6.82 (d, J¼1.8 Hz, 1H), 7.07–7.05 (m,
2H), 7.15–7.18 (m, 2H), 7.32–7.36 (m, 3H), 7.39–7.43 (m, 4H), 8.85 (s,
1H); 13C NMR (100 MHz, CDCl3) d 109.7, 124.6, 124.6, 128.1, 128.2,
128.9, 129.6, 129.8, 129.9, 130.0, 130.3, 132.8, 135.3, 137.0, 142.3,
186.2; IR (Nujol, n/cmꢂ1) 1660, 1595, 1558, 1457, 1418, 1390, 1262,
1169, 1122, 1079, 1027, 922, 879, 760, 717, 697. Anal. Calcd for
4.4.9. 4-(1,2-Diphenylvinyl)-2-methylthiophene-3-
carbaldehyde (10a)
1H NMR (400 MHz, CDCl3) d 2.75 (s, 3H), 6.74 (s, 1H), 6.93 (s, 1H),
7.10–7.11 (m, 2H), 7.15–7.20 (m, 5H), 7.22–726 (m, 3H); 13C NMR
(100 MHz, CDCl3) d 16.0, 120.9, 127.2, 127.8, 128.0, 128.6, 129.4,
C
19H14O2: C, 83.19; H, 5.42. Found: C, 83.26; H, 5.42.
129.7, 131.2, 133.6, 136.2, 136.5, 139.8, 151.5, 187.2; IR (Nujol, n/cmꢂ1
)
1674, 1598, 1506, 1458, 1376, 704; HRMS (ESI) calcd for
4.4.3. 2-(1-Methyl-2-phenylvinyl) furan-3-carbaldehyde (4b)
1H NMR (400 MHz, CDCl3) d 2.36 (d, J¼1.2 Hz, 3H), 6.85 (d,
J¼2.1 Hz, 1H), 7.07 (d, J¼1.2 Hz, 1H), 7.03–7.36 (m, 1H), 7.38–7.42
(s, 5H), 10.08 (s, 1H); 13C NMR (100 MHz, CDCl3) d 16.2, 109.2,
123.4, 126.1, 127.9, 128.4, 129.4, 134.7, 136.0, 141.9, 164.7, 185.58; IR
(Nujol, n/cmꢂ1) 1733, 1675, 1568, 1455, 1378, 1140, 889, 751, 701;
HRMS (ESI) calcd for C14H12O2Na ([MþNa]þ): 235.0735, found:
235.0794.
C
20H16NOSNa ([MþNa]þ): 327.0802, found: 327.0861.
4.4.10. 4-(1,2-Diphenylvinyl)-2,5-dimethylthiophene-3-
carbaldehyde (10b)
1H NMR (400 MHz, CDCl3) d 2.33 (s, 3H), 2.70 (s, 3H), 6.61(s, 1H),
7.12–7.21 (m, 10H), 9.75 (s, 1H); 13C NMR (100 MHz, CDCl3) d 13.3,
15.5, 127.2, 127.6, 128.1, 128.4, 129.3, 129.5, 132.7, 132.8, 134.4, 135.1,
136.6, 139.4, 142.2, 148.2, 187.5; IR (Nujol, n/cmꢂ1) 1678.92, 1463.11,

5980
Y. Kuninobu et al. / Tetrahedron 64 (2008) 5974–5981
1416.03, 1376.92, 742.05, 705.57, 649.55; HRMS (ESI) calcd for
C
4.4.18. 2-Formylthiophene-3-carboxylic acid phenylamide (16b)
1H NMR (400 MHz, CDCl3) d 7.17 (t, J¼7.5 Hz, 1H), 7.39 (t,
J¼7.8 Hz, 2H), 7.78 (d, J¼7.8 Hz, 2H), 7.85 (d, J¼4.8 Hz, 1H), 7.94 (d,
J¼4.8 Hz,1H), 9.99 (s, 1H), 10.87 (br, 1H); 13C NMR (100 MHz, CDCl3)
d 120.3, 120.4, 124.7, 129.1, 134.2, 135.0, 137.9, 142.1, 174.8, 183.8; IR
(Nujol, n/cmꢂ1) 3328, 3097, 1659, 1598, 1539, 1514, 1443, 1419, 1316,
21H18OSNa ([MþNa]þ): 341.0976, found: 341.0934.
4.4.11. 3-(3-Formylthiophen-2-yl) propionic acid ethyl ester (12a)
1H NMR (400 MHz, CDCl3) d 1.25 (t, J¼7.2 Hz, 3H), 2.74 (t,
J¼7.2 Hz, 2H), 3.51 (t, J¼7.2 Hz, 2H), 4.14 (q, J¼7.2 Hz, 2H), 7.13 (d,
J¼5.4 Hz, 1H), 7.39 (d, J¼5.4 Hz, 1H), 10.04 (s, 1H); 13C NMR
(100 MHz, CDCl3) d 14.2, 23.4, 35.8, 60.8, 123.4, 128.0, 137.0, 171.7,
184.6, 185.6; IR (Nujol, n/cmꢂ1) 2980, 1732, 1681, 1520, 1446, 1374,
1234,1181,1043, 725; HRMS (ESI) calcd for C10H12O3SNa ([MþNa]þ):
235.0405, found: 235.0429.
1260, 1205, 906, 772; HRMS (ESI) calcd for
C12H9NO2SNa
([MþNa]þ): 254.0252, found: 254.0203.
4.4.19. 4-Formyl-5-methylthiophene-3-carboxylic acid
phenylamide (16c)
1H NMR (400 MHz, CDCl3) d 2.88 (s, 3H), 7.13 (t, J¼7.8 Hz, 1H),
7.37 (t, J¼7.8 Hz, 2H), 7.79 (d, J¼7.8 Hz, 2H), 8.21 (s, 1H), 11.64 (s,
1H); 13C NMR (100 MHz, CDCl3) d 14.8, 120.4, 124.2, 128.9, 131.8,
132.0, 137.8, 138.5, 159.2, 160.1, 186.6; IR (Nujol, n/cmꢂ1) 1653, 1559,
4.4.12. 3-(2-Formyl-thiophen-3-yl) propionic acid ethyl ester (12b)
1H NMR (400 MHz, CDCl3) d 1.22 (t, J¼7.2 Hz, 3H), 2.75 (t,
J¼7.5 Hz, 2H), 3.30 (t, J¼7.5 Hz, 2H), 4.12 (q, J¼7.2 Hz, 2H), 7.05 (d,
J¼4.5 Hz, 1H), 7.66 (d, J¼4.5 Hz, 1H), 10.06 (s, 1H); 13C NMR
(100 MHz, CDCl3) d 14.1, 23.6, 35.1, 60.7, 130.5, 134.6, 138.1, 149.5,
172.0, 182.2; IR (Nujol, n/cmꢂ1) 1731, 1660, 1427, 1393, 1373, 1241,
1190,1096,1041, 752; HRMS (ESI) calcd for C10H12O3SNa ([MþNa]þ):
235.0405, found: 235.0385.
1456, 1377, 1193, 763; HRMS (ESI) calcd for
C13H11NO2SNa
([MþNa]þ): 268.0408, found: 268.0379.
4.4.20. 3-Formylthiophene-2-carboxylic acid (4-trifluoro-
methylphenyl) amide (16d)
1H NMR (400 MHz, CDCl3) d 7.61–7.67 (m, 4H), 7.92 (d, J¼8.4 Hz,
4.4.13. 3-(4-Formyl-2,5-dimethylthiophen-3-yl) propionic acid
ethyl ester (12c)
2H), 9.96 (s, 1H); 13C NMR (100 MHz, CDCl3) d 120.1, 126.2, 126.3,
126.3,130.8,134.8,135.2, 141.0,148.6,158.1,187.7; IR (Nujol, n/cmꢂ1
)
1H NMR (400 MHz, CDCl3) d 1.22 (t, J¼7.2 Hz, 3H), 2.31 (s, 3H),
2.51 (t, J¼7.7 Hz, 2H), 2.69 (s, 3H), 3.06 (t, J¼7.7 Hz, 2H), 4.09 (q,
J¼7.2 Hz, 2H), 10.05 (s, 1H); 13C NMR (100 MHz, CDCl3) d 12.3, 13.6,
22.3, 34.5, 60.3, 131.2, 134.5, 135.9, 151.4, 173.1, 185.2; IR (Nujol, n/
cmꢂ1) 1734, 1675, 1558, 1457, 1375, 1297, 125, 1172, 1101, 1037;
HRMS (ESI) calcd for C12H16O3SNa ([MþNa]þ): 263.0718, found:
263.0682.
1675, 1619, 1602, 1554, 1504, 1430, 1412, 1319, 1254, 1158, 1122,
1106, 1073, 1008, 846. Anal. Calcd for C13H8F3NS: C, 52.17; H, 2.69;
N, 4.68. Found: C, 52.00; H, 2.95; N, 4.57.
4.4.21. 3-Formylthiophene-2-carboxylic acid (4-methoxyphenyl)
amide (16e)
1H NMR (400 MHz, CDCl3) d 3.81 (s, 3H), 6.91 (d, J¼9.0 Hz, 2H),
7.58–7.61 (m, 2H), 7.73 (d, J¼9.0 Hz, 2H), 9.95 (s, 1H), 11.90 (s, 1H);
13C NMR (100 MHz, CDCl3) d 55.4, 114.1, 121.8, 129.8, 131.0, 134.4,
135.0, 149.6, 156.5, 157.4, 187.4; IR (Nujol, n/cmꢂ1) 1875, 1674, 1644,
1565, 1504, 1402, 1278, 1241, 1193, 1170, 1124, 1111, 1029, 857, 828,
800, 714; HRMS (ESI) calcd for C13H11NO3SNa ([MþNa]þ): 284.0357,
found: 284.0303.
4.4.14. 3-(2-Formyl-1-methyl-1H-pyrrol-3-yl) propionic acid ethyl
ester (12d)
1H NMR (400 MHz, CDCl3) d 1.25 (t, J¼7.1 Hz, 3H), 2.62 (t, J¼7.8 Hz,
2H), 3.08 (t, J¼7.8 Hz, 2H), 3.90 (s, 3H), 4.13 (q, J¼7.1 Hz, 2H), 6.03 (d,
J¼2.4 Hz,1H), 6.75 (d, J¼2.4 Hz,1H), 9.76 (s,1H); 13C NMR (100 MHz,
CDCl3) d 14.2, 20.9, 35.8, 36.9, 60.5, 109.2, 127.7, 131.1, 137.3, 172.6,
178.2; IR (Nujol, n/cmꢂ1) 1734, 1657, 1507, 1461, 1376, 1184; HRMS
(ESI) calcd for C11H15NO3Na ([MþNa]þ): 232.0950; found: 232.0908.
4.4.22. 3-Formylthiophene-2-carboxylic acid (2-methoxyphenyl)
amide (16f)
1H NMR (400 MHz, CDCl3) d 3.98 (s, 3H), 6.94 (d, J¼8.1 Hz, 1H),
7.00 (t, J¼7.8 Hz,1H), 7.12 (t, J¼7.8 Hz,1H), 7.55 (d, J¼5.4 Hz,1H), 7.59
4.4.15. 3-(3-Oxo-pentyl) thiophene-2-carbaldehyde (12e)
1H NMR (400 MHz, CDCl3) d 1.06 (t, J¼7.3 Hz, 3H), 2.44 (q,
J¼7.3 Hz, 2H), 2.85 (t, J¼7.4 Hz, 2H), 3.46 (t, J¼7.4 Hz, 2H), 7.11 (d,
J¼5.3 Hz, 1H), 7.38 (d, J¼5.3 Hz, 1H), 10.05 (s, 1H); 13C NMR
(100 MHz, CDCl3) d 7.7, 22.1, 36.0, 43.4, 123.2, 128.0, 136.7, 155.3,
184.7, 209.1; IR (Nujol, n/cmꢂ1) 1714, 1676, 1519, 1457, 1411, 1387,
1234, 1114, 730; HRMS (ESI) calcd for C10H12O2SNa ([MþNa]þ):
219.0546, found: 219.0444.
(d, J¼5.4 Hz,1H), 8.47 (d, J¼8.1 Hz,1H),10.06 (s,1H),11.33 (s,1H); 13
C
NMR (100 MHz, CDCl3) d 55.8, 110.4, 120.9, 121.4, 124.8, 127.3, 129.6,
133.1, 136.5, 148.2, 149.3, 158.1, 186.5; IR (Nujol, n/cmꢂ1) 3120, 3086,
2769,1683,1633,1603,1542,1508,1427,1402,1332,1266,1224,1193,
1179, 1164, 1129, 1030, 931, 822, 802, 771, 746; HRMS (ESI) calcd for
C
13H11NO3SNa ([MþNa]þ): 284.0357, found: 284.0331.
4.4.23. 3-Formylthiophene-2-carboxylic acid phenethylamide (16g)
1H NMR (400 MHz, CDCl3) d 2.97 (t, J¼7.5 Hz, 2H), 3.69–3.74 (m,
2H), 7.21–7.34 (m, 5H), 7.51 (d, J¼5.1 Hz, 1H), 7.54 (d, J¼5.1 Hz, 1H),
9.69 (br, 1H), 9.90 (s, 1H); 13C NMR (100 MHz, CDCl3) d 35.4, 41.4,
126.4, 128.5, 128.7, 129.3, 133.6, 135.8, 138.8, 148.0, 160.0, 186.8; IR
(Nujol, n/cmꢂ1) 3254, 3117, 1674, 1615, 1556, 1515, 1307, 1225, 1195,
819. Anal. Calcd for C14H13NO2S: C, 64.84; H, 5.05; N, 5.40. Found: C,
65.11; H, 5.26; N, 5.41.
4.4.16. 2-tert-Butyl-3,5-dimethyl-2,2a,6,6a-tetrahydro-4-thia-2-
azacyclobuta[a]pentalen-1-one (13)
1H NMR (400 MHz, CDCl3) d 1.32 (s, 9H), 2.21 (s, 3H), 2.40 (s, 3H),
2.53 (ddd, J¼1.2, 10.2, 16.8 Hz, 1H), 2.92 (dd, J¼1.2, 16.8 Hz, 1H), 4.05
(ddd, J¼2.4, 4.2, 10.2 Hz, 1H), 4.57 (d, J¼4.2 Hz, 1H); 13C NMR
(100 MHz, CDCl3) d 13.0,14.7, 24.5, 28.3, 53.3, 53.7, 58.7,126.9,129.7,
140.3, 145.1, 169.9; IR (Nujol, n/cmꢂ1) 1716, 1458, 1376, 1294, 1260,
1229, 1192, 1129, 1084, 1013, 843, 729; HRMS (ESI) calcd for
C
14H19NOSNa ([MþNa]þ): 272.1085, found: 272.1082.
4.4.24. 3-Formylthiophene-2-carboxylic acid cyclohexyl-
amide (16h)
4.4.17. 3-Formylthiophene-2-carboxylic acid phenylamide (16a)
1H NMR (400 MHz, CDCl3) d 7.15 (t, J¼7.5 Hz,1H), 7.37 (t, J¼7.5 Hz,
2H), 7.58 (s, 2H), 7.79 (d, J¼7.5 Hz, 2H), 9.93 (s, 1H); 13C NMR
(100 MHz, CDCl3) d 120.4,124.6,129.0,130.1,134.4,135.2,137.9,149.3,
157.8, 187.4; IR (Nujol, n/cmꢂ1) 1671, 1646, 1624, 1559, 1540, 1404,
1322, 1273, 1245, 1189, 1120, 1013, 691. Anal. Calcd for C12H9N2S: C,
62.32; H, 3.92; N, 6.06. Found: C, 62.04; H, 4.03; N, 6.09.
1H NMR (400 MHz, CDCl3) d 1.26–2.01 (m, 10H), 3.96 (br, 1H),
7.52 (d, J¼5.4 Hz, 1H), 7.56 (d, J¼5.1 Hz, 1H), 9.61 (br, 1H), 9.95 (s,
1H); 13C NMR (100 MHz, CDCl3) d 24.5, 25.6, 31.5, 32.6, 48.7, 129.0,
133.7, 135.6, 138.9, 186.9; IR (Nujol, n/cmꢂ1) 3285, 3083, 1678, 1619,
1544, 1514, 1348, 1322, 1257, 1241, 1229, 1151, 1137, 1096, 924, 824,
792. Anal. Calcd for C12H15N2S: C, 60.73; H, 6.37; N, 5.90. Found: C,
60.43; H, 6.46; N, 5.68.

Y. Kuninobu et al. / Tetrahedron 64 (2008) 5974–5981
5981
4.4.25. 6-Hydroxy-1,3-dimethyl-5-phenyl-5,6-dihydrothieno
[3,4-c]pyrrol-4-one (17a)
185.6; IR (Nujol, n/cmꢂ1) 3280, 1674, 1635, 1597, 1538, 1498, 1129,
784, 694; HRMS (ESI) calcd for C17H14N2O2Na ([MþNa]þ): 301.0953,
found: 301.0881.
1H NMR (400 MHz, CDCl3) d 2.37 (s, 3H), 2.45 (s, 3H), 3.98 (d,
J¼11.7 Hz, 1H), 6.12 (d, J¼11.4 Hz, 1H), 7.15 (t, J¼8.1 Hz, 1H), 7.31 (t,
J¼8.4 Hz, 2H), 7.61 (d, J¼8.1 Hz, 2H); 13C NMR (100 MHz, CDCl3)
d 12.4, 12.5, 79.4, 121.2, 124.9, 128.8, 131.1, 131.4, 137.8, 138.7, 139.5,
162.9; IR (Nujol, n/cmꢂ1) 3316, 1668, 1597, 1560, 1497, 1261, 1160,
1094, 1042, 938, 896, 802, 783, 762, 696, 683; HRMS (ESI) calcd for
4.4.32. 3-Formyl-1-methyl-1H-indole-2-carboxylic acid
phenylamide (20b)
1H NMR (400 MHz, CDCl3) d 4.17 (s, 3H), 7.18 (t, J¼7.3 Hz, 1H),
7.29–7.34 (m, 1H), 7.40 (t, J¼7.2 Hz, 2H), 7.44–7.51 (m, 2H), 7.72 (d,
J¼7.7 Hz, 1H), 8.19 (d, J¼8.2 Hz, 1H), 9.00 (s, 1H), 10.48 (s, 1H); 13C
NMR (100 MHz, CDCl3) d 31.9, 110.9, 120.1, 120.7, 122.4, 123.1, 124.5,
C
14H13NO2SNa ([MþNa]þ): 282.0565, found: 282.0531.
4.4.26. 4-Hydroxy-5-phenethyl-4,5-dihydrothieno[2,3-c]-
pyrrol-6-one (17b)
124.7, 127.3, 129.1, 133.6, 138.0, 138.6, 161.8, 184.7; IR (Nujol, n/cmꢂ1
)
1673, 1656, 1532, 1462, 1377, 1312, 746; HRMS (ESI) calcd for
1H NMR (400 MHz, CDCl3) d 3.00 (t, J¼7.5 Hz, 1H), 3.65 (m, 1H),
3.86 (m, 1H), 7.09–7.17 (m, 6H), 7.22 (t, J¼7.7 Hz, 2H), 7.09 (d,
J¼4.8 Hz 1H), 7.21–7.29 (m 5H), 7.61 (d, J¼4.8 Hz, 1H); 13C NMR
(100 MHz, CDCl3) d 35.0, 41.8, 80.2, 121.2, 126.5, 128.6, 128.8, 128.9,
129.3, 135.3, 139.0, 154.0; IR (Nujol, n/cmꢂ1) 3193, 1657, 1462, 1377,
1291.38, 1280.30, 1114.65, 747.58, 697.16; HRMS (ESI) calcd for
C
17H13N2O2Na ([MþNa]þ): 301.0953, found: 301.1014.
Acknowledgements
Financial support by a Grant-in-Aid for Scientific Research on
Priority Areas (No. 18037049, ‘‘Advanced Molecular Trans-
formations of Carbon Resources’’) from the Ministry of Education,
Culture, Sports, Science, and Technology of Japan, and for Young
Scientists (B) (No. 18750088) from Japan Society for the Promotion
of Science, and Okayama Foundation for Science and Technology is
gratefully acknowledged. We thank Professor Isao Kadota at
Okayama University for measurements of ESI-TOF mass spectra.
C
14H13NO2SNa ([MþNa]þ): 282.0565, found: 282.0592.
4.4.27. 3-Formylfuran-2-carboxylic acid phenylamide (18a)
1H NMR (400 MHz, CDCl3) d 6.99 (d, J¼1.8 Hz, 1H), 7.20 (t,
J¼7.5 Hz, 1H), 7.40 (t, J¼7.5 Hz, 2H), 7.58 (d, J¼1.8 Hz, 1H), 7.72 (d,
J¼7.5 Hz, 2H), 9.43 (br, 1H), 10.47 (s, 1H); 13C NMR (100 MHz, CDCl3)
d 111.6, 120.3, 125.1, 127.7, 129.2, 136.9, 144.2, 149.7, 154.8, 187.6; IR
(Nujol, n/cmꢂ1) 3274, 3138, 3119, 1684, 1655, 1607, 1597, 1545, 1499,
1444, 1419, 1326, 1262, 1232, 1181, 786, 693; HRMS (ESI) calcd for
References and notes
12H9NO3Na ([MþNa]þ): 238.0480, found: 238.0416.
1. Comprehensive Heterocyclic Chemistry; Meth-Cohn, O., Ed.; Pergamon: New
York, NY, 1984; Vol. 1.
C
2. (a) Comprehensive Heterocyclic Chemistry; Bird, C. W., Cheeseman, G. W. H., Eds.;
Pergamon: New York, NY, 1984; Vol. 4; (b) Katritzky, A. R.; Pozharskii, A. F.
Handbook of Heterocyclic Chemistry, 2nd ed.; Pergamon: Oxford, 2000.
3. For the reviews, see: (a) Ritleng, V.; Sirlin, C.; Pfeffer, M. Chem. Rev. 2002, 102,
1731; (b) Kakiuchi, F.; Chatani, N. Adv. Synth. Catal. 2003, 345, 1077.
4. Tsuji, J.; Nagashima, H. Tetrahedron 1984, 40, 2699.
5. Jordan, R. F.; Taylor, D. F. J. Am. Chem. Soc. 1989, 111, 778.
6. (a) Murai, S.; Kakiuchi, F.; Sekine, S.; Tanaka, Y.; Kamatani, A.; Sonoda, M.;
Chatani, N. Nature 1993, 366, 529; (b) Kakiuchi, F.; Sato, T.; Igi, K.; Chatani, N.;
Murai, S. Chem. Lett. 2001, 386.
7. Kakiuchi, F.; Yamamoto, Y.; Chatani, N.; Murai, S. Chem. Lett. 1995, 681.
8. Fukumoto, Y.; Sawada, K.; Hagihara, M.; Chatani, N.; Murai, S. Angew. Chem., Int.
Ed. 2002, 41, 2779.
9. We have also reported the amidation hydroarylation of heteroaromatic com-
pounds via C–H bond activation. See: Kuninobu, Y.; Tokunaga, Y.; Takai, K.
Chem. Lett. 2007, 36, 872.
4.4.28. 2-Formylfuran-3-carboxylic acid phenylamide (18b)
1H NMR (400 MHz, CDCl3) d 7.16 (t, J¼7.5 Hz, 1H), 7.32 (s, 1H),
7.39 (t, J¼7.5 Hz, 2H), 7.76 (s, 1H), 7.80 (d, J¼7.8 Hz, 2H), 9.92 (s, 1H),
11.37 (br,1H); 13C NMR (100 MHz, CDCl3) d 116.5,120.2,120.3,124.6,
129.1, 138.0, 148.0, 148.2, 157.5, 182.4; IR (Nujol, n/cmꢂ1) 3193, 3117,
3038, 1676, 1624, 1612, 1600, 1563, 1496, 1420, 1328, 1257, 1212,
1177, 1163, 1151, 1093, 908, 802, 755, 692, 599; HRMS (ESI) calcd for
C
12H9NO3Na ([MþNa]þ): 238.0480, found: 238.0482.
4.4.29. 4-Formyl-5-methyl-furan-3-carboxylic acid
phenylamide (18c)
1H NMR (400 MHz, CDCl3) d 2.69 (s, 3H), 7.12 (t, J¼7.5 Hz, 1H),
7.36 (t, J¼7.5 Hz, 2H), 7.78 (d, J¼7.5 Hz, 2H), 7.22 (s, 1H), 11.43 (s,
1H); 13C NMR (100 MHz, CDCl3) d 12.7, 111.85, 120.0, 124.2, 128.9,
138.4, 149.5, 158.9, 168.2, 186.6; IR (Nujol, n/cmꢂ1) 1663, 1628, 1599,
1563, 1462, 1403, 1377, 1338, 760; HRMS (ESI) calcd for
10. For intramolecular hydroarylation of an olefin moiety, see: Tan, K. L.; Bergman,
R. G.; Ellman, J. A. J. Am. Chem. Soc. 2002, 124, 3202.
11. For our recent reports on rhenium-catalyzed functionalizations via C–H bond
activation of a benzene ring, see: (a) Kuninobu, Y.; Kawata, A.; Takai, K. J. Am.
Chem. Soc. 2005, 127, 13498; (b) Kuninobu, Y.; Tokunaga, Y.; Kawata, A.; Takai, K.
J. Am. Chem. Soc. 2006, 128, 202; (c) Kuninobu, Y.; Nishina, Y.; Shouho, M.; Takai,
K. Angew. Chem., Int. Ed. 2006, 45, 2766; (d) Kuninobu, Y.; Nishina, Y.; Nakagawa,
C.; Takai, K. J. Am. Chem. Soc. 2006, 128, 12376.
C
13H11NO3Na ([MþNa]þ): 252.0637, found: 252.0668.
12. Investigation of solvents: dioxane, 34%; THF, 45%; hexane, 67%;
1,2-dichloroethane, 76%; toluene, 76%.
4.4.30. 2-Formyl-1-methyl-1H-pyrrole-3-carboxylic acid
phenylamide (19)
13. Investigation of reaction temperature: 25 ꢁC, 0%; 50 ꢁC, 14%; 70 ꢁC, 33%; 90 ꢁC,
76%.
1H NMR (400 MHz, CDCl3) d 3.94 (s, 3H), 6.83 (d, J¼2.4 Hz, 1H),
6.88 (d, J¼2.4 Hz, 1H), 7.10 (t, J¼7.4 Hz, 1H), 7.34 (t, J¼7.6 Hz, 2H),
7.75 (d, J¼7.7 Hz, 2H), 9.99 (s, 1H), 10.81 (s, 1H); 13C NMR (100 MHz,
CDCl3) d 36.3, 113.3, 120.1, 123.9, 128.5, 128.8, 129.7, 130.4, 138.5,
160.5, 180.7; IR (Nujol, n/cmꢂ1) 3293, 1676, 1610, 1593, 1560, 1522,
1490, 1315, 1254, 1188; HRMS (ESI) calcd for C13H12N2O2Na
([MþNa]þ): 251.0797, found: 251.0820.
14. Investigation of reaction time: 1 h, 19%; 3 h, 47%; 8 h, 52%; 24 h, 76%.
15. There has been a report on whether the hydroarylation occurs at the 4-position
of heteroaromatic compounds; however, the reaction did not proceed. See:
Kakiuchi, F.; Sekine, S.; Tanaka, Y.; Kamatani, A.; Sonoda, M.; Chatani, N.; Murai,
S. Bull. Chem. Soc. Jpn. 1995, 68, 62.
16. There has been a report on the hydroarylation of an alkynoate at 4-position
with pyrroles. See: Oyamada, J.; Lu, W.; Jia, C.; Kitamura, T.; Fujiwara, Y. Chem.
Lett. 2002, 20.
17. Another possible mechanism is an electrophilic pathway (Friedel–Crafts type
mechanism). In this pathway,
a
heteroaryl-rhenium complex and Hþ are
4.4.31. 3-Formyl-1-methyl-1H-indole-2-carboxylic acid
phenylamide (20a)
formed as intermediates. When we examined the rhenium-catalyzed amidation
in the presence of tributylamine as a Lewis base, the reaction proceeded
without decreasing the yield. Thus, we are tempted to assume that this reaction
proceeds via C–H bond activation.
1H NMR (400 MHz, CDCl3) d 4.25 (s, 3H), 7.17 (t, J¼7.4 Hz, 1H),
7.37–7.50 (m, 5H), 7.88 (d, J¼8.3 Hz, 2H), 8.04 (d, J¼7.8 Hz, 1H),
10.35 (s, 1H); 13C NMR (100 MHz, CDCl3) d 33.3, 111.1, 113.7, 118.9,
120.7, 123.9, 124.7, 125.4, 127.2, 129.0, 136.6, 137.6, 138.2, 158.2,
18. Insertion of unsaturated molecules into an Re–H bond followed by reductive
elimination can also give the same product; however, we have observed that
the insertion into an Re–C bond occurs faster. See Ref. 11.