Palladium-catalyzed cross-coupling reaction of organobismuth compounds with aryl and alkenyl chlorides

Article abstract of DOI:10.1055/s-2004-831298

Cross-coupling reactions of hypervalent organobismuth compounds, 6-tert-butyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azabismocines, with aryl and alkenyl chlorides are efficiently catalyzed by the Pd(OAc)₂/dppf [dppf = 1,1′-bis(diphenylphosphino)fe

Full text of DOI:10.1055/s-2004-831298

LETTER
1921
Palladium-Catalyzed Cross-Coupling Reaction of Organobismuth Com-
pounds with Aryl and Alkenyl Chlorides
a
b
a
b
a,c
P
O
alladium-Catalyz
s
e
d
Cross-
C
a
oupling
R
m
e
action of
O
rganobi
u
smuth CompoundsYamazaki, Toshifumi Tanaka, Shigeru Shimada,* Yohichi Suzuki, Masato Tanaka*
a
b
c
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan
Department of Industrial Chemistry, College of Industrial Technology, Nihon University, Narashino, Chiba 275-8575, Japan
Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8503, Japan
Fax +81(29)8614511; E-mail: s-shimada@aist.go.jp
Received 8 June 2004
t-Bu
Abstract: Cross-coupling reactions of hypervalent organobismuth
compounds, 6-tert-butyl-5,6,7,12-tetrahydrodibenz[c,f][1,5]azabis-
mocines, with aryl and alkenyl chlorides are efficiently catalyzed by
O
O
N
N
Bi Ph
Bi
R
the Pd(OAc) /dppf [dppf = 1,1¢-bis(diphenylphosphino)ferrocene]
2
system.
2
2
2
2
2
a: R = Ph
b: R = Me
c: R = -C(CH3)=CH2
d: R = -C≡CPh
e: R = Cl
Key words: cross-coupling, organometallic reagents, bismuth, pal-
ladium, hypervalent
1
Transition metal-catalyzed cross-coupling reactions of or-
ganometallic compounds with organic halides and tri-
flates are one of the most important reactions to make C-
C bonds. Recently, enormous development has been
achieved in this methodology and a number of active cat-
Figure 1 Structures of organobismuth compounds 1 and 2a–e
1
ate yield and the yield was improved by the addition of
CsF (Table 1, entries 5 and 6).
alyst systems have been developed to enable the efficient Table 2 shows the representative results of the effect of
coupling of aryl chlorides, which are generally cheaper phosphine ligands on the reaction of 2a with 3a and 2-
and more easily available, but less reactive than the corre- chloronaphthalene (3b). The reaction of 2a with 3a effi-
sponding bromides and iodides.2,3
ciently proceeded when bidentate phosphines with rela-
tively large bite angles were used (Table 2, entries 1, 2,
and 4–6), and 10 mol% of dppf showed the best result.
8
We became interested in using organobismuth com-
pounds in organic synthesis because bismuth is a low tox-
ic element and the use of organobismuth compounds in
Among monodentate phosphines tested,
PCy3
4
(Cy = cyclohexyl) showed the highest activity (Table 2,
organic synthesis was limited. Recently, we have report-
ed that organobismuth compounds are capable reagents
for the cross-coupling reaction with organic triflates,
iodides and bromides. In particular, hypervalent organo- BiPh , 1, and 2a with 4-Chlorobenzonitrile
Table 1 Cross-Coupling Reaction of Organobismuth Compounds,
5
3
bismuth compounds, 6-tert-butyl-5,6,7,12-tetrahydro-
dibenz[c,f][1,5]azabismocines, have proved to be highly
Pd(PPh3)4
(10 mol %)
6
'Bi-Ph'
+
4-PhC H CN
6
4
reactive and recoverable reagents for the cross-coupling
NMP, 100 °C
5
d
4-ClC6H4CN
reaction with aryl bromides. Herein, we wish to report
the first application of organobismuth compounds to the
cross-coupling reaction with aryl and alkenyl chlorides.
1
2 h, (additive)
Entry
‘Bi-Ph’
BiPh3
BiPh3
1
Additive (equiv) Yield (%)a
The performance of three organobismuth compounds, 1b
–
2
0
5
a,c,7
BiPh , 1 (Figure 1),
and 2a for the cross-coupling re-
3
2b
CsF (4)
–
action with aryl chlorides was evaluated by the reaction
with 4-chlorobenzonitrile (3a) in the presence of 10 mol% 3c
6
of Pd(PPh ) in NMP (NMP = 1-methyl-2-pyrrolidinone)
3
4
4c
1
CsF (2)
–
8
at 100 °C for 12 hours. BiPh and 1 afforded the cross-
3
coupled product in very low yields and the addition of CsF
showed no improvement (Table 1, entries 1–4). On the
other hand, 2a gave the cross-coupled product in moder-
5c
2a
66
82
6c
2a
CsF (2)
a
Yields were determined by GC using hexadecane as an internal stan-
dard.
b
BiPh , 0.13 mmol; ArCl, 0.41 mmol; NMP, 3 mL.
3
SYNLETT 2004, No. 11, pp 1921–1924
0
6
.0
9
.2
0
0
4
c
1
or 2a, 0.30 mmol; ArCl, 0.25 mmol; NMP, 3 mL.
Advanced online publication: 06.08.2004
DOI: 10.1055/s-2004-831298; Art ID: U16604ST
©
Georg Thieme Verlag Stuttgart · New York

1
922
O. Yamazaki et al.
LETTER
entry 10), which, however, was not as high as the reaction rides catalyzed by the Pd(OAc) –dppf system.1 Phenyl
0
2
with dppf. P(t-Bu) , which is effective for Suzuki– compound 2a and methyl compound 2b efficiently react-
3
9
Miyaura and some other cross-coupling reactions, was ed with electron-deficient and -neutral aryl chlorides in
not very suitable for the reaction of 2a (Table 2, entries the absence (Table 3, entries 1, 2 and 10–15) or in the
1
1–13). For the less reactive 3b, cross-coupled product presence of CsF (Table 3, entries 6, 7), while 2a did not
was obtained in a moderate yield when dppf was used and react with a deactivated aryl chloride, 4-chlorotoluene, ef-
the addition of CsF (2 equiv) considerably improved the ficiently (Table 3, entry 16). Pyridyl, thienyl and alkenyl
yield (Table 2, entries 14, 15). Ph P(CH ) PPh and chlorides also smoothly coupled with 2a (Table 3, entries
2
2 4
2
Ph P(CH ) PPh were less efficient than dppf for the reac- 17–21). Isopropenyl compound 2c also reacted with 3a
2
2 5
2
tion of 3b (Table 2, entries 16, 17).
and 3b under the same reaction conditions as those for 2a
and 2b, although the yields were moderate (Table 3, en-
tries 3 and 8). On the other hand, phenylethynyl com-
pound 2d is much less reactive than 2a–c and required the
addition of CsF and higher reaction temperature even in
the reaction with 3a (Table 3, entry 4) and did not give the
cross-coupled product in the reaction with 3b (Table 3,
entry 9).
Table 3 summarizes the scope and limitation of the cross-
coupling reaction of 6-tert-butyl-5,6,7,12-tetrahydro-
dibenz[c,f][1,5]azabismocines with aryl and alkenyl chlo-
Table 2 Effect of Phosphine Ligands on the Cross-Coupling Reac-
tion of 2a with Aryl Chlorides
As reported previously,5d the cyclic 5,6,7,12-tetrahydro-
dibenz[c,f][1,5]azabismocine structure is stable and the
bismuth compound can be recovered almost quantitative-
ly as chloride 2e, which can easily be converted to 2a–d
and reused.6
Pd(OAc)2 (10 mol %)
2
a
ligand
+
Ar-Ph
NMP, 100 °C, 12 h
Ar-Cl
(CsF, 2 equiv)
c,10
Entry ArCl
Ligand (mol%)
dppf (20)
CsF
No
Yield (%)a
88
Figure 2 shows a plausible reaction mechanism of the
present cross-coupling reaction. The cross-coupling reac-
tion of 2 seems to follow a typical reaction cycle of the
cross-coupling reaction of organometallic compounds
with organic halides and triflates like the cross-coupling
reaction of 1.
1
CN
Cl
2
3
dppf (10)
No
No
93
25
Ph P(CH ) PPh
2
2 2
2
2
2
2
(
10)
4
5
6
Ph P(CH ) PPh
No
No
No
85
90
92
In order to gain information on the cause of the reactivity
2
2 3
(
10)
difference among BiPh , 1, and 2, the following two sets
3
of experiments were carried out. The first was the reaction
Ph P(CH ) PPh
2
2 4
1
1
of these Bi-Ph compounds with (Ph P) PdCl(C H CN),
(
10)
3
2
6
4
which is associated with path (ii) in Figure 2. The yield of
Ph P(CH ) PPh
2
2 5
4-biphenylcarbonitrile after heating in DMF-d at 100 °C
7
(
10)
for one hour in the presence of two equivalents of PPh3
was 44%, 59%, and quantitative, respectively, for BiPh3,
7
8
9
0
1
PPh (40)
No
No
No
No
No
No
No
No
41
3
1
2
, and 2a, suggesting the exceptionally high reactivity of
a. The other set of experiments was intended to examine
P(o-tolyl) (40)
Trace
Trace
72
3
the possible Bi-C oxidative addition, which is envisioned
P(2-furyl) (40)
3
to lead to catalyst decomposition [path (iv), Figure 2]. The
1
1
1
1
1
P(Cy) (40)
31
3
P NMR spectrum of a 1:1 mixture of BiPh , 1 or 2a and
3
Pd(PPh ) in DMF-d revealed the palladium species de-
P(t-Bu) (40)
13
3 4
7
3
composing upon heating at 100 °C, the rate being in the
2
P(t-Bu) (30)
60
12
3
order BiPh >1>2a. In this set of experiments, we were
3
3b
unable to detect the species coming from Bi-C oxidative
addition with Pd(PPh ) . However, the oxidative addition
P(t-Bu) (20)
24
3
3
4
4
Cl
dppf (10)
66
of Bi-C bonds of 1 and 2a towards a Pt(0) complex does
13
take place, 1 being much more reactive than 2a. We pre-
sume that the decomposition of Pd(PPh ) is triggered by
3
4
1
5
6
dppf (10)
Yes
Yes
93
65
Bi-C oxidative addition to Pd(0), which is probably re-
versible and can be competitive with the desired oxidative
addition of C-Cl bonds. On the basis of these experiments,
we conclude that the higher efficiency of 2a probably re-
sults from (1) the higher ability to transfer the organic
group on the bismuth atom in the transmetallation step
1
Ph P(CH ) PPh
2
2 4
2
2
(
10)
17
Ph P(CH ) PPh
Yes
10
2
2 5
(
10)
a
Yields were determined by GC using hexadecane as an internal
[
path (ii), Figure 2] and (2) the lower ability of the Bi-C
standard.
b
Pd (dba) (5 mol%) was used instead of Pd(OAc) .
bond for oxidative addition to the Pd(0) species that leads
to the decomposition of the catalyst [path (iv), Figure 2].
2
3
2
Synlett 2004, No. 11, 1921–1924 © Thieme Stuttgart · New York

LETTER
Palladium-Catalyzed Cross-Coupling Reaction of Organobismuth Compounds
1923
Table 3 Cross-Coupling Reaction of 2a–d with Various Aryl and
Alkenyl Chlorides
Although the effect of CsF was not clearly understood, co-
ordination of the fluoride anion to the bismuth center may
take place, which facilitates the transfer of organic group
in the transmetallation step and retards the direct oxidative
addition of Bi-C bond to Pd(0) species.
Pd(OAc)2 (10 mol %)
dppf (10 mol %)
1
2
1
R -R2
'
Bi-R ' + R -Cl
NMP, 100 °C, 12 h
CsF, 2 equiv)
2a–2d
(
In conclusion, bismuth compounds 2a–d are useful and
easily recoverable reagents for the cross-coupling reaction
with aryl chlorides. For relatively reactive aryl chlorides,
the addition of coordinating additives such as CsF or
bases is not necessary, which is often required for the
cross-coupling reaction of other organometallic reagents.
2
Yield (%)a
Entry
1
2a–d
R -Cl
CsF
No
2a
Quant.
CN
Cl
2
2b
2c
2d
2a
No
No
Yes
No
(92)
62
3
Pd(0)
R'-Cl
R-Bi
4b
5
58
(iv)
(i)
R-Bi
Cl
66
R-R'
R'-Pd-Cl
(
R-Pd-Bi
(
iii)
6
7
8
9
2a
2b
2c
2d
2a
Yes
Yes
Yes
Yes
No
93
R-Bi
(95)
(53)
0
ii)
catalyst
decomposition
Bi-Cl
R-Pd-R'
Figure 2 A plausible mechanism of the reaction of 2a–d with aryl
1
1
1
0
1
2
92
and alkenyl chlorides
MeO2C
F3C
Cl
Cl
2a
2a
No
No
79
Cl
Acknowledgment
This work was partially supported by the Japan Science and Tech-
nology Corporation (JST) through the CREST (Core Research for
Evolutional Science and Technology) program. O.Y. thanks JST for
a postdoctoral fellowship.
O
Quant.
O
1
1
3
4
2b
2a
No
No
75
References
Cl
Quant.
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6
2b
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No
(99)
(10)
(
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(
2) For a recent review, see: Littke, A. F.; Fu, G. C. Angew.
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1
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7
8
2a
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92
42
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N
Cl
S
(
d) Schnyder, A.; Indolese, A. F.; Studer, M.; Blaser, H.-U.
1
2
9
0
2a
2a
Yes
No
58
90
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1c
61d
2
2a
No
O
O
(
h) Choudary, B. M.; Madhi, S.; Chowdari, N. S.; Kantam,
Cl
Cl
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2
003, 125, 16194.
a
Isolated yields. GC yields using hexadecane as an internal standard
(
4) For reviews on the utilization of organobismuth compounds
in organic synthesis, see: (a) Suzuki, H.; Ikegami, T.;
are shown in parentheses.
b
Reaction temperature: 120 °C.
Matano, Y. Synthesis 1997, 249. (b) Suzuki, H.; Matano, Y.
In Chemistry of Arsenic, Antimony and Bismuth; Norman, N.
c
2
0 mol% of Pd(OAc) and dppf were used.
2
d
Yield of diphenylated product.
Synlett 2004, No. 11, 1921–1924 © Thieme Stuttgart · New York

1
924
O. Yamazaki et al.
LETTER
C., Ed.; Blackie Academic and Professional: London, 1998,
Chap. 6. (c) Elliott, G. I.; Konopelski, J. P. Tetrahedron
(10) Typical Procedure: A mixture of 2a (161 mg, 0.30 mmol),
4-CF C H Cl (46 mg, 0.25 mmol), Pd(OAc) (5.6 mg, 0.025
3
6
4
2
2001, 57, 5683. (d) Organobismuth Chemistry; Suzuki, H.;
mmol) and dppf (14 mg, 0.025 mmol) in 3 mL of NMP was
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heated at 100 °C for 12 h under N . The crude mixture was
dissolved in EtOAc (90 mL) and washed with aq HCl (4 M,
2
3 × 10 mL) and H O (10 mL). The organic layer was dried
2
(
5) (a) Rao, M. L. N.; Shimada, S.; Tanaka, M. Org. Lett. 1999,
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Suzuki, Y.; Tanaka, M. Angew. Chem. Int. Ed. 2003, 42,
845.
over Na SO , filtered, and concentrated in vacuo. The
2
4
1
residue was separated with a short pad of silica gel, eluting
with EtOAc–hexane (1:10) to give a mixture containing
cross-coupled product and then with CH Cl –EtOAc (1:1) to
4
2
2
give pure 2e (145 mg, 98%). The former mixture was further
purified with PTLC to give 4-trifluoromethylbiphenyl (45
mg, 79%).
(
1
(11) Fitton, P.; Rick, E. A. J. Organomet. Chem. 1971, 28, 287.
3
1
(
6) (a) Ohkata, K.; Takemoto, S.; Ohnishi, M.; Akiba, K.
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a broad signal suggesting a rapid exchange of coordinated
and uncoordinated PPh . The signals shifted upfield
3
861. (c) Shimada, S.; Yamazaki, O.; Tanaka, T.; Suzuki, Y.;
gradually and reached that of free PPh after complete
3
Tanaka, M. J. Organomet. Chem. 2004, in press.
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(
(
7) Shimada, S.; Rao, M. L. N.; Tanaka, M. Organometallics
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2
000, 19, 931.
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3
3
at –50 °C and is complete within 1 h at 0 °C, while that of 2a
2
toward Pt(PEt ) is slow at r.t. and is not complete, and
3
3
Dierkes, P. Chem. Rev. 2000, 100, 2741.
seems to reach equilibrium at about 60% conversion.
(
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Synlett 2004, No. 11, 1921–1924 © Thieme Stuttgart · New York