Cross-coupling reaction of organobismuth dialkoxides with aryl bromides and iodides catalyzed by Pd(PPh3)4

Article abstract of DOI:10.1016/S0022-328X(02)01716-3

Cross-coupling reaction of organobismuth compounds bearing 2,6-pyridinedimethoxide ligands with aryl bromides and iodides was efficiently catalyzed by Pd(PPh₃)₄. Addition of two equivalents of Cs₂CO₃ or CsF impr

Full text of DOI:10.1016/S0022-328X(02)01716-3

Journal of Organometallic Chemistry 659 (2002) 117ꢀ120
/
www.elsevier.com/locate/jorganchem
Cross-coupling reaction of organobismuth dialkoxides with aryl
bromides and iodides catalyzed by Pd(PPh3)4
a
Maddali L.N. Rao , Shigeru Shimada *, Osamu Yamazaki , Masato Tanaka
a,
a
a,b,
*
a
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
b
Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuda-cho, Midori-ku, Yokohama 226-8503, Japan
Received 4 June 2002; received in revised form 16 July 2002; accepted 22 July 2002
Abstract
Cross-coupling reaction of organobismuth compounds bearing 2,6-pyridinedimethoxide ligands with aryl bromides and iodides
was efficiently catalyzed by Pd(PPh . Addition of two equivalents of Cs CO or CsF improved the yields of the products, in
3
)
4
2
3
particular for the reaction of aryl bromides. # 2002 Elsevier Science B.V. All rights reserved.
Keywords: Organobismuth compounds; Cross-coupling reaction; Palladium; Aryl halides
1
. Introduction
nyl-triflates (Scheme 1) and the reactions of Ar Bi with
3
aryl halides and triflates (Scheme 2) readily proceed to
form the corresponding cross-coupled products in good
yields [11,12].
Transition metal-catalyzed cross-coupling reaction of
organometallic compounds with organic halides and
triflates is one of the most important reactions to make
The reaction of compounds 1 with aryl- and alkenyl-
triflates proceeded in the presence of Pd(PPh ) without
3 4
2
C bonds, in particular for those containing sp - or
Cꢀ
/
sp-C atoms [1]. Various organometallic compounds such
as organotin, boron, silicon, zinc, and magnesium
compounds have been successfully utilized for the
cross-coupling reactions.
On the other hand, organobismuth compounds are
useful reagents for the transition metal-mediated or
any additives. However, the reactivity of 1 to aryl
bromides seemed to be much lower than that to triflates:
the reaction of 1b with 1-naphthyl triflate gave 80% of
cross-coupled product while that of 1b with 1-bromo-
naphthalene afforded only 15% of cross-coupled pro-
duct [11]. We recently found that the addition of
coordinating salt such as K CO or CsF considerably
-
catalyzed coupling reaction with various substrate [2];
2
3
improved the reactivity of Ar Bi toward aryl triflates,
3
for example, pentavalent and trivalent organobismuth
compounds have been utilized for the Heck-type aryla-
tion of alkenes [3], arylation of alcohols and amines [4],
cross-coupling reaction with acid chlorides [5], allyl
halides [6] and terminal alkynes [7], homocoupling
biaryl formation [5a,8], carbonylation reactions [9],
and arylation of vinyl epoxides [10]. We have recently
demonstrated that organobismuth compounds are also
useful reagents for the cross-coupling reaction with aryl
or alkenyl triflates and aryl halides: the reactions of
bromides, and iodides [12]. Here, we report the palla-
dium-catalyzed cross-coupling reaction of 1a and 1d
with aryl bromides and iodides and the influence of salt
additives.
2. Results and discussion
2.1. Reaction of 1a and 1d with aryl bromides
organobismuth dialkoxides 1aꢀ1d with aryl- and alke-
/
Under the reaction conditions suitable for the cross-
coupling reaction of 1a with aryl triflates (10 mol%
*
Corresponding authors. Tel.: ꢁ
511
E-mail address: s-shimada@aist.go.jp (S. Shimada).
/
81-298-61-4588; fax: ꢁ81-298-61-
/
Pd(PPh ) , 100 8C, 12 h in NMP (1-methyl-2-pyrroli-
4
0
3 4
dinone)) [11], the reaction of 1a with 1-bromonaphtha-
022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 7 1 6 - 3

118
M.L.N. Rao et al. / Journal of Organometallic Chemistry 659 (2002) 117ꢀ120
/
products in excellent yields (Table 1, entries 9, 11ꢀ
/
12,
4). On the other hand, as observed in the reaction of
aꢀ1d with aryl triflates [11], an electron-rich aryl
1
1
/
bromide, 4-bromotoluene, afforded the cross-coupled
product only in a low yield even in the presence of
Cs CO . (Table 1, entry 13). Methylation with 1d (Table
2
3
1, entries 5, 8, 10) also proceeded albeit less efficiently
than the phenylation with 1a.
Scheme 1.
2.2. Reaction of 1a and 1d with aryl iodides
Aryl iodides, as expected, are more reactive than aryl
bromides toward 1a and 1d. Phenylation of 1-iodo-
naphthalene with 1a gave 1-phenylnaphthalene in a
good yield in the absence of additives (Table 2, entry 1),
and the yield became quantitative by the addition of two
equivalents of Cs CO (Table 2, entry 3) [13]. Electron-
Scheme 2.
lene gave only 15% of cross-coupled product, 1-phenyl-
naphthalene, together with biphenyl (13%). However,
the reactivity was dramatically enhanced by addition of
Cs CO (two equivalents to ArBr) to form the product
2
3
deficient aryl iodides afforded phenylated products in
excellent yields even in the absence of additives (Table 2,
2
3
entries 4, 6ꢀ7). It is noteworthy that even electron-rich
/
in 88% yield. CsF (40%) and K CO (32%) also showed
2
3
aryl iodides gave phenylarenes in good yields when two
equivalents of CsF or Cs CO was added to the reaction
slight improvement in the yield while NEt , LiCl, and
3
2
3
KF were not effective.
system (Table 2, entries 9ꢀ
/
10 and 12ꢀ13).
/
The reaction of 1a with electron-deficient aryl bro-
mides, 4?-bromoacetophenone and 4-bromobenzonitrile,
gave the cross-coupled products in moderate to good
yields even in the absence of additives, while the yield
became quantitative by the addition of Cs CO (Table 1,
2.3. Effects of salt additives
2
3
The improvement of the yield by the addition of salts
entries 3ꢀ
/
4 and 6ꢀ7) [13]. Other electron-deficient aryl
/
may be attributed to the formation of higher coordi-
nated bismuth ‘ate’ complexes. The enhancement of the
reactivity by coordinating additives is also known in the
cross-coupling reaction of other organometallic com-
pounds. For example, cross-coupling reaction of boro-
nic acids or boronic esters requires base additives;
anionic boronate intermediates seem to be the actual
species which undergo the transmetalation [1b,1c].
Cross-coupling reaction of organosilicon compounds
usually requires fluoride salts as activators; pentacoor-
dinate fluorosilicates are the key intermediates in this
reaction [14].
bromides and 2-bromopyridine also gave phenylated
Table 1
Reaction of organobismuth dialkoxides 1a and 1d with aryl bromides
a
Pd(PPh3)4 (10 mol%)
1
1a or 1dꢁArꢀBr
ArꢀR :
NMP; 100
ꢀ
C (additive; two equivalents)
b
Entry
1a/1d
Ar
Additive
Yield (%)
c
1
1a
1a
1a
1a
1d
1a
1a
1d
1a
1d
1a
1a
1a
1a
1-Naphthyl
4-AcC
no
Cs
no
Cs
Cs
no
Cs
Cs
Cs
Cs
Cs
Cs
Cs
Cs
15
88
2
3
4
5
6
7
8
9
2
CO
3
6
H
4
63
2
CO
CO
3
99
69
2
3
It is well known that bismuth often forms hypervalent
compounds; organobismuth compounds can accommo-
6
4-NCC H
4
79
2
CO
2
CO
2
CO
2
CO
2
CO
2
CO
2
CO
2
CO
3
3
3
3
3
3
3
3
quant (95)
52
96
date up to nine coordinations [15]. Unlike Ar Bi,
3
compounds 1aꢀ1d already have intramolecular coordi-
/
4-PhCOC
6
H
4
1
1
1
1
1
0
1
2
3
4
80
85
nation by a nitrogen atom. However, their solid state
structures have disclosed that they form dimers by the
intermolecular coordination by the oxygen atom to the
bismuth atom [16]. Although the formation of a stable
ate complex from 1a with Cs CO was not observed [17],
3-AcC
3-CF
4-MeC
2-Pyridyl
6
H
4
3
C
6
H
4
quant
36
6 4
H
99
2
3
a
1a or 1d:ArBrꢂ1.2:1.
we presume that 1aꢀ1d can accommodate additional
/
b
Yields were determined by GLC analysis of the crude reaction
mixture by using hexadecane as an internal standard. Isolated yield is
shown in parentheses.
coordination of the salt promoters, which is likely to be
associated with the reactivity enhancement of 1a and 1d
in the cross-coupling reaction.
c
Reaction time, 12 h.

M.L.N. Rao et al. / Journal of Organometallic Chemistry 659 (2002) 117ꢀ
/120
119
Table 2
Reaction of organobismuth dialkoxides 1a and 1d with aryl-iodides
In the previous paper [11], we suggested that cycle A is
more likely based mainly on the following information,
a
(
1) Biꢀ
/
C bond is very weak [18]; (2) 1c is more reactive
Pd(PPh3)4 (10 mol%)
a or 1dꢁArꢀI NMP; 80 ꢀC (additive; two equivalents) ArꢀR :
1
1
than 4-acetylphenyl triflate in oxidative addition reac-
tion to Pt(PEt ) [19].
3
4
b
Entry 1a/1d Ar
Time (h) Additive Yield (%)
However, further study supported cycle B rather than
cycle A, (1) oxidative addition of 1a toward Pd(PPh3)4
was not observed by NMR. Instead, gradual decom-
position of Pd(PPh ) took place when the mixture of
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
1a
1a
1a
1a
1d
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1-Naphthyl
6
6
6
3
6
3
3
6
6
6
6
6
6
6
6
No
CsF
74
86
3
4
Cs
2
CO
3
99(93)
96
69
4-AcC
6
6
H
4
No
No
No
No
No
Pd(PPh3)4 and 1a in (CD ) NCDO was heated at
3 2
100 8C; (2) electron deficient aryl halides gave better
yields of cross-coupled products than electron rich aryl
halides; this observation is compatible with the oxidative
addition step of cycle B; (3a) the improvement of the
yields by salt additives and (3b) higher reactivity of (p-
MeC H ) Bi or Ph Bi than (p-FC H ) Bi in the cross-
4-AcC
H
4
Quant
97
3-CF
3
C
6
H
4
4-MeC
6
H
4
60
CsF
Cs CO
No
CsF
85
1
1
1
1
1
1
2
3
83(78)
55
61
4-MeOC
6
H
4
6
4 3
3
6
4 3
coupling reaction with 1-bromonaphthalene [12] suggest
that electron-rich organobismuth species have higher
reactivity probably because they have higher ability to
transfer aryl-group in the transmetalation step of cycle
B; (4) [trans-Pd(Br)(p-NCC H )(PPh ) ], an intermedi-
Cs
No
Cs
2
CO
3
79
57
2-Pyridyl
2
CO
3
93
a
1a or 1d:ArIꢂ1.2:1.
6
4
3 2
b
Yields were determined by GLC analysis of the crude reaction
mixture by using hexadecane as an internal standard. Isolated yields
are shown in parentheses.
ate in cycle B, reacted with 1a at 100 8C in NMP for 6 h
to produce the cross-coupled product, 4-biphenylcarbo-
nitrile, in 84% yield. Based on these results, it is likely
that the cross-coupling reaction of 1aꢀd and Ar Bi with
/
3
2
.4. Reaction mechanism
organic triflates and aryl halides proceeds through cycle
B. The oxidative addition step and the transmetalation
step are probably comparable in their reaction rate and
either of them is rate-determining depending on sub-
strates and reaction conditions. If the reactivity of aryl
halides or bismuth compounds is low, decomposition of
the catalyst becomes competitive to the cross-coupling
reaction and the yield of the cross-coupled product
decreases.
Previously, we have proposed two possible catalytic
cycles, cycle A and cycle B in Fig. 1, for the cross-
coupling reaction of compounds 1 with aryl and alkenyl-
triflates [11]. Cycle A is triggered by the oxidative
addition of Biꢀ
transmetalation with Arꢀ
/
C bond to Pd(0), followed by the
/X and subsequent reductive
elimination to give cross-coupled product and Pd(0)
species. Cycle B is generally accepted as a mechanism for
the cross-coupling reaction of organometallic com-
pounds such as organoboron and organotin com-
3. Experimental
pounds: oxidative addition of Arꢀ
/
X to Pd(0) species, a
transmetalation step to form a diorganopalladium
intermediate, and a subsequent reductive elimination
step to form the cross-coupled product and the Pd(0)
species [1].
3.1. General
All manipulations of air-sensitive materials were
carried out under a nitrogen atmosphere using standard
Schlenk tube techniques. Anhydrous NMP was pur-
chased from Kanto Chemicals and degassed before use.
Compounds 1a and 1d were prepared as described
previously [16]. [Trans-Pd(Br)(p-NCC H )(PPh ) ] [20]
6
4
3 2
was prepared as described in the literature for the
preparation of [trans-Pd(Cl)(p-NCC H )(PPh ) ] [21].
6
4
3 2
3.2. Reaction of 1a and 1d with aryl halides
3.2.1. Typical reaction procedure
A mixture of 1a (144 mg, 0.30 mmol), 4-bromoben-
zonitrile (46 mg, 0.25 mmol), Cs CO (163 mg, 0.50
mmol), and Pd(PPh ) (29 mg, 0.025 mmol) in 3 ml of
2
3
Fig. 1. Two possible catalytic cycles for the cross-coupling reaction of
organobismuth compounds.
3 4
NMP was heated at 100 8C for 6 h under N . After the
2

120
M.L.N. Rao et al. / Journal of Organometallic Chemistry 659 (2002) 117ꢀ120
/
(
(
g) Y. Matano, J. Syn. Org. Chem. Jpn. 59 (2001) 834;
h) Y. Matano, Chem. Abstr. 135 (2001) 371248j.
addition of hexadecane (internal standard), the mixture
was analyzed by GC to determine the yield of 4-
biphenylcarbonitrile (100%). Biphenyl was not detected
by GC analysis. The crude mixture was dissolved in
EtOAc (90 ml) and washed with water (10 ml), 10%
aqueous (aq.) HCl (10 ml), water (10 ml) and brine (10
ml). The organic layer was dried over Na SO , filtered
[
[
3] (a) R. Asano, I. Moritani, Y. Fujiwara, S. Teranishi, Bull. Chem.
Soc. Jpn. 46 (1973) 2910;
(
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(
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(1986) 3615;
and concentrated in vacuo. The residue was purified by
preparative TLC (hexaneꢀEtOAcꢂ5/1) to give 43 mg
95%) of 4-biphenylcarbonitrile.
/
/
(
(
(
(
(
d) D.H.R. Barton, J.P. Finet, J. Khamsi, Tetrahedron Lett. 27
1986) 3619;
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3
with 1a
.3. Reaction of [trans-Pd(Br)(p-NCC H )(PPh ) ]
6 4 3 2
[
[
5] (a) D.H.R. Barton, N. Ozbalik, M. Ramesh, Tetrahedron 44
(
(
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Trans. 1 (1992) 1593.
6] (a) M. Wada, H. Ohki, J. Synth. Org. Chem. Jpn. 47 (1989) 425;
6
4
3 2
3
mg, 0.25 mmol) in 1.5 ml of NMP was heated at 100 8C
(
b) M. Wada, H. Ohki, Chem. Abstr. 111 (1989) 38573n;
for 6 h under N . The crude mixture was dissolved in
2
(c) X. Huang, J.L. Wu, Chin. Chem. Lett. 8 (1997) 759;
(d) X. Huang, J.L. Wu, Chem. Abstr. 127 (1997) 358654d.
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EtOAc (45 ml) and washed with water (10 ml), 10% aq.
HCl (10 ml), water (10 ml) and brine (10 ml). The
organic layer was dried over Na SO , filtered and
[
[
[
2
4
8] T. Ohe, T. Tanaka, M. Kuroda, C.S. Cho, K. Ohe, S. Uemura,
Bull. Chem. Soc. Jpn. 72 (1999) 1851.
concentrated in vacuo. The residue was purified by
preparative TLC (hexaneꢀEtOAcꢂ5/1) to give 19.0 mg
84%) of 4-biphenylcarbonitrile.
/
/
9] (a) C.S. Cho, T. Ohe, O. Itoh, S. Uemura, J. Chem. Soc. Chem.
Commun. (1992) 453;
(
(
(
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Acknowledgements
We are grateful to the Japan Science and Technology
Corporation (JST) for financial support through the
Core Research for Evolutional Science and Technology
[12] M.L.N. Rao, O. Yamazaki, S. Shimada, T. Tanaka, Y. Suzuki,
M. Tanaka, Org. Lett. 3 (2001) 4103.
[
13] In the reaction of 1a, biphenyl was occasionally produced as a by-
product in 10ꢀ40% yields based on 1a.
/
(
CREST) program and for postdoctoral fellowships to
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M.L.N.R. and O.Y. We also thank Mr. T. Tanaka for
his help.
(b) T. Hiyama, in: F. Diederich, P.J. Stang (Eds.), Metal-
Catalyzed Cross-Coupling Reactions (Chapter 10), Wiley-VCH,
1
998.
[
[
15] T. Ogawa, in: H. Suzuki, Y. Matano (Eds.), Organobismuth
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(
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(
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/
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