close

Вход

Забыли?

вход по аккаунту

?

Highly efficient orthopalladated complexes of second and third benzyl amine for catalyzing the Suzuki cross-coupling reaction.

код для вставкиСкачать
Full Paper
Received: 18 April 2010
Revised: 30 June 2010
Accepted: 30 June 2010
Published online in Wiley Online Library: 1 September 2010
(wileyonlinelibrary.com) DOI 10.1002/aoc.1713
Highly efficient orthopalladated complexes
of second and third benzyl amine for catalyzing
the Suzuki cross-coupling reaction
Kazem Karami∗ and Mina Mohamadi Salah
In this work, ortho-palladated complexes [Pd(µ-Cl)(C6 H4 CH2 NRR -κ 2 -C,N)]2 and [Pd(C6 H4 CH2 NH2 -2-C,N)Cl(Y)] were tested
in the Suzuki–Miyaura cross-coupling reaction. Cyclopalladated Pd(II) complexes as thermally stable catalysts can activate
aryl bromides and chlorides. These complexes were active and efficient catalysts for the Suzuki–Miyaura reaction of aryl
bromides and even less reactive aryl chlorides. The cross-coupled products of a variety of aryl bromides and aryl chloride with
c 2010 John Wiley & Sons,
phenylboronic acid in methanol as solvent at 60 ◦ C were produced in excellent yields. Copyright Ltd.
Keywords: ortho-palladated complexes; Suzuki cross-coupling; Palladium catalyst
Introduction
828
Palladacycle complexes have received great interest due to
their applications in many areas such as organic synthesis.[1 – 3]
Homogeneous transition metal-catalyzed reactions represent
one of the most important and well-studied reaction types in
microwave-assisted organic synthesis.[4] In a continuation of our
recent investigations on the application of the new palladacycle
complexes[5] in C–C cross-coupling, we now wish to report the
extension of its utilization under heating in the Suzuki reactions.
The Suzuki–Miyaura reaction,[6] the coupling of arylbronic acids
and aryl halides, is a versatile and important tool in organic
chemistry.[7 – 15] This reaction has consequently found widespread
use in organic synthesis processes.[16] The reactivity decreases
drastically in the order ArI > ArBr > ArCl and, for that reason,
aryl bromides and chlorides, while being cheaper and more
readily available and therefore much more useful substrates to
synthetic chemists, often do not react efficiently.[5] Among the
various methods known to biaryl synthesis, the Suzuki–Miyaura
reaction is a powerful method for the formation of C (sp2)–C
(sp2) bonds under mild reaction conditions.[17] In addition to
the C (sp2)–C (sp2) cross-couplingof aryl bromides, very recently
the Suzuki–Miyaura coupling has been extended to C (sp3)–C
(sp2) and C (sp3)–C (sp3) coupling[18] of various halides with
phenylboronic acids. Traditional the Suzuki reaction usually
proceeds using P- and N-ligand-based palladium catalysts and
much attention has been paid to improve the Suzuki reaction
by designing various new ligands.[19] Arylboronic acid, used in
Suzuki coupling reactions, is largely unaffected by the presence
of water and is commercially available at the laboratory scale.[16]
Almost any Pd(II) or Pd(0) derivative, usually associated with
phosphine, substituted with electron-withdrawing groups, has
high turnover numbers.[20] Palladacycles are likely to operate
in a common phosphine-free Pd(0):Pd(II) catalytic cycle, while
the differences between various types of palladacycle precursors
are accounted for by the kinetics of the catalyst preactivation
step.
Appl. Organometal. Chem. 2010, 24, 828–832
The palladacycles are initially reduced and the catalysis is
performed via a classical Pd(0)/Pd(II) cycle. In a few instances a
Pd(II)/Pd(IV) mechanism could not be ruled out.[21] Here we report
that many palladacycles with NC coordination (complexes 4a, 5a,
4b, 5b, 6b, 4c, 5c, Scheme 1), derived from readily available and
very inexpensive ligands, can also be used as catalyst precursors
for the Suzuki reaction, and some of them are very efficient
allowing the reactions to be carried out under mild conditions.
The complexes 4a, 5a, 4b, 5b, 6b, 4c, 5c (Scheme 1) are thermally
stable and not sensitive to oxygen and moisture as the metal
centers are stabilized by a five-member ring. These complexes were
conveniently prepared according to the literature methods.[22]
Experimental
Materials and Techniques
All chemicals were purchased from Merck. 1 H (300 MHz), 31 P
(121.5 MHz) and 13 C (100 MHz) NMR spectra were recorded on
a Bruker Avance Spectrometer. Shimadzu GC 14-A and thinlayer chromatography on precoated silica gel fluorescent 254 nm
(0.2 mm) were used for monitoring the reactions. Conversions
were determined by GC, based on aryl halides. The cross-coupled
biphenyl and its derivative products were characterized by its 1 H
NMR spectra.
General Procedure for the Synthesis of Cyclopalladated
Complex {Pd(C6 H4 CH2 NRR ) XY} (R, R = H or Me or Et or
t-Bu; X = Cl or Br; Y = PPh3 or 4-Picoline or Me3 Py)
Palladium (II) acetate (0.224 g, 1 mmol) was heated with secondary
or tertiary benzylamine [1a, EtNHCH2 Ph; 1b, t-BuNHCH2 Ph; 1c,
∗
Correspondence to: Kazem Karami, Department of Chemistry, Isfahan University of Technology, Isfahan, Iran. E-mail: karami@cc.iut.ac.ir
Department of Chemistry, Isfahan University of Technology, Isfahan, Iran
c 2010 John Wiley & Sons, Ltd.
Copyright Efficient orthopalladated complexes of second and third benzyl amine
Scheme 1. The synthesis of complex palladium catalyst.
Scheme 2. The Suzuki cross-coupling reaction.
Appl. Organometal. Chem. 2010, 24, 828–832
c 2010 John Wiley & Sons, Ltd.
Copyright wileyonlinelibrary.com/journal/aoc
829
(Me)2 NCH2 Ph), 1 mmol] at 50 ◦ C in benzene (15 cm3 ) for 1 day.
The resulting green suspension was 2a, 2b, 2c in Scheme 1.
A methanol suspention (13 cm3 ) containing 2a, 2b, 2c
(0.6 mmol) and sodium chloride or sodium bromide (1.118 mmol)
was stirred for 12 h at room temperature. The resulting precipitates
were filtered off to give 3a, 3b, 3c in Scheme 1. Addition of PPh3 ,
sym-collidine or 4-picoline (1.0 mmol) to a suspension of 3a, 3b, 3c
(0.501 mmol) in CH2 Cl2 (15 cm3 ) gave a clear solution immediately.
After stirring for 8 h at room temperature, the solution was filtered
through the plug of Celite or MgSO4 . Crude complexes resulted
that precipitated as solids. These solids were dissolved in CH2 Cl2
at room temperature and n-hexane were added to give a powder,
which was filtered off and then air-dried to give complexes 4a, 5a,
4b, 5b, 6b, 4c and 5c in Scheme 1.
(4a): IR (cm−1 , KBr); ν(N–H) 3186, ν(C N) 1615, 1 H NMR
(300 MHz, CDCl3 , ppm); δ = 1.40 (t, 3H, CH3 ), 2.43 (s, 3H, CH3 ), 3.07
(m, 1H, CH2 ), 3.33 (m, 1H, CH2 ), 3.87 (dd, 1H, CH2 , 2 JHH = 13.5 Hz,
3J
2
3
HH = 2.5 Hz), 4.55 (dd, 1H, CH2 , JHH = 13.5 Hz, JHH = 2.5 Hz),
3
4.03 (s, 1H, NH), 6.12 (d, 1H, Ph, JHH = 7.5 Hz), 6.82 (m, 2H, Ph),
7.02 (d, 1H, Ph, 3 JHH = 7.5 Hz), 7.17 (d, 2Hm , Py, 3 JHH = 10 Hz),
8.71 (d, 2Ho , Py, 3 JHH = 10 Hz). 13 C NMR (100 MHz, CDCl3 , ppm);
Caliphatic {δ = 14.71, 21.17, 48.82, 60.33}, Caromatic {δ = 121.46,
124.47, 125.18, 126.02, 149.66, 153.48, 125.93 (Cm , Py), 131.86 (Cp ,
Py), 152.77 (Co , Py)}. Elemental analysis calcd: C, 43.55; H, 4.63; N,
6.77. Found: C, 43.72; H, 4.71; N, 6.89%.
(5a): IR (cm−1 , KBr); ν(N–H) 3160, ν(C N) 1621, 1 H NMR
(300 MHz, CDCl3 , ppm); δ = 1.43 (t, 3H, CH3 ), 2.38 (s, 3H, CH3 ),
3.04 (s, 3H, CH3 ), 3.24 (s, 3H, CH3 ), 3.20 (m, 1H, CH2 ), 3.375 (m,
1H, CH2 ), 3.91 (dd, 1H, CH2 , 2 JHH = 12.5 Hz, 3 JHH = 5 Hz), 4.57
(dd, 1H, CH2 , 2 JHH = 12.5 Hz, 3 JHH = 5 Hz), 4.11 (s, 1H, NH), 5.75
(d, 1H, Ph, 3 JHH = 7.5 Hz), 6.72 (t, 1H, Ph, 3 JHH = 7.5 Hz), 6.98
(m, 2H, Ph), 7.07 (d, 1H, Pym , 4 JHH = 5 Hz). 13 C NMR (100 MHz,
CDCl3 , ppm); Caliphatic {δ = 14.60, 20.76, 27.89, 28.15, 48.81, 60.47},
Caromatic {δ = 121.29, 123.69, 123.89, 124.26, 129.83, 148.09, 125.18
(Cm , Py), 130.19 (Cm , Py), 128.85 (Cp , Py), 149.64 (Co , Py), 158.60
(Co , Py)}. Elemental analysis calcd: C, 46.23; H, 5.25; N, 6.34. Found:
C, 46.4; H, 5.41; N, 6.5%.
(4b): IR (cm−1 , KBr); ν(C N) 1615, 1 H NMR (300 MHz, CDCl3 ,
ppm); δ = 2.44 (s, 3H, CH3 ), 2.95 (s, 6H, CH3 ), 3.99 (s, 2H. CH2 ),
6.07 (d, 1H, Ph, 3 JHH = 10 Hz), 6.78–6.82 (m, 2H, Ph), 7.08 (d, 1H,
Ph, 3 JHH = 10 Hz), 7.21 (d, 2Hm , Py, 3 JHH = 5 Hz), 8.73 (d, 2Ho , Py,
3J
13
HH = 5 Hz). C NMR (100 MHz, CDCl3 , ppm); Caliphatic {δ = 21.16,
52.69, 74.00}, Caromatic {δ = 121.55, 124.44, 125.27, 132.27, 148.09,
149.80, 126.04 (Cm , Py), 147.60 (Cp , Py), 152.58 (Co , Py)}. Elemental
analysis calcd: C, 48.80; H, 5.18; N, 7.58. Found: C, 48.99; H, 5.27; N,
7.74%.
(5b): IR (cm−1 , KBr); ν(C N) 1622, 1 H NMR (300 MHz, CDCl3 ,
ppm); δ = 2.37 (s, 3H, CH3 ), 3.00 (s, 6H, CH3 ), 3.16 (s, 6H, CH3 ),
4.01 (s, 2H, CH2 ), 5.73 (d, 1H, Ph, 3 JHH = 10 Hz), 6.69–6.72 (m, 2H,
Ph), 6.98 (d, 1H, Ph, 3 JHH = 10 Hz), 7.03 (d, 2Hm , Py, 4 JHH = 5 Hz).
13
C NMR (100 MHz, CDCl3 , ppm); Caliphatic {δ = 20.74, 28.08, 52.36,
73.90}, Caromatic {δ = 121.40, 124.20, 125.24, 131.30, 147.68, 149.66,
123.73 (Cm , Py), 145.89 (Cp , Py), 158.79 (Co , Py)}. Elemental analysis
calcd: C, 51.40; H, 5.83; N, 7.04. Found: C, 51.64; H, 5.9; N, 7.12%.
(6b): 1 H NMR (300 MHz, CDCl3 , ppm); δ = 2.885 (s, 6H, CH3 ),
4.105 (s, 2H, CH2 ), 6.35 (d, 1H, Ph, 3 JHH = 7.5 Hz), 6.41 (t, 1H, Ph,
3
JHH = 7.5 Hz), 6.85 (t, 1H, Ph, 3 JHH = 7.5 Hz), 7.02 (d, 1H, Ph,
3J
HH = 7.5 Hz), 7.39 (m, 6Hm , PPh3 ),7.44 (m, 3Hp , PPh3 ), 7.75 (m,
6Ho , PPh3 ). 31 P {1 H} NMR (121.5 MHz, CDCl3 , ppm): δ = 42.92 (s, 1P,
Pd–PPh3 ). 13 C NMR (100 MHz, CDCl3 , ppm); Caliphatic {δ = 50.52,
73.26, 73.29}, Caromatic {δ = 122.31, 123.79, 124.87, 124.93, 148.46,
150.79, 127.94–128.05} (Cm , PPh3 ), 130.46–131.20 (Cp , PPh3 ),
135.30–135.37 (Co , PPh3 , 2 JPC = 28 Hz), 137.82–137.93 (Ci , PPh3 ,
1J
PC = 44 Hz). Elemental analysis calcd: C, 60.24; H, 5.05; N, 2.6.
Found: C, 60.38; H, 5.13; N, 2.74%.
(4c): IR (cm−1 , KBr); ν(N–H) 3183, 1 H NMR (300 MHz, CDCl3 ,
ppm); δ = 1.32 (s, 9H, CH3 ), 4.02 (d, 1H, CH2 , 2 JHH = 15 Hz),
4.76 (d, 1H, CH2 , 2 JHH = 15 Hz), 4.36 (s, 1H, NH), 6.19 (d, 1H,
Ph, 3 JHH = 5 Hz), 6.35 (t, 1H, Ph, 3 JHH = 5 Hz), 6.79 (t, 1H,
Ph, 3 JHH = 5 Hz), 6.95 (d, 1H, Ph, 3 JHH = 5 Hz), 7.36 (m, 6Hm ,
PPh3 ), 7.45 (m, 3Hp , PPh3 ), 7.74 (m, 6Ho , PPh3 ). 31 P {1 H} NMR
(121.5 MHz, CDCl3 , ppm): δ = 40.24 (s, 1P, Pd–PPh3 ), 41.19 (s, 1P,
Pd–PPh3 ). 13 C NMR (100 MHz, CDCl3 , ppm); Caliphatic {δ = 29.73,
30.49, 54.27, 55.13, 57.64}, Caromatic {δ = 121.02, 121.27, 123.85,
124.63, 134.43, 137.84, 127.94–128.17 (Cm , PPh3 ), 130.50–131.02
(Cp , PPh3 ), 135.19–135.23 (Co , PPh3 , 2 JPC = 16), 136.96–137.06
K. Karami and M. M. Salah
35 min under reflux (60 ◦ C). A small aliquot of the reaction mixture
was diluted in MeOH for direct GC analysis.
Table 1. Suzuki coupling reactions
Entry
Aryl halide
Product
Compounds Characterization Data
1
(1) Biphenyl;[23a] (2) 3-methylbiphenyl;[23b] (3) 2-phenylbenzaldehyde, 79;[23c] (4) 1-phenylnaphtalene;[23d] (5) 4-methoxybiphenyl;[23e] (6) biphenyl;[23a] (7) 4-nitrobiphenyl;[23e] and (8) 4methoxybiphenyl.[23e]
2
Results and Discussion
3
4
5
6
7
8
(Ci , PPh3 , 1 JPC = 40)}. Elemental analysis calcd: C, 61.49; H, 5.51; N,
2.47. Found: C, 61.63; H, 5.6; N, 2.56%.
(5c): IR (cm−1 , KBr); ν(N–H) 3181, ν(C N) 1617, 1 H NMR
(300 MHz, CDCl3 , ppm); δ = 1.33 (s, 9H, CH3 ), 2.41 (s, 3H, CH3 ), 3.95
(d, 1H, CH2 , 2 JHH = 15 Hz), 4.60 (d, 1H, CH2 , 2 JHH = 15 Hz), 4.14 (s,
1H, NH), 6.15 (d, 1H, Ph, 3 JHH = 9 Hz), 6.76 (t, 1H, Ph, 3 JHH = 9 Hz),
6.95 (m, 2H, Ph), 7.17 (d, 2Hm , Py, 3 JHH = 6 Hz), 8.66 (d, 2Ho , Py,
3
JHH = 6 Hz). 13 C NMR (100 MHz, CDCl3 , ppm); Caliphatic {δ = 21.12,
30.11, 56.40, 58.39}, Caromatic {δ = 120.32, 124.32, 124.91, 132.00,
147.21, 149.33, 125.85 (Cm , Py), 135.41(Cp , Py), 152.62 (Co , Py)}.
Elemental analysis calcd: C, 51.40; H, 5.83; N, 7.04. Found: C, 51.56;
H, 5.94; N, 7.16%.
General Procedure for the Suzuki Coupling Reaction
830
A typical experimental procedure was carried out for the Suzuki
cross-coupling reaction under an air atmosphere (Table 1). A
reaction tube was charged with aryl bromide (0.5 mmol), aryl
boronic acid (0.75 mmol), solvent (6 ml), base (1.5 mmol) and Pd
complex (0.01 mmol) in Scheme 2. The mixture was heated for
wileyonlinelibrary.com/journal/aoc
The syntheses of cyclopalladated complexes 4a, 5a, 4b, 5b,
6b, 4c and 5c are shown in Scheme 1. In this article we
report reactivity of [Pd(µ-Cl)(C6 H4 CH2 NRR -κ 2 -C,N)]2 with Y,
giving monopalladium(II) derivatives including [Pd(C6 H4 CH2 NH2 2-C,N)Cl(Y)] (4a, 5a, 4b, 5b, 6b, 4c, 5c; Scheme 1) similar to previous
work.[22] This article also presents the reactivity of a characteristic
feature of the palladacycles such as the thermostability, which
makes it possible to perform the reactions at temperatures above
100 ◦ C needed for less reactive substrates (e.g. non-activated aryl
bromides).
In the 13 C NMR spectra of mononouclear complexes derives from
secondary benzylamines (4a, 5a) methylen and methyl carbons
resonated at 14.60–14.71 and 60.33–60.47 ppm.
In the 13 C NMR spectra of complexes (4c, 5c) quarternary carbons
resonated at 57.64–58.39 ppm and methyl carbons resonated
29.73, 30.49, 55.13 ppm in 4c and at 30.11 ppm in 5c, respectively.
However, when bulky ligands such as PPh3 were ligated to the
palladium metal, each methyl carbon of the t-Bu group resonated
separately, indicating that the three methyl carbons are situated
in different environments.
In the 13 C NMR spectra of mononouclear complexes derived
from tertiary benzylamines, methyl carbons resonated at 74.00
(4b), 73.90 (5b), 73.26 and 73.29 (6b). However, when bulky ligands
such as PPh3 were ligated to the palladium metal, each methyl
carbon of dimethyl group resonated separately, indicating that
the two methyl carbons are situated in different environments.
When symmetric ligands such as 4-picolline and sym-collidine
were coordinated to the palladium metal, all of the methyl carbons
resonated in same region, indicating that the methyl carbons are
situated in similar environments.
In the aromatic region observed in the 13 C NMR spectra, where
six different resonances are attributed to the carbon atoms of
the PdC6 H4 group, this fact is in very good agreement with the
structures depicted in Scheme 1. Morever, in the 13 C NMR spectra
complexes 4a–5c one of the aromatic carbons, C–Pd, appeared at
a considerably lower field – 153.48, 148.09, 137.84, 149.33, 150.79,
149.80 and 149.66 ppm respectively – and the expected signals
for the PPh3 , 4-picolline and sym-collidine groups were observed.
This data strongly support the idea that the -C,N chelate structure
is formed by ortho-palladation,
Effect of the Catalyst and Solvent
The key component in the reaction was the catalyst. Thus, we
employed 4a, 5a, 4b, 5b, 6b, 4c and 5c as precatalysts for initial
optimization. Similarly the solvent plays a crucial role in the rate
and the product distribution of Suzuki coupling reactions. To clarify
the solvent effect in Suzuki coupling reactions, we investigated a
series of reactions by taking the model reaction in different solvents
and catalyst that are shown in Table 2. The results (Table 2) for
c 2010 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2010, 24, 828–832
Efficient orthopalladated complexes of second and third benzyl amine
Table 2. Effect of the catalyst and solvent on Suzuki coupling
reactionsa
Table 4. Suzuki coupling of aryl–halidea
Entry
Pd-catalyst
4a
5a
4b
5b
6b
4c
5c
MeOH
THF
DMF
Toluene
Acetonitrile
100
100
100
100
100
99
100
78
67
79
80
77
65
77
50
44
43
62
52
53
50
Trace
Trace
Trace
Trace
Trace
Trace
Trace
63
69
70
70
73
59
65
a
Reaction conditions: 0.5 mmol bromobenzene, 0.75 mmol PhB(OH)2 ,
1.5 mmol Na2 CO3 , 6 ml solvent, 0.01 mmol Pd-catalyst, 60 ◦ C, 40 min.
Halide
1
2
3
4
5
6
7
8
Br
Br
Br
Br
Br
Cl
Cl
Cl
R
H
3-Me
2-CHO
H
4-OMe
H
4-NO2
4-OMe
Yieldb (%)
100
94
95
95
92
80
83
71
a Reaction conditions: 0.5 mmol aryl halide, 0.75 mmol PhB(OH) ,
2
1.5 mmol Na2 CO3 , 6 ml MeOH, 0.01 mmol 5a, 60 ◦ C, 40 min.
b Determined by GC based on aryl-halide.
Table 3. Effect of the catalyst and base on Suzuki coupling reactiona
Pd-cat
4a
5a
4b
5b
6b
4c
5c
K2 CO3
Cs2 CO3
Na2 CO3
Et3 N
NaOAc
100
100
100
100
100
98
100
95
97
100
90
97
91
95
100
100
100
100
100
100
100
49
51
52
48
55
48
50
Trace
Trace
Trace
Trace
Trace
Trace
Trace
Scheme 3. General mechanism for the Suzuki cross-coupling reaction.
a
Reaction conditions: 0.5 mmol bromobenzene, 0.75 mmol PhB(OH)2 ,
1.5 mmol base, 6 ml MeOH, 0.01 mmol Pd-catalyst, 60 ◦ C, 40 min.
all palladium catalysts of this table except complex 4c showed
higher reactivity with the polar and protic solvent MeOH than with
other polar and non-polar solvents. This may be due to the higher
solubility of the catalyst in methanol.
Effect of the Catalyst and Base
It is known that the base is involved in several steps of the catalytic
cycle, most notably in the transmetallation step where hydrolysis
of the Ar–PdL–X intermediate to more reactive Ar–PdL–OR is
known to accelerate the rate of the reaction.[24] Similarly, several
bases were employed in Suzuki–Miyaura reactions. The results
for all palladium catalysts with Na2 CO3 and K2 CO3 , indicated in
Table 3, had the best reactivity of the bases.
Comparison of Aryl-bromide and Aryl-chloride Reaction
Appl. Organometal. Chem. 2010, 24, 828–832
Conclusion
We have demonstrated the preparations and catalytic studies of
the Suzuki cross-coupling reactions of mononuclear palladacycles
supported by pendant benzylamine ligands. Under optimized
conditions, 4a, 5a, 4b, 5b, 6b, 4c, 5c exhibit catalytic efficiency
with lower and higher catalyst loadings, and with lesser and
more reactive substrates in Suzuki coupling reactions. Preliminary
studies on the modification of benzylamine with different
substituents on nitrogen and their application in the synthesis
of metal complexes are currently being undertaken.
References
[1] R. B. Bedford, L. T. Pilarski, Tetrahedron Lett. 2008, 49, 4216.
[2] R. B. Bedford, M. Betham, J. P. H. Charmant, A. L. Weeks, Tetrahedron
2008, 64, 6038.
[3] R. B. Bedford, M. E. Limmert, J. Org. Chem. 2003, 68, 8669.
c 2010 John Wiley & Sons, Ltd.
Copyright wileyonlinelibrary.com/journal/aoc
831
There are some drawbacks with the Pd-mediated Suzuki crosscoupling reaction in that only aryl-iodides and aryl-bromides can
be used effectively. Recent progress on increasing the rate of arylchloridesovercame this problem.[25] Stronger C–Cl bond strength
is responsible for a slower rate of reaction of aryl-halides, because
an oxidative addition step was suggested which is often the ratedetermining step in cross-coupling catalytic cycles.[24] Efficiency of
the obtained optimum conditions was investigated for a series of
aryl-halides. Table 4 shows that 5a is a high reactive catalyst system
which can catalyze the Suzuki cross-coupling of even an extremely
electron-rich compound such as 4-chloroanisole (Table 4, entry 8)
as well as less active aryl-bromides. The less reactive aryl-chloride
seems to need a longer reaction time.
The main components of the mechanism for the Suzuki coupling
are believed to be a pre-dissociation and or reduction step in which
the Pd(II) source is converted to the more active and coordinatively
unsaturated Pd(0) catalyst.[26] The observed palladium mirror
assures the formation of Pd(0) species during the reaction. As far as
we know, there is no previous report on palladium mirror formation
in Suzuki reactions catalyzed by cyclopalladated complexes. The
next steps are an oxidative addition of aryl halide to the Pd(0)
active catalyst followed by a transmetallation step in which the
aryl group is transferred from boron to palladium, and finally a
reductive elimination to release the product (Scheme 3). Therefore,
the relative contribution of steric and electronic effects is very
important, particularly for less reactive aryl halides.[27 – 29]
K. Karami and M. M. Salah
[4] B. K. Singh, N. Kaval, S. Tomar, E. Van der Eycken, V. S. Parmar, Org.
Process Res. Dev. 2008, 12, 468.
[5] A. R. Hajipour, K. Karami, A. Pirisedigh, A. E. Ruoho, J. Organomet.
Chem. 2009, 694, 2548.
[6] N. Miyaura, T. Yanagi, A. Suzuki, Synth. Commun. 1981, 11, 513.
[7] N. Miyaura, A. Suzuki, Chem. Rev. 1995, 95, 2457.
[8] C. Baillie, W. Chen, J. Xiao, Tetrahedron Lett. 2001, 42, 9085.
[9] R. Frenette, R. W. Friesen, Tetrahedron Lett. 1994, 35, 9177.
[10] D. Zim, A. L. Monteiro, J. Dupont, Tetrahedron Lett. 2000, 41, 8199.
[11] F. Bellina, A. Carpita, R. Rossi, Synthesis. 2004, 2419.
[12] A. F. Littke, G. C. Fu, Angew. Chem. Int. Ed. 1998, 37, 3387.
[13] A. F. Littke, C. Dai, G. C. Fu, J. Am. Chem. Soc. 2000, 122, 4020.
[14] S. Y. Liu, M. J. Choi, G. C. Fu, J. Chem. Soc., Chem. Commun. 2001,
2408.
[15] G. C. Fu, J. Org. Chem. 2004, 69, 3245.
[16] T. Z. Nichele, C. Favero, A. L. Monteiro, Cata. Commun. 2009, 10, 693.
[17] a) S. P. Stanforth, Tetrahedron 1998, 54, 263; b) A. Suzuki,
F. Diederich, P. J. Stang, in Metal Catalysed Cross-Coupling Reaction.
Eds. Wiley-VCH: Weinheim 1998, 49; c) W. A. Herrmann,
C. P. Reisinger, M. Spiegler, J. Organomet. Chem. 1998, 557, 93;
d) S. Kotha, K. Lahiri, D. Kashinath, Tetrahedron. 2002, 58, 9633.
[18] a) S. Chowdhury, P. E. Georghiou, TetrahedronLett. 1999, 40, 7599; b)
M. L. Yao, M. Z. Deng, Synthesis. 2000, 1095; c) M. Gray, I. P. Andrews,
D. F. Hook, J. Kitteringham, M. Voyle, Tetrahedron Lett. 2000,
41, 6237; d) M. Feuerstein, D. Laurenti, C. Bougeant, H. Doucet,
M. Santelli, Chem. Commun. 2001, 325; e) G. Zou, Y. K. Reddy,
J. R. Falck, Tetrahedron Lett. 2001, 42, 7213; f) M. R. Netherton, C. Dai,
K. Neuschuetz, G. C. Fu, J. Am. Chem. Soc. 2001, 123, 10099.
[19] C. Pan, M. Liu, L. Zhang, H. Wu, J. Ding, J. Cheng, Catal. Commun.
2008, 9, 508.
[20] D. Zim, A. L. Monteiro, J. R. Dupont, Tetrahedron Lett. 2000, 41, 8199.
[21] a) E. Peris, J. Mata, J. A. Loch, R. H. Crabtree, Chem. Commun. 2001,
201; b) E. Peris, R. H. Crabtree, Crood. Chem. Rev. 2004, 248, 2239; c)
J. L. Bolliger, O. Blacque, C. M. Frech, Angew. Chem. Int. Ed. 2007, 46,
6514.
[22] Y. Fuchita, H. Tsuchiya, A. Miyafuji, Inorg. Chim. Acta. 1995, 233, 91.
[23] a) Q. Xu, W. L. Duan, Z. Y. Lei, Z. B. Zhu, M. Shi, Tetrahedron. 2005,
61, 11225; b) J. Lemo, K. Heuze, D. Astruc, Org. Lett. 2005, 7, 2253;
c) C. Stroh, M. Mayor, C. V. Hanisch, Eur. J. Org. Chem. 2005, 3697;
d) Z. Zhang, Z. Wang, J. Org. Chem. 2006, 71, 7485; e) L. C. Liang,
P. S. Chien, M. H. Huang, Organometallics. 2005, 24, 353.
[24] S. R. Chemler, D. Trauner, S. J. Danishefsky, Angew Chem. In. Ed.
English. 2001, 40, 4544.
[25] a) W. A. Herrmann, C.-P. Reisinger, M. Spiegler, J. Organomet. Chem.
1998, 557, 93; b) T. Weskamp, V. P. W. Böhm, W. A. Herrmann,
J. Organomet. Chem. 1999, 585, 348; c) V. P. W. Böhm,
C. W. K. Gstöttmayr, T. Weskamp, W. A. Herrmann, J. Organomet.
Chem. 2000, 595, 186; d) C. Zhang, J. Huang, M. L. Trudell,
S. P. Nolan, J. Org. Chem. 1999, 64, 3804; e) C. Zhang,; M. L. Trudell,
Tetrahedron Lett. 2000, 41, 595; f) W. Shen, Tetrahedron Lett. 1997,
38, 5575; g) A. Fürstner, A. Leitner, Synlett. 2001, 290.
[26] a) B. Punji, C. Ganedamoorthy, M. S. Balakrishna, J. Mol. Catal.
A. Chem. 2006, 259, 78; b) T. Rosner, J. Le Bars, A. Pfaltz,
D. G. Blackmond, J. Am. Chem. Soc. 2001, 123, 1848.
[27] K. W. Anderson, M. Mendez-Perez, J. Priego, S. L. Buchwald, J. Org.
Chem. 2003, 68, 9563.
[28] M. W. Hooper, M. Utsunomiya, J. F. Hartwig, J. Org. Chem. 2003, 68,
2861.
[29] J. P. Stambuli, R. Kuwano, J. F. Hartwig, Angew. Chem. Int. Ed. 2002,
41, 4746.
832
wileyonlinelibrary.com/journal/aoc
c 2010 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2010, 24, 828–832
Документ
Категория
Без категории
Просмотров
0
Размер файла
199 Кб
Теги
suzuki, second, benzyl, reaction, couplings, catalyzing, amin, cross, complexes, orthopalladated, third, efficiency, highly
1/--страниц
Пожаловаться на содержимое документа