Synthesis of biaryls via cross-coupling reaction of arylboronic acids with aryl chlorides catalyzed by NiCl2/Triphenylphosphine complexes

Article abstract of DOI:10.1016/S0040-4020(00)00814-0

The cross-coupling reaction of tolylboronic acids (1.3 equiv.) with chloroarenes in toluene was carried out at 80-100°C in the presence of a NiCl₂/PPh₃ catalyst (3 mol%) and K₃PO₄·nH₂O (2.6 equiv.). The reaction can be applied to various electron-deficient and -rich chloroarenes and is economical as the industrial process. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00814-0

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 8657±8660
Synthesis of Biaryls via Cross-Coupling Reaction of Arylboronic
Acids with Aryl Chlorides Catalyzed by
NiCl /Triphenylphosphine Complexes
2
*
Kaoru Inada and Norio Miyaura
Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan
Received 16 June 2000; accepted 14 September 2000
AbstractÐThe cross-coupling reaction of tolylboronic acids (1.3 equiv.) with chloroarenes in toluene was carried out at 80±1008C in the
presence of a NiCl /PPh catalyst (3 mol%) and K PO ´nH O (2.6 equiv.). The reaction can be applied to various electron-de®cient and -rich
chloroarenes and is economical as the industrial process. q 2000 Elsevier Science Ltd. All rights reserved.
2
3
3
4
2
Introduction
phine-bound aryls which is often unavoidable in the
palladium-catalyzed coupling, and the process is economi-
7
Various palladium complexes catalyze the cross-coupling
reaction of arylboronic acids with aryl iodides, bromides
or tri¯ates for the synthesis of biaryls, but economical
cal as recycling of the catalyst is not required. Here, we
reinvestigated the nickel-catalyzed cross-coupling reaction
of arylboronic acids with chloroarenes in the presence of
1
and readily available chloroarenes are a desirable substrate
for large-scale preparation in industry. Bulky and electron-
donating phosphines such as tri(t-butyl)phosphine, di(t-
NiCl
in the presence of a NiCl
economical NiCl ±triphenylphosphine complexes were
found to achieve higher catalyst ef®ciency than the NiCl
dppf complexes for various chloroarenes when the reaction
2 3 2 3
(PPh ) /2PPh , which had been carried out in dioxane
5,6
(dppf) complex (Scheme 1). The
2
2
2
3
butyl)(2-phenylphenyl)phosphine,
and N-heterocyclic
/
2
4
carbene have recently been found to be highly effective
as the ligand for the palladium-catalyzed coupling reactions
of chloroarenes. However, the reduction of NiCl (dppf) with
was carried out in the presence of K
toluene (Scheme 1).
PO ´nH O suspended in
3 4 2
2
BuLi or DIBAL produces an active and economical catalyst
for the cross-coupling reaction of arylboronic acids with
5
6
Results and Discussion
Reaction conditions
aryl chlorides and mesylates. The nickel catalyst has an
advantage over the palladium/phosphine complexes
because of their high catalyst activity for various chloro-
arenes having an electron-withdrawing and -donating
group, there is no appreciable side-reaction with the phos-
The effects of the catalyst, reaction time, and temperature on
the cross-coupling reaction of 3-chloroanisole with 4-tolyl-
boronic acid in the presence of K PO ´nH O (2.6 equiv.) are
3
4
2
summarized in Table 1.
A 3 mol% of NiCl (PPh ) in toluene achieved 100%
2
3 2
conversion within 2 h at 808C which is apparently faster
than the reaction catalyzed by NiCl (dppf) in dioxane
2
(
entry 1). The presence of 4 equiv. of PPh to NiCl can
3 2
stabilize the labile nickel(0) species because the yield of
the biaryl increased to 99% in the presence of additional
two equivalents of PPh (entry 2). The presence of further
3
excess of ligand slowed down the reaction, but the addition
of 4 and 10 equiv. of PPh to NiCl (PPh ) also resulted in
Scheme 1. Biaryl coupling of chloroarenes with arylboronic acids.
Keywords: coupling reactions; boron compounds; chloroarenes; biaryls.
* Corresponding author. Tel./fax: 181-11-706-6561;
e-mail: miyaura@org-mc.eng.hokudai.ac.jp
3
2
3 2
9
8% and 94% yields after 6 h at 808C. It was also interesting
that the reduction of the nickel(II) complex to the nickel(0)
5,6
prior to the coupling was not necessary to generate an
active catalyst, though it was critical in a similar reaction
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00814-0

8
658
K. Inada, N. Miyaura / Tetrahedron 56 (2000) 8657±8660
Table 1. Effect of catalysts (all reactions were carried out in toluene (3 ml)
at 808C by using 3-chloroanisole (1.0 mmol), 4-tolylB(OH) (1.3 mmol),
and a nickel catalyst)
complex was treated with DIBAL-H prior to the coupling
reaction (entries 7 and 8). The nickel(II) chloride complex
has an advantage over the nickel(0) complexes in its
insensitivity to air, but care must be taken such that it is
2
a
Temp. (8C) Time (h) Yield (%)
Entry
Catalyst (mol%)
in situ reduced to the corresponding nickel(0) species when8
1
2
3
4
5
6
7
8
9
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
NiCl
2
2
2
2
2
2
2
2
2
2
(PPh
(PPh
(PPh
(PPh
(PPh
(PPh
(PPh
(PPh
3
3
3
3
3
3
3
3
)
)
)
)
)
)
)
)
2
2
2
2
2
2
2
2
(3)
80
80
80
80
80
60
70
90
80
80
2
1.5
6
2.5
24
6
6
2
2
2
90
99
96
99
63
8
86
99
94
71
heating with ArB(OH)2 and K PO ´nH O in toluene.
K PO ´nH O in polar solvent and KOH in toluene leads to
3 4 2
3
4
2
/2PPh
/2PPh
/2PPh
/2PPh
/2PPh
/2PPh
/2PPh
3
3
3
3
3
3
3
(3)
(3)
(1)
(0.5)
(3)
b
the hydrolysis of the nickel chlorides (Scheme 2).
(3)
(3)
Scope and limitation
(PCy
(dppf) (3)
3
)
2
(3)
The synthesis of biaryls via the cross-coupling reaction of
the representative chloroarenes is summarized in Table 3.
1
0
a
GC yields.
The catalyst was treated with DIBAL-H (2 equiv.) to reduce to the
nickel(0) complex.
b
Chloroarenes having an electron-withdrawing group at the
para or meta position gave excellent yields of biaryls
exceeding 90% (entries 1±5). The electron-withdrawing
group may accelerate the rates of oxidative addition and
the transmetalation among the three steps involved in the
catalytic cycle. The reaction was much slower in electron-
rich chloroarenes, resulting in moderate yields at 808C, but
the reaction smoothly proceeded at 1008C (entries 6±8). The
retarding effect of a neighboring hetero atom which chelates
to the nickel(II) metal center was observed in some
substrates including 2-(methoxycarbonyl)chlorobenzene,
in dioxane (entry 3). A 1 mol% of catalyst gave a com-
parable yield to that obtained with 3 mol% catalyst (entry
4
even after 24 h (entry 5). The reaction proceeded smoothly
at over 808C and was slow at lower than 708C (entries 6±8).
Although less effort was directed to optimization of phos-
phine ligands, an analogously high yield was achieved by
the tri(cyclohexyl)phosphine complex (PCy ) and the dppf
3
complex was less effective than the PPh complex (entries 9
3
and 10).
), whereas the 0.5 mol% loading resulted in 63% yield
2
1
-chloropyridine, and 2-chloroquinoline (entries 4, 9, and
0). Such effect is not signi®cant in the palladium-catalyzed
cross-coupling reaction of arylboronic acids, but the
The effects of bases and solvents on the NiCl /PPh -cata-
2
3
lyzed biaryl coupling are summarized in Table 2.
More than two equivalents of the ®nely powdered and
hydrated potassium phosphate which contains 2±3 mol of
water worked ef®ciently as the base, whereas the anhydrous
phosphate and K CO did not mediate the reaction (entries
2
3
1
±5). On the other hand, no coupling reaction was observed
in the presence of a strong base such as the ®nely powdered
NaOH or KOH in toluene (entry 6), and the reaction resulted
in signi®cantly low yields when using K PO ´nH O in polar
3
4
2
solvents (entries 10 and 11). The reaction mixture turned to
a milky emulsion suggesting the formation of nickel(II)
hydroxide or nickel oxide. On the other hand, NaOH and
KOH mediated the reaction when the nickel chloride
Scheme 2. Reduction of Ni(II) to Ni(0) complex.
Table 3. Synthesis of biaryls (all reactions were carried out in toluene
Table 2. Effect of bases and solvents (all reactions were carried out in
toluene (3 ml) at 808C in the presence of 3-chloroanisole (1.0 mmol), 4-
tolylB(OH) (1.3 mmol), and a nickel catalyst)
(3 ml) at 808C in the presence of chloroarene (1.0 mmol), 4-tolylB(OH)
(0.03 mmol), and PPh
2
3
(1.3 mmol), K
(0.06 mmol), unless otherwise noted)
3
PO
4
´nH
2
O (2.6 mmol), NiCl (PPh
2
3
)
2
2
a
Yield (%)
a
Yield (%)
Entry
Base (equiv.)
CO (2.6)
Solvent
Time (h)
Entry
ArCl
Time (h)
1
2
3
4
5
6
7
8
9
K
K
K
K
K
2
3
3
3
3
3
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Dioxane
DME
6
6
2
6
6
6
6
6
2
2
2
38
99
99
96
74
0
95
99
77
7
1
2
3
4
5
6
7
8
9
10
4-NCC
2-NCC
6
H
H
4
Cl
Cl
2
2
2
2
2
2
2
2
16
16
87
97
(92)
37
(99)
64
PO
PO
PO
PO
4
´nH
2
2
2
2
O (2.6)
6
4
4
´nH
´nH
´nH
O (2.6)
O (2.0)
O (1.0)
4-OHCC
2-MeO CC
3-MeOC
4-MeOCH
4-H NC
4-Me NC
2-chloropyridine
2-chloroquinoline
6
H
4
Cl
b
4
4
2
6
H
4
Cl
83
6
H
4
Cl
OC
Cl
Cl
b
b
c
KOH (2.6)
KOH (2.6)
NaOH (2.6)
2
6
H
4
Cl
74
81
68
b
2
6
H
4
64
41
b
2
6
H
4
d
K
K
K
3
PO
3
PO
3
PO
4
4
4
´nH
´nH
´nH
2
2
2
O (2.6)
O (2.6)
O (2.6)
15
50
d
1
1
0
1
88
DMF
1
a
Isolated yields and GC yields are in parentheses.
At 1008C for 2 h.
At 1008C for 8 h.
a
b
c
d
GC yields.
The catalyst was treated with DIBAL-H (2 equiv.) to reduce to the
nickel(0) complex.
b
At 1008C for 16 h in the presence of 4-tolylB(OH)
2
(2 mmol).

K. Inada, N. Miyaura / Tetrahedron 56 (2000) 8657±8660
8659
from Nakalai Tesque Co. was used directly. Dioxane and
toluene were distilled from benzophenone ketyl.
Effect of catalysts (Table 1)
The ¯ask was charged with a NiCl complex (0.005±
2
0
PPh ), 4-tolylboronic acid (1.3 mmol), and K PO ´nH O
.03 mmol), a phosphine ligand (if used, 2 equiv. of
Scheme 3. Retarding effect of neighboring group.
3
3
4
2
(
2.6 mmol), and then ¯ushed with argon. Toluene (3 ml)
and 3-chloroanisole (1.0 mmol) were successively added
to the ¯ask, and the mixture was then stirred at the tempera-
ture for the period shown in Table 1.
Effects of base and solvents (Table 2)
The ¯ask was charged with NiCl (PPh ) (0.03 mmol), PPh
3
2
3 2
(
(
(
0.06 mmol), 4-tolylboronic acid (1.3 mmol), and a base
1.0±2.6 mmol), and then ¯ushed with argon. A solvent
3 ml) and 3-chloroanisole (1.0 mmol) were successively
added to the ¯ask, and the mixture was then stirred at
08C for the period shown in Table 2. Potassium and sodium
hydroxide were ground to a powder before use (entries
±8). The reduction of the NiCl complex was carried out
8
6
2
as follows (entries 7 and 8). The ¯ask charged with
NiCl (PPh ) (0.03 mmol), PPh (0.06 mmol), and toluene
2
3 2
3
(3 ml) under argon. The mixture was treated with n-BuLi in
hexane (4 equiv.) at room temperature for 30 min to give a
solution of the nickel(0) complex. p-Tolylboronic acid
Scheme 4. Regioselectivity in 2,4-dichlorobenzaldehyde.
(
(
1.3 mmol), 3-chloroanisole (1.0 mmol), and K PO ´nH O
3 4 2
2.6 mmol) were added to the catalyst solution, and the
nickel(II) intermediates generated by oxidative addition of
chloroarene seems to be more Lewis acidic than those
generated from the palladium catalysts (Scheme 3). The
intra- or intermolecular coordination of the neighboring
resulting mixture was stirred for 6 h at 808C.
Representative procedure (Table 3)
9
hetero atom may retard either the transmetalation step or
the reductive elimination step.
NiCl (PPh ) (0.03 mmol), PPh (0.06 mmol), 4-tolylboro-
2
3 2
3
nic acid (0.177 g, 1.3 mmol), and K PO ´nH O (2.6 mmol)
3
4
2
were added to a ¯ask equipped with a magnetic stirring bar,
a septum inlet, and re¯ux condenser. The ¯ask was
thoroughly ¯ashed with argon and then charged with
toluene (2 ml) and 3-chloroanisole (0.142 g, 1.0 mmol).
The resulting mixture was stirred at 808C for the period
shown in Table 3. The product was extracted with toluene,
The regioselectivity in the coupling reaction of 2,4-
dichlorobenzaldehyde is shown in Scheme 4.
The nickel-catalyzed reaction yielded para- and ortho-
coupling products in a ratio of 69: 31 accompanied with a
di-coupling product. The yield of the di-coupling product
was dependent on the stoichiometry of tolylboronic acid,
but all attempts at the selective coupling at the para position
were unsuccessful. However, an analogous reaction
washed with water and brine, and dried over MgSO . The
4
addition of alkaline hydrogen peroxide is a convenient way
to oxidize the residual arylboronic acid to phenol and
triphenylphosphine to the oxide. However, the oxidation
should be absolutely avoided because the nickel forms an
explosive peroxide. Chromatography over silica gel with
catalyzed by a Pd(dba) /phosphine catalyst exhibited the
2
opposite regioselectivity favoring the ortho-coupling:
5
and 36/64 with dppf ligand.
/6ˆ50/50 with PPh , 34/66 with PCy , 34/66 with dppb,
0
3
3
hexane/ethyl acetate gave 3-methoxy-4 -methylbiphenyl.
IR (Nujol) 1210 cm ; H NMR (400 MHz, CDCl ) d
21
1
3
2
.39 (s, 3H), 3.86 (s, 3H), 6.87 (dd, Jˆ2.4, 8.0 Hz, 1H),
7
.10 (dd, Jˆ1.7, 2.4 Hz, 1H), 7.16 (d, Jˆ7.8 Hz, 1H),
Experimental
7.24 (d, Jˆ7.9 Hz, 2H), 7.34 (dd, Jˆ7.8, 8.0 Hz, 1H),
7
(12), 198 (M , 100), 199 (18); exact mass calcd for C H O
.49 (d, Jˆ7.9 Hz, 2H); MS m/z 155 (21), 167 (19), 187
1
Reagents
A green crystal of NiCl (PPh ) was synthesized from
NiCl ´6H O and PPh in hot acetic acid. The reaction of
14
14
1
98.1045, found 198.1049.
2
3 2
1
0
The following biaryls were prepared by the above general
procedure, unless otherwise noted.
2
2
3
NiCl ´6H O with a commercially available phosphine in
2
2
benzene at 508C gave the nickel chloride complexes with
dppf (1,1 -bis(diphenylphosphino)ferrocene) and tricyclo-
0
hexylphosphine (PCy ). 4-Tolylboronic acid and chloro-
0
21
4-Cyano-4 -methylbiphenyl. IR (Nujol) 2220 cm ; H
NMR (400 MHz, CDCl ) d 2.41 (s, 3H), 7.28 (d,
3
1
1
1
12
3
arenes were commercially available. K PO ´nH O (nˆ2±3)
Jˆ8.0 Hz, 2H), 7.49 (d, Jˆ8.0 Hz, 2H), 7.66 (d,
3
4
2

8
660
K. Inada, N. Miyaura / Tetrahedron 56 (2000) 8657±8660
Jˆ8.3 Hz, 2H) 7.70 (d, Jˆ8.3 Hz, 2H); MS m/z 75 (3), 82
100); exact mass calcd for C H N 169.0891, found
12 11
169.0891.
1
6), 91 (8), 140 (4), 152 (4), 165 (16), 177 (7), 193 (M , 100);
(
exact mass calcd for C H N 193.0891, found 193.0888.
1
4
11
2-Chloro-4-(4-methylphenyl)benzaldehyde. IR (Nujol)
1690 cm ; H NMR (400 MHz, CDCl ) d 2.42 (s, 3H),
0
50 cm ; H NMR (400 MHz, CDCl ) d 2.42 (s, 3H),
21
1
4
8
7
-Formyl-4 -methylbiphenyl. IR (Nujol) 1710, 1200,
3
2
1
1
7.29 (d, Jˆ8.2 Hz, 2H), 7.52 (d, Jˆ8.2 Hz, 2H), 7.60 (dd,
Jˆ1.6, 8.1 Hz, 1H), 7.66 (d, Jˆ1.6 Hz, 1H), 7.98 (d,
Jˆ8.1 Hz, 1H), 10.49 (s, 1H); MS m/z 139 (1), 166 (23),
3
.29 (d, Jˆ8.0 Hz, 2H), 7.55 (d, Jˆ8.0 Hz, 2H), 7.74 (d,
Jˆ8.3 Hz, 2H), 7.94 (d, Jˆ8.3 Hz, 2H), 10.05 (s, 1H); MS
1
m/z152 (29), 167 (22), 196 (M , 100), 197 (15); exact mass
1
201 (3), 229 (96), 230 (M , 100); exact mass calcd for
calcd for C H O 196.0888, found 196.0878.
12
C H ClO 230.0498, found 230.0487.
14 11
1
4
0
21
-Cyano-4 -methylbiphenyl. IR (Nujol) 2300 cm ; H
1
2
NMR (400 MHz, CDCl ) d 2.42, (s, 3H), 7.30 (d,
2,4-Di(4-methylphenyl)benzaldehyde. IR (Nujol) 1690
cm ; H NMR (400 MHz, CDCl ) d 2.41 (s, 3H), 2.44
2
1
1
3
3
Jˆ8.0 Hz, 2H), 7.42 (dt, Jˆ1.2, 7.7 Hz, 1H), 7.46 (d,
(s, 3H), 7.27±7.34 (m, 6H), 7.57 (d, Jˆ8.3 Hz, 2H), 7.64
(d, Jˆ1.7 Hz, 1H), 7.69 (dd, Jˆ8.3, 1.7 Hz, 1H), 8.08 (d,
Jˆ8.3 Hz, 1H), 10.01 (s, 1H); MS m/z 91 (1), 194 (2), 258
Jˆ8.0 Hz, 2H), 7.51 (d, Jˆ7.7 Hz, 1H), 7.63 (dt, Jˆ1.2,
7
.7 Hz, 1H), 7.75 (d, Jˆ7.7 Hz, 1H); MS m/z 63 (6), 82
1
7), 91 (6), 96 (8), 165 (31), 193 (M , 100); exact mass
1
(
calcd for C H N 193.0891, found 193.0891.
(2), 285 (61), 286 (M , 100); exact mass calcd for C H O
21
18
286.1358, found 286.1355.
1
4
11
0
-Methoxycarbonyl-4 -methylbiphenyl. IR (Nujol) 1720
cm ; H NMR (400 MHz, CDCl ) d 2.39 (s, 3H), 3.66
2
2
1
1
References
3
(
7
7
(
s, 3H), 7.18±7.24 (m, 4H), 7.36 (dd, Jˆ1.4, 7.6 Hz, 1H),
.38 (ddd, Jˆ1.4, 7.6, 7.6 Hz, 1H), 7.51 (ddd, Jˆ1.4, 7.6,
.6 Hz, 1H), 7.80 (dd, Jˆ1.4, 7.8 Hz, 1H); MS m/z76 (5), 98
1. (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
(b) Miyaura, N. In Advances in Metal-Organic Chemistry;
Liebeskind, L. S. Ed.; JAI: London, 1998; Vol. 6, pp 187±243.
(c) Suzuki, A. In Metal-Catalyzed Cross-Coupling Reactions;
Diederich, F., Stang, P. J. Eds.; Eiley-VCH: Weinheim, 1998; p 49.
3), 115 (9), 128 (3), 139 (10), 152 (47), 167 (26), 195 (100),
1
26 (M , 73); exact mass calcd for C H O 226.0994,
2
found 226.1003.
15 14 2
2
. Littke, A. F.; Dai, C. D.; Fu, G. C. J. Am. Chem. Soc. 2000, 122,
4020.
0
160, 1090 cm ; H NMR (400 MHz, CDCl ) d 2.38 (s,
4
1
3
-Methoxymethoxy-4 -methylbiphenyl. IR (Nujol) 1230,
2
1 1
3. Wolfe, J. P.; Singer, R. A.; Yang, B. H.; Buchwald J. Am. Chem.
Soc. 1999, 121, 9550.
3
H), 3.50 (s, 3H), 5.21 (s, 2H), 7.09 (d, Jˆ8.8 Hz, 2H), 7.22
(
d, Jˆ8.1 Hz, 2H), 7.44 (d, Jˆ8.1 Hz, 2H), 7.50 (d,
1
M , 59); exact mass calcd for C H O 228.1150, found
4. Zhang, C.; Huang, J.; Trudell, M. L.; Nolan, S. P. J. Org. Chem.
1999, 64, 3804.
Jˆ8.8 Hz, 2H); MS m/z 155 (9), 184 (100), 198 (65), 228
(
5. (a) Saito, S.; Sakai, M.; Miyaura, N. Tetrahedron Lett. 1996, 37,
2993. (b) Saito, S.; Oh-tani, S.; Miyaura, N. J. Org. Chem. 1997, 62,
1
5
16
2
228.1159.
8
024. (c) Indolese, A. F. Tetrahedron Lett. 1997, 38, 3513. (d) Galland,
0
21
-Amino-4 -methylbiphenyl. IR (Nujol) 1630, 1280 cm ;
H NMR (400 MHz, CDCl ) d 2.37 (s, 3H), 3.69 (s, 2H),
3
4
J.-C.; Savignac, Genet, J.-P. Tetrahedron Lett. 1999, 40, 2323.
6. (a) Percec, V.; Bae, J.-Y.; Hill, D. H. J. Org. Chem. 1995, 60, 1060.
(b) Kobayashi, Y.; Mizojiri, R. Tetrahedron Lett. 1996, 37, 8531.
(c) Ueda, M.; Saito, A.; Miyaura, N. Tetrahedron 1998, 54, 13079.
7. Kong, K.-C.; Cheng, C.-H. J. Am. Chem. Soc. 1991, 113, 6313;
Morita, D. K.; Stille, J. K.; Norton, J. R. J. Am. Chem. Soc. 1995,
1
6
.74 (d, Jˆ8.5 Hz, 2H), 7.20 (d, Jˆ7.9 Hz, 2H), 7.39 (d,
1
67 (6), 182 (29), 183 (M , 100); exact mass calcd for
Jˆ8.5 Hz, 2H), 7.43 (d, Jˆ7.9 Hz, 2H); MS m/z 155 (1),
1
C H N 183.1048, found 183.1055.
13
13
1
17, 8576; Goodson, F. E.; Wallow, T. I.; Novak, B. M. J. Am.
Chem. Soc. 1997, 119, 12441.
8. The NiCl catalysts often afforded good results without the
treatment with reducing agent, but the high ef®ciency of the
0
-(N, N-Dimethylamino)-4 -methylbiphenyl. IR (Nujol)
350 cm ; H NMR (400 MHz, CDCl ) d 2.37 (s, 3H),
4
1
2
2
2
1
1
3
2
5
c
.98 (s, 6H), 6.80 (d, Jˆ8.8 Hz, 2H), 7.20 (d, Jˆ8.1 Hz,
5
b
H), 7.45 (d, Jˆ8.1 Hz, 2H), 7.48 (d, Jˆ8.8 Hz, 2H); MS
catalyst can be achieved by using the reduced nickel catalyst.
The present procedure by using a combination of NiCl (PPh )
1
m/z 91 (3), 105 (9), 167 (12), 195 (15), 211 (M , 100), 212
(16); exact mass calcd for C H N 211.1361, found 211.1386.
2
3 2
3 4 2
and K PO ´H O in toluene will give comparable results to that
1
5
17
obtained with the reduced catalysts.
1
2
-(4-Methylphenyl)quinoline.
H
NMR (400 MHz,
9. 2-Pyridylnickel(II) and -palladium(II) chloride, see: (a) Isobe,
K.; Nanjo, K.; Nakamura, Y.; Kawaguchi, S. Bull. Chem. Soc. Jpn.
1986, 59, 2141. (b) Isobe, K.; Nakamura, Y.; Kawaguchi, S. Bull.
Chem. Soc. Jpn. 1980, 53, 139.
CDCl ) d 2.44 (s, 3H), 7.33 (d, Jˆ8.1 Hz, 2H), 7.49±7.53
3
(
(
m, 1H), 7.70±7.74 (m, 1H), 7.81 (d, Jˆ8.1 Hz, 1H), 7.86
d, Jˆ8.5 Hz, 1H), 8.07 (d, Jˆ8.1 Hz, 2H), 8.16 (d,
Jˆ8.5 Hz, 1H), 8.20 (d, Jˆ8.5 Hz, 1H); MS m/z 95 (5),
10. Venanzi, L. M. J. Chem. Soc. 1985, 719; Cotton, A.; Faut,
O. D.; Goodgame, M. L. J. Am. Chem. Soc. 1961, 83, 344
11. Booth, G.; Chatt, J. J. Chem. Soc. 1965, 3238.
1
09 (6), 204 (7), 219 (M , 100), 220 (18); exact mass
1
calcd for C H N 219.1048, found 219.1049.
1
6
13
1
(4-tolylBO) more than 90% were used for the reaction. The
2. The highly dry 4-tolylboronic acids containing the boroxine
2
1
-(4-Methylphenyl)pyridine. IR (Nujol) 1590, 1560 cm ;
2
3
1
H NMR (400 MHz, CDCl ); d 2.40 (s, 3H), 7.20 (dd,
3
preparation of arylboronic acids, see; Onak, T. Organoborane
Chemistry; Academic: New York, 1975; Nesmeyanov, A. N.;
Sokolik, R. A. Methods of Elemento-Organic Chemistry; North-
Holland: Amsterdam, 1967; Vol. 1.
Jˆ4.8, 6.6 Hz, 1H), 7.27 (d, Jˆ8.3 Hz, 2H), 7.67±7.72
(
MS m/z 77 (5), 78 (6), 83 (14), 91 (11), 154 (10), 169 (M ,
m, 2H), 7.88 (d, Jˆ8.3 Hz, 2H), 8.67 (d, Jˆ2.6 Hz, 1H);
1