Palladium-catalyzed cross-coupling reaction of arylboronic acids with chloroformate or carbamoyl chloride

Article abstract of DOI:10.1055/s-2004-837211

The first palladium-catalyzed cross-coupling reaction between substituted arylboronic acids and chloroformate or carbamoyl chloride is described. One-carbon homologation from arylboronic acids was achieved to give corresponding esters or amides in good yi

Full text of DOI:10.1055/s-2004-837211

LETTER
355
Palladium-Catalyzed Cross-Coupling Reaction of Arylboronic Acids with
Chloroformate or Carbamoyl Chloride
P
Y
alladium-Catalyz
a
e
d
Cross-
C
-
oupling
Z
Reaction of
A
ry
h
lboronic Ac
e
ids n Duan, Min-Zhi Deng*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Graduate School of the Chinese Academy of
Sciences, 354 Fenglin Lu, Shanghai 200032, P. R. China
Fax +86(21)64166128; E-mail: dengmz@mail.sioc.ac.cn
Received 12 October 2004
ride. Herein, we report a convenient preparation of aryl-
Abstract: The first palladium-catalyzed cross-coupling reaction
carboxylic esters and arylcarboxamides from arylboronic
acids and chloroformate or carbamoyl chloride under mild
conditions.
between substituted arylboronic acids and chloroformate or car-
bamoyl chloride is described. One-carbon homologation from aryl-
boronic acids was achieved to give corresponding esters or amides
in good yields.
The coupling reactions were carried out using 3-meth-
Key words: cross-coupling reaction, palladium, boronic acid, aryl- ylphenylboronic acid and ethyl chloroformate as starting
carboxylic ester, arylcarboxamide
materials to optimize the conditions (Table 1). Consider-
ing the property of chloroformate is similar to that of acid
chloride, we initially tried to conduct the coupling reac-
Arylcarboxylic esters and arylcarboxamides are useful tion under our previous conditions for the Suzuki-type
building blocks both for laboratory synthesis as well as in- coupling reaction of cyclopropylboronic acids with acid
1
12
dustrial manufacturing. Among the methods for prepar- chlorides. But no desired cross-coupling product was
ing these compounds, metal-catalyzed carbonylation of observed (entry 1). When Pd(PPh ) was used instead of
3
4
aryl halides using carbon monoxide as the carbonyl source PdCl (dppf), the expected product was obtained in a low
2
in the presence of amines or alcohols is a popular way.2 yield (entry 2). Using K PO ·3H O as the base and
3
4
2
The toxicity of carbon monoxide and the troublesome gas Pd(PPh ) as the catalyst, a moderate yield was obtained
3
4
handling procedures limit it for the high-throughput (entry 3). We had found that the addition of a catalytic
3
chemistry involved in pharmaceutical industry. To avoid amount of Cu O can promote the Suzuki-type coupling re-
2
1
3
the use of gaseous carbon monoxide, modified processes actions of arylboronic acids with a-bromoacetates or a-
appeared by using the solid carbon monoxide releasing bromoacetamides.14 When a catalytic amount of Cu O
2
reagents such as Ni(CO) , and Mo(CO)6,5 and
4
4
6
Na Fe(CO) . Alternative ways to the above process are
the carbamoylation of aryl halides with carbamoyl-
2
4
Table 1 Effect of the Reaction Conditions on the Coupling Reac-
tion of 3-Methylphenylboronic Acid and Ethyl Chloroformatea
7
8
9
stannanes, carbamoylsilanes or DMF. But to the best
of our knowledge, alkoxycarbonylation of aryl halides
with alkoxycarbonylmetals has not yet been reported.
Jousseaume and his coworkers reported a palladium-cata-
lyzed carbamoylation and alkoxylcarbonylation process
CH3
CH3
Pd, Base
Additive
+
2
ClCO Et
B(OH)2
CO2Et
Conditions
Ag O, K CO , PdCl (dppf)
Yield (%)b
of organotin reagents to provide the corresponding esters Entry
1
0
or amides. This method tolerates a range of functional
groups because of the low polarity of the tin–carbon bond.
However, it was limited by the toxicity of the organotin
reagents.
1c
–
2
2
3
2
2c
Ag O, K CO , Pd(PPh )
3 4
37
54
73
49
49
37
2
2
3
3
4
5
6
K PO ·3H O, Pd(PPh )
3
4
2
3 4
In comparison with organotin and other organometallics,
organoboron reagents are non-toxic, air-stable and readily
available. Thus, the organoboron chemistry directed to-
ward organic synthesis has been widely developed. It is
also well known that the palladium-catalyzed Suzuki-type
reaction is an efficient method for the construction of
carbon-carbon bonds. To expand the scope of Suzuki-type
reaction, we investigated the cross-coupling reaction of
arylboronic acids with chlorofomate or carbamoyl chlo-
Cu
O, K
PO
·3H
O, Pd(PPh )
3
2
3
4
2
Cu O, K CO , Pd(PPh )
1
1
2
2
3
3
Cu O, KF·2H O, Pd(PPh )
3 4
2
2
7
Cu O, KOH, Pd(PPh )
2 3 4
a
All reactions were carried out using a mixture of 3-methylphenyl-
boronic acid (0.6 mmol), ethyl chloroformate (0.5 mmol), Cu O (6
mol%), base (3.3 equiv) and catalyst (3 mol%) in 4 mL of toluene, for
2
2
4 h, at 80 °C, under Ar atmosphere (except for entries 1 and 2).
Isolated yields.
b
SYNLETT 2005, No. 2, pp 0355–0357
0
1.
0
2.
2
0
0
5
c
Ag O (2.0 equiv), K CO (2.0 equiv) was used.
2
2
3
Advanced online publication: 17.12.2004
DOI: 10.1055/s-2004-837211; Art ID: U27904ST
©
Georg Thieme Verlag Stuttgart · New York

3
56
Y.-Z. Duan, M.-Z. Deng
LETTER
was used in this reaction, an improved yield was obtained Table 3 Palladium-Catalyzed Cross-Coupling Reactions of Various
Arylboronic Acids with N,N-Dibutylcarbamoyl Chloridea
(
entry 4). Further studies on the effect of bases did not
make any improvement (entries 5–7).
O
O
Pd(0), Base
The reactions of various arylboronic acids with chlorofor-
mate were explored under the optimized conditions
Ar–B(OH)2
+ Cl
N
Ar
N
toluene, 80 °C
(
Table 1, entry 4). The results are collected in Table 2.
As shown in Table 2, the cross-coupling reactions pro-
ceed readily to give the corresponding arylcarboxylic es- Entry Arylboronic acid
Product (b)
Yield
b
(
%)
ters in good yields. The substituent at the ortho position of
the arylboronic acid somewhat affects the reaction (en-
tries 2 and 5). It is noticeable that electronic effect signif-
icantly influences the coupling reaction. The presence of
an electron-donating group on the aromatic ring of aryl
boronic acid benefits the reaction (entries 3, 4 and 6),
while the presence of an electron-drawing group is unfa-
vorable for the reaction (entry 8).
1
2
3
4
5
6
7
O
N
93
60
93
86
87
87
89
B(OH)2
B(OH)2
CH3
O
N
CH3
Table 2 Palladium-Catalyzed Cross-Coupling Reactions of Various
a
Arylboronic Acids with Ethyl Chloroformate
B(OH)2
O
Cu2O, Pd(PPh3)4
Ar–B(OH)2 + ClCO2C2H5
ArCO2C2H5
N
K3PO4·3H2O, Toluene, 80 °C
H3C
H3CO
Cl
H3C
Entry Arylboronic acid
Product (a)
Yield
b
(
%)
B(OH)2
O
1
59
60
73
N
B(OH)2
CO C H
2
2
5
H3CO
2
3
CH3
CH3
B(OH)2
O
B(OH)2
CO2C2H5
CO2C2H5
N
CH3
CH3
Cl
B(OH)2
B(OH)2
O
4
5
6
7
8
H C
H C
73
36
78
54
21
3
3
N
F3C
B(OH)2
CO2C2H5
F3C
OCH3
OCH3
B(OH)2
CO2C2H5
B(OH)2
O
H CO
3
Cl
O
3
H CO
N
O
B(OH)2
2 2 5
CO C H
O
Cl
a
All the reactions were carried out using a mixture of the organic
boronic acid (0.6 mmol), N,N-dibutyl chloroformamide (0.5 mmol),
Cu O (6 mol%), Pd(PPh (3 mol%), and base (3.3 equiv) in 4 mL
B(OH)2
CO2C2H5
CO2C2H5
)
3 4
O
2
toluene, for 24 h, at 80 °C, under Ar atmosphere.
b
Isolated yields.
B(OH)2
The coupling reaction of arylboronic acids with N,N-dibu-
tylcarbamoyl chloride was also investigated under the
same conditions. The carbomylation proceeded smoothly
for arylboronic acids bearing either electron-donating or
electron-withdrawing groups with good to excellent
yields (Table 3). The substituent at the ortho position
a
All reactions were carried out using a mixture of arylboronic acid
0.6 mmol), ethyl chloroformate (0.5 mmol), Cu O (6 mol%),
(
2
K PO ·3H O (1.65 mmol) and Pd(PPh ) (3 mol%) in 4 mL of
3
4
2
3 4
toluene, for 24 h, at 80 °C, under Ar atmosphere.
b
Isolated yield.
Synlett 2005, No. 2, 355–357 © Thieme Stuttgart · New York

LETTER
Palladium-Catalyzed Cross-Coupling Reaction of Arylboronic Acids
357
affects the reaction a little (entry 2). This process tolerates
a number of functional groups on the aromatic ring
(4) (a) Corey, E. J.; Hegedus, L. S. J. Am. Chem. Soc. 1969, 91,
233. (b) Crandall, J. K.; Mickaely, W. J. J. Organomet.
Chem. 1973, 51, 375.
1
(
entries 4–7).
(
5) Kaiser, N.-F. K.; Hallberg, A.; Larhed, M. J. Comb. Chem.
In summary, it was found that the Suzuki-type cross-cou-
pling reactions of arylboronic acids with ethyl chlorofor-
mate or N,N-dibutylcarbamoyl chloride could readily take
place to give the corresponding aryl esters and amides by
2002, 4, 109.
(6) Collman, J. P.; Winter, S. R.; Komoto, R. G. J. Am. Chem.
Soc. 1976, 95, 249.
7) Lindsay, C. M.; Widdowson, D. A. J. Chem. Soc., Perkin
Trans. 1 1988, 569.
8) Cunico, R. F.; Maity, B. C. Org. Lett. 1999, 4, 4357.
9) Hosoi, K.; Nozaki, K.; Hiyama, T. Org. Lett. 2002, 4, 2849.
10) Balas, L.; Jousseaume, B.; Shin, H.; Berlhac, J.-B.; Wallian,
(
15
using catalytic amounts of Cu O and Pd(PPh ) . This
2
3 4
(
(
process is an efficient route to achieve aryl esters and
amides with various functional groups from arylboronic
acids. A detailed mechanistic study as well as an exami-
nation of the scope of the reaction is currently underway
in our laboratory.
(
F. Organometallics 1991, 10, 366.
(11) (a) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
(
(
b) Suzuki, A. J. Organomet. Chem. 1999, 576, 147.
c) Hassan, J.; Sevignon, M.; Gozzi, C.; Schulz, E.; Lemaire,
M. Chem. Rev. 2002, 102, 1359.
Acknowledgment
(12) Chen, H.; Deng, M.-Z. Org. Lett. 2000, 2, 1649.
(
(
(
13) Liu, X.-X.; Deng, M.-Z. Chem. Commun. 2002, 6, 622.
14) Duan, Y.-Z.; Deng, M.-Z. Tetrahedron Lett. 2003, 44, 3423.
15) General Procedure: m-Tolylboronic acid (82 mg, 0.6
mmol), Pd(PPh ) (17 mg, 0.015 mmol), Cu O (4 mg, 0.028
We thank the NNSF of China and State Key Laboratory of Organo-
metallic Chemistry, Chinese Academy of Sciences, for financial
support. A generous supply of arylboronic acids from Inc. of
Frontier Scientific is also gratefully acknowledged.
3
4
2
mmol), K PO ·3H O (439 mg, 1.65 mmol) were placed in a
3
4
2
flask under Ar atmosphere. Toluene (4 mL) and ethyl
chloroformate (50 mL, 0.5 mmol) were added and the
reaction mixture was stirred at 80 °C for 24 h. The reaction
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3
d = 7.70–7.86 (m, 2 H), 7.30–7.35 (m, 2 H), 4.36 (q, J = 7.2
(
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(
1
26), 65 (23), 120 (16), 89 (12), 63 (10). IR (neat): 2983,
719, 1280, 1201, 1107, 1084, 746, 684 cm . Anal. Calcd
–
1
for C H O : C, 73.17; H, 7.32; Found: C, 73.03; H, 7.45.
1
0
12
2
Synlett 2005, No. 2, 355–357 © Thieme Stuttgart · New York