Palladium(II)-catalyzed sequential hydroxylation-carboxylation of biphenyl using formic acid as a carbonyl source

Article abstract of DOI:10.1021/ol049166l

(Equation Presented) A simultaneous hydroxylation-carboxylation of biphenyl occurred to give 4′-hydroxy-4-biphenylcarboxylic acid, which has wide potential application as a polyester monomer.

Full text of DOI:10.1021/ol049166l

ORGANIC
LETTERS
2
004
Vol. 6, No. 14
437-2439
Palladium(II)-Catalyzed Sequential
Hydroxylation−Carboxylation of
Biphenyl Using Formic Acid as a
Carbonyl Source
2
Fumitoshi Shibahara,†,‡ Shinsuke Kinoshita, and Kyoko Nozaki*
§
,†,§
ConVersion and Control by AdVanced Chemistry, PRESTO, Japan Science and
Technology, 1-8, Honcho 4-Chome, Kawaguchi 332-0012, Japan, and Department of
Chemistry and Biotechnology, Graduate School of Engineering, The UniVersity of
Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
nozaki@chembio.t.u-tokyo.ac.jp
Received May 7, 2004
ABSTRACT
A simultaneous hydroxylation−carboxylation of biphenyl occurred to give 4′-hydroxy-4-biphenylcarboxylic acid, which has wide potential
application as a polyester monomer.
The cleavage and functionalization of an unreactive C-H
bond by the aid of transition metal catalysts is one of the
lation-carboxylation of biphenyl to provide 4′-hydroxy-4-
biphenylcarboxylic acid, which has wide potential application
as a polyester monomer. Efficient carboxylation of other
aromatic compounds is also presented. The use of formic
acid is the key for the present carboxylation reactions.8
When biphenyl (1) was treated with formic acid and
K S O in a mixture of trifluoroacetic acid and dichlo-
1
,2
hottest topics in organic and organometallic chemistry.
3
Since their first report in 1967, Fujiwara and co-workers
developed the electrophilic subsitution of an aromatic hydro-
gen atom by palladium(II) under acidic conditions. The
,9
1
resulting organopalladium species, an aryl-Pd σ-complex,
2
2
8
4
5
6
10
reacts with alkenes, carbon monoxide, carbon dioxide, and
3 2
romethane at 50 °C, using Pd(OCOCF ) as a catalyst,
7
oxygen, providing a variety of substituted arenes. Here we
report our unexpected finding of a simultaneous hydroxy-
(5) With CO: (a) Jintoku, T.; Taniguchi, H.; Fujiwara, Y. Chem. Lett.
987, 1156. (b) Jintoku, T. Fujiwara, Y.; Kawata, I.; Taniguchi, H. J.
1
†
PRESTO, Japan Science and Technology.
Present address of Dr. F. Shibahara Department of Chemistry, Faculty
Organomet. Chem. 1990, 385, 297. (c) Taniguchi, Y.; Yamaoka, Y.; Nakata,
K.; Takaki, K.; Fujiwara, Y. Chem. Lett. 1995, 345. (d) Lu, W.; Yamamoto,
Y.; Taniguchi, Y.; Kitamura, T.; Takaki, K.; Fujiwara, Y. J. Organomet.
Chem. 1999, 580, 290. With rhodium: (e) Grushin, V.; Marshall, W. J.;
Thorn, D. L. AdV. Synth. Catal. 2001, 343, 161.
(6) With CO2: Sugimoto, H.; Kawata, I.; Taniguchi, H.; Fujiwara, Y. J.
Organomet. Chem. 1984, 266, C44. See also ref 5d.
(7) With O2: (a) Jintoku, T.; Taniguchi, H.; Fujiwara, Y. Chem. Lett.
1987, 1865. (b) Jintoku, T.; Takaki, K.; Fuchita, Y.; Fujiwara, Y. Bull.
Chem. Soc. Jpn. 1990, 63, 438.
(8) Formaldehyde as a carbonyl source: Fuji, K.; Morimoto, T.; Kakiuchi,
K. Angew. Chem., Int. Ed. 2003, 42, 2409.
(9) Hydrocarboxylation of alkyne or alkene with formic acid: (a)
Simonato, J.-P.; Walter, T.; Mtivier, P. J. J. Mol. Catal. A: Chem. 2001,
171, 91. (b) Simonato, J. P. J. Mol. Catal. A: Chem. 2001, 171, 91. Using
Pd catalyst under CO: (c) Zagarian, D.; Alper H. Organometallics 1993,
12, 712. (d) El Ali, B.; Alper, H. J. Org. Chem. 1993, 58, 3595.
‡
of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan.
§
The University of Tokyo.
(
1) (a) Shilov, A. E.; Shul’pin, G. B. Chem. ReV. 1997, 97, 2879. (b)
Jia, C.; Kitamura, T.; Fujiwara, Y. Acc. Chem. Res. 2001, 34, 633.
2) (a) Kakiuchi, F.; Murai, S. ActiVation of UnreactiVe Bonds and
(
Organic Synthesis; Murai, S., Ed.; Springer: Berlin, 1999. (b) Ritleng, V.;
Sirlin, C.; Pfeffer, M. Chem. ReV. 2002, 102. 1731. (c) Kakiuchi, F.; Murai,
S. Acc. Chem. Res. 2002, 35, 826. (d) Jun, C.-H.; Moon, C. W.; Lee, D.-Y.
Chem. Eur. J. 2002, 8, 2423.
(
3) (a) Moritani, I.; Fujiwara, Y. Tetrahedron Lett. 1967, 1119. (b)
Fujiwara, Y.; Moritani, I.; Danno, S.; Teranishi, S. J. Am. Chem. Soc. 1969,
1, 7166.
4) With a CdC bond: (a) Jia, C.; Lu, W.; Kitamura, T.; Fujiwara, Y.
9
(
Org. Lett. 1999, 1, 2097. (b) Jia, C.; Lu, W.; Oyamada, J.; Kitamura, T.;
Matsuda, K.; Irie, M.; Fujiwara, Y. J. Am. Chem. Soc. 2000, 122, 7252.
1
0.1021/ol049166l CCC: $27.50 © 2004 American Chemical Society
Published on Web 06/16/2004

Scheme 1. Hydroxylation-Carboxylation of Biphenyl (1)
Scheme 2. Control Experiments Using Possible Intermediates
-5
3
a
Pd(OCOCF
3 2 2 2 8 3
) (20 mol), K S O (6 mmol), CF COOH (2 mL),
CH
2
Cl (1 mL), 48 h, 50 °C, and then treatment with H O
2
2
a
Substrate 3, 4, 5a, or 5b (2 mmol), HCOOH (0.5 mL, 13 mmol),
Pd(OCOCF (20 mol), K (6 mmol), CF COOH (2 mL),
CH Cl (1 mL), 48 h, 50 °C, and then treatment with H O.
)
3 2
2
S O
2 8
3
hydroxy-biphenylcarboxylic acid 2 was obtained in 45%
Scheme 1a).11 This is the first example in which the two
2
2
2
(
reactions, hydroxylation and carboxylation,5 proceeded
simultaneously on one molecule with such high chemose-
lectivity. The reaction of benzene at 50 °C also gave
7
to the reaction conditions. The results are summarized in
reactions i-iii in Scheme 2. (i) No reaction proceeded with
4-hydroxybenzoic acid (4% yield), but benzoic acid was the
4
-biphenylcarboxylic acid (para-3). (ii) The carboxylation
major product (58%). At 40 °C, 4-hydroxybenzoic acid,
took place for 4-hydroxybiphenyl (4) to give the hydroxy-
carboxylic acid 2, but the yield was low (6%). Byproducts
due to the oxidative dimerization of 4 lowered the yield of
2
8
-hydroxybenzoic acid, and benzoic acid were formed in 2,
, and 17% yields, respectively. From naphthalene, a mixture
of 1-hydroxy-5-naphthoic acid (6% yield) and 1-hydroxy-
2
. (iii) 4-Biphenyl esters of trifluoroacetic acid (5a) and
formic acid (5b) provided 2 after aqueous workup in 56 and
2% yields, respectively. These yields are much higher than
4-naphthoic acid (6% yield) was obtained.
2
Although decomposition of formic acid into CO and H O
6
may be anticipated, the reaction was confirmed to be unique
for formic acid on the basis of the following control
experiments. Biphenylcarboxylic acid 312 was the major
product when 1 was treated with CO (1 atm) instead of
formic acid under otherwise the same reaction conditions;
no trace of 2 was detected either in the absence or in the
presence of water (Scheme 1b).
that from 4 or from 1. Thus, observations i-iii strongly
suggest that, at 50 °C, biphenyl (1) was first oxidized to
give a protected hydroxybiphenyl either 5a or 5b,14 fol-
lowed by subsequent carboxylation. The final product 2 was
obtained after aqueous workup.
The existence of a trace amount of water, which may
possibly be included in or be generated from formic acid,
played an essential role for the hydroxylation-carboxylation
The reaction temperature was essential for the chemose-
lectivity. When the reaction of 1 with formic acid was carried
out at 40 °C, 4-hydroxybiphenyl (4) was the major product
1
5
reaction. Trifluoroacetic anhydride is known to react with
water immediately to form trifluoroacetic acid. Thus, when
1
3
(
30% yield) and 3 was obtained in 7%. At 80 °C, on the
1
was treated in the presence of 0.25 mL of trifluoroacetic
other hand, the simple carboxylation product 3 was obtained
in 40% yield. No trace of 2 was found in either case. It is
likely that the electrophilic substitution of an aromatic C-H
bond by Pd(II) initiates both the hydroxylation and the
anhydride under otherwise the same reaction conditions as
in Scheme 1a, 2 was not given at all but the simple
carboxylation product 3 was obtained in 46% yield.
The system is effective not only for the sequential
hydroxylation-carboxylation of biphenyl but also for the
simple carbonylation of aromatic C-H bonds. The results
are summarized in Table 1. Carbonylation of benzene (6a)
with formic acid was performed in trifluoroacetic acid.
Benzoic acid (7a) was obtained with a catalyst turnover
number (TON) of 106 at 80 °C for 70 h (Table 1, entry 1).
The TON is higher than the reported values for the
1
carboxylation reactions. The temperature dependency of the
reaction may be explained as follows: at 40 °C, the aryl-
Pd σ-complex intermediate preferentially underwent the
oxidation to 4, and at 80 °C, the aryl-Pd predominantly gave
biphenylcarboxylic acid 3.
The reaction process of the hydroxylation-carboxylation
was disclosed by subjecting several possible intermediates
5c,d
conventional Fujiwara carbonylation with CO. The higher
reactivity with ortho-para orientation was observed for
electron-rich arenes. This substituent-effect agrees with the
(10) Existence of the cosolvent dichloromethane was essential for
obtaining 2. In the absence of dichloromethane, 1 did dissolve and no
reaction took place.
(11) Byproducts were mostly of higher molecular weights, possibly
5
isomers of functionalized biphenyl dimers, as was suggested by size
exclusion chromatography.
electrophilic nature of the reaction. Thus, from toluene (6b),
regioisomers of toluic acid were obtained in an ortho:meta:
para ratio of 25:10:65 (entry 2). The orientation was sensitive
to steric factors; cumene (6c) and tert-butylbenzene (6d)
afforded the corresponding carboxylic acids with meta-para
orientation (entries 3, 4). It is noteworthy that the highest
(12) A mixture of meta and para isomers was obtained. The ortho
carbonylated product was obtained not as 2-biphenylcarboxylic acid but as
a mixture of benzo[c]chromen-6-one and 9-fluorenone. See Supporting
Information for details.
(13) 1,2-Dichloroethane was used as a cosolvent instead of dichlo-
romethane.
2438
Org. Lett., Vol. 6, No. 14, 2004

tion conditions, an electrophilic substitution of Pd(II) on
an arene is known to give the arylpalladium complex,
Ar-Pd(tfa). Reductive elimination of Ar-OR (R )
Table 1. Palladium-Catalyzed Carboxylation of Benzene and
Its Derivatives Using Formic Acid as a Carbonyl Sourcea
1
CF
Ar-Pd(tfa) or Ar-Pd-OCOH (the right half of Scheme
). Reductive elimination through Pd(IV) species was also
3
C(dO) or HC(dO)) may proceed from either
1
6
3
1
4b
proposed. As an alternative route to ArOCOCF
3
, metal-
catalyzed trifluoroacetoxylation by peracid may be sug-
1
7
gested. For the carboxylation, the common intermediate
entry
6 (X)
6a (H)
6b (Me)
6c (iso-Pr)
6d (tert-Bu)
6e (OAc)
6f (I)
TON
o:m:p
Ar-Pd(tfa) may possibly add to a carbonyl group of formic
1
2
3
4
5
6
7
8
106b
99c
30d
18
acid in a nucleophilic manner. The subsequent â-hydride
25:10:65
13:20:67
0:33:67
elimination would give the carboxylation product (the left
half of Scheme 3). Although the oxidative addition of a
106
130
19
e
formyl C-H to a low-valent metal has been reported, it is
less probable to proceed under the current reaction conditions
where the electron-deficient Pd(II) predominates. Another
possible pathway for the carboxylation is the decomposition
42:0:58
36
6
120
20:20:60
48:20:32
8h:18:74
6g (Cl)
1 (Ph)f
g
a
2
of formic acid into CO and H O. In fact, the carbonylation
A mixture of arenes (10 mmol) and formic acid (1 mL, 26 mmol) in
trifluoroacetic acid (2 mL) was heated at 80 °C for 70 h in the presence of
Pd(OCOCF3)2 (20 µmol) and K2S2O8 (6 mmol). Dimerization product
biphenyl) was not detected. Regioisomers of dimethylbiphenyls were
5
of Ar-Pd(tfa) by CO is well-known. However, the decom-
position of formic acid was not detected in TFA at 50 °C
for 80 h, at least in the absence of palladium. Thus, even if
the decomposition of formic acid is the key step for the
carbonylation, the decomposition should take place on the
Pd metal, and probably, the CO thus produced would directly
undergo the carbonylation without being released from the
metal center.
b
c
(
d
obtained as byproducts with a TON of 22. Complex mixture was produced
e
as byproducts resulting from radical oxidation of 6c. f Products were
obtained as hydroxybenzoic acid after aqueous workup. Product was 2.
g
-Hydroxybiphenyl was obtained as a byproduct with a TON of 5. h Ortho-
4
carbonylated product was obtained not as 2-biphenylcarboxylic acid but as
a mixture of benzo[c]chromen-6-one and 9-fluorenone in a ratio of 65:35.
In conclusion, we found that the sequential hydroxylation-
carboxylation of biphenyl (1) provides hydroxybiphenylcar-
boxylic acid (2). The para-substituted isomer, 4′-hydroxy-
TON (130) was achieved with phenyl acetate (6e), which
afforded a mixture of ortho- and para-hydroxybenzoic acid
after aqueous workup (entry 5). Aryl halides gave carboxy-
lated products, leaving the halogen-carbon bond untouched
4
-biphenylcarboxylic acid, is an attractive monomer for
polyaromatic esters, widely used as engineering plastic with
extremely high thermal stability. This new route may be more
advantageous than conventional processes, which employ
multiple-step methods involving production of hydroxybi-
phenyl 4, protection of its hydroxyl group, and then car-
(entries 6, 7). Phenol and anisol gave complex mixtures as
products, while electron-deficient arenes such as R,R,R-
trifluorotoluene and acetophenone were inert under the
reaction conditions.
Although the mechanism of neither the hydroxylation
nor the carboxylation is clear at this moment, possible
reaction pathways are drawn in Scheme 3. Under the reac-
2
0
boxylation of the protected 4.
Supporting Information Available: Experimental pro-
cedure for the hydroxy-carboxylation of 1 and 6a, the
carboxylation of 1 and 6a-g, control experiments, and
characterization of all the products. This material is available
free of charge via the Internet at http://pubs.acs.org.
Scheme 3. Possible Reaction Pathways for the
Hydroxylation-Carboxylation of Biphenyl
OL049166L
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1
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(
Abstr. 1993, 118, 22024. (b) Kikuchi, T.; Nishiyana, M.; Aoki, T.; Watanabe,
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Org. Lett., Vol. 6, No. 14, 2004
2439