Oxidative carbomethoxylation of alkenes using a Pd(II)/molybdovanadophosphate (NPMoV) system under carbon monoxide and air

Article abstract of DOI:10.1021/jo0255779

Oxidative carbomethoxylation of cyclopentene (1) under carbon monoxide and air by the use of a catalytic amount of Pd(OAc)₂ and molybdovanadophosphate (NPMoV) led to dimethyl cis-1,2-cyclopentanedicarboxylate (2) and dimethyl cis-1,3-cyclopentanedicarboxylate (3) in good yields. Total yields of 2 and 3 were found to be improved by adding a small amount of NH₄Cl. Several alkenes were similarly converted into the corresponding dimethyl dicarboxylates. The role of Cl^- in the present catalytic system is suggested.

Full text of DOI:10.1021/jo0255779

an alternative redox couple in the carbomethoxylation.6
If the Pd(II)-catalyzed carbonylation can be performed
in the absence of CuCl2 using molecular oxygen as the
terminal oxidant, such a system would be very attractive
from environmental and industrial viewpoints. However,
the carbonylation of alkenes with CO by Pd(II) using O2
as the reoxidizing agent is usually difficult to carry out.
Therefore, there has been little study on Pd(II)-catalyzed
carbonylation using molecular oxygen as the terminal
oxidant.7
Oxid a tive Ca r bom eth oxyla tion of Alk en es
Usin g a P d (II)/Molybd ova n a d op h osp h a te
(NP MoV) System u n d er Ca r bon Mon oxid e
a n d Air
Takahiro Yokota, Satoshi Sakaguchi, and
Yasutaka Ishii*
Department of Applied Chemistry, Faculty of Engineering
and High Technology Research Center, Kansai University,
Suita, Osaka 564-8680, J apan
ishii@ipcku.kansai-u.ac.jp
Received February 1, 2002
Abstr a ct: Oxidative carbomethoxylation of cyclopentene (1)
under carbon monoxide and air by the use of a catalytic
amount of Pd(OAc)2 and molybdovanadophosphate (NPMoV)
led to dimethyl cis-1,2-cyclopentanedicarboxylate (2) and
dimethyl cis-1,3-cyclopentanedicarboxylate (3) in good yields.
Total yields of 2 and 3 were found to be improved by adding
a small amount of NH4Cl. Several alkenes were similarly
converted into the corresponding dimethyl dicarboxylates.
The role of Cl- in the present catalytic system is suggested.
Recently, we have reported that molybdovanadophos-
phate (NPMoV)/hydroquinone/O2 is an efficient reoxida-
tion system for the Pd(OAc)2-catalyzed acetoxylation and
acetalization of substituted alkenes.8 For example, cy-
clohexene and acrylonitrile are readily converted into
2-cyclohexenyl acetate and cyanoacetaldehyde diethyl-
acetal, respectively, in quantitative yields under mild
conditions. In addition, cyclotrimerization of internal and
terminal alkynes was efficiently induced by the Pd(II)/
chlorohydroquinone/NPMoV/O2 to give polyalkylbenzenes
in good yields.9 Thus, 4-octyne and tert-butylacetylene led
to hexa-n-propylbenzene and 1,3,5-tri-tert-butylbenzene,
respectively. Although the Wacker-type oxidation of
cyclopentene to cyclopentanone has been very difficult
to carry out so far, this transformation was successfully
performed by Pd(OAc)2 and NPMoV supported on acti-
vated carbon using molecular oxygen as the terminal
oxidant.10 Moreover, we reported that the Pd(OAc)2/
chlorohydroquinone/NPMoV system catalyzes carbony-
lation of terminal alkynes in different ways by varying
the solvent.11 For instance, phenylacetylene was con-
verted into methyl phenylpropionate in methanol and
phenylmaleic anhydride in dioxane. This reaction pro-
vides a new carbonylation system catalyzed by Pd(OAc)2
using NPMoV and molecular oxygen as the reoxidant.
To extend our work on the Pd(OAc)2/NPMoV/O2 system
in organic synthesis, we examined the carbomethoxyla-
tion of several alkenes with CO in methanol.
Pd(II)-catalyzed carboalkoxylation of alkenes with CO
in alcohol is known to produce R,â-unsaturated esters,
â-alkoxy esters, and succinate derivatives (eq 1), and it
is reported that the selectivity of these products was
markedly influenced by the presence of a cocatalyst like
a mercury salt1 or a base2 and the reaction conditions
under a particular CO pressure.3 Similarly, cyclic alkenes
such as cyclopentene, cycloheptene, cyclooctene, and
norbornene also undergo carboalkoxylation by PdCl2 to
afford the corresponding 1,2- and 1,3-diesters.2 However,
these reactions call for the use of a stoichiometric amount
of copper(II) chloride and sodium acetate. The Pd(II)-
catalyzed carboalkoxylation of alkenes by using excess
CuCl2 as the reoxidant results in the formation of
chlorinated byproducts and corrosion by the chloride
anion. Another disadvantage in the reaction using the
PdCl2/CuCl2/CO/O2 system is that the CO is easily
converted into CO2 by the reaction with H2O under the
influence of CuCl2 in the presence of PdCl2 (eq 2).2,4 To
overcome these drawbacks, several reoxidation systems
other than the CuCl2/O2 were examined. Among them,
the use of alkyl nitrites is thought to be a good method,
and the carboalkoxylation of ethylene to succinate ester
is currently carried out by this method on an industrial
scale.5 The benzoquinone/Pd(II) system is also used as
(6) (a) Pisano, C.; Nefkens, S. C. A.; Consiglio, G. J . Mol. Catal. A:
Chem. 1999, 143, 263. (b) Sperrle, M.; Consiglio, G. J . Mol. Catal. A:
Chem. 1999, 143, 263. (c) Bianchini, C.; Mantovani, G.; Meli, A.;
Oberhauser, W.; Bru¨ggeller, P.; Stampfl, T. J . Chem. Soc., Dalton
Trans. 2001, 690.
* To whom correspondence should be addressed. Fax: +81-6-6339-
4026.
(7) (a) Morris, G. E.; Oakley, D.; Pippard, D. A.; Smith, J . H. J .
Chem. Soc., Chem. Commun. 1987, 410. (b) Toda, S.; Miyamoto, M.;
Kinoshita, H.; Inomata, K. Bull. Chem. Soc. J pn. 1991, 64, 3600.
(8) Yokota, T.; Fujibayashi, S.; Sakaguchi, S.; Nishiyama, Y.; Ishii,
Y. J . Mol. Catal. A: Chem. 1996, 114, 113.
(9) Yokota, T.; Sakurai, Y.; Sakaguchi, S.; Ishii, Y. Tetrahedron Lett.
1997, 38, 3923.
(1) (a) Heck, R. F. J . Am. Chem. Soc. 1972, 94, 2712. (b) Stille, J .
K.; J ames, D. E.; Hines, L. F. J . Am. Chem. Soc. 1973, 95, 5062.
(2) Fenton, D. M.; Steinwand, P. J . J . Org. Chem. 1972, 37, 2034.
(3) J ames, D. E.; Stille, J . K. J . Am. Chem. Soc. 1976, 98, 1810.
(4) (a) Hamed, O.; El-Qisairi, A.; Henry, P. M. J . Org. Chem. 2001,
66, 180. (b) Romano, U.; Tesei, R.; Mauri, M. M.; Rebora, P. Ind. Eng.
Chem. Prod. Res. Dev. 1980, 19, 396.
(10) Kishi, A.; Higashino, T.; Sakaguchi, S.; Ishii, Y. Tetrahedron
Lett. 2000, 41, 99.
(5) Uchiumi, S.; Ataka, K.; Matsuzaki, T. J . Organomet. Chem. 1999,
576, 279.
(11) Sakurai, Y.; Sakaguchi, S.; Ishii, Y. Tetrahedron Lett. 1999, 40,
1701.
10.1021/jo0255779 CCC: $22.00 © 2002 American Chemical Society
Published on Web 05/22/2002
J . Org. Chem. 2002, 67, 5005-5008
5005

TABLE 2. Bism eth oxyca r bon yla tion of Cyclop en ten e
(1) to Dim eth yl cis-1,2-Cyclop en ta n ed ica r boxyla te (2) a n d
Dim eth yl cis-1,3-Cyclop en ta n ed ica r boxyla te (3) Usin g th e
P d (II)/NP MoV Ca ta lytic System u n d er Va r yin g P r essu r e
of CO/Air a
Cyclopentene (1) was chosen as a model substrate and
allowed to react with a mixed gas of CO and air in the
presence of Pd(OAc)2 and NPMoV under various condi-
tions (Table 1). The reaction led to dimethyl cis-1,2-
cyclopentanedicarboxylate (2) and dimethyl cis-1,3-
cyclopentanedicarboxylate (3) as major products (eq 3).
run CO (atm) air (atm) time (h) yield (%)b ratio of 2/3
1
2
3
4
5
6
7
5
10
15
20
30
15
5
5
10
15
20
30
5
6
9
9
10
10
8
81
80
83
72
65
63
85
54/46
63/37
65/35
69/31
74/26
68/32
53/47
15
7
a
Compound 1 (2 mmol) was added to a solution of Pd(OAc)2
TABLE 1. Ca r bom eth oxyla tion of Cyclop en ten e (1) to
Dim eth yl cis-1,2-Cyclop en ta n ed ica r boxyla te (2) a n d
Dim eth yl cis-1,3-Cyclop en ta n ed ica r boxyla te (3) Usin g th e
P d (II)/NP MoV Ca ta lytic System u n d er Va r iou s Rea ction
Con d ition sa
(2.5 mol %), NPMoV (35 mg), NH4Cl (3 mol %), and MeSO3H (10
mol %) in MeOH (10 mL) and stirred under CO/air at 60 °C.
Compound 1 was almost consumed every run. Total yield of 2
b
and 3.
run
temp (°C) time (h) conv (%) yield (%)b ratio of 2/3
improved. When NaCl was used in place of NH4Cl, the
yields of 2 and 3 were almost the same as those in the
reaction using NH4Cl (run 6). These results show that
the addition of a small amount of chloride ion markedly
facilitates the present carbomethoxylation of 1. The use
of PdCl2 in place of Pd(OAc)2 without NH4Cl resulted in
2 and 3 in moderate yields (run 7). Even in the use of
the PdCl2 catalyst, the addition of NH4Cl to the catalytic
system was effective in improving the yields of 2 and 3
(run 8). The reaction in the absence of MeSO3H under
these conditions resulted in the reduction of carbonylated
products, 2 and 3 (run 9). No carbonylation took place in
the absence of both NH4Cl and MeSO3H even at higher
a temperature (100 °C) (run 10). In a previous paper, we
showed that the catalytic potential of the NPMoV in the
oxidation of isophorone with O2 is considerably enhanced
by the addition of an acidlike MeSO3H to the catalytic
system.12 Ba¨ckvall et al. described that the precipitation
of Pd(0) is depressed by the addition of a small amount
of a strong acid to the reaction system.13 Therefore, it is
thought that the MeSO3H has a similar effect in the
present reaction. The reaction of 1 under CO (5 atm) and
pure O2 (1 atm) in place of air led to 2 and 3 in a
somewhat lower yield (61%) (run 11). It is interesting to
note that the carbomethoxylation at 40 °C gave 2 in
preference to 3 in good yield (75%), although the reaction
must be prolonged to 19 h (run 12). When the reaction
temperature was raised to 70 °C, the carbomethoxylation
was completed within 3 h to give 2 and 3 in 79% yield
(run 13). Reactions at higher temperatures afforded 3
rather than 2 (runs 12-15).
1
2c
60
60
60
60
100
60
60
60
60
100
60
6
6
6
48
5
6
6
6
9
9
6
19
3
3
1
96
17
25
62
72
99
74
88
54
25
96
92
97
92
82
81
8
54/46
54/46
3d
<1
20
34
79
61
79
41
<1
61
75
79
63
42
4d
65/35
41/59
57/43
49/51
53/47
59/41
5d
6e
7d,f
8f
9g
10d,g
11h
12
13
14
15
56/44
63/37
48/52
41/59
40/60
40
70
80
100
a
Compound 1 (2 mmol) was added to a solution of Pd(OAc)2
(2.5 mol %), NPMoV (35 mg), NH4Cl (3 mol %), and MeSO3H (10
mol %) in MeOH (10 mL) and stirred under CO/air (5/5 atm).
Total yield of 2 and 3. c In the absence of NPMoV. In the
b
d
absence of NH4Cl. e NaCl was used instead of NH4Cl. f PdCl2 was
g
h
used instead of Pd(OAc)2. In the absence of MeSO3H. Under
CO/O2 (5/1 atm).
The carbomethoxylation of 1 (2 mmol) under CO (5
atm)/air (5 atm) catalyzed by Pd(OAc)2 (2.5 mol %) and
NPMoV (35 mg) in the presence of NH4Cl (3 mol %) in
methanol (10 mL) acidified with MeSO3H (10 mol %) at
60 °C for 6 h produced 2 and 3 in a ratio of 54:46 in 81%
total yield and 96% conversion of 1 (run 1). A gap between
the consumed cyclopentene and the resulting products
was found to be due to the formation of oligomers derived
from cyclopentene and CO. Indeed, a small amount of a
tarry residue was left after removal of the solvent and
the products. The geometry of the resulting diesters 2
and 3 was found to be of the cis configuration by
comparing these spectral data with those reported previ-
ously.3 The cis geometry of dicarboxylic acid obtained by
hydrolysis of 2 could be determined by a single-crystal
X-ray analysis. The reaction course leading to cis-2 is
rationally explained by a reaction mechanism discussed
below. The reaction in the absence of NPMoV under these
conditions gave 2 (8%) in an amount comparable to that
of the Pd(OAc)2 present (run 2). In the absence of NH4Cl
under these conditions, the reaction was considerably
retarded (runs 3 and 4). To improve the slow carbonyla-
tion in the absence of NH4Cl at 60 °C, the reaction was
run at 100 °C (run 5). The yields of 2 and 3 slightly
increased, but the selectivity of the reaction was not
The carbonylation of 1 under varying CO and air
pressures is shown in Table 2. An approximately 1:1
mixture of 2 and 3 was obtained by the reaction of 1
under CO (5 atm) and air (5 atm) (run 1), and increasing
the CO and air pressures caused an increase of the
formation of 3 (runs 2-5). No significant influence on the
yield of 2 and 3 was observed in the range of 5-15 atm
of CO and air (runs 1-3), but the formation of 2 and 3
was gradually decreased in the reaction at over 20 atm
of CO and air (runs 4 and 5). The reaction under CO (15
atm) and air (5 atm) resulted in a decrease of 2 and 3
(12) Hanyuu, A.; Sakurai, Y.; Fujibayashi, S.; Sakaguchi, S.; Ishii,
Y. Tetrahedron Lett. 1997, 38, 5659.
(13) Ba¨ckvall, J . -E.; Hopkins, R. B. Tetrahedron Lett. 1988, 29,
2885.
5006 J . Org. Chem., Vol. 67, No. 14, 2002

SCHEME 1
(run 6), while the reaction at higher pressures of CO (5
atm) and air (15 atm) led to 2 and 3 in high yield (85%,
run 7). It is interesting to note that the reaction at 1 atm
of CO and 5 atm of air produced various carbonylated
products such as monoesters, methyl 1-cyclopentenecar-
boxylate (4, 29%), methyl cyclopentane carboxylate (5,
18%), and cyclopentanone (16%) in addition to 2 (2%) and
3 (13%) (eq 4).
On the basis of these results, the carbonylation of
several alkenes was attempted under CO (5 atm) and air
(5-15 atm) (Table 3).
under these conditions to form the corresponding diester
and ketone (run 6). Ethylene was selectively carbonylated
into dimethyl succinate, and acetal based on the Wacker
oxidation was not observed.
TABLE 3. Bism eth oxyca r bon yla tion of Va r iou s Alk en es
Usin g th e P d (II)/NP MoV Ca ta lytic System a
A plausible reaction path for the present carbomethox-
ylation is outlined in Scheme 1. The reaction is initiated
by the coordination of cyclopentene 1 followed by CO to
Pd(II) to form a Pd complex (A), which then reacts with
methanol to form a carbomethoxypalladium complex (B).
The cis addition of the palladium species to the coordi-
nated cyclopentene double bond forms a σ-bonded pal-
ladium complex (C). It is probable that CO insertion into
the complex C followed by methanolysis of the resulting
palladium-acyl intermediate gives rise to dimethyl cis-
1,2-cyclopentanecarboxylate 2. On the other hand, â-hy-
drogen elimination from the complex C and recoordina-
tion of the Pd(II) species forms a σ-complex (E) through
the formation of a π-complex (D). The complex E reacts
with CO followed by methanolysis to afford dimethyl cis-
1,3-cyclopentanecarboxylate 3.
To obtain further information on the reaction course
of the present carbomethoxylation, the carbomethoxyla-
tion of methyl 1-cyclopentenecarboxylate (4) was exam-
ined under CO (5 atm) and air (5 atm) at 60 °C for 6 h.
However, the reaction was not induced at all and the
starting 4 was recovered (eq 5). This shows that 4 is a
stable compound and that 2 and 3 are not formed through
4. Since â-hydrogen elimination is only capable of occur-
ring when a palladium species and the hydrogen atom
are located in the cis position, the formation of 4 from
the complex C is impossible. For the formation of 4,
therefore, dissociation of the palladium-hydride species
from the π-complex D and its recoordination from the
opposite side is needed to form a σ-complex (F ). The fact
that the present carbonylation provides 2 and 3 having
cis configurations shows that the reaction proceeds
without dissociation of the Pd-H species from the
complex D.
a
Substrate (2 mmol) was added to a solution of Pd(OAc)2 (2.5
mol %), NPMoV (35 mg), NH4Cl (3 mol %), and MeSO3H (10 mol
%) in MeOH (10 mL) and stirred under CO (5 atm)/air at 60 °C.
Ethylene (0.5 atm, ca. 1.5 mmol) was introduced into the
b
autoclave containing the catalytic solution and stirred at 50 °C.
Although cyclohexene was not carbonylated at all,
cycloheptene and cyclooctene were slightly carbonylated
to form the corresponding diesters in low yields (runs
1-3). This tendency bears a close resemblance to the
results reported by Stille et al. except for the result of
the oligomerization of norbornene under our conditions.3
The carbomethoxylation of styrene gave dimethyl 2-phe-
nylsuccinate in fair yield (45%) together with a small
amount of acetophenone (run 5). The yield of the succi-
nate derivative was improved by raising the pressure of
air (runs 4 and 5). p-Methylstyrene was also carbonylated
J . Org. Chem, Vol. 67, No. 14, 2002 5007

It is interesting to note that the reaction of 1 under
low pressures of CO (0.5 atm) and O2 (0.5 atm) proceeded
despite the presence or absence of NH4Cl. The reaction
in the presence of NH4Cl was completed within 1 h to
give 4 as a main product, while in the absence of NH4Cl
a longer reaction time was needed and a regioisomeric
mixture of methyl 2-cyclopentenecarboxylate (7) and
methyl 3-cyclopentenecarboxylate (8) was formed in place
of 4 (eqs 6 and 7). This observation suggests that the
isomerization of 7 and 8 to 4 did not take place in the
absence of NH4Cl though 4 is thermodynamically more
stable than 7 and 8. Therefore, the formation of 7 and 8
may be explained by the â-elimination of Pd-H from the
complexes C and E before the coordination of CO to C or
E. In the case of the presence of NH4Cl in the reaction
system, the resulting 7 and 8 seem to be isomerized to
the stable 4. The formation of the saturated monoester
5 under a low pressure of CO strongly suggests that the
Pd-H species is generated in the course of the reaction.
Thus, it is probable that the CO insertion into a σ-com-
plex derived from hydropalladation of the Pd-H to 1
followed by methanolysis of the resulting palladium-acyl
intermediate leads to 5. In the reaction without NH4Cl
under a low pressure of CO, the formation of 3, 7, and 8
may indicate that the complex E is more stable than the
complex C and that the â-elimination of Pd-H from the
complex E occurs in preference to that from the complex
C. On the basis of these facts, the Cl- ion is thought to
facilitate the formation of the Pd-H species.
NPMoV in the presence of a very small amount of the
Cl- ion under mild conditions.
Exp er im en ta l Section
Gen er a l. All solvents and reagents were purchased from
commercial sources and used without further purification unless
otherwise noted. 1H and 13C NMR were measured at 270 and
67.5 MHz, respectively, in CDCl3 with Me4Si as the internal
standard. Infrared (IR) spectra were measured using a NaCl
plate or the KBr method. GLC analyses were performed with a
flame ionization detector using a 25 m (0.22 mm i.d., 0.25 µm
film thickness) fused silica capillary column (BP1). All yields
were determined by GLC analyses using undecane as the
internal standard.
Typ ica l P r oced u r e for th e Ca r bom eth oxyla tion of Cy-
clop en ten e (1). A solution of Pd(OAc)2 (2.5 mol %), NPMoV (35
mg),8,14 NH4Cl (3 mol %), MeSO3H (10 mol %), and cyclopentene
(1) (2 mmol) in MeOH (10 mL) was placed in a stainless
autoclave (50 mL). The autoclave was pressurized with 5 atm
of air and then with 5 atm of CO at room temperature. The
reaction mixture was allowed to react under stirring at 60 °C
until the CO and O2 uptake had not been observed (6 h). After
the reaction, the solvent was removed under reduced pressure
and the residue was dissolved in diisopropyl ether. The solution
was filtered, washed with diluted NaHCO3, and dried over
anhydrous MgSO4. After removal of diisopropyl ether under
reduced pressure, the residual liquid was separated by HPLC
that was performed on GPC columns to give dimethyl cis-1,2-
cyclopentanedicarboxylate (2) and dimethyl cis-1,3-cyclopen-
tanedicarboxylate (3) as a clear liquid, respectively, in 81% total
yield. The biscarbomethoxylated products from cycloalkene3 and
styrene6a and compounds 5,15 7,16 and 817 were previously
reported. Other products were commercially available and
identified through comparison of the isolated product with an
authentic sample.
Dim eth yl 2-p-Tolylsu ccin a te: 1H NMR (270 MHz, CDCl3)
δ 7.17-7.10 (m, 4H), 4.08-4.03 (m, 1H), 3.66 (s, 6H), 3.20-3.14
(m, 1H), 2.68-2.60 (m, 1H), 2.31 (s, 3H); 13C NMR (67.5 MHz,
CDCl3) δ 173.3, 171.7, 137.1, 134.5, 129.4, 127.4, 52.2, 51.7, 46.6,
37.6, 21.0.
Ack n ow led gm en t. This work was partly supported
by Daicel Chemical Company and a Grant-in-Aid for
Scientific Research (S) from the Ministry of Education,
Culture, Sports and Technology (MEXT), J apan.
Su p p or tin g In for m a tion Ava ila ble: Preparation of NP-
MoV and an X-ray structure for cis-1,2-cyclopentanedicarboxy-
lic acid. This material is available free of charge via the
Internet at http://pubs.acs.org.
J O0255779
(14) See Supporting Information for preparation.
(15) Davis, C. R.; Swenson, D. C.; Burton, D. J . J . Org. Chem. 1993,
58, 6843.
(16) Trost, B. M.; Whitman, P. J . J . Am. Chem. Soc. 1974, 96, 7421.
(17) Lizotte, K. E.; Marecki, P. E.; Mertes, M. P. J . Org. Chem. 1983,
48, 3594.
In conclusion, the carbomethoxylation of alkenes with
CO in methanol using air as the terminal oxidant was
successfully achieved by using Pd(OAc)2 combined with
5008 J . Org. Chem., Vol. 67, No. 14, 2002