Synthesis of maleic anhydrides and maleic acids by Pd-catalyzed oxidative dicarbonylation of alk-1-ynes

Article abstract of DOI:10.1002/ejoc.200210706

We have found that carbon dioxide effectively promotes the Pd-catalyzed oxidative carbonylation of terminal alkynes to give maleic anhydrides in fair yields. Reactions were carried out in aqueous dioxane at 60-80 °C in the presence of catalytic amounts of PdI₂ in conjunction with KI and under a 4:1:10 mixture of CO/air/CO₂ (60 atm total pressure at 25 °C). By working in the presence of a large excess of water, maleic acids were formed selectively with unprecedented catalytic efficiencies for this kind of reaction. In the latter case, the use of an excess of carbon dioxide tended to inhibit, rather than promote, the reaction. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejoc.200210706

FULL PAPER
Synthesis of Maleic Anhydrides and Maleic Acids by Pd-Catalyzed Oxidative
Dicarbonylation of Alk-1-ynes
Bartolo Gabriele,*[a] Lucia Veltri,[b] Giuseppe Salerno,[b] Mirco Costa,[c] and
Gian Paolo Chiusoli[c]
Keywords: Anhydrides / Carbonylation / Maleic acids / Palladium
We have found that carbon dioxide effectively promotes the
Pd-catalyzed oxidative carbonylation of terminal alkynes to
give maleic anhydrides in fair yields. Reactions were carried
out in aqueous dioxane at 60−80 °C in the presence of cata-
lytic amounts of PdI2 in conjunction with KI and under a
4:1:10 mixture of CO/air/CO2 (60 atm total pressure at 25 °C).
By working in the presence of a large excess of water, maleic
acids were formed selectively with unprecedented catalytic
efficiencies for this kind of reaction. In the latter case, the
use of an excess of carbon dioxide tended to inhibit, rather
than promote, the reaction.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
and under a pressure of 2 atm of CO was reported many
years ago.[9] In a later report, maleic anhydrides were ob-
tained with good selectivities and under mild conditions by
the oxidative carbonylation of alk-1-ynes in THF/HCO2H/
H2O in the presence of PdCl2 as catalyst, CuCl2 as cocata-
lyst, and O2 as reoxidant {Equation (1), [OX] ϭ 1/2 O2,
[OXH2] ϭ H2O}.[10] More recently, the use of PdCl2 as the
catalyst and CuCl2 as the oxidizing agent in water/dioxane
has been described {Equation (1), [OX] ϭ 2 CuCl2,
OXH2 ϭ 2 CuCl ϩ 2 HCl}.[11] Halide-free catalytic systems
have also been reported, both homogeneous [Pd(OAc)2 in
conjunction with chlorohydroquinone (HQ-Cl), molybdov-
anadophosphate (NPMoV) and CH3SO3H][12] and hetero-
geneous [PdII/zirconium phosphate].[13]
Maleic anhydrides and acids are important classes of car-
bonyl compounds. Maleic anhydrides are useful intermedi-
ates in organic synthesis,[1Ϫ3] and have found application
both in the preparation of biologically active molecules[4]
and as monomers for polymerization.[5] Maleic acids are
mainly employed as starting materials for polymerization
reactions,[6] and have also found application as synthetic in-
termediates.[7]
Pd-catalyzed oxidative carbonylation of alk-1-ynes 1 in
the presence of small amounts of water represents a valu-
able method for the direct synthesis of maleic anhydrides 2
starting from readily available substrates [Equation (1)].[8]
In the framework of our investigations on the car-
bonylation of alkynes, we have previously studied the PdI2/
KI-catalyzed carbonylation of 1 carried out in dioxane un-
der reductive conditions (CO/H2O in the absence of O2),
which led selectively to 3-substituted furan-2(5H)-ones 3 in
the absence of CO2 [Equation (2)][14] and to a ca. 1:1 mix-
ture of 3 and 2 in the presence of CO2 (40 atm)
[Equation (3)].[15Ϫ16]
(1)
The stoichiometric formation of phenylmaleic anhydride
by carbonylation of phenylacetylene in the presence of
PdCl2 and HgCl2 in acetone/H2O (9:1, v/v) at room temp.
[a]
`
Dipartimento di Scienze Farmaceutiche, Universita della
(2)
(3)
Calabria,
87036 Arcavacata di Rende, Cosenza, Italy
Fax (internat.) ϩ 39-0984/492044
Email: b.gabriele@unical.it
[b]
[c]
`
Dipartimento di Chimica, Universita della Calabria,
87036 Arcavacata di Rende, Cosenza, Italy
`
Dipartimento di Chimica Organica e Industriale, Universita di
Parma,
Parco Area delle Scienze 17/A, 43100 Parma, Italy
1722
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejoc.200200706
Eur. J. Org. Chem. 2003, 1722Ϫ1728

Synthesis of Maleic Anhydrides and Maleic Acids
FULL PAPER
We now report the selective synthesis of 2 by Pd-cata- 6Ϫ7). In some cases (Runs 5, 7), substrate conversion was
lyzed and CO2-promoted oxidative carbonylation of 1, not complete even after 15 h; prolonging the reaction time,
based on the use of a very simple catalytic system (PdI2 ϩ however, to 24Ϫ36 h to achieve quantitative conversion was
10 equiv. of KI), in water/dioxane as the solvent and with not accompanied by a significant improvement in the yield
oxygen as the oxidizing agent [Equation (4)]. This catalytic of 2.
system has also proved useful — with unprecedented cata-
lytic efficiencies for this kind of reaction — for the prep-
aration of maleic acids 4 from 1 by working in 1,2-dime-
thoxyethane (DME) with water as the cosolvent [Equa-
tion (5)]. In the latter case, the use of an excess of carbon
dioxide tends to inhibit, rather than promote, the reaction.
When phenylacetylene (1a) and tert-butylacetylene (1g)
were employed, small amounts of furanones 3 were formed
as byproducts (Runs 1 and 7, respectively); moreover, in the
case of 1a, a mixture of regioisomeric spiro derivatives 5a
(26% total yield) was also detected in the reaction mixture.
All these byproducts were formed by competitive reductive
carbonylation processes.[16] Unidentified high-molecular-
mass products accounted for the substrate conversion in the
examples reported in Runs 2Ϫ5 and 7.
(4)
(5)
A very interesting feature of the present reaction is the
effect exerted by an excess of CO2 (40 atm) on promoting
the overall oxidative carbonylation process leading to 2.
That carbon dioxide actually acted as a promoter, and not
as a reagent, was unequivocally demonstrated by experi-
ments carried out with 13CO2, which showed that no signifi-
cant 13C incorporation occurred in the final product. The
results obtained by carrying out the same experiments re-
ported in Table 1, but in the absence of added CO2, are
shown in Table 2. As it can be seen from Table 2, the pro-
moting effect of CO2 was particularly striking in the case
of arylacetylenes 1aϪe (cf. Runs 8Ϫ12 with Runs 1Ϫ5), and
less important for alkylacetylenes 1fϪg (cf. Runs 13Ϫ14
with Runs 6Ϫ7). In fact, by working in the absence of CO2,
the yields of arylmaleic anhydrides dropped considerably
(from 57Ϫ75% to 5Ϫ45%) in favor of the formation of fu-
ranone 3a and spirolactones 5a in the case of 1a (Run 8),
and of unidentified high-molecular mass products in the
other cases (Runs 9Ϫ12).
Results and Discussion
Synthesis of Maleic Anhydrides 2
Oxidative carbonylation reactions of alk-1-ynes 1 were
carried out in dioxane at 60Ϫ80 °C in the presence of PdI2
(5 ϫ 10Ϫ3 to 1 ϫ 10Ϫ2 equiv.), KI (0.05Ϫ0.10 equiv.), and
H2O (2.0Ϫ2.5 equiv.) under a 4:1:10 mixture of CO/air/CO2
(60 atm total pressure at 25 °C) and afforded maleic anhy-
drides 2 in fair to excellent yields [48Ϫ96%, Equation (4)].
Representative results obtained with different alk-1-ynes 1
are shown in Table 1.
Arylacetylenes were sufficiently reactive to allow the re-
action to be conducted at 60 °C with a substrate/catalyst
molar ratio of 200 (Runs 1Ϫ5). π-Donating groups on the
ring, such as a methoxy substituent in the para position,
tended to enhance the reactivity of a substrate (cf. Run 4
with Run 1), while lower yields and conversions were ob-
tained when an electron-withdrawing substituent, such as
The CO2 effect can be interpreted on the basis of the
chloro, was present (Run 5). Alkylacetylenes were less reac- reaction mechanism that leads to 2. As we have already
tive than arylacetylenes, so the reaction was carried out at reported,[15Ϫ16] the carbonylation process is initiated by an
80 °C with a substrate/catalyst molar ratio of 100 (Runs IϪPdϪCO2H species (formed by H2O attack on coordi-
Table 1. Synthesis of maleic anhydrides 2 by oxidative carbonylation of alk-1-ynes 1 in dioxane in the presence of PdI2, KI (KI/PdI2
molar ratio ϭ 10), H2O and CO2; p(CO) ϭ 16 atm, p(air) ϭ 4 atm, p(CO2) ϭ 40 atm; substrate concentration: 0.5 mmol/mL; t ϭ 15 h
Run
1
R
H2O/1/PdI2
T [°C]
Conv. of 1 (%)[a]
Yield of 2 (%)[b]
1
2
1a
1b
1c
1d
1e
1f
Ph
500:200:1
200:200:1
500:200:1
500:200:1
500:200:1
200:100:1
200:100:1
60
60
60
60
60
80
80
97
90
100
98
76
98
73
63 (58)[c]
75 (68)
65 (56)
75 (70)
57 (49)
96 (90)
48 (44)[e]
p-MeC6H4
p-tBuC6H4
p-MeOC6H4
p-ClC6H4
Bu
3
4[d]
5
6
7
1g
tBu
[a]
Based on initial amount of 1, by GLC. [b] GLC yield (isolated yield) based on 1. [c] The reaction also led to the formation of 3-phenyl-
[d]
[e]
5H-furan-2-one (3a) (4%) and a mixture of regioisomeric spiro derivatives 5a (26%).
to the formation of 3-tert-butyl-5H-furan-2-one (3g) (4%).
Reaction time was 8 h. The reaction also led
Eur. J. Org. Chem. 2003, 1722Ϫ1728
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1723

B. Gabriele, L. Veltri, G. Salerno, M. Costa, G. P. Chiusoli
FULL PAPER
Table 2. Effect of the absence of CO2 on the reaction of alk-1-ynes 1 with CO, H2O and O2 in dioxane in the presence of PdI2/KI (KI/
PdI2 molar ratio ϭ 10); p(CO) ϭ 16 atm, p(air) ϭ 4 atm; substrate concentration.: 0.5 mmol/mL; t ϭ 15 h
Run
1
R
H2O/1//PdI2
T [°C]
Conv. of 1 (%)[a]
Yield of 2 (%)[b]
[c]
8
9
10
11[d]
12
13
14
1a
1b
1c
1d
1e
1f
Ph
500:200:1
200:200:1
500:200:1
500:200:1
500:200:1
200:100:1
200:100:1
60
60
60
60
60
80
80
100
64
100
86
64
100
78
5
p-MeC6H4
p-tBuC6H4
p-MeOC6H4
p-ClC6H4
Bu
44
35
45
37
90[e]
36[f]
1g
tBu
[a]
[b]
[c]
Based on initial amount of 1, by GLC.
GLC yield based on 1. The reaction also led to the formation of 3-phenyl-5H-furan-2-
[d] [e]
one (3a) (12%) and a mixture of regioisomeric spiro derivatives 5a (65%).
formation of 3-butyl-5H-furan-2-one (3f) (7%). The reaction also led to the formation of 3-tert-butyl-5H-furan-2-one (3g) (6%).
Reaction time was 8 h.
The reaction also led to the
[f]
nated CO), which then inserts the triple bond and CO to leading to reductive-carbonylation products 3 and 5a[15Ϫ16]
give the acylpalladium intermediate I. Tautomerization of and to unidentified high-molecular-mass products obtained
the latter leads to the π-allylpalladium complex II, from when the reaction is carried out in the absence of CO2. This
which 2 is formed by [Pd0 ϩ HI] elimination from the particular stability is probably associated to the fact that
HϪOϪCϪPdI unit. (Scheme 1; anionic iodide ligands are the equilibrium according to Equation (6) is much more
omitted for clarity).
favored in an aprotic, low-polararity solvent, such as diox-
ane, rather then in a polar, protic solvent, such as an al-
cohol, that interacts strongly with HI. In the presence of a
large excess of CO2, however, the concentration of
HϪPdϪI is lowered through the equilibrium shown in
Scheme 2, which involves the formation of
a
palladiumϪformate species through insertion of CO2 into
the PdϪH bond. As reported in the literature,[19] this is the
way that CO2 usually inserts into a palladiumϪhydride
bond. Our results mentioned above with 13CO2 clearly show
that the other possible mode of insertion, leading to a
hydroxycarbonylapalladium species IϪPdϪCO2H, is not at
work under our conditions, since it would lead to some 13
C
incorporation into the final product, in contrast to what
was actually observed.
Scheme 1
Pd0 is then reoxidized according to the usual mecha-
nism[17] involving oxidative addition of I2, which is formed
in turn by oxidation of HI with oxygen. Palladium hydride
complexes, however, can also be formed under the reaction
conditions. In fact, an IϪPdϪH species equilibrates with
Pd0 and HI deriving from the oxidative process leading to
2 [Equation (6)]; moreover, it can be formed by decar-
boxylation of IϪPdϪCO2H intermediates [Equation (7)].
Scheme 2
Synthesis of Maleic Acids 4
Our catalytic system also proved useful for the direct syn-
thesis of maleic acids 4 when oxidative carbonylation of alk-
1-ynes 1 was carried out using H2O as co-solvent [Equa-
tion (5)]. The best results, in terms of substrate conversion
rate and product yields, were obtained by using a 3:1 mix-
ture DME/H2O as the solvent (Table 3). Unprecedented
catalytic efficiencies for this kind of reaction were obtained
under these conditions.
(6)
Maleic and fumaric acids have previously been obtained
as byproducts (5Ϫ35% yield, catalytic efficiencies not
(7)
In contrast to the situation we have already observed in higher than 3.5 mol of product per mol of Pd used) in the
alcoholic solvents under oxidative carbonylation reaction reported in ref.[3] leading mainly to maleic anhy-
conditions,[17Ϫ18] this IϪPdϪH species is apparently rather drides 2. To the best of our knowledge, the only other ex-
stable in dioxane and can be responsible for side reactions ample of direct synthesis of maleic acids by oxidative car-
1724
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 1722Ϫ1728

Synthesis of Maleic Anhydrides and Maleic Acids
FULL PAPER
Table 3. Synthesis of maleic acids 4 by oxidative carbonylation of alk-1-ynes 1 in 3:1 DME/H2O in the presence of PdI2 and 10 equiv.
of KI; 1/PdI2 molar ratio ϭ 2000; p(CO) ϭ 16 atm, p(air) ϭ 4 atm; substrate concentration: 1 mmol/mL; T ϭ 80 °C
Run
1
R
t [h]
Conv. of 1 (%)[a]
Yield of 4 (%)[b]
Molar ratio of 4/PdI2
15
1a
1a
1b
1d
1e
1f
Ph
Ph
3
3
5
3
5
8
8
96
23
97
100
100
76
71 (75)[c]
0
1420
0
1280
1260
1100
960
400
16[d]
17
p-MeC6H4
p-MeOC6H4
p-ClC6H4
Bu
64 (63)[e]
63 (53)
55 (48)
48 (41)[f]
20 (17)
18
19
20
21
1g
tBu
75
[a]
Based on initial amount of 1, by GLC. [b] GLC yield (isolated yield) based on 1. [c] The reaction also led to the formation of 2a (10%).
During the purification procedure, 2a converted into 4a, so the isolated yield reported refers to the overall amount of carboxylic acid
obtained. See Exp. Sect. for details.
[d]
[e]
The reaction was carried out under 60 atm of a 4:1:10 mixture of CO/air/CO2. The reaction
also led to the formation of 2b (7%). During the purification procedure, 2b converted into 4b, so the isolated yield reported refers to the
[f]
overall amount of diacid obtained. See Exp. Sect. for details. The product was a mixture with its (E) isomer [(Z)/(E) ϭ 10:1].
bonylation of alk-1-ynes has been described by us, using the ried out in DME with water as cosolvent afford maleic ac-
PdI2/KI catalytic system, but in N,N-dimethylacetamide/ ids, and are inhibited by added CO2.
water as the solvent and with phenylacetylene (1a) as the
substrate.[17] Under those conditions, however, the yields
and catalytic efficiencies obtained (27% yield of 4a and 3%
of phenylfumaric acid, starting with a 1a/PdI2 molar ratio
Experimental Section
General: Melting points were determined with a Reichert Thermo-
var melting point apparatus and are uncorrected. Elemental analy-
ses were carried out with a Carlo Erba Elemental Analyzer Mod.
of 1000) were significantly lower than those obtained in the
present work.
Carboxylic acids 4 are clearly formed by attack of H2O
on the acylpalladium intermediate I [Equation (8)]. In con-
trast to the reaction leading to anhydrides 2 considered in
the previous section, the use of an excess of carbon dioxide
in this case tended to inhibit, rather than promote, the reac-
tion (cf. Run 16 with Run 15). The latter result is under-
standable, since HI prefers to protonate water, rather than
undergo oxidative addition to Pd0, in a largely aqueous me-
dium and, as a consequence, the equilibrium according to
Equation (6) is shifted to the left and no promoting effect
can take place. On the other hand, the inhibiting effect is
easily explained by considering that CO2 may effectively
compete with the substrate for coordination to the pal-
ladium atom. In fact, palladium complexes with carbon di-
oxide, stabilized by suitable ligands, have been reported in
the literature.[19]
1
1106. H and 13C NMR spectra were taken with a Bruker AC300
spectrometer using Me4Si as internal standard and recorded at 300
and 75 MHz, respectively. Chemical shifts (δ) and coupling con-
stants (J) are given in ppm and in Hz, respectively. IR spectra were
taken with a PerkinϪElmer Paragon 1000 PC FT-IR spectrometer.
Mass spectra were obtained using an HP 5972A GC-MS apparatus
at 70 eV ionization voltage. All reactions were analyzed by TLC
on silica gel 60 F254 or by GLC using a Shimadzu GC-14A gas
chromatograph and capillary columns with polymethylsilicone ϩ
5% phenylsilicone as the stationary phase (HP-5). Column chroma-
tography was performed on silica gel 60 (Merck, 70Ϫ230 mesh).
1,4-Dioxane was distilled under nitrogen from sodium before use.
Preparation of Substrates: Starting materials phenylacetylene (1a),
1-ethynyl-4-methylbenzene (1b), 1-chloro-4-ethynylbenzene (1e),
hex-1-yne (1f), and 3,3-dimethylbut-1-yne (1g) were commercially
available and were used without further purification. 1-tert-Butyl-
4-ethynylbenzene (1c)[20] and 1-ethynyl-4-methoxybenzene (1d)[21]
were prepared according to literature procedures. 13CO2 (13C ϭ
99%, 18O ϭ 6%) was purchased from Isotec Inc. (USA).
(8)
Typical Procedure for Oxidative Carbonylation of Alk-1-ynes 1 to
Maleic Anhydrides 2 and Separation of Products: A 250-mL stain-
less steel autoclave was charged in the presence of air with PdI2
(15.0 or 30.0 mg, 4.2 ϫ 10Ϫ2 or 8.3 ϫ 10Ϫ2 mmol), KI (70.0 or
138.0 mg, 0.42 or 0.83 mmol), a solution of 1 (8.3 mmol) in anhy-
drous dioxane (16.6 mL), and H2O (see Table 1 for the H2O/1/PdI2
molar ratio, reaction temperature and reaction time for each sub-
strate). While stirring, the autoclave was pressurized with CO2 (40
atm), CO (up to 56 atm) and air (up to 60 atm), then heated at
the required temperature for the required time. After cooling, the
autoclave was degassed, the solvent was evaporated under reduced
pressure, and the products separated by column chromatography
(SiO2): 2a, 3a and 5a (mixture of regioisomers)[9] [hexane/EtOAc,
Conclusions
In conclusion, we have shown that a very simple catalytic
system, consisting of PdI2 in conjunction with an excess of
KI, is able to catalyze the oxidative dicarbonylation of alk-
1-ynes 1 to either maleic anhydrides 2 or maleic acids 4 with
high catalytic efficiencies. Reactions that are carried out in
dioxane as the solvent in the presence of small amounts of
water lead to maleic anhydrides, and are effectively pro-
moted by an excess of CO2. In contrast, the reactions car- 7:3 to 1:1; order of elution: 3a (yield: 27 mg, 2%), 2a (838 mg, 58%),
Eur. J. Org. Chem. 2003, 1722Ϫ1728
www.eurjoc.org  2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1725

B. Gabriele, L. Veltri, G. Salerno, M. Costa, G. P. Chiusoli
FULL PAPER
5a (220 mg, 18%)]; 2b (hexane/EtOAc, 9:1; 1.06 g, 68%); 2c (hex-
(m, 2 H aromatic), 7.54 (s, 1 H, ϭCH), 8.01Ϫ8.08 (m, 2 H aro-
ane/EtOAc, 9:1; 1.07 g, 56%); 2d (hexane/EtOAc, 8:2; 1.19 g, 70%); matic) ppm. 13C NMR ([D6]acetone): δ ϭ 56.0, 115.5, 121.0, 123.2,
2e (hexane/EtOAc, 9:1; 848 mg, 49%); 2f (hexane/EtOAc, 8:2;
1.15 g, 90%); 2g (hexane/EtOAc, 8:2; 563 mg, 44%). Lactone 3g 133 (10), 132 (100), 117 (25), 89 (23), 63 (12). C11H8O4 (204.18):
132.0, 146.9, 164.0, 165.4, 166.5 ppm. MS: m/z ϭ 204 (41) [Mϩ],
could not be isolated owing to the very small amounts obtained
(Table 1, Run 7), but was separated from the crude mixture derived
from the reaction carried out in the absence of CO2 (Table 2, Run
14) [hexane/EtOAc, 8:2; order of elution: 3g (50 mg, 4%), 2g
(396 mg, 31%)]. Lactone 3f was formed only from the reaction car-
ried out in the absence of CO2 (Table 2, Run 13) [hexane/EtOAc,
8:2; order of elution: 3f (46 mg, 4%), 2f (1.06 g, 83%)].
calcd. C 64.71, H 3.95; found C 64.88, H 3.97.
3-(4-Chlorophenyl)furan-2,5-dione (2e): Yield 848 mg, starting from
1.13 g of 1e (49%). Pale yellow solid, m.p. 142Ϫ143 °C (ref.[25]
143Ϫ144 °C). IR (KBr): ν˜ ϭ 1852 (w), 1821 (w), 1765 (s), 1610
(w), 1491 (w), 1225 (s), 1093 (m), 902 (m), 839 (m) cmϪ1. 1H NMR
([D6]DMSO): δ ϭ 7.61Ϫ7.68 (m, 2 H aromatic), 7.78 (s, 1 H, ϭ
CH), 8.03Ϫ8.10 (m, 2 H aromatic) ppm. 13C NMR ([D6]acetone):
δ ϭ 122.9, 127.2, 130.2, 131.5, 138.7, 146.2, 164.9, 165.9 ppm. MS:
m/z ϭ 210 (8) [Mϩ ϩ 2], 208 (24) [Mϩ], 173 (4), 138 (33), 137 (10),
136 (100), 101 (15), 75 (13), 68 (8). C10H5ClO3 (208.60): calcd. C
57.58, H 2.42, Cl 17.00; found C 57.41, H 2.41, Cl 16.96.
Typical Procedure for Oxidative Carbonylation of Alk-1-ynes 1 to
Maleic Acids 4 and Separation of Products: A 250-mL stainless steel
autoclave was charged in the presence of air with PdI2 (2.0 mg, 5.6
ϫ 10Ϫ3 mmol), KI (9.2 mg, 5.6 ϫ 10Ϫ2 mmol), a solution of 1
(11.1 mmol) in DME (8.3 mL), and H2O (2.8 mL). While stirring,
the autoclave was pressurized with CO (up to 16 atm) and air (up
to 20 atm), and then heated at 80 °C for the required time (see
Table 3). After cooling, the autoclave was degassed and the solvent
evaporated under reduced pressure. A 1  solution of NaOH
(25 mL) was added to the residue, and the mixture was heated at
75 °C for 1 h. After cooling, Et2O was added and the phases were
separated. The aqueous layer was washed 1Ϫ2 times with Et2O,
acidified with diluted sulfuric acid, and finally extracted several
times with Et2O. After drying with Na2SO4, the solvent was evapo-
rated to give the product, which was dried in vacuo for several
hours {4a: 1.60 g, 75%; 4b 1.44 g, 63%; 4d: 1.31 g, 53%; 4e: 1.21 g,
48%; 4f [10:1 (Z)/(E) mixture]: 784 mg, 41%; 4g: 325 mg, 17%}.
3-Butylfuran-2,5-dione (2f): Yield 1.15 g, starting from 682 mg of
1f (90%). Pale yellow oil. IR (film): ν˜ ϭ 1842 (m), 1772 (s), 1641
(m), 1249 (s), 998 (w), 969 (w), 895 (m) cmϪ1. H NMR (CDCl3):
1
δ ϭ 0.96 (t, J ϭ 7.3 Hz, 3 H, Me), 1.43 (sext, J ϭ 7.3, 2 H,
CH2CH2CH3), 1.59Ϫ1.70 (m, 2 H, CH2CH2CH3), 2.54 (td, J ϭ
7.6, 1.7 Hz, 2 H, ϭCHCH2), 6.63 (t, J ϭ 1.7 Hz, 1 H, ϭCH) ppm.
13C NMR (CDCl3): δ ϭ 166.0, 164.2, 153.9, 128.6, 29.0, 25.7, 22.3,
13.6 ppm. MS: m/z ϭ 154 (Ͻ 0.5) [Mϩ], 126 (17), 112 (100), 111
(23), 84 (38), 81 (28), 67 (17). C8H10O3 (154.16): calcd. C 62.33, H
6.54; found C 62.15, H 6.56.
3-tert-Butylfuran-2,5-dione (2g): Yield 563 mg, starting from
680 mg of 1g (44%). Colorless solid, m.p. 70Ϫ72 °C. IR (KBr): ν˜ ϭ
2956 (m), 1837 (w), 1769 (s), 1737 (s), 1627 (w), 1461 (w), 1437 (w),
1369 (w), 1308 (w), 1264 (m), 1250 (m), 1199 (m), 1174 (m), 958
3-Phenylfuran-2,5-dione (2a): Yield 838 mg, starting from 848 mg
of 1a (58%). Pale yellow solid, m.p. 118Ϫ119 °C (ref.[22] 119Ϫ120
°C). IR (KBr): ν˜ ϭ 3116 (w), 1821 (m), 1765 (s), 1611 (m), 1300
1
(m), 899 (s), 755 (w) cmϪ1. H NMR (CDCl3): δ ϭ 1.35 (s, 9 H,
tBu), 6.54 (s, 1 H, ϭCH) ppm. 13C NMR (CDCl3): δ ϭ 28.0, 33.3,
127.0, 161.5, 163.6, 164.2 ppm. MS: m/z ϭ 154 (Ͻ 0.5) [Mϩ], 139
(8), 126 (72), 111 (47), 110 (43), 109 (22), 108 (16), 95 (71), 83 (53),
81 (38), 80 (18), 79 (18), 67 (100), 65 (22), 53 (18). C8H10O3
(154.16): calcd. C 62.33, H 6.54; found C 62.28, H 6.57.
1
(w), 1226 (s), 1061 (w) 902 (m), 793 (m), 757 (m) cmϪ1. H NMR
(CDCl3): δ ϭ 7.00 (s, 1 H, ϭCH), 7.47Ϫ7.60 (m, 3 H aromatic),
7.94Ϫ7.99 (m, 2 H aromatic) ppm. 13C NMR (CDCl3): δ ϭ 124.6,
126.9, 129.0, 129.4, 132.7, 146.8, 163.7, 164.6 ppm. MS: m/z ϭ 174
(41) [Mϩ], 146 (1), 118 (3), 103 (9), 102 (100), 90 (3), 76 (10), 63 (6).
C10H6O3 (174.15): calcd. C 68.97, H 3.47; found C 69.01, H 3.45.
3-Phenylfuran-2(5H)-one (3a): Yield 27 mg, starting from 848 mg
of 1a (2%). Colorless solid, m.p. 86Ϫ87 °C (ref.[26] 84Ϫ86 °C). IR
(KBr): ν˜ ϭ 1747 (vs), 1493 (w), 1441 (m), 1116 (s), 1059 (m), 956
3-(4-Methylphenyl)furan-2,5-dione (2b): Yield 1.06 g, starting from
964 mg of 1b (68%). Pale yellow solid, m.p. 106Ϫ108 °C (ref.[23]
108Ϫ109 °C). IR (KBr): ν˜ ϭ 1832 (w), 1757 (s), 1607 (m), 1231
(m), 791 (m), 740 (m), 691 (m), 656 (w), 522 (w) cmϪ1. H NMR
1
1
(m), 902 (m), 829 (w) cmϪ1. H NMR (CDCl3): δ ϭ 2.42 (s, 3 H,
(CDCl3): δ ϭ 4.94 (d, J ϭ 2.0 Hz, 2 H, CH2), 7.37Ϫ7.46 (m, 3 H
aromatic), 7.65 (t, J ϭ 2.0 Hz, 1 H, ϭCH), 7.80Ϫ7.88 (m, 2 H
aromatic) ppm. MS: m/z ϭ 160 (36) [Mϩ], 132 (16), 115 (10), 104
(11), 103 (100), 77 (22), 63 (9), 51 (13). C10H8O2 (160.17): calcd. C
74.99, H 5.03; found C 75.12, H 5.01.
Me), 6.90 (s, 1 H, ϭCH), 7.27Ϫ7.33 (m, 2 H aromatic), 7.83Ϫ7.89
(m, 2 H aromatic) ppm. 13C NMR (CDCl3): δ ϭ 21.7, 123.2, 124.2,
129.0, 130.1, 143.9, 146.6, 163.9, 164.8 ppm. MS: m/z ϭ 188 (38)
[Mϩ], 117 (10), 116 (100), 115 (71), 89 (8), 63 (10). C11H8O3
(188.18): calcd. C 70.21, H 4.28; found C 70.89, H 4.26.
3-Butylfuran-2(5H)-one (3f): Yield 46 mg, starting from 682 mg of
1f (4%). Pale yellow oil. IR (film): ν˜ ϭ 2958 (s), 2931 (s), 2873 (m),
1750 (vs), 1652 (w), 1454 (m), 1337 (m), 1201 (m), 1111 (m), 1069
3-(4-tert-Butylphenyl)furan-2,5-dione (2c): Yield 1.07 g, starting
from 1.31 g of 1c (56%). Pale yellow solid, m.p. 106Ϫ107 °C. IR
(KBr): ν˜ ϭ 2967 (m), 1837 (w), 1821 (w), 1768 (s), 1604 (m), 1232
(s), 1041 (s), 835 (m) cmϪ1 1H NMR (CDCl3): δ ϭ 0.93 (t, J ϭ
.
1
(s), 930 (w), 904 (m), 843 (m) cmϪ1. H NMR (CDCl3): δ ϭ 1.35
7.3 Hz, 3 H, Me), 1.32Ϫ1.45 (m, 2 H, CH2CH3), 1.50Ϫ1.62 (m, 2
H, CH2CH2CH3), 2.26Ϫ2.34 (m, H, CH2CH2CH2CH3),
2
(s, 9 H, tBu), 6.95 (s, 1 H, ϭCH), 7.50Ϫ7.56 (m, 2 H aromatic),
7.89Ϫ7.95 (m, 2 H aromatic) ppm. 13C NMR (CDCl3): δ ϭ 31.0,
35.2, 123.3, 124.1, 126.4, 128.9, 146.7, 156.8, 164.0, 164.8 ppm. MS:
m/z ϭ 230 (Ͻ 0.5) [Mϩ], 223 (6), 205 (2), 167 (3), 150 (9), 149
(100), 104 (6), 93 (2), 76 (4), 65 (2), 57 (14). C14H14O3 (230.26):
calcd. C 73.03, H 6.13; found C 72.87, H 6.15.
4.76Ϫ4.79 (m, 2 H, CH2O), 7.12Ϫ7.14 (m, 1 H, ϭCH) ppm. MS:
m/z ϭ 140 (5) [Mϩ], 125 (25), 111 (17), 98 (100), 95 (17), 79 (15),
69 (30), 55 (38). C8H12O2 (140.18): calcd. C 68.55, H 8.63; found
C 68.43, H 8.65.
3-tert-Butylfuran-2(5H)-one (3g): Yield 50 mg, starting from
680 mg of 1g (4%). Colorless oil. IR (film): ν˜ ϭ 2960 (s), 2871 (m),
3-(4-Methoxyphenyl)furan-2,5-dione (2d): Yield 1.19 g, starting
from 1.10 g of 1d (70%). Pale yellow solid, m.p. 142Ϫ143 °C (ref.[24] 1753 (vs), 1641 (w), 1461 (m), 1365 (m), 1347 (w), 1311 (w), 1157
143Ϫ144 °C). IR (KBr): ν˜ ϭ 1845 (w), 1833 (w), 1763 (s), 1606 (s),
(m), 1063 (s), 1038 (m), 1007 (s), 953 (w), 831 (m), 786 (w) cmϪ1
1H NMR (CDCl3): δ ϭ 1.26 (s, 9 H, tBu), 4.73 (d, J ϭ 1.7, CH2),
.
1511 (m), 1265 (m), 1238 (s), 1180 (m), 1011 (w), 899 (m), 837 (m)
1
cmϪ1. H NMR ([D6]DMSO): δ ϭ 3.85 (s, 3 H, OMe), 7.06Ϫ7.13 7.09 (t, J ϭ 1.7 Hz, 1 H, ϭCH) ppm. MS: m/z ϭ 140 (42) [Mϩ],
1726
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 1722Ϫ1728

Synthesis of Maleic Anhydrides and Maleic Acids
FULL PAPER
125 (55), 98 (36), 97 (84), 95 (39), 81 (42), 79 (100), 77 (27), 69
(41), 67 (48), 55 (47), 53 (56). C8H12O2 (140.18): calcd. C 68.55, H
8.63; found C 68.66, H 8.62.
Acknowledgments
`
This work was supported by the Ministero dell’Universita e della
Ricerca Scientifica e Tecnologica (Progetto d’Interesse Nazionale
PIN MM03027791).
(Z)-2-Phenylbut-2-enedioic Acid (4a): Yield 1.60 g, starting from
1.13 g of 1a (75%). Colorless solid, m.p. 115Ϫ116 °C. IR (KBr):
ν˜ ϭ 3260Ϫ2435 (s, br), 1697 (vs), 1632 (s), 1427 (m), 1307 (m),
1214 (m), 1233 (m), 918 (m), 698 (m) cmϪ1. 1H NMR ([D6]DMSO):
δ ϭ 6.39 (s, 1 H, ϭCH), 7.43Ϫ7.52 (m, 3 H aromatic), 7.54Ϫ7.64
(m, 2 H aromatic), 13.05 (br, 2 H, 2 CO2H) ppm. 13C NMR
([D6]DMSO): δ ϭ 117.0, 126.7, 129.1, 130.4, 133.5, 148.6, 166.1,
168.9 ppm. C10H8O4 (192.17): calcd. C 62.50, H 4.20; found C
62.66, H 4.18.
[1]
For some recent examples of synthesis of 2 by non-car-
bonylative approaches, see:
[1a]
A. Kar, N. P. Argade, Tetra-
[1b]
hedron Lett. 2002, 43, 6563Ϫ6564.
R. M. Adlington, J. E.
Baldwin, R. J. Cox, G. J. Pritchard, Synlett 2002, 820Ϫ822. [1c]
E. M. Beccalli, M. L. Gelmi, A. Marchesini, Eur. J. Org. Chem.
1999, 1421Ϫ1426.
Maleic anhydrides can be useful precursors for the preparation
of succinic anhydrides, which are important intermediates for
[2]
(Z)-2-(4-Methylphenyl)but-2-enedioic Acid (4b): Yield 1.44 g, start-
ing from 1.29 g of 1b (63%). Pale yellow solid. IR (KBr): ν˜ ϭ
3310Ϫ2353 (s, br), 1726 (s), 1694 (s), 1603 (s), 1205 (s), 875 (m),
the preparation of biologically active molecules. For some re-
cent examples, see:
Ye, C. W. Lange, X. Li, D. Grobelny, M. Casabonne, D. Tyrrel,
[2a]
D. E. Levy, F. Lapierre, W. Liang, W.
1
831 (m), 817 (m), 691 (m), 609 (m) cmϪ1. H NMR ([D6]DMSO):
K. Holme, A. Nadzan, R. E. Galardy, J. Med. Chem. 1998, 41,
[2b]
199Ϫ223.
N. A. Porter, D. M. Scott, I. J. Rosenstein, B.
δ ϭ 2.33 (s, 3 H, Me), 6.33 (s, 1 H, ϭCH), 7.23Ϫ7.31 (m, 2 H
aromatic), 7.43Ϫ7.51 (m, 2 H aromatic), 8.27 (br, 2 H, 2 CO2H)
ppm. 13C NMR ([D6]DMSO): δ ϭ 20.8, 111.5, 126.5, 129.6, 140.3,
148.6, 166.0, 168.9 ppm. C11H10O4 (206.19): calcd. C 64.08, H 4.89;
found C 63.97, H 4.91.
Giese, A. Veit, H. G. Zeitz, J. Am. Chem. Soc. 1991, 113,
[2c]
1791Ϫ1799.
W. C. Groutas, M. J. Brubaker, M. A. Stanga,
J. C. Castrisos, J. P. Crowley, E. J. Schatz, J. Med. Chem. 1989,
32, 1607Ϫ1611.
[3] [3a]
M. Essers, B. Wibbeling, G. Haufe, Tetrahedron Lett. 2001,
[3b]
42, 5429Ϫ5433.
760Ϫ762.
K. Abou-Hadeed, Chimia 2000, 54,
[3c]
(Z)-2-(4-Methoxyphenyl)but-2-enedioic Acid (4d): Yield 1.31 g,
starting from 1.47 g of 1d (53%). Pale yellow solid, m.p. 139Ϫ140
°C. IR (KBr): ν˜ ϭ 3250Ϫ2820 (s, br), 1746 (s), 1693 (s), 1597 (s),
S. C. Fields, W. H. Dent, F. R. Green, E. G.
Tromiczak, Tetrahedron Lett. 1996, 37, 1967Ϫ1970.
For some recent examples, see:
[4]
[4a]
P. Nuhn, A. Herrmann, M.
[4b]
1
1217 (s), 1181 (s), 1022 (w), 1009 (w), 832 (m), 603 (m) cmϪ1. H
Radman, Pharmazie 1999, 54, 93Ϫ98.
Branchaud, J. Org. Chem. 1998, 63, 3544Ϫ3549.
emi, J. M. Dolence, C. D. Poulter, J. C. Vederas, J. Org. Chem.
1996, 61, 6296Ϫ6301.
R. M. Slade, B. P.
[4c]
E. S. Rat-
NMR ([D6]acetone): δ ϭ 3.86 (s, 3 H, OMe), 6.32 (s, 1 H, ϭCH),
6.98Ϫ7.06 (m, 2 H aromatic), 7.57Ϫ7.65 (m, 2 H aromatic), 8.0
(br, 2 H, 2 CO2H) ppm. 13C NMR ([D6]acetone): δ ϭ 55.8, 114.7,
115.3, 126.8, 129.3, 150.2, 162.5, 166.4, 169.3 ppm. C11H10O5
(222.19): calcd. C 59.46, H 4.54; found C 59.77, H 4.56.
[4d]
R. A. Bit, P. D. Davis, L. H. Elliott,
W. Harris, C. H. Hill, E. Keech, H. Kumar, G. Lawton, A.
Maw, J. S. Nixon, D. R. Vesey, J. Wadsworth, S. E. Wilkinson,
J. Med. Chem. 1993, 36, 21Ϫ29. [4e] G. Pattenden, M. W. Turv-
ill, A. P. Chorlton, J. Chem. Soc., Perkin Trans. 1 1991,
2357Ϫ2361.
(Z)-2-(4-Chlorophenyl)but-2-enedioic Acid (4e): Yield 1.21 g, start-
ing from 1.52 g of 1e (48%). Pale yellow solid, m.p. 154Ϫ155 °C.
IR (KBr): ν˜ ϭ 3170Ϫ2740 (s, br), 1714 (s), 1702 (s), 1633 (m),
[5] [5a]
D. Teomim, A. Nyska, A. J. Domb, J. Biomed. Mater. Res.
[5b]
1999, 45, 258Ϫ267.
R. Po, L. Fiocca, L. Abis, J. Polym.
[5c]
1437 (m), 1303 (w), 1217 (s), 1093 (w), 923 (w), cmϪ1 1H NMR
.
Sci., Part A: Polym. Chem. 1997, 35, 3241Ϫ3248.
Trumbo, Polym. Bull. 1996, 37, 161Ϫ167.
D. L.
([D6]acetone): δ ϭ 5.52 (br, 2 H, 2 CO2H), 6.43 (s, 1 H, ϭCH),
7.49Ϫ7.55 (m, 2 H aromatic), 7.64Ϫ7.70 (2 H aromatic) ppm. 13C
NMR ([D6]acetone): δ ϭ 118.5, 129.4, 130.0, 133.7, 136.6, 148.7,
166.0, 168.7 ppm. C10H7ClO4 (226.61): calcd. C 53.00, H 3.11, Cl
15.64; found C 52.91, H 3.12, Cl 15.71.
[6] [6a]
I. A. Novakov, A. V. Navrotskii, Y. M. Starovoitova, N. S.
Chuprynina, N. N. Sigaeva, E. A. Shirokova, Y. B. Monakov,
[6b]
Polym.-Plast. Technol. Eng. 2002, 41, 133Ϫ149.
A. B. Sa-
mui, A. S. Patankar, R. S. Satpute, P. C. Deb, Synth. Met. 2001,
[6c]
125, 423Ϫ427.
B. J. Lee, G. Choi, Y. S. Kwon, Thin Solid
[6d]
Films 1996, 285, 564Ϫ567.
V. K. Krishnan, J. Sreekumar,
J. Polym. Mater. 1996, 13, 153Ϫ156. [6e] F. Hui, P. Garciacama-
cho, R. Rosset, Analusis 1995, 23, 58Ϫ65.
2-Butylbut-2-enedioic Acid (4f) [10:1 (Z)/(E) Mixture]: Yield
784 mg, starting from 910 mg of 1e (41%). Pale yellow solid. IR
(KBr): ν˜ ϭ 3700Ϫ3100 (s, br), 1716 (s), 1705 (s), 1647 (m), 1421
[7] [7a]
E. I. Klimova, L. R. Ramirez, M. M. Garcia, R. G. Espi-
(m), 1259 (m), 1214 (m), 896 (w) cmϪ1 1H NMR (CDCl3): δ ϭ
.
nosa, N. N. Meleshonkova, Russ. Chem. Bull. 1996, 45,
[7b]
2602Ϫ2609.
G. Baccolini, A. Munyaneza, C. Boga, Tetra-
0.88Ϫ0.97 [m, 3 H, Me, isomer (Z) ϩ 3 H, Me, isomer (E)],
1.31Ϫ1.60 [m, 4 H, CH2CH2CH3, isomer (Z) ϩ 4 H, CH2CH2CH3,
isomer (E)], 2.42 [t, J ϭ 7.7 Hz, 2 H, CH2CH2CH2CH3, isomer
(Z)], 2.79 [t, J ϭ 7.4 Hz, 2 H, CH2CH2CH2CH3, isomer (E)], 5.88
[s, 1 H, ϭCH, isomer (Z)], 6.85 [s, 1 H, ϭCH (isomer E)], 9.77 [br.,
2 H, 2 CO2H (isomer Z) ϩ 2 H, 2 CO2H, isomer (E)]. C8H12O4
(172.18): calcd. C 55.81, H 7.02; found C 55.69, H 7.00.
hedron 1996, 52, 13695Ϫ13702.
[8]
B. Gabriele, G. Salerno, ‘‘Cyclocarbonylation’’, in: Handbook
of Organopalladium Chemistry for Organic Synthesis, vol. II
(Ed.: E. Negishi), John Wiley & Sons, New York, 2002, p.
2623Ϫ2641.
R. F. Heck, J. Am. Chem. Soc. 1972, 94, 2712Ϫ2716.
D. Zargarian, H. Alper, Organometallics 1991, 10, 2914Ϫ2921.
J. Li, G. Li, H. Jiang, M. Chen, Tetrahedron Lett. 2001, 42,
6923Ϫ6924.
Y. Sakurai, S. Sakaguchi, Y. Ishii, Tetrahedron Lett. 1999, 40,
1701Ϫ1704.
P. Giannoccaro, M. Aresta, S. Doronzo, C. Ferragina, Appl.
Organomet. Chem. 2000, 14, 581Ϫ589.
B. Gabriele, G. Salerno, M. Costa, G. P. Chiusoli, Tetrahedron
Lett. 1999, 40, 989Ϫ990.
[9]
[10]
[11]
(Z)-2-tert-Butylbut-2-enedioic Acid (4g): Yield 325 mg, starting
from 912 g of 1g (17%). Pale yellow solid, m.p. 123Ϫ124 °C. IR
(KBr): ν˜ ϭ 3300Ϫ2500 (s, br), 1731 (s), 1701 (s), 1645 (s), 1423 (s),
[12]
[13]
[14]
[15]
1271 (m), 1246 (w), 1219 (m), 881 (m) cmϪ1
.
1H NMR
([D6]DMSO): δ ϭ 1.13 (s, 9 H, tBu), 5.70 (s, 1 H, ϭCH), 12.43 (br,
2 H, 2 CO2H) ppm. 13C NMR ([D6]DMSO): δ ϭ 28.7, 34.7, 115.2,
160.2, 166.1, 169.3 ppm. C8H12O4 (172.18): calcd. C 55.81, H 7.02;
found C 55.73, H 6.99.
B. Gabriele, G. Salerno, M. Costa, G. P. Chiusoli, Chem. Com-
mun. 1999, 1381Ϫ1382.
Eur. J. Org. Chem. 2003, 1722Ϫ1728
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1727

B. Gabriele, L. Veltri, G. Salerno, M. Costa, G. P. Chiusoli
FULL PAPER
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[18i]
G. P. Chiusoli, M. Costa, L. Cucchia, B. Gabriele, G. Salerno,
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B. Gabriele, G. Salerno, A.
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B. Gabriele, M. Costa, G. Salerno, G. P. Chiusoli, J. Chem.
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Soc., Perkin Trans. 1. 1994, 83Ϫ87.
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B. Gabriele, G. Salerno, F. De Pascali, M. Costa, G. P.
[18b]
Chiusoli, J. Chem. Soc., Perkin Trans. 1 1997, 147Ϫ154.
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[24]
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[18f]
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B. Gabriele, G. Salerno, F. De
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593Ϫ594, 409Ϫ415.
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[18h]
A.
Received December 17, 2002
1728
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 1722Ϫ1728