Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
1999-04-09
2002-03-12
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S092000, C560S217000
Reexamination Certificate
active
06355830
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for producing dicarboxylic acid monoesters by transesterification of a dicarboxylic acid monoester which are useful as intermediates for medicines and agricultural chemicals, main starting materials for polyester polyols, nylons, fibers, lubricants, plasticizers, etc., or additives thereto or precursors thereof, especially useful as starting materials for synthesis of asymmetrical diesters of dicarboxylic acids.
BACKGROUND ART
Transesterifications using catalysts containing tin, titanium, etc. are well known, but these catalysts are deactivated if acids are present in the reaction systems. Therefore, these catalysts cannot be used for substrates containing carboxylic acid in the structure, such as dicarboxylic acid monoesters.
Under the circumstances, many processes for the production of dicarboxylic acid monoesters have been proposed, and these are roughly classified into the following five processes.
(a) Monoesterification of dicarboxylic acids:
Fiziol. Akt. Veshchestva, 7, 129-31(1975).
J. Chem. Res. Synopses, (5), 119(1977). JP-A-4-112854
(b) Decomposition of dicarboxylic acid diesters:
Tetrahedron Lett., 32(34), 4239-42(1991).
Chem. Lett., (7), 539-40(1995).
(c) Ring opening of cyclic dicarboxylic acid anhydrides with alcohols or metal alkoxides:
Synlet, 6, 650-2(1995).
(d) Condensation reaction:
J. Org. Chem., 33(2), 838-40(1968).
Tetrahedron Lett., (32), 2721-3(1974).
J. Organomet. Chem., 364(3), C29-32(1989).
(e) Synthesis of malonic monoesters from Meldrum's acid:
Tetrahedron Lett., 30(23), 3073-6(1989).
However, these processes (a)-(e) all have the following problems.
In the process (a), both the two carboxyl groups are esterified to produce diesters as by-products, and in the process (b), both the ester groups are hydrolyzed to produce dicarboxylic acids as by-products. Therefore, according to these processes, it is difficult to obtain monoesters with a high selectivity, and thus it is difficult to industrially efficiently obtain the desired monoesters. In the process (c), the reaction is carried out under a high pressure and special pressure reaction vessels such as autoclave are needed, resulting in increase of production cost. Moreover, according to this process, two kinds of monoesters are produced at the same time, and, hence, it is difficult to obtain selectively a monoester with a carboxyl group of the desired position being monoesterified. Furthermore, according to this process, when optically active monoesters are obtained using optically active cyclic dicarboxylic acid anhydrides as a starting material, there is the possibility that optical purity of the monoesters greatly decreases. In the case of the processes (d) and (e), the kinds of dicarboxylic acid monoesters which can be synthesized are limited and it is difficult to apply these processes to the production of a wide variety of dicarboxylic acid monoesters.
For these reasons, a process for industrially producing a wide variety of dicarboxylic acid monoesters at a high selectivity has been desired. Moreover, a process for producing dicarboxylic acid monoesters using optically active starting materials without causing a great reduction in optical purity has also been desired.
In general, transesterification between esters and metal alkoxides is known. However, when a dicarboxylic acid monoester as a starting material for esters and a metal alkoxide are subjected to transesterification in an organic solvent, production of a metal salt of the dicarboxylic acid monoester takes place in preference to transesterification, and since the resulting metal salt is hardly soluble in the organic solvent, it is considered that the desired transesterification hardly proceeds. There is no report on actually performing such reaction.
DISCLOSURE OF INVENTION
The present inventors have found that contrary to the above conventional common knowledge, even if a metal salt of dicarboxylic acid monoester represented by the formula (1) is produced in the reaction system, the transesterification satisfactorily proceeds by selecting the reaction conditions.
The object of the present invention is to provide a process for producing dicarboxylic acid monoesters according to which a wide variety of dicarboxylic acid monoesters can be obtained at a high selectivity by substituting a desired alkoxy group for an alkoxy group of the ester moiety of dicarboxylic acid monoesters which can be synthesized by known processes, and, furthermore, and optically active dicarboxylic acid monoesters can be produced from optically active starting materials with less deterioration of optical purity.
As a result of an intensive research conducted by the present inventors in an attempt to attain the above object, it has been found that a wide variety of dicarboxylic acid monoesters can be obtained at a high selectivity by subjecting an alcohol and a dicarboxylic acid monoester or an alkali salt of a dicarboxylic acid monoester to transesterification in the presence of a metal alkoxide or by subjecting a metal alkoxide and a dicarboxylic acid monoester or an alkali metal salt of a dicarboxylic acid monoester to transesterification in the presence of an organic solvent. Thus, the present invention has been accomplished.
That is, the present invention relates to a process for producing a dicarboxylic acid monoester represented by the formula (3) which comprises subjecting a dicarboxylic acid monoester or an alkali metal salt of a dicarboxylic acid monoester represented by the formula (1) as a starting material and a metal alkoxide represented by the formula (2) to transesterification in the presence of an organic solvent:
R
1
OOC—(CH
2
)
m
—X—(CH
2
)
n
—COOM
1
(1)
wherein R
1
represents a straight-chain or branched-chain alkyl group, alkoxyalkyl group or alkylthioalkyl group of 1-18 carbon atoms, of which one or more hydrogen atoms may be substituted with phenyl group, naphthyl group, toluyl group or fluorine atom, m and n each represent an integer of 0-12 (m+n≦18), X represents a group represented by one of the formula (X1) to the formula (X5), and M
1
represents a hydrogen atom or an alkali metal,
in which Z
1
and Z
2
each represent a hydrogen atom, a fluorine atom, a phenyl group, a naphthyl group or a straight-chain or branched-chain alkyl group or alkenyl group of 1-12 carbon atoms,
in which Z
3
, Z
4
, Z
5
and Z
6
each represent a hydrogen atom, a fluorine atom, a chlorine atom or a bromine atom,
in which Z
1
and Z
2
are as defined in the formula (X1),
in which Z
1
and Z
2
are as defined in the formula (X1),
in which Z
1
and Z
2
are as defined in the formula (X1);
R
2
OM
2
(2)
wherein R
2
represents a straight-chain or branched-chain alkyl group, alkoxyalkyl group or alkylthioalkyl group of 1-18 carbon atoms, of which one or more hydrogen atoms may be substituted with phenyl group, naphthyl group, toluyl group or fluorine atom, and M
2
represents an alkali metal]; and
R
2
OOC—(CH
2
)
m
—X—(CH
2
)
n
—COOM
1
(3)
wherein R
2
is as defined in the formula (2), and m, n, X and M
1
are as defined in the formula (1).
Furthermore, the present invention relates to a process for producing a dicarboxylic acid monoester represented by the formula (5) which comprises subjecting a dicarboxylic acid monoester or an alkali metal salt of a dicarboxylic acid monoester represented by the formula (1) as a starting material and an alcohol represented by the formula (4) to transesterification in the presence of a metal alkoxide represented by the above formula (2):
R
3
OH (4)
wherein R
3
represents a straight-chain or branched-chain alkyl group, alkoxyalkyl group or alkylthioalkyl group of 1-18 carbon atoms, of which one or more hydrogen atoms may be substituted with phenyl group, naphthyl group, toluyl group or fluorine atom; and
R
3
OOC—(CH
2
)
m
—X—(CH
2
)
n
—COOM
1
(5)
wherein R
3
is as defined in the formula (4), and m, n, X and M
1
are as defined in the formula (1)
BEST MODE FOR CARRYING OUT THE INVENTION
Fujii Junji
Ikemoto Tetsuya
Sakano Kunihiko
Killos Paul J.
Mitsubishi Rayon Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Oh Taylor V.
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