Producing unsaturated esters by a lanthanide metal alkoxide...

Details Producing unsaturated esters by a lanthanide metal alkoxide... Producing unsaturated esters by a lanthanide metal alkoxide...

1999-12-14

2002-01-29

Geist, Gary (Department: 1623)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acid esters

Reexamination Certificate

active

06342627

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to process for producing unsaturated esters.
DESCRIPTION OF THE RELATED ART
There has been known alkali metal alkoxides disclosed in U.S. Pat. No. 2,744,884 and organotin compounds disclosed in Japanese Patent Application Kokai (Laid-Open) No. 56-104851 as catalysts for accelerating transesterification reactions. For the synthesis of unsaturated esters, these catalysts, however, had a drawback in that they required vigorous reaction conditions accompanied by side reactions such as polymerization of unsaturated esters and addition of substrate alcohols to the unsaturated esters.
SUMMARY OF THE INVENTION
An object of the invention is to provide a transesterification process for producing unsaturated esters, which process can be conducted under less vigorous conditions and is not accompanied by undesirable side reactions.
The present invention provides a process for producing an unsaturated ester of the formula (3):
where R
1
, R
2
and R
3
independently represent:
a hydrogen atom, a halogen atom,
an alkyl group which may be substituted,
an alkenyl group which may be substituted,
an aralkyl group which may be substituted or
an aryl group which may be substituted; and
R
5
represents:
an alkyl group which may be substituted with an alkoxy group, a phenoxy group, a cyano group, a dialkylamino group, a cycloalkyl group or a halogen atom,
an aralkyl group which may be substituted with an alkyl group, an alkoxy group, a phenoxy group, a nitro group, a cyano group or a halogen atom, or
an aryl group which may be substituted with an alkyl group, an alkoxy group or a halogen atom;
which comprises:
subjecting an unsaturated ester of the formula (1):
where R
1
, R
2
and R
3
have the same meaning as defined above and
R
4
represents an alkyl group having 1 to 10 carbon atoms which may be substituted or a phenyl group which may be substituted,
to a transesterification reaction with a hydroxy compound of the formula (2):
R
5
OH  (2)
wherein R
5
has the same meaning as defined above, in the presence of a lanthanoide metal alkoxide.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is described in detail below.
In the present invention preferably used catalysts include at least one lanthanoide alkoxide selected from alkoxide compounds of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, as a catalyst, and more preferred are the alkoxide compounds of La and Sm, which are industrially readily available.
Polymers of the lanthanum alkoxide may be also used in addition to monomers depending on the type of the metal or the aliphatic hydrocarbon groups.
Examples of the lanthanoide metal alkoxide include compounds of the formula (4):
Ln(OR
6
)(OR
7
)(OR
8
)  (4)
wherein Ln is a lanthanoide metal element and R
6
, R
7
and R
8
are the same or different and represent an alkyl group having 1 to 10 carbon atoms.
R
6
, R
7
and R
8
may be an alkyl group having 1 to 10 carbon atoms which may be straight-chained, branched or cyclic, and the alkyl groups may bond together at their terminals to form a divalent or trivalent alkoxide residue they may combine to form a 2-or 3-valent alkoxide. Examples thereof include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, n-hexyl, n-octyl, cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.
Methoxides, ethoxides, n-propoxides, i-propoxides, t-butoxides and the like are preferably used as the alkoxide because of their easy preparation. More preferably, n-propoxides, i-propoxides and t-butoxides are used because of their good solubility in the solvent listed below. Still more preferably, i-propoxides are used because of their low costs for the catalyst preparation and their advantages in the preparation operations.
The lanthanoide metal alkoxide (2) can be prepared by known methods and they may be isolated after preparation thereof and then used in the present process or used directly as solutions without being isolated after their preparation.
The lanthanoide metal alkoxide may be contacted with a hydroxy compound (2) and then the resulting compound may be used in the present transesterification reaction.
The amount of the lanthanoide metal alkoxide to be used is not particularly limited. It is usually 0.001-200 mole %, preferably 0.01-20 mole % per mol of the unsaturated ester (1).
After completion of the transesterification reaction, the lanthanoide metal alkoxide can be recovered by removing the solvent and product, for example, by distillation and/or filtration.
The recovery of the catalyst compound can be facilitated by using a supported lanthannoid metal alkoxide, for example, on a polymer, silica gel, or active carbon, alternatively the lanthanoide alkoxide can be microencapsulated with resins by conventional methods, thereby reuse of the recovered catalyst can be improved.
The unsaturated esters used as a starting material in the present invention are compounds of the formula (1). In the formula, R
1
, R
2
and R
3
independently represent:
a hydrogen atom, a halogen atom,
an alkyl group which may be substituted,
an alkenyl group which may be substituted,
an aralkyl group which may be substituted or
an aryl group which may be substituted.
Examples of the alkyl group which may be substituted include a straight or branched or cyclic alkyl group having 1 to 10 carbon atoms which may be substituted with at least one group selected from a halogen atom(e.g., fluorine, chlorine, bromine and iodine), and (C
1
-C
3
)alkoxy group(e.g., methoxy, ethoxy, n-propoxy, and i-propoxy).
Specific examples thereof include methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl, n-hexyl, cyclohexyl, menthyl, chloromethyl, dichloromethyl, trichloromethyl, bromomethyl, dibromomethyl, tribromomethyl, 1-chloroethyl, 2-chloroethyl, 1-bromoethyl, 2-bromoethyl, 1,2-dichloroethyl, 1,2-dibromoethyl, 2,2,2-trichloroethyl, 2,2,2-tribromoethyl, methoxymethyl and 2-methoxyethyl.
Examples of the alkenyl group which may be substituted include a straight or branched or cyclic alkenyl group having 2 to 10 carbon atoms which may be substituted with at least one group selected from a halogen atom(e.g., fluorine, chlorine, bromine and iodine) and (C
1
-C
3
) alkoxy group(e.g., methoxy, ethoxy, n-propoxy, and i-propoxy).
Specific examples of the alkenyl group include vinyl, 1-methylvinyl, 1-propenyl, 2-methyl-l-propenyl, 2,2-dichlorovinyl, 2,2-dibromovinyl, 2-chloro-2-fluorovinyl, 2-chloro-2-trifluoromethylvinyl and 2-bromo-2-tribromomethylvinyl.
Examples of the aralkyl which may be substituted include benzyl, diphenylmethyl, phenylethyl, naphthylmethyl and naphthylethyl, all of which may be substituted on their aromatic ring with at least one group selected from a (C
1
-C
10
)alkyl group described above, a (C
1
-C
6
)alkoxyl group(e.g., methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, s-butoxy, t-butoxy and cyclohexoxy) and a halogen atom and the like.
Examples of the aryl group which may be substituted include phenyl, 1-naphthyl and 2-naphthyl, and all of which may be substituted on their aromatic rings with at least one group selected from the above-mentioned (C
1
-C
10
)alkyl group, (C
1
-C
6
)alkoxyl group, a halogen atom and the like.
In the formula (1), R
4
represents an alkyl group having 1-10 carbon atoms or a phenyl group which may be substituted. Examples of the alkyl group having 1-10 carbon atoms may be the same groups as exemplified for R
6
, R
7
and R
8
. Examples of the phenyl group which may be substituted include a phenyl group which may be substituted with at least one group selected from the same (C
1
-C
10
)alkyl groups, (C
1
-C
6
)alkoxyl groups and the halogen atoms as described above.
Specific examples of the unsaturated esters (1) include:
methyl acrylate, methyl crotonate, methyl methacrylate, methyl tiglate, methyl 3,3-dimethylacrylate, methyl 2-pentenoate, methyl 2-fluoroacrylate, methyl 3,3-dichloroacrylate, methyl 4,4-dichlorocrotonate, methyl 2-dichloromethylacrylate, methyl 5,5-dichloropenta-2,4-dienate, methyl 3-benzylacrylate

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