Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2000-05-02
2001-12-25
Padmanabhan, Sreeni (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S204000, C560S241000, C560S247000
Reexamination Certificate
active
06333430
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for preparing a tert-alkyl carboxylic acid ester. More specifically, the present invention relates to a process for preparing a tert-alkyl carboxylic acid ester having a tert-alkyl moiety which is useful as its protective group. The tert-alkyl carboxylic acid ester is useful for pharmaceuticals such as antibiotics, raw materials for chemicals, intermediates, and the like.
2. Discussion of the Related Art
As processes for preparing a tert-alkyl carboxylic acid ester, there have been known 1) a process comprising reacting an acid chloride of a carboxylic acid with a tertiary alcohol in the presence of dimethylaniline [
Organic Synthesis III,
142], 2) a process comprising treating malonic acid with isobutylene as a vinylidene compound in the presence of sulfuric acid [
Organic Synthesis IV,
261], and the like.
However, in the process 1), there are some defects such that the preparation process is long, and the procedures are complicated since this process necessitates a process for preparing an acid chloride of a carboxylic acid, and that this process is economically disadvantageous since this process necessitates an expensive base such as dimethylaniline. Also, in the process 2), there are some defects that the reaction product is easily hydrolyzed by sulfuric acid used in the reaction, and the vinylidene compound is likely to be polymerized under the given reaction conditions.
An object of the present invention is to provide a process for simply, conveniently and industrially advantageously preparing a tert-alkyl carboxylic acid ester in a high yield.
The above and other objects of the present invention will be apparent from the following description.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a process for preparing a tert-alkyl carboxylic acid ester represented by the formula (III):
wherein R
1
is an organic group; and each of R
2
and R
3
is independently an alkyl group having 1 to 4 carbon atoms, comprising reacting a carboxylic acid represented by the formula (I):
R
1
—COOH (I)
wherein R
1
is as defined above,
with a vinylidene compound represented by the formula (II):
wherein R
2
and R
3
are as defined above,
in the presence of a phosphorus halide.
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, as described above, there can be obtained a tert-alkyl carboxylic acid ester represented by the formula (III):
wherein R
1
is an organic group; and each of R
2
and R
3
is independently an alkyl group having 1 to 4 carbon atoms, by reacting a carboxylic acid represented by the formula (I):
R
1
—COOH (I)
wherein R
1
is as defined above,
with a vinylidene compound represented by the formula (II):
wherein R
2
and R
3
are as defined above,
in the presence of a phosphorus halide.
The carboxylic acid represented by the formula (I) is not limited to specified ones, as long as the object of the present invention is not hindered. In the formula (I), R
1
includes, for instance, alkyl groups, aralkyl groups, aryl groups and heterocyclic groups, each of which may have a substituent.
Representative examples of the alkyl group include substituted or unsubstituted, linear or branched alkyl groups having 1 to 20 carbon atoms, preferably 1 to 8 carbon atoms. Concrete examples of the alkyl groups include, for instance, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, pentyl group, heptyl group, and the like.
Representative examples of the aralkyl group include substituted or unsubstituted, linear or branched aralkyl groups having 7 to 20 carbon atoms, preferably 7 to 10 carbon atoms. Concrete examples of the aralkyl groups include, for instance, benzyl group, phenylethyl group, phenylpropyl group, and the like.
Representative examples of the aryl group include substituted or unsubstituted aryl groups having 1 to 5 aromatic rings. Concrete examples of the aryl groups include, for instance, aryl groups having 6 to 20 carbon atoms such as phenyl group, naphthyl group and phenanthryl group.
Representative examples of the heterocyclic group includes substituted or unsubstituted heterocyclic groups having 1 to 3 atoms selected from the group consisting of oxygen atom, nitrogen atom and sulfur atom. Concrete examples of the heterocyclic groups include, for instance, furyl group, pyrrolyl group, imidazolyl group, pyridyl group, pyrimidinyl group, oxazolyl group, thienyl group, thiazolyl group, benzofuryl group, quinolyl group, 8-oxo-5-thia-1-azabicyclo[4,2,0]oct-2-ene-2-yl group, and the like.
The substituent which may exist in R
1
is not limited to specified ones as long as the object of the present invention is not hindered. Examples of the substituents include substituted or unsubstituted, linear or branched alkyl groups having 1 to 20 carbon atoms, such as methyl group, ethyl group, propyl group, butyl group and pentyl group; substituted or unsubstituted aryl groups having 6 to 20 carbon atoms, such as phenyl group and naphthyl group; substituted or unsubstituted, linear or branched aralkyl groups having 7 to 20 carbon atoms, such as benzyl group and phenylethyl group; substituted or unsubstituted heterocyclic groups having 1 to 3 atoms selected from the group consisting of oxygen atom, nitrogen atom and sulfur atom, such as furyl group, pyrrolyl group, imidazolyl group, pyridyl group, pyrimidinyl group, oxazolyl group, thienyl group, thiadiazolyl group and benzofuryl group; substituted or unsubstituted, linear or branched alkoxy groups having 1 to 10 carbon atoms, such as methoxy group, ethoxy group and propoxy group; halogen atoms, such as fluorine atom, chlorine atom, bromine atom and iodine atom; alkyl esters which may have a substituent such as a substituted or unsubstituted alkyl ester group such as methoxycarbonyl group, ethoxycarbonyl group or propoxycarbonyl group, an aryl ester group such as phenoxycarbonyl group, or a substituted or unsubstituted aralkyl ester group such as benzyloxycarbonyl group or nitrobenzyloxycarbonyl group; substituted or unsubstituted alkyl ketones, such as acetyl group and propionyl group; substituted or unsubstituted aryl ketones, such as benzoyl group; amide groups such as carbamoyl group, acetoamino group and benzamide group; ureido groups such as carbamoylamino group and phenylaminocarbamoyl group, and the like.
In the vinylidene compound represented by the formula (II), each of R
2
and R
3
is independently an alkyl group having 1 to 4 carbon atoms. Concrete examples of the alkyl groups include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, and the like. Representative examples of the vinylidene compound include isobutylene, 2-methyl-1-butene, 2-methyl-1-pentene, and the like. Among them, isobutylene can be preferably used.
The amount of the vinylidene compound represented by the formula (II) is not limited to specified ones. It is desired that the amount of the vinylidene compound is usually not less than 1.5 moles, preferably not less than 1.8 moles, per one mole of the carboxylic acid represented by the formula (I), from the viewpoint of reactivity, and not more than 10 moles, preferably not more than 3 moles, per one mole of the carboxylic acid represented by the formula (I), from the viewpoint of economics.
In the present invention, one of great features resides in that the carboxylic acid is reacted with the vinylidene compound in the presence of a phosphorus halide. Since the phosphorus halide is employed in the reaction, the tert-alkyl carboxylic acid ester can be simply, conveniently and industrially advantageously prepared in a high yield.
The phosphorus halide includes, for instance, phosphorus halides such as phosphorus oxytrichloride, phosphorus trichloride, phosphorus pentachloride and dichlorophosphonic acid. Among those phosphorus halides, phosphorus oxytrichloride, phosphorus trichloride and dichlorophosphonic acid are preferable, from the viewpoin
Itaya Nobushige
Katsura Tadashi
Shintaku Tetsuya
Sugi Kiyoshi
Birch & Stewart Kolasch & Birch, LLP
Padmanabhan Sreeni
Sumika Fine Chemicals Co., Ltd.
Witherspoon Sikarl A.
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