Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2002-02-04
2003-12-02
Killos, Paul J. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
Reexamination Certificate
active
06657074
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to process for preparing acylated 1,3-dicarbonyl compounds by rearrangement of corresponding enol esters. The invention also relates to the preparation of the corresponding tautomer compounds of the acylated 1,3-dicarbonyl compounds.
BACKGROUND OF THE INVENTION
The rearrangement of certain enol esters which results in an acylated 1,3-dicarbonyl compounds has been reported in the patent and journal literature wherein certain types catalysts have been disclosed as facilitating the rearrangement reaction. Some of the catalysts that have been disclosed are two molar aluminum chloride, 4-dimethylaminopyridine, aminopyridine derivatives, N-alkylimidazole derivatives, molten sodium acetate, Lewis acid and cyanide source. See U.S. Pat. No. 4,695,653 and references cited and discussed therein.
SUMMARY OF THE INVENTION
Surprisingly, it has now been discovered that an azide catalyst/reagent may be used to facilitate the rearrangement of enol esters to the corresponding acylated 1,3-dicarbonyl compound and/or the corresponding tautomer forms of the acylated 1,3-dicarbonyl compound (future reference to acylated “1,3-dicarbonyl compounds” or other similar descriptors such as “cyclohexanedione derivatives” etc. should be read where appropriate to include the tautomer forms unless otherwise indicated). The acylated 1,3-dicarbonyl compounds produced by the instantly disclosed process are useful themselves as agrochemicals (e.g. pesticides, herbicides, etc.) or may be used as intermediates in the preparation of useful agrochemicals. The azide catalyst/reagent system used in the instant invention has advantages over those previously used. Catalysts such as dimethylaminopyridine must be recovered. Cyanide catalysts and reagents produce hydrogen cyanide which contaminates process streams. The azide catalysts and reagents of the instant invention have the advantage that upon acidification they form hydrozoic acid which decomposes to nitrogen. The instant invention overcomes the need for certain costly catalyst/reagent recovery and waste treatment systems previously associated with the preparation of acylated 1,3-dicarbonyl compounds.
DETAILED DESCRIPTION OF THE INVENTION
One embodiment of the invention is the process for preparing an acylated cyclical 1,3-dicarbonyl compounds or tautomers thereof, comprising the step of rearrangement of the corresponding enol ester, wherein said rearrangement is conducted in the presence of a alkali metal azide. The acylated cyclical 1,3-dicarbonyl compounds are 1,3-cyclohexanediones that are substituted at the 2-position on the cyclohexane ring with an acyl radical. The enol ester compounds that are the starting materials for the process are the O-acyl enol esters of 1,3-cyclohexanediones.
Another aspect of the invention is the process wherein the rearrangement is conducted in the presence of either:
(a) a catalytic amount of an alkali metal azide and a molar excess, with respect to the enol ester, of a base; or
(b) a stoichiometric amount, with respect to the enol ester, of an alkali metal azide and a catalytic amount of a phase-transfer catalyst.
Another embodiment of the invention is the process for preparing the compounds of formula I:
and tautomers thereof, wherein
R is a group C
1
-C
10
alkyl, C
3
-C
6
cycloalkyl or phenyl, wherein the phenyl nucleus is unsubstituted or substituted by one to three groups selected from the group consisting of halogen, C
1
-C
4
alkyl, C
1
-C
4
alkoxy, C
1
-C
4
haloalkyl, nitro or cyano; A is —OR
2
, —SR
2
or —NR
3
R
4
radical;
R
2
, R
3
and R
4
are each independently, hydrogen, C
1
-C
6
alkyl, C
1-C
6
haloalkyl, C
2
-C
10
alkoxyalkyl, C
2
-C
10
alkylthioalkyl; C
3
-C
6
alkenyl which is unsubstituted or substituted by halogen, C
1
-C
4
alkoxy or C
1
-C
4
alkylthio; C
3
-C
6
alkynyl; phenyl, C
6
-C
20
alkylaryl or C
6
-C
20
aralkyl, wherein the phenyl nucleus is unsubstituted or substituted by one to three groups selected from the group consisting of halogen, C
1
-C
4
alkyl, C
1
-C
4
alkoxy, C
1
-C
4
haloalkyl, nitro or cyano; or
R
3
and R
4
, together with the nitrogen atom to which they are attached, form a 5- or 6-membered heterocyclic ring system which may contain an additional oxygen or sulfur atom in the ring; and salts thereof, said process comprising the step of rearrangement of the corresponding enol ester, wherein said rearrangement is conducted in the presence of a alkali metal azide.
In the above definitions the alkyl radicals comprise both straight chain and branched radicals, e.g. methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, as well as all stereoisomers of the higher carbon number radicals. Alkenyl and alkynyl also comprise straight chain and branched radicals, e.g. vinyl, allyl, methallyl, butenyl, methylbutenyl and dimethylbutenyl, ethynyl, propynyl, butynyl, methylbutynyl and dimethylbutynyl, as well as all stereoisomers of the higher carbon number radicals.
By “cycloalkyl” is meant a group that encompasses cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.
By “aryl” is meant either a non-heteroaromatic ring system or heteroaromatic ring system. By “alkylaryl” is meant an aryl group substituted by one or more alkyl groups. By “aralkyl” is meant an alkyl group substituted by one or more aryl groups.
Halogen is fluorine, chlorine, bromine or iodine.
A 5- or 6-membered heterocyclic ring system —NR
3
R
4
which may contain an additional oxygen or sulfur atom in the ring includes aromatic and non-aromatic ring systems and for example includes pyrrole, pyrolidine, pyridine, piperidine, morpholine or thiomorpholine. These rings may also be substituted for example by one to three groups selected from the group consisting of halogen, C
1
-C
4
alkyl, C
1
-C
4
alkoxy, C
1
-C
4
haloalkyl, nitro or cyano
The cyclohexanedione derivatives of the formula I have good herbicidal and plant growth regulating properties.
Tautomerism is a type of isomerism in which migration of a hydrogen atom results in two or more structures, called tautomers. The cyclohexanedione derivatives of formula I can be obtained in different tautomeric forms. For example, methyl 4-propanoyl-3,5-cyclohexanedione-1-carboxylate can be obtained in the tautomer form of methyl 4-(propyl-1-hydroxymethylidene)-3,5-cyclohexanedione-1-carboxylate as well as other tautomer forms (see for example Tautomerism Scheme below):
The alkali metal azide used in the instant process for preparing the cyclohexanediones of formula I include for example lithium azide, sodium azide, potassium azide and cesium azide. The alkali metal azide may function either as a catalyst alone or additionally as a base reagent. When the alkali metal azide functions as a catalyst it is necessary to use an additional base reagent. The alkali metal azide may also be employed in sufficient quantities so that it additionally serves a base reagent for the process. In either case a phase-transfer catalyst may be used to enhance the reactivity of the alkali metal azide catalyst/base. It is to be expected that under certain conditions cation exchange may occur so that the actual catalytic or reagent azide species that facilitates the rearrangement reaction is an azide with a different counter cation.
The scope of the invention disclosed herein should not be construed to be limited by any particular chemical theory relating to the complexation, equilibration, reaction or acid-base chemistry of the components used to make the final product.
Suitable phase-transfer catalysts that may be employed in the instant process include complexing agents which solublize cations in non-polar solvents (e.g. crown ethers such as 18-crown-6). The phase-transfer catalysts may be employed to increase the reaction rate of the rearrangement or otherwise reduce the energy input or quantity of reagents necessary to drive the reaction to completion. Whether a phase-transfer catalyst is used will depend a cost/benefit analysis for the given circumstances and the desired process design parameters (e.g. solvent systems, te
Killos Paul J.
Rose M. Allen
Syngenta Crop Protection Inc.
LandOfFree
Process for the preparation of acylated 1,3-dicarbonyl... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the preparation of acylated 1,3-dicarbonyl..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of acylated 1,3-dicarbonyl... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3152460