Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2002-03-04
2003-07-29
Raymond, Richard L. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
C560S240000
Reexamination Certificate
active
06600064
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for the preparation of hydroxybenzoic benzyl esters by reacting dibenzyl ethers with alkylcarbonyloxybenzoic or alkoxycarbonyloxybenzoic acid in the molar ratio 1:1 to 1:50 at 10 to 200° C. and pressures in the range from 0.1 to 50 bar in the presence of acid as catalyst.
Benzyl salicylate is used as stabilizer in fragrance compositions and sunscreens. Benzyl salicylate and processes for its preparation are already known.
Thus, EP-A 117,502 describes, for example, the preparation of benzyl salicylate by esterifying salicylic acid or transesterifying salicylic esters with benzyl alcohol.
Benzyl salicylate can also be prepared by reacting alkali metal salicylates with benzyl chloride, optionally in the presence of phase-transfer reagents (JP 63/218652, EP-A 534,817). A disadvantage is the formation of salts that must be disposed of and thus reduce the economic feasibility of these processes.
The object was to develop a process, starting from dibenzyl ethers, for the preparation of hydroxybenzoic benzyl esters that can be carried out under mild reaction conditions and leads to good yields in a cost-effective manner.
SUMMARY OF THE INVENTION
The present invention relates to a process for the preparation of hydroxybenzoic benzyl esters of the formula
in which
R
1
to R
5
are identical or different and are C
1
-C
6
-alkyl, C
1
-C
6
-alkoxy-, C
1
-C
6
-halogenoalkyl, C
1
-C
6
-halogenoalkoxy-, CN, CO(C
1
-C
6
-alkyl), NO
2
, or halogen,
comprising reacting dibenzyl ethers of the formula
in which
R
1
, R
2
, and R
3
are as defined above,
or mixtures of such dibenzyl ethers and benzyl alcohols of the formula
in which
R
1
, R
2
, and R
3
are as defined above,
with alkylcarbonyloxybenzoic or alkoxycarbonyloxybenzoic acids of the formula
in which
R
4
and R
5
are as defined above and
R
6
is hydrogen or a straight-chain or branched, saturated or unsaturated, optionally halogen-substituted alkyl, aralkyl, aryl, alkoxy, aralkoxy, or aryloxy group having 1 to 50 carbon atoms,
in the presence of one or more acids as catalyst.
DETAILED DESCRIPTION OF THE INVENTION
The process according to the invention can be carried out in a cost-effective manner and under mild reaction conditions.
The radicals R
1
to R
5
are generally defined as follows:
Alkyl generally means a straight-chain or branched hydrocarbon radical having 1 to 6 (preferably 1 to 4, particularly preferably 1 or 2) carbon atoms. For example, mention may be made of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl, hexyl, and isohexyl. Preference is given to methyl and ethyl.
Alkoxy generally means a straight-chain or branched alkoxy radical having 1 to 6 (preferably 1 to 4, particularly preferably 1 or 2) carbon atoms. For example, mention may be made of methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, pentoxy, isopentoxy, hexoxy, and isohexoxy. Preference is given to methoxy and ethoxy.
Halogenoalkyl generally means a straight-chain or branched hydrocarbon radical having 1 to 6 (preferably 1 to 4, particularly preferably 1 or 2) carbon atoms having 1 to 10 (preferably 1 to 8, particularly preferably 1 to 5) halogen atoms. For example, mention may be made of chloromethyl, fluoromethyl, trifluoromethyl, fluoroethyl, fluoropropyl, and hexafluorobutyl. Preference is given to fluoromethyl and trifluoromethyl.
Halogenoalkoxy generally means a straight-chain or branched alkoxy radical having 1 to 6 (preferably 1 to 4, particularly preferably 1 or 2) carbon atoms having 1 to 10, preferably 1 to 8, particularly preferably having 1 to 5, halogen atoms. For example, mention may be made of chloromethoxy, fluoromethoxy, trifluoromethoxy, fluoroethoxy, fluoropropoxy, and hexa-fluorobutoxy. Preference is given to fluoromethoxy and trifluoromethoxy.
Halogen generally means fluorine, chlorine, bromine, or iodine, preferably fluorine or chlorine.
Preferred substituents for R
1
to R
5
are methyl, trifluoromethyl, methoxy, fluorine, or chlorine.
Alkyl, aralkyl, aryl, alkoxy, aralkoxy, and aryloxy groups (i.e., for R
6
) generally comprise 1 to 50 carbon atoms, preferably 1 to 10 carbon atoms.
The following hydroxybenzoic benzyl esters can, for example, be prepared by the process according to the invention: benzyl 2-hydroxybenzoate (benzyl salicylate); benzyl 3-hydroxybenzoate, benzyl 4-hydroxybenzoate; benzyl 3-chloro-2-hydroxybenzoate, benzyl 4-chloro-2-hydroxybenzoate, benzyl 5-chloro-2-hydroxybenzoate; benzyl 6-chloro-2-hydroxybenzoate; benzyl 3-bromo-2-hydroxybenzoate, benzyl 3-fluoro-2-hydroxybenzoate, benzyl 4-fluoro-2-hydroxybenzoate, benzyl 2-fluoro-3-hydroxybenzoate, benzyl 2-fluoro4-hydroxybenzoate; benzyl 3-fluoro-2-hydroxybenzoate, benzyl 2-fluoro-5-hydroxybenzoate, benzyl 2-fluoro-6-hydroxybenzoate, benzyl 2-hydroxy-3-methylbenzoate, benzyl 2-hydroxy-4-methylbenzoate, benzyl 3-hydroxy-2-methylbenzoate, benzyl 4-hydroxy-2-methylbenzoate, benzyl 2-fluoro-6-hydroxy4-methoxybenzoate, benzyl 3-trifluoromethyl-2-hydroxybenzoate, benzyl 4-trifluoromethyl-2-hydroxybenzoate, benzyl 2-trifluoromethyl-3-hydroxybenzoate, benzyl 2-fluoroethyl-4-hydroxybenzoate, and benzyl 4-fluorobutyl-2-hydroxybenzoate.
The dibenzyl ether used in the process according to the invention is unsubstituted dibenzyl ether or a substituted dibenzyl ether. Particular preference is given to using unsubstituted dibenzyl ether.
In the process according to the invention, it is possible to use dibenzyl ethers or dibenzyl ether/benzyl alcohol mixtures as are formed, for example, in the preparation of benzyl alcohol from benzyl chloride. The content of dibenzyl ether in the mixture can be 50 to 100% by weight, preferably 60 to 99% by weight, particularly preferably 70 to 98% by weight.
For the process according to the invention, mention may be made, for example, of the following alkylcarbonyloxybenzoic and alkoxycarbonyl oxybenzoic acids: 2-formyloxybenzoic acid, 3-formyloxybenzoic acid, 4-formyloxybenzoic acid, 2-acetoxybenzoic acid, (2-acetylsalicylic acid); 3-acetoxybenzoic acid, 4-acetoxybenzoic acid, 2-propionyloxybenzoic acid, 2-butyryloxybenzoic acid, 2-benzoyloxybenzoic acid, 2-acetoxy-3-chloro benzoic acid, 2-acetoxy-4-chlorobenzoic acid, 2-acetoxy-5-chlorobenzoic acid, 2-acetoxy-6-chlorobenzoic acid, 2-acetoxy-3-bromobenzoic acid, 2-acetoxy-3-chlorobenzoic acid, 2-formyloxy-3-fluorobenzoic acid, 2-acetoxy-3-fluorobenzoic acid, 2-acetoxy4-fluorobenzoic acid, 3-acetoxy-2-fluorobenzoic acid, 2-fluoro4-propionyloxybenzoic acid, 2-butyroxy-3-fluorobenzoic acid, 2-fluoro-5-hydroxybenzoic acid, 6-acetoxy-2-fluorobenzoic acid, 2-acetoxy-3-methylbenzoic acid, 2-acetoxy-4-methylbenzoic acid, 3-acetoxy-2-methylbenzoic acid, 4-acetoxy-2-methylbenzoic acid, 6-acetoxy-2-fluoro4-methoxybenzoic acid, 2-acetoxy-3-trifluoromethyl-benzoic acid, 2-acetoxy4-trifluoromethylbenzoic acid, 3-acetoxy-2-trifluoromethyl-benzoic acid, 4-acetoxy-2-fluoroethylbenzoic acid, 2-acetoxy-4-fluorobutyl-benzoic acid, 2-methoxycarbonyloxybenzoic acid, 2-ethoxycarbonyloxybenzoic acid, 3-methoxycarbonyloxybenzoic acid, or trifluoroacetoxybenzoic acid.
Preference is given to alkylcarbonyloxybenzoic and alkoxycarbonyloxybenzoic acids having 2 to 30 carbon atoms, particularly preferably 2 to 12 carbon atoms. Very particular preference is given alkylcarbonylsalicylic acids.
The process according to the invention is preferably carried out with removal of the water that is formed. It is appropriate to remove the water by distillation or by passing through an inert gas, such as, for example, nitrogen. To remove the water that is formed, preference is given to using water-withdrawing agents, for example, zeolites, aluminum oxides, or clay earths. Particular preference is given to removing the water that is formed by carrying out the reaction in the presence of the corresponding anhydride of the alkylcarbonyloxybenzoic or alkoxycarbonyloxybenzoic acid used as water-withdrawing agent. Very particularly preferred anhydrides are acetylsalicylic anhydrides.
In the process according to the invention, preference is give
Ooms Pieter
Schenke Bernd-Ulrich
Akorli Godfried R.
Bayer Aktiengesellschaft
Eyl Diderico van
Raymond Richard L.
Tucker Zachary C.
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