Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Patent
1995-03-24
1996-12-03
Chan, Nicky
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C07D30906
Patent
active
055809944
DESCRIPTION:
BRIEF SUMMARY
This is an application under 35 USC .sctn. 371 of PCT/EP 93/03670 filed Dec. 23, 1993.
The present invention relates to a process for preparing tetra-hydropyran-4-carboxylic acid and its esters by reaction of 2,7-dioxaspiro[4.4]nonane-1,6-dione with water or alcohols in the presence of acidic catalysts at elevated temperatures.
From J. Chem. Soc. 1930, pages 2525 to 2530, a process for preparing tetrahydropyran-4-carboxylic acid esters is known in which .beta.,.beta.'-dichlorodiethyl ether is reacted with the sodium salt of diethyl malonate to give diethyl tetrahydropyran-4,4-dicarboxylate, and this is converted to tetrahydropyran-4-carboxylic acid via tetrahydropyran-4,4-dicarboxylic acid and finally esterified to give the desired tetrahydropyran-4-carboxylic acid ester.
EP-A-284 969 furthermore discloses preparing tetrahydropyran-4-carboxylic acid esters by reaction of 3-(2-hydroxyethyl)butyrolactone or its esters and ethers with alcohols in the presence of acidic catalysts.
A disadvantage of the known processes is that they proceed either in numerous reaction steps and with production of salt or only with low yields.
It is an object of the present invention to make the compounds I more accessible.
We have found that this object is achieved by a novel and improved process for preparing tetrahydropyran-4-carboxylic acid and its esters of the formula I ##STR3## where R is hydrogen, C.sub.1 -C.sub.8 -alkyl, C.sub.3 -C.sub.8 -cycloalkyl, aryl, C.sub.7 -C.sub.12 -alkylphenyl or C.sub.7 -C.sub.12 -phenylalkyl, which comprises reacting 2,7-dioxaspiro[4.4]nonane-1,6-dione of the formula II ##STR4## with water or alcohols of the formula III and from 0.01 to 100 bar.
The 2,7-dioxaspiro[4.4]nonane-1,6-dione II can preferably be reacted in molten (m.p.: 108.degree. to 109.degree. C.) or dissolved form, together with the alcohol III or water and, if appropriate, an inert gas such as nitrogen, carbon dioxide or argon, to give tetrahydropyran-4-carboxylic acid and its esters I.
Reaction temperatures of from 200.degree. to 300.degree. C., in particular from 220.degree. to 270.degree. C. and a pressure of from 0.1 to 5 bar are particularly advantageous.
The reaction can be performed batchwise or continuously, eg. as a solid-bed reaction using solid-bed catalysts, for example in a liquid-phase or trickle procedure in the liquid or gas phase, eg. in solid form in a fluidized bed or with solid-bed catalysts suspended in the liquid phase or homogeneous catalysts.
The material discharged from the reaction can be condensed by means of a suitable cooling device and then worked up by fractional distillation. The tetrahydropyran-4-carboxylic acid and its esters I can be separated off and unreacted 2,7-dioxaspiro-[4.4]nonane-1,6-dione II or the ethers or esters of 3-(2'-hydroxyethyl)dihydro-2(3H)furanone, eg. 3-(2'-methoxyethyl)dihydro-2-(3H)-furanone, which may be contained in the material discharged from the reaction, can be recycled (cf. EP-A-284 963).
The reaction in the liquid phase can be carried out, for example, in such a way that a mixture of 2,7-dioxaspiro[4.4]nonane-1,6-dione II and the respective alcohol III (or water) is heated to the desired reaction temperature in the presence of a suspended solid-bed catalyst or of a homogeneous dissolved catalyst. After the necessary reaction time has passed, the reaction mixture is cooled and the catalyst removed, eg. by filtration or neutralization. The reaction mixture can then be fractionally distilled to obtain the desired tetrahydropyran-4-carboxylic acid ester.
The molar ratio of alcohol III or water to the 2,7-dioxaspiro-[4.4]nonane-1,6-dione II is customarily from 0.5:1 to 50:1, preferably from 1:1 to 30:1, particularly preferably from 2:1 to 20:1.
In the case of heterogeneous catalysts, the reaction is carried out with catalyst loadings of from 0.1 to 10, in particular from 0.1 to 5, g of lactone II per g of catalyst and hour.
Suitable alcohols of the general formula III are, for example, methanol, ethanol, n-propanol, isopropanol, tert-butanol, n-butanol, isobutanol, se
REFERENCES:
patent: 4837346 (1989-06-01), Becker et al.
patent: 5371246 (1994-12-01), Borchers et al.
patent: 5414097 (1995-05-01), Fischer et al.
J. Chem. Soc. 1930, pp. 2525 to 2530.
Fischer Rolf
Goetz Norbert
Kuekenhoehner Thomas
Schnurr Werner
BASF - Aktiengesellschaft
Chan Nicky
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