Organic compounds -- part of the class 532-570 series – Organic compounds – Phosphorus esters
Reexamination Certificate
2000-05-24
2001-08-21
Lambkin, Deborah C. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Phosphorus esters
C558S137000, C558S167000, C558S171000, C558S177000, C558S179000, C558S180000, C558S184000, C562S008000
Reexamination Certificate
active
06278012
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for the preparation of phosphinic acid esters and to the use of the products prepared by this process.
Phosphinic acid esters are valuable synthetic building blocks and can be used, for example, for the preparation of polymers and plastics in order to obtain flame-resistant materials.
Thus, DE 26 52 007 A1 describes flame-resistant epoxy resins through incorporation of carboxyl-functional phosphinic acids. U.S. Pat. No. 5,399,428 A1 describes flame-resistant linear polyesters through incorporation of carboxyl-functional phosphinic acids.
DE 25 40 283 A1 describes the addition of phosphines onto &agr;,&bgr;-unsaturated carboxylic acids in the presence of aqueous hydrochloric acid, followed by oxidation.
DE 28 49 003 describes the preparation of phosphorus-containing cyanohydrin derivatives by the addition of phosphonous acid esters onto acroleincyanohydrin derivatives.
Phosphinic acid esters are obtained by adding phosphonous acid monoesters onto 1-olefins in the presence of peroxidic catalysts. However, the yields are only low. The addition of phosphonous acid monoesters onto activated double bonds in the presence of alkoxides as catalyst proceeds better. Suitable unsaturated compounds are &agr;,&bgr;-unsaturated carboxylic acid esters or nitriles, &agr;,&bgr;-unsaturated ketones and alkyl vinyl sulfones and vinyl acetate (Houben-Weyl, Volume 12/1, pp. 258-259).
The phosphonous acid monoesters themselves are prepared from phosphonous acid dihalides by reaction with alcohols or by hydrolysis and subsequent esterification.
Functional phosphinic acids are obtained by reacting phosphonous acid dihalides (dihalophosphines) with activated olefinic compounds, such as, for example, acrylic or methacrylic acid derivatives, followed by hydrolysis (Houben-Weyl, Volume 12/1, p. 230; K. K. Khairullin, T. I. Sobchuk, A. N. Pudovik, Zh. Obshch. Khim. 37, 710 (1967)). Byproducts formed in the hydrolysis with organic acids are their halides.
In addition, phosphonous acid dihalides can be reacted with alkyl halides in the presence of aluminum chloride (Houben-Weyl, Volume 12/1, p. 232).
Phosphinic acid esters can also be prepared from dialkyl phosphonites by the Michaelis-Arbuzov reaction. The abovementioned dialkyl phosphonites are in turn prepared from phosphonous acid dihalides and hydroxyl compounds.
The abovementioned phosphonous acid dihalides, which can be employed as starting materials for other syntheses, for example methyldichlorophosphine, have hitherto themselves been prepared in a complex synthesis from phosphorus trihalides and alkyl halides in the presence of aluminum chloride (Houben-Weyl, Volume 12/1, p. 306). The reaction is highly exothermic and can only be controlled with difficulty in industry. In addition, various byproducts are formed which, like some of the abovementioned starting materials, are toxic and/or corrosive, i.e. are highly undesired.
SUMMARY OF THE INVENTION
There is therefore a need for a process for the preparation of phosphinic acid esters which can be carried out in a simple manner and in which uniform products are obtained in high yield. A process of this type should also be significantly superior to the processes known hitherto in environmental terms.
The invention thus has the object of providing a process for the preparation of phosphinic acid esters which avoids the abovementioned disadvantages and starts from elemental yellow phosphorus as starting material.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
This object is achieved by a process of the type mentioned at the outset which comprises
a) reacting elemental yellow phosphorus with alkylating agents in the presence of a base to give a mixture which comprises, as principal constituents, the (metal) salts of alkylphosphonous, phosphorous and hypophosphorous acids,
b) esterifying the principal constituents of the mixture from a) to give an ester mixture,
c) isolating the ester of the alkylphosphonous acid from the ester mixture,
d) adding the resultant ester of the alkylphosphonous acid onto an olefin containing a functional group.
The process according to the invention has considerable advantages over the processes known hitherto since it has a positive balance in the product distribution and at the same time avoids the phosphine and phosphonous acid dihalide starting materials, which are regarded as undesired, and in addition produces no halogenated organic byproducts.
The alkylating agents are preferably alkyl halides, dialkyl sulfates, trialkyl phosphates, dialkyl carbonates and/or formic acid ortho-esters.
The alkylating agents employed are particularly preferably methyl chloride, methyl bromide and/or dimethyl sulfate.
The bases are preferably hydroxides, carbonates, bicarbonates, amides, alkoxides and/or amine bases, such as, for example, amines and ammonia.
The reaction in step a) is preferably carried out in a two-phase system comprising aqueous alkali or alkaline-earth metal hydroxide or mixtures thereof and an organic solvent.
The organic solvents employed in step a) are preferably straight-chain or branched alkanes, alkyl-substituted aromatic solvents, water-immiscible or only partially water-miscible alcohols or ethers, alone or in combination with one another.
The organic solvent employed is particularly preferably toluene, alone or in combination with alcohols.
The reaction can, if desired, also be carried out in a non-aqueous system, for example by using solid sodium hydroxide or amines.
The reaction is preferably carried out in the presence of a phase-transfer catalyst.
The phase-transfer catalyst is preferably a tetraalkylphosphonium halide, triphenylalkylphosphonium halide or tetraorganylammonium halide.
The temperature during the reaction is preferably from −20 to +80° C.
The temperature is particularly preferably from −10 to +30° C.
The reaction is preferably carried out under a pressure of from 0 to 10 bar.
Step a) of the process according to the invention is preferably carried out by suspending or dissolving the yellow phosphorus in a solvent or solvent mixture and then reacting it with an alkyl halide and a compound of the formula MOH or M′ (OH)
2
or mixtures thereof, where M is an alkali metal and M′ is an alkaline-earth metal.
The yellow phosphorus and the alkyl halide are preferably reacted with one another in a molar ratio of from 1:1 to 1:3, where the molar ratio of yellow phosphorus to the compound of the formula MOH or M′ (OH)
2
is from 1:1 to 1:5.
The principal constituents of the mixture from a) are preferably esterified in step b) using a linear or branched alcohol of the general formula R—OH, where R is a linear or branched alkyl radical having 1 to 10 carbon atoms.
In another preferred embodiment of the process according to the invention, the principal constituents of the mixture from a) are converted into a mixture of alkylphosphonous, phosphorous and hypophosphorous acids using mineral acids, with the (metal) salts of the mineral acids simultaneously being precipitated, and the mixture of these acids subsequently being esterified.
The water formed during the esterification is preferably removed by azeotropic distillation.
In other words, the esterification of the phosphonous acid to the corresponding monoester can be achieved by reaction with relatively high-boiling alcohols with removal of the resultant water by azeotropic distillation.
The precipitation of the metal salts, usually the alkali or alkaline-earth metal mineral salts, is preferably carried out here by replacement of the solvent water by the alcohol to be used in reaction step b).
The alkali or alkaline-earth metal mineral salt which has already precipitated is preferably filtered off before the esterification.
The alcohol is preferably n- or i-butanol, n-hexanol, ethylhexanol and/or amyl alcohol.
The mineral acid is preferably hydrochloric acid, sulfuric acid and/or phosphoric acid.
The mineral acid is particularly preferably hydrochloric acid.
The phosphines formed in small amounts during s
Breuer Heinz-Peter
Horold Sebastian
Sicken Martin
Weferling Norbert
Clariant GmbH
Hanf Scott E.
Lambkin Deborah C.
Pang Andrew
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