IE43625B1 - Production of organic phosphorus compounds containing carboxylic groups - Google Patents

Abstract

Carboxyl-containing organic phosphorus compounds of the general formula I where the substituents are as defined in Claim 1, are obtained by reacting in a first stage phosphines with alpha , beta -unsaturated carboxylic acid in the presence of aqueous hydrochloric acid, admixing in a second stage the resulting phosphonium chlorides without interim isolation with an oxidising agent, and isolating the resulting compounds of the general formula I from the oxidation product. The main advantages of the process of the invention over the known processes are for example that relatively readily obtainable starting materials can be used, that the reaction involved is a 1-pot reaction where there is no need to isolate intermediates, and that the process leads in a simple manner and good yield to readily isolable and uniform end products of high purity.

Description

The present invention relates to a novel process for making organic phosphorus compounds containing carboxylic groups and corresponding to the following general formula (I) RP(O)R1R2 (I) 2 in which R and R each stand for linear and/or branched, identical or different alkyl-, cycloaikyl-, aryl-, alkylaryl- and aralkyl groups having from 1 to 18, preferably fran 1 to 6,more preferably 1 or 2, carbon atcms, and in which one of R1 2 and R may stand for a hydroxylic group or for the substituent R, the substituent R being a radical of the following general formula (II) -CHR3-CHR4-COOH (II) 4 in which R and R each stand for linear and/or branched, identical or different alkyl-, cycloaikyl-, aryl-, alkylaryl- and aralkyl groups having from 1 to 18, preferably from 1 to 6, carbon atoms, and/or stand for hydrogen atoms.

The above compounds are colorless crystalline solid substances. 3 6 2 5 - 3 It has already been descr Lbed that carboxyalkylmethyl phosphinic acids can be produced in yields of 54% by the additive combination of methanephosphonous acid dichloride with an a,β-unsaturated carboxylic acid, preferably with acrylic acid, followed by hydrolysis, as shown in che following reaction schemes HOOC-CH=CH„+CH,PCl„-> Z +2H2O C1OCCH2CH2P(O) (CII3)C1-—HJOOCCH2CH2P (0) (CH3) (OH) -2IIC1 (KK. Khairullin, T.I. Sobchuk and A.N. Pudovik; Zh.

Obshch. Khim. 37, 710 (1967)), A.J. Razumov and V.V. Moskvia (cf. Zh. Obshch.

Kim. 34, 2589 (1964); 35, 1149 (1965) have obtained carboxyalkyldialkylphosphine oxides by subjecting dialkylphosphinic acid esters to an Arbuzov-reaction with halogeno-substituted acetals, hydrolyzing the acetal grouping to aldehyde and oxidizing the latter with peracetic acid to the carboxylic group, where it is possible for the hydrolysis to be combined with the oxidation. The reaction mechanism may be represented as follows: R' 2 P-OR +X( CH2) nCH (OC2H5) 2->R ’2P (0) (CH2) nCH (OC^Hg) 2+ -RX Ox -+R'2P(O) (CHo)nCHO—>R'2P(0) (CH- COOH.

(R‘ and R are alkyl groups).

It has also been described that alkali metal phosphides can be treated with halogeno-carboxylic acid esters or with the sodium salts of halogenocarboxylic acids and converted to carboxyphosphines, thus: 43635 - 4 R' 2PK+X (CH2) nCOOR->-R ’ 2P (CH2) nCOOR -KX (R* and R are alkyl groups).

Treatment of the compounds so made with an alka.line liquor and/or mineral acid results in the forma5 tion of the free carboxylic acids (cf. K. Issleib and G. Thomas, Chem. Ber. 93, 803 (1960) and K. Issleib, R. KSmmel and H. Zimmermann, Ang. Chemie 77, 172 (1965)) By treatment with a customary oxidizing agent, such as hydrogen peroxide (cf. Houben-Weyl, Methoden der lo Organischen Chemie, vol. XII/1, page 140 et seq., Georg Thieme Verlag, Stuttgart (1963)), the above carboxy phosphines can be transformed to the corresponding carboxy phosphine oxides.

It is also known that nitrile groups can be sub15 jected to an acid or alkaline hydrolysis and converted in this manner to carboxylic groups. In those cases in which a tertiary phosphine is hydrolyzed (cf. F. G.

Mann and I.T. Millar, J. Chem. Soc. 1952, 4453; M.M. Rabaut, I. Hechenbleikner, H.A. Currier, F.C. Schafer and V.P. Wystrach, j. Am. Chem. Soc. 81, 1103 (1959), the resulting hydrolyzed material is subsequently oxidized. Thus, for example, it has been described (cf.

M. Grayson, P.T. Keough and G.A. Johnson, J. Am. Chem. Soc. 81, 4803 (.1959) that bis -(2- carboxyethyl) 25 methyl phosphine, which is made from bis -(2- cyanoethyl) - methyl phosphine, can be oxidized in the form of its hydrochloride with an alkali in an aqueous medium so as to give bis - (2 - carboxyethyl) - methyl phosphine oxide in a yield of 50% (cf. U.S. Patent 3,784,30 638).

The same result is obtained in those cases in which a tertiary phosphine oxide is hydrolyzed. Thus, for example, bis - (2 - carboxyethyl) - methyl phosp4 3 6 3 5 - 5 hine oxide is obtained by hydrolyzing bis-(2-cyanoethyl)-methyl phosphine oxide in an alkaline or acid medium (cf. J. Pelton and W.G. Carpenter, J. Polymer Sci., Pt A 1, 863 (1963); V.K. Khairullln, G.V. Dimitrieva, I.A. Aleksandrova and Μ.Λ. Vasyanina, Izv.

Akad. Nauk, USSR, Sec. Khim 12, 2744 (1973).

All the processes for making organic phosphorus compounds containing carboxylic groups described hereinabove have a plurality of disadvantageous effects, and are therefore highly undesirable, in respect of the following points.

The yields are in some cases scarcely higher than 50%, or it is necessary for the reaction to be carried out in several stages so as to obtain the final compound. The hydrolysis necessary in certain cases, especially the nitrile hydrolysis, entails the formation of stoichiometric proportions of salts, which are very difficult to remove quantitatively from the final products, at the price of the considerably impaired yields. In addition of this, the above known processes often call for the use of starting materials which are extremely difficult to prepare, at least commercially. In other words, these are starting materials which are not readily available and therefore not very suitable for use in commercial processes. It is accordingly highly desirable to have a process permitting the desired final products to be made in simple manner from commercially readily available starting material.

It has also been found that it is not possible for the direct reaction of a phosphine of general formula III R3R5PH (HI) with an a,β-unsaturated carboxylic acid of general formula IV 43633 chr3=ch4-cooh (IV), 4' 5 R and R being as defined earlier herein, and R having the same meaning as R except that it is not permitted to be hydrogen, to be stopped at the secondary or tertiary phosphine stage. This addition reaction has rather been found to go beyond these stages with the resultant formation of compounds, which are termed phosphobetaines and are compounds having a phosphonium cation, of which the charge is intramolecularly compensated by a carboxyiate ion.

Needless to say their transformation into the compounds of the present invention entails considerable expenditure of energy.

The present invention now unexpectedly provides a novel process for making organic phosphorus compounds containing carboxylic groups and corresponding to the following general formula I RP(O)RJ-R2 (I) 2 in which R and R each stand for linear and/or branched, identical or different alkyl-, cycloaikyl-, aryl-, alkylaryl- and aralkyl groups having from 1 to 18, preferably from 1 to 6, more preferably 1 or 2, 2 carbon atoms, and in which one of R and R may stand for a hydroxylic group or for the substituent R, the substituent R being a radical of the following general formula II -CHR3-CHR4-COOH (II) 4 in which R and R each stand for linear and/or branched, identical or different alkyl-, cycloaikyl-, aryl-, 3° alkylaryl- and aralkyl groups having from 1 to 18, 3 6 3 5 preferably from 1 to 6, carbon atoms, or stand for hydrogen atoms, which process comprises: reacting, in a first step, one or more phosphines of general formula III (ill) in which R has the meaning given above, and R has the same meaning as R with the exception of hydrogen with an a,β-unsaturated carboxylic acid of general formula IV chr3=cr4-cooh (IV) in which R3 and R4 also have the meanings given above the reaction being effected in the presence of aqueous hydrochloric acid and optionally a solvent; omitting isolating the resulting phosphonium chlorides of general formula V 5_6_®.τ7®„ηθ /RrVp®H/ Cl' (V) in which R5 has the meaning given above, and R6 has the same meaning as R or R, and oxidising in known manner, in a second step, said phosphonium chlorides with an oxidant; and separating the resulting compounds of general formula I from the oxidation mixture.

An even more unexpected result resides in the fact that it has been possible by the use of hydrochloric acid to stop the additive combination reaction of the formula III phosphines with the formula IV «,β-unsaturated carboxylic acids at the secondary and tertiary phosphine stages, respectively (cf. Examples 5 and 6 below).

It is a further unexpected result that the reaction, - 8 which is incidentally easy to carry out as a single pot reaction without any need to isolate the secondary or tertiary phosphine intermediate compounds, produces high yields of the formula I carboxyphosphorus compounds .

The aqueous hydrochloric aoid may be used in admixture with a solvent being miscible therewith, e.g. acetonitrile.

The reaction should preferably be effected at temperatures of 0 to 120°C, more preferably 15 to 1O5°C.

It is also preferable for the reaction to be effected under inert gas, e.g. nitrogen.

With respect to the formula V phosphonium chlorides obtained in this invention, it is possible for them to be oxidized with a known oxidant, e.g. aqueous hydrogen peroxide of 3 to 30% strength or chlorine, the oxidant being preferably used in an excess of about 10 weight%, based on the quantity theoretically necessary, so as to ensure complete oxidation. The formula III phosphines and the formula IV a,β-unsaturated carboxylic acids should' preferably be used in stoichiometric proportions, based on the formula I final product. The reaction remains however unaffected if more than the stoichiometric proportion of the formula III phosphines is used. The formation of a compound of formula I 2 wherein one of R and R is a hydroxyl group is illustrated in Example 4 below.

A further preferred embodiment of the present process provides for the formula III phosphine to be first added to aqueous hydrochloric acid and solvent, if any, and for the formula IV a,β-unsaturated carboxylic acid to be then metered into the mixture at the rate necessary to maintain said mixture at a temperature of 15 to 35°C, or alternatively for the formula IV α,β43625 - 9 unsaturated carboxylic acid to bo first added to the aqueous hydrochloric acid and solvent, if any, and for the formula III phosphine to be then added while maintaining a temperature of 15 to 35°C. In either case, the resulting reaction solution is heated to about 100° C and continuously admixed at that temperature with the oxidant until the reaction is complete. The temperature indicated is maintained during a post-reaction period of a further 30 to 60 minutes. Next, the formula I carboxy-phosphorus compounds which are crystalline solid materials are isolated in known manner, e.g. by filtration or centrifugation, from the reaction product, if desired after prior removal of the aqueous hydrochloric acid and solvent, if any, by distillation.

The process of the present invention offers considerable advantages in respect of the following points: Relatively readily accessible starting materials are used. The reaction is effected as a single pot reaction without any need to isolate intermediates. The reaction is easy to carry out and produces high yields of readily separable, uniform and very pure final products.

The following Examples illustrate at least the first step of the process of the present invention. However, this process may be stopped at the stage of the formula V phosphonium chlorides, which could be isolated, were their isolation desired; this possibility is illustrated by Examples 5 and 6 hereinafter.

EXAMPLE 1 (hoocch2ch2)2P(0)ch3 An agitator-provided apparatus scavenged with nitrogen was charged with 865 g (12 mols) of acrylic acid in 600 cc of concentrated hydrochloric acid and 4363s - 10 1.2 1 of water, ffext, 290 g (6 mols) of methyl phosphine was introduced together with nitrogen as inert gas within about 3.5 hours. The temperature was maintained at 15 to 35°C hy cooling from the outside. The introduction 5 of nitrogen was continued and the reaction solution was gradually heated to 100°C.

At that temperature, 700 cc of a 30% agueous Η2Ο2_ solution was added within 3 hours. Following this, the reaction solution was heated for a further hour to 100°C On cooling, the material began to crystallize. The solid material was filtered off, the mother liquor was concentrated, and further solid material was recovered from the mother liquor.

The yield was 1170 g^94% of the theoretical. Melting point: 173-174°C.

Analysis: Found: C 40.5% H 6.5% P 14.8% Calculated: 40.39% 6.30% 14.88% Acid number in mg KOH/g. 538 538.3 EXAMPLE 2 The reaction was effected as described in Example 1 but in hydrochloric acid and acetonitrile. Melting point 173°C.

EXAMPLE 3 The reaction was effected as described in Example 1, but the oxidation was effected by introducing chlorine gas at 100°c. Melting point 174°C. - ll EXAMPLE 4 HOOCCH2CH2P(0)(CH3)(OH) An apparatus scavenged with nitrogen was charged with 700 cc of concentrated hydrochloric acid and 99 g (2 mols) of methylphosphine was added. The resulting methyl phosphin^um chloride solution was then admixed dropwise at 15 to 25°C with 72 g (1 mol) of acrylic acid. Methylphosphine in excess was removed by the slow addition of altogether 800 cc of water and by gradually heating to 1O5°C. The temperature was maintained and 300 cc of a 30% aqueous I^O^-solution was added, and the whole was heated for a further 30 minutes.

The solvent was completely eliminated and the residue was taken up in acetone. The resulting solid material was filtered off, the filtrate was concentrated and further solid material was recovered from the filtrate.

The total yield was 91.5%.

Melting point: 91°C.

The acid number in mg KOH/g was 732 (theoretical number 737.88) Found: P 20.4% C 31.5% H 6.2% Calculated: .36% 31.59% .97% EXAMPLE 5 /’(hoocch2ch2 ) 2®ph (CH3)7C1® An agitator-provided apparatus scavenged with nitrogen was charged with 142 g (2 mols) of acrylic acid in 100 cc of concentrated hydrochloric acid and 200 cc of water. Next, 60 g (1.2 mols) c. methyl phosphine was introduced together with nitrogen as - 12 inert gas within 1 hour. The temperature was maintained at 20 to 30°C by cooling from the outside. The solvent was concentrated as far as possible, the filtrate was freed from the solvent, and further solid material was recovered therefrom.

Yield: 91%. Melting point: 147°C Analysis: Found: Calculated: c 36.7% 36.8% 10 Jl 6.3% 6.2% Cl 15.5% 15.5% P 13.5% 13.6% EXAMPLE 6 Z’(hoocch2ch2®ph2 (ch3)79ci An agitator-provided apparatus scavenged with I nitrogen was charged with 150 g of methyl phosphine (3.1 mols) in 1 liter of acetonitrile. Next, a solution of 111 g (1.55 mol) of acrylic acid in 170 cc of concentrated hydrochloric acid was added within in hour under nitrogen,. The temperature was maintained at 15°C by cooling from the outside. Following this, the whole was heated to boiling temperature for as long as necessary to remove the methyl phosphine in excess. The solvent was distilled off and 222 g of crystalline solid material was obtained. Yield=92% of the theoretical.

Analysis: Found: Calculated: C 30.8% 30.69% H 6.3% 6.44% Cl 22.9% 22.65% P 19.5% 19.78% 3 6 2 5 - 13 EXAMPLE 7 (ch3)2p(o)ch2ch2cooh An agitator-provided apparatus scavenged with nitrogen was charged with 72 g (1 mol) of acrylic acid in 150 cc of water and 15( > cc of concentrated hydrochloric acid. Next, 62 g of dimethyl-phosphine (1 mol) was added within 1 hour. The temperature was maintained at 25 to 40° C by cooling from the outside. The introduction of nitrogen was continued and the reaction solution was gradually heated to 100°C. At that temperature, 120 cc of a 30% aqueous HjOg-solution was added within 30 minutes and the whole was heated for a further hour. The solvent was distilled off, the residue was recrystallized from acetonitrile and the final product was obtained in a yield of 138 g, corresponding to 92% of the point was 128°C.

Analysis: Pound: C 40.4% H 7.4% P 19.8% Acid number in mg KOH/g 420 theoretical. The melting Calculated: 40.01% 7.39% .63% 373.8 EXAMPLE 8 /BOOCCH(CH3)CH272P(O)(CHg) 172 g (2 mols) of methacrylic acid was reacted as described in Example 1 with 50 g of methylphosphine (1.04 mol) in 150 cc of concentrated hydrochloric acid and 200 cc of water. Next, the whole was oxidized with 110 cc of a 30% aqueous HgOg-solutron. The solvent was distilled off, together with low-boiling fractions, and glassy material was obtained as the residue, which did not tend to crystallize.

The yield was 196g=83% of the theoretical Analysis Found: C 46,1% II 7.3% Calculated P 12.8% 45.77% 7.25% 13.11% Acid number in mg KOH/g 481 475.1 EXAMPLE 9 Use of organic phosphorus compounds containing carboxylic groups for imparting flame-retardant properties to synthetic fibers. 500 g of dimethyl terephthalate and 360 cc of ethylene glycol were placed in a vessel provided with an agitator, column and condenser and subjected to an ester interchange reaction with 0.115 g of manganese acetate at about 200°C under atmospheric pressure, in conventional manner. After the ester interchange reaction was complete, the reaction product was stabilized by means of 0.040 g of phosphorous acid and admixed with 0.180 g of antimony trioxide and 34.1 g of bis-(2-carboxyethyl) - methyl - phosphine oxide obtained as described in Example 1. Next, the pressure was reduced within 1 hour to 0.1-0.2 mm Hg and the temperature was increased to 275°C. Following this, the polycondensation was terminated within 80 minutes.

The viscosity of the copolymer so obtained determined on a solution of 1 g of the polymer in 100 cc of a phenol/tetrachloroethane mixture (3:2 ratio by weight) at 25°C, was eta rel.=.1.82, based on the phenol tetrachloroethane - mixture. The copolymer had a melting point of 25O°C.and contained 0.9 weight % of phosphorus. Filaments and fibers were made as usual from the copoly- 15 mer and found to compare favorably in respect of their good flame-retardant properties with filaments and fibers made from products which were free from the phosphorus compounds of the present invention.

Claims (18)

1. A process for making organic phosphorus compounds containing carboxylic groups and corresponding to the following general formula I 5 1^(0)11¼ 2 (I) 1 2 in which R ami R each stand for linear and/or branched, identical or different alkyl-, cycloaikyl-, aryl-, alkylaryl- and aralkyl groups having from 1 to 18 carbon 1 2 10 atoms, and in which one of R and R may stand for a hydroxylic group or for the substituent R, the substituent R being a radical of the following general formula XX -CHR 3 -CHR 4 -COOH (II) 15 in which R 3 and R 4 each stand for linear and/or branched, identical or different alkyl-, cycloaikyl-, aryl-, alkylaryl- and aralkyl groups having from 1 to 18 carbon atoms, or stand for hydrogen atoms, which process comprises: reacting in a first step, one or more phosphines 20 of general formula III R 3 R 5 PH (III) 3 5 in which R has the meaning given above, and R has the same meaning as R with the exception of hydrogen with an a,β-unsaturated carboxylic acid of general 25 formula IV CHR 3 =CR 4 -COOII (IV) 3 4 in which R and R also have the meanings given above, the reaction being effected in the presence of agueous hydrochloric acid and optionally a solvent; omitting - 17 isolating the resulting phosphonium chlorides of general formula V /kR 5 R 6 P®IJ / ,S Cl® (V) in which r5 has the meaning given above, and R® has the 3 same meaning as R or R, and oxidising in known manner, in a second step, said phosphonium chlorides with an oxidant; and separating the resulting compounds of general formula I from the oxidation mixture.

2. A process as claimed in claim 1, wherein R^ and/or R have 1 to 6 carbon atoms per radical.

3. h process as claimed in claim 1 or 2, wherein 1 2 R and/or R have 1 or 2 carbon atoms per radical.

4. A process as claimed in claim 1, 2 or 3, wherein R^ and/or R^ have 1 to 6 carbon atoms in the radical.

5. A process as claimed in claim 1, 2, 3 or 4, wherein the solvent is a solvent miscible with hydrochloric acid.

6. A process as claimed in claim 5, wherein the solvent is acetonitrile.

7. A process as claimed in any one of claims 1 to 6, wherein the reaction is effected at temperatures of 0 to 120°C.

8. A process as claimed in claim 7, wherein the reaction is effected at temperatures of 15 to 105°C.

9. A process as claimed in any one of claims 1 to 8, wherein the reaction is effected under inert gas.

10. A process as claimed in claim 9, wherein the inert gas is nitrogen.

11. A process as claimed in any one of claims 1 to 10, wherein the formula V phosphonium chlorides present in the first step reaction product are oxidized 43635 - 18 with a 3 to 30 weight % aqueous hydrogen peroxide solution.

12. A.process as claimed in any one o£ claims 1 to 11, wherein the oxidant used for oxidizing the phosp5 honium chlorides is used in an excess of about 10 weight %, based on the theoretical quantity.

13. A process as claimed in any one of claims 1 to 12, wherein the formula ΪΧΧ phosphines and the formula IV a,β-unsaturated carboxylic acids are used in 10 stoichiometric proportions, based on the formula I final product.

14. A process as claimed in any one of claims 1 to 13, wherein the formula III phosphine is added to the aqueous hydrochloric acid and solvent, if any, the 15. Formula IV a,β-unsaturated carboxylic acid is metered into the mixture at the rate necessary to maintain the mixture at a temperature of 15 to 35°C, the resulting solution is heated to about 100°C, continuously admixed, at that temperature with the oxidant until the reaction 20 is complete, and the reaction mixture is maintained at that temperature for a further period of 30 to 60 minutes, the resulting formula I organic phosphorus compounds containing carboxylic groups being separated in known manner from the reaction product, if desired 25 after prior distillative removal of the hydrochloric acid and solvent, if any.

15. A process as claimed in claim 14, modified in that the formula IV a,β-unsaturated carboxylic acid is added to the aqueous hydrochloric acid and solvent, 30 if any, and the formula III compound is added to the mixture at the rate necessary to maintain the mixture at a temperature of 15 to 35°C.

16. A process for making organic phosphorus 4 3 6 3 5' - 19 compounds containing carboxylic groups conducted substantially as described in any one of Examples 1 to 4, 7 and 8 herein.

17. A process as claimed in claim 1, wherein 5 the first step is conducted substantially as described in Example 5- or 6.

18. , Organic phosphorus compounds containing carboxylic groups whenever obtained by a process as claimed in any one of claims 1 to 17.