MC2435A1 - Processes for obtaining polyfluorocarboxylic acids and their salts - Google Patents

Description

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10 07

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PATENT FOR INVENTION

Title of the invention:

PROCESSES FOR OBTAINING POLYFLUOROCARBOXYLIC ACIDS AND THEIR SALTS

Names of the inventors:

Hédi TRABELSI and Aimé CAMBON

The invention relates to the synthesis of new polyfluorocarboxylic acids and their salts of general formula:

RF(CH2)nx /

COOM

C

XR'

in which Rp represents a perfluorinated group. linear or branched, containing 4 to 18 carbon atoms, n is an integer equal to 2, 3, or 11, R' can be a hydrogen atom or a COOM group (M can be a hydrogen atom or a sodium or potassium atom), R can be a hydrogen atom, an alkyl group containing 1 to 18 carbon atoms possibly substituted, an aryl or aralkyl radical possibly substituted, an allyl, methallyl, or propargyl radical, a polyoxyethyl group, an oxoalkyl group R"COCH2- (R" can be a biphenyl group substituted by an alkyl group containing 1 to 10 carbon atoms or an aralkyl radical or a nitrile function), a COOH group, a perfluorinated aliphatic chain having 4 to 18 carbon atoms, or a polyfluorinated group Rp(CH2>2NI) lt'(( ))CH2-. or a group Rp(CH2)nCR'(COOM)-(CH2)m-2 -( m-2 is equal to 4,5,6,8,10,11,12,14. n, R' and M have the same meanings as before).

As possible substituents on alkyl, arylc or aralkyl radicals, we can mention hydroxy, mercapto, oxo or carboxyl groups.

These compounds can be used as surfactants in the formation of liposome-type fluorocarbon membrane bilayers, liquid crystals, Langmuir blodgel films or precursors of such agents.

?

Description of the invention

Access to perfluorocarboxylic acids by various methods described by numerous authors was hampered by the poor reactivity of certain raw materials and the use of excessively expensive reagents: 5-3-F-alkylpropanoic acids are obtained in low yields by the magnesium route from 2-F-alkylethyl iodides, magnesium, and carbon dioxide. Alongside acid formation, the reaction leads to dimerization products [J. Org. Chem. 23 (1958) 1166; J. Fluorine Chem. 16 (1980) 193; Eur. Pat. No. 271212 (1988); J. Fluorine Chem. 56 (1992) 193]. Polyfluorocarboxylic acids in which the alkyl F-1β group is separated from the carboxylic group by more than two methylene groups are obtained in yields of 50 to 93% by the addition of iodoperfluoroalkanes to ex,p unsaturated acids or their derivatives [J. Org. Chem. 27 (1962) 4491; Liebigs Ann. Chem. (1992) 209; J. Fluorine Chem. 56 (1992) 285]. This radical-type reaction can be carried out catalytically, thermally, or photochemically, with or without free radical initiators. However, it requires rigorous control of experimental conditions due to numerous possible side reactions (telomerization, disproportionation, etc.). Electrochemical fluorination of carboxylic acid halides leads to perfluorinated ethers and alkanes concurrently with the expected long-chain perfluorocarboxylic acids [J. Fluorine Chem. 17(1981) 423]. Oxidation of F-alkylethenes with ozone is complex and requires further treatment with another oxidant [U.S. Patent No. 4,138,417]. Oxidation of F-alkylethenes can be achieved using oxidants such as the very expensive ruthenium dioxide [J. Fluorine Chem. 13(1979) 175] or by using a large excess of potassium permanganate [European Patent No. 0,234,013(1987)]. The preparation of perfluorocarboxylic acids from iodoperfluoroalkanes, zinc, and carbon dioxide is carried out in aprotic solvents after delicate activation of the zinc [U.S. Patent No. 4,221,734]. The oxidation of iodoperfluoroalkanes by oleum provides perfluorocarboxylic acids in high yields but requires special treatment to recover the iodine [U.S. Patent No. 4,400,325].

In the present invention, we describe simple and rapid preparation processes that allow a wide variety of polyfluorocarboxylic acids and their salts to be obtained in satisfactory yields. Their general formula is:

30

RFlCH2) /COOM X

R NR'

in which Rp represents a perfluorinated group, linear or branched, containing 4 to 18 35 carbon atoms, n is an integer equal to 2, 3 or 11, R' can be an atom

3

of hydrogen or a COOM group (M can be a hydrogen atom or a sodium or potassium atom), R can be a hydrogen atom, an alkyl group containing 1 to 18 possibly substituted carbon atoms, an aryl or possibly substituted aralkyl radical, an allyl, methallyl or propargyl radical, a polyoxyethyl group, a 2-oxoalkyl group R"COCH2- (R" can be a biphenyl group substituted by an alkyl group containing 1 to 10 carbon atoms or an aralkyl radical or a nitrile function), a COOH group, a perfluorinated aliphatic chain having 4 to 18 carbon atoms or a polyfluorinated group RF(CH2)2NHC(0)CH2- or an RF(CH2)nCR'(COOM)-(CH2)m-2- group (m-2 is equal to 4, 5, 6, 8, 10, 11, 12, 14. n, R' and M have the same meanings as before). As substituents possibly present on alkyl, aryl or aralkyl radicals, we can mention the hydroxy, mercapto, oxo or carboxylic groups.

The compounds of formula (1), in which R' is a CO2H group, R and M are similar and each represent a hydrogen atom, n is an integer equal to 2, 3 or 11 and rf a perfluorinated aliphatic chain having 4 to 18 carbon atoms, i.e. 15 the compounds of formula:

R (CH ) COiH

KF(.L.H2Jn^ / ^

H/ ▲H

2q are obtained with yields of around 88%. The diesters used as starting compounds are prepared from dialkyl malonates and 1-iodo-Cu-F-alkylalkanes according to a process we have already described [Patent MC No. 2334 (1996)] and allow access, after hydrolysis, to the corresponding polyfluorocarboxylic diacids of formula (I). These diacids (I) have proven to be particularly interesting precursors for the development of vesicular systems or new surfactants.

25 Thus, for example, the compounds according to the invention in which R, R1 and M are identical and each represent a hydrogen atom, n is equal to 2, 3 or 11 and RF a perfluorinated aliphatic chain having 4 to 18 carbon atoms, that is to say the compounds of formula:

RF(CH2)nCO2II (II)

30

are prepared by thermal decarboxylation of the corresponding polyfluorocarboxylic diacids of formula (I).

The homologs of diacids (1), that is to say the compounds according to the invention in which R' is a COOM group (M represents a hydrogen atom), R an alkyl group containing from 1 to 18 carbon atoms, optionally substituted, a

35 aryl radical, or possibly substituted aralkyl radical, 1111 allyl, methallyl or

4

propargyl, a polyoxyethyl group, a 2-oxoalkyl group R"COCH2- (R" can be a biphen group substituted by an alkyl group containing 1 to 10 carbon atoms or an aralkyl radical or a nitrile function), a COOH group, a perfluorinated aliphatic chain having 4 to 18 carbon atoms or a group

5 polyfluorinated compounds rf(CH2)2NHC(0)CH2- or an RF(CH2)nCR'(C00M)-(CH2)m-2 group (m-2 is equal to 4, 5, 6, 8, 10, 11, 12, 14 and n, R', and M have the same meanings as before), that is to say, compounds with the formula:

RF(CHo)n CO.H

C ( H1)

io r/ nCO2H

are prepared according to the same method as compounds (1). Hydrolysis of the corresponding diesters provides the diacids of formula (III) in high yields. The synthesis of the diesters used as starting compounds has been described [Patent MC No. 2334 (1996)].

^ Sodium or potassium acid salts of compounds (III), that is, compounds with the formula:

RF(CH-,)n CO?Na(K)

V (iv)

r/ VX>2Na(K)

Dispersed in water, these salts spontaneously self-assemble upon simple agitation to form stable vesicular systems. These salts are prepared by reacting a stoichiometric amount of an aqueous solution of sodium hydroxide or potassium hydroxide with the corresponding diacids (the reaction is carried out at room temperature for 3 to 6 days depending on the compound used), or by saponification of the diesters of the corresponding acids. This latter reaction is performed by heating to 70°C in ethanol or methanol.

25

The presence of a stoichiometric amount of sodium or potassium hydroxide for approximately 48 hours results in the transformation of the corresponding diesters into diacid salts with quantitative yields. These salts are obtained as a white powder and exhibit excellent surface activity.

Thermal decarboxylation of diacids (III) constitutes the most common route

30 convenient and most general for obtaining secondary polyfluorocarboxylic acids of formula:

RF(CH2)n

CHCO^H ( V)

R/

35

These compounds are obtained with yields of 80 to 97%

5

The following examples illustrate the present invention without, however, limiting it. Example 1: Preparation of (2-F-alkylethyl)malonic acids.

5.1 ± 3 moles of dimethyl (2-F-alkylethyl)malonate (diethyl) in solution in 10 mL of absolute methanol (ethanol) 2.10⁻² moles of crushed potassium hydroxide are added. The mixture is heated to 90°C overnight while being stirred. After evaporation of the solvent, the mixture is acidified with 30 mL of 36-37% HCl. Then, 30 mL of diethyl oxide is slowly added, and the mixture is stirred at room temperature for 1 hour. Next, 30 mL of water is added, and the mixture is extracted three times with 60 mL of diethyl oxide. The organic phase is washed twice with 40 mL of water. After drying the organic phase and evaporating the solvent, a solid remains, which is purified by recrystallization in chloroform (see Table 1).

Table 1.

RF(CH2)2CH(C02H)2 Yield (%) F °C

c4f9(ch2)2ch(c02h)2

87

106

c6f13(ch2)2ch(c02h)2

88

109

c8f17(ch2)2ch(c02h)2

88

137

Example 2: Preparation of 4-F-alkylbutanoic acids.

5.10~3 moles of alkyl-(2-F-alkylvletyl)-maionic acid are heated in a metal bath at 195°C until gas evolution ceases (approximately 30 minutes). Following the reaction, the product formed is purified by recrystallization in toluene in the presence of a small amount of animal black (see Table 2).

Table 2.

RFCH2CH2CH2C02H Yield (%) F °C

30

c4f9ch2ch2ch2 co2h

90

32

c6f]3ch2ch2ch2 co2h

90

53

c8f17ch2ch2ch2co2h

90

93

35

Example 3: Preparation of alkyl-(2-F-alkylethyl)-malonic acids.

6

The procedure is the same as for 2-F-alkylethyl malonic acids. The compounds obtained are purified by silica column filtration (diethyl oxide eluent) when solid and by distillation when liquid (see Table 3).

Table 5. 3.

RF(CH2)2C(R1)(C02H)2 Yield (%) F°C rf

10

c4f9

ch3(ch2)10-

87

68

C4F9

ch3(ch2)| ,-

89

66

c6fn ch3(ch2)6-

91

111

c6fb ch3(ch2)7-

92

109

c6fi3

ch3(ch2)s-

95

106

c6f13

ch3(ch2)tr

90

104

c6f13

ch3(ch2) l0-

87

100

c6f13

ch3(ch2)j

90

96

c6f13

ch3(ch2)12-

92

94

c6f13

ch3(CH2)i3-

88

90

c6f13

ch3(CH2),s-

87

80

c6f]3

ch3(ch2)16-

87

86

c6f13

ch3(ch2)17-

89

85

c6f,3

ch2 = chch2-

86

51

c6f13

o-q-CHj-

85

147

qfn ch3(ch2)10-

95

108

c8f17

ch3(ch2)ir

87

121

Example 4: Preparation of sodium salts of alkyl-(2-F-alkylethyl)-malonic acids Method A: by neutralization of the corresponding diacids.

2.10⁻² moles of alkyl (2-F-alkylethyl)malonic acid are dissolved in 40 mL of distilled water and 8 mL of a 0.5 M NaOH solution. The mixture is stirred at temperature

/

The mixture is left at room temperature until the starting acid has completely disappeared, i.e., 3 to 6 days (the reaction is monitored by thin-layer chromatography). The mixture is extracted twice with 20 mL of diethyl oxide. The water is evaporated to dryness, and then the residue is dried under vacuum (see Table 4).

5

Method B: by saponification of the diesters of the corresponding acids.

2.10⁻³ moles of alkyl-(2-F-alkylethyl)-malonic acid in solution in 10 mL of absolute methanol (ethanol) are added to 2.10⁻³ moles of crushed sodium hydroxide. The mixture is heated to 75°C with stirring for 48 hours. After evaporation of the solvent, the residue is rinsed with diethyl oxide. The acid salt is obtained as a white powder (see Table 4).

Table 4.

Rf(CH2)2 C(R)(NaCO2)2

Yield (%)

ys (mN/m)

Yi (mN/m)

cmc (mol/L)

15

rf ri

C4fq

CH3(CH2)ir

89

26.0

11.0

7.8 10"3

c6f13

CH3(CH2)6-

90

24.4

18.9

2.9 10"3

c6f13

CH3(CH2)7-

91

19.7

20.3

11.1 10"3

20

c6f13

CH3(CH2)8-

92

17.8

10.8

O O

c6f13

CH3(CH2)9-

95

19.0

13.3

2.3 10"3

c6f13

CH3(CH2)10-

90

18.75

2.4

1.1 10"3

q>f]3

CH3(CH2),

92

18.0

1.4

9.0 10'4

25

c6f13

CH3(CH2)I2-

90

18.7

/

6.5 10"4

c6f13

CH3(CH2)13-

92

21.2

/

6.3 104

c6f13

CH3(CH2)|^-

95

25.4

4.8

5.0 10"4

c6f13

ch3(ch2)16-

92

24.7

3.0

2.45 10"4

30

cfif13

CH3(CH2)17-

92

28.0

6.1

8.2 104

cxf17

CH3(CH2), j-

90

19.5

6.4

8.8 10"4

35

Example 5: Preparation of secondary acids by decarboxylation of α-kyl-(2-F-alkylethyl)-malonic acids.

8

5.10-3 moles of alkyl-(2-F-alkylethylD-malonic acid are heated in a metal bath at 195°C until gas evolution ceases (approximately 30 minutes). At the end of the reaction, the product formed is purified either by distillation under reduced pressure (Kugelrohr apparatus) or on a silica gel column (diethyl oxide - petroleum ether eluent). 5 (See Table 5.)

Table 5.

Rf(CH2)2CH(R,)C02H Yield (%) Eb °C / mmHg F °C

10 RF R1

c4f9

ch3(ch2)1()-

83

120/0.02

/

c5f]3

ch3(ch2)8-

80

140/0.02

/

c6f13

ch3(ch2)9-

86

/

40

qf13

ch3(ch2)10-

87

/

32

c6f13

ch3(ch2)15-

95

/

57

c6f,3

ch2 = chch2-

90

82/0.02

/

c6f13

OOch2-

97

/

69

c8f17

ch3(ch2)]0-

87

/

41

Claims (1)

25 Demands 1/ Polyfluorocarboxylic acids and their salts with general formula: Rf(ch2) y COOM 30 R XR' in which Rf represents a perfluorinated group, linear or branched, containing 4 to 18 carbon atoms, n is an integer equal to 2, 3, or 11, R' can be a hydrogen atom or a COOM group (M can be a hydrogen atom or a sodium or potassium atom), R can be a hydrogen atom, an alkyl group containing 1 to 18 possibly substituted carbon atoms, an aryl radical, or 9 aralkyl possibly substituted, an allyl, methallyl or propargyl radical, a polyoxyethyl group, a 2-oxoalkyl group R"COCH2- (R" can be a biphenyl group substituted by an alkyl group containing 1 to 10 carbon atoms or an aralkyl radical or a nitrile function), a COOH group, a perfluorinated aliphatic 5-chain having 4 to 18 carbon atoms or a polyfluorinated group RF(CH2)2NHC(0)CH2- or an RF(CH2)nCR'(COOM)-(CH2)m-2- group (m-2 is equal to 4,5,6,8,10,11,12,14. n, R' and M have the same meanings as before). As possible substituents on alkyl, aryl or aralkyl radicals, we can mention hydroxy, mercapto, oxo or carboxylic groups. 2/ Polyfluorinated compounds according to claim 1, in which n is equal to 2, 3 or 11. 3/ Polyfluorinated compounds according to claims 1 or 2, wherein R represents a hydrogen atom and R' may be a hydrogen atom or a COOM group 15 (M can be a hydrogen atom or a sodium or potassium atom). 4 / Polyfluorinated compounds according to claims 1 or 2, wherein R is an alkyl group containing from 1 to 18 carbon atoms optionally substituted by at least one hydroxyl group or an acid function, an aryl or aralkyl radical, an allyl, methyl or propargyl radical, a 2-oxoalkyl group R"COCH2- ( R" 20 represents a biphenyl group) and R' represents a hydrogen atom or a COOM group (with M which can be a hydrogen atom or a sodium or potassium atom). 5 / Polyfluorinated compounds according to claims 1 to 4, wherein Rf is radical 25 linear perfluorinated containing 4, 6, 8 or 10 carbon atoms. 6 / Processes for preparing polyfluorocarboxylic acids and their salts according to examples 1 to 5. 7 / These compounds can be used as surfactants in the formation of liposome-type fluorocarbon membrane bilayers, liquid crystals, Langmuir Blodget films or precursors of such agents.