KR20010101674A - Process for the preparation of 4,4'-bis(2-benzoxazolyl)stilbenes - Google Patents

Abstract

The present specification includes a first step of reacting a compound of Formula 2 with an aminophenol compound of Formula 3 to obtain a compound of Formula 5 and a second step of reacting a compound of Formula 5 with a strong base to obtain a compound of Formula 1 Two-step process (a) or

Reacting a compound of formula 2 with an amino compound of formula 3 to obtain an intermediate compound of formula 4, a second step of closing the compound to yield a compound of formula 5 and a compound of formula 5 with a strong base A low-cost, simple process for preparing a 4,4'-bis (2-benzoxazolyl) stilbene compound of Formula 1, comprising a three step process (b) comprising a third step of obtaining a compound of Formula 1 This is described.

Formula 1

Formula 2

Formula 3

Formula 4

Formula 5

In Formula 1, 3, 4 and 5 above,

R ₁ is hydrogen, C ₁ -C ₈ alkyl, —CO ₂ R ₂ , —NHCOR ₂ or —OR ₂ ,

R ₂ is C ₁ -C ₄ alkyl.

Stilbene compounds prepared according to the invention are used in polymeric materials, in particular polyethylene terephthalate (PET).

Description

Process for the preparation of 4,4'-bis (2-benzoxazolyl) stilbenes}

The present invention relates to a process for the preparation of 4,4'-bis (2-benzoxazolyl) stilbene and to the use of these compounds as fluorescent brighteners in polymeric materials.

The novel process for the preparation of 4,4'-bis (2-benzoxazolyl) stilbene of formula 1 may be carried out in a two step process (a).

In a two step process (a), the compound of formula 2 is reacted with an aminophenyl compound of formula 3 to give a compound of formula 5. The compound of formula 5 is then reacted with a strong base to give a compound of formula 1.

In a three step process (b), the compound of formula 2 is reacted with an amino compound of formula 3 to obtain an intermediate compound of formula 4. Subsequently, the compound of formula 4 is ring-closed to obtain a compound of formula 5. The compound of formula 5 is then reacted with a strong base to give a compound of formula 1.

In Formula 1, 3, 4 and 5 above,

R ₁ is hydrogen, C ₁ -C ₈ alkyl, —CO ₂ R ₂ , —NHCOR ₂ or —OR ₂ ,

R ₂ is C ₁ -C ₄ alkyl.

C ₁ -C ₄ alkyl and C ₁ -C ₈ alkyl are linear or branched alkyl radicals such as methyl, ethyl, n-propyl, isopropyl, n-butyl, secondary-butyl, tert-butyl, amyl Isoamyl, tert-amyl, hexyl, heptyl, octyl or isooctyl.

The novel method of preparation is preferably associated with a compound of formula 1 wherein R ₁ is hydrogen or C ₁ -C ₅ alkyl.

2-aminophenol (compound 3) to 2- [4- (chloromethyl) phenyl] benzoxazole (compound 5) unsubstituted or substituted with 4- (chloromethyl) benzoyl chloride (compound 2) The reaction in step (a) of step (a) can be carried out by adding different condensing agents in different solvents.

Suitable solvents are organic solvents which are inert under the given reaction conditions. Suitable solvents include, for example, aromatic and aliphatic hydrocarbons such as nitrobenzene, chlorobenzene, o-dichlorobenzene, 1,2,3-trimethylbenzene, toluene, xylene, xylene isomer mixtures, tetrahydronaphthalene, α-chloronaphthalene, acetylene tetrachloride, ethylene dichloride or polyphosphoric acid.

Particular preference is given to the use of trimethylbenzene, toluene, xylene, xylene isomer mixtures, polyphosphoric acid or N-methyl-2-pyrrolidone.

Suitable condensing agents are preferably boric acid, polyphosphoric acid, sulfuric acid or toluenesulfonic acid.

The reaction can be carried out within a wide temperature range of 80 to 200 ° C, preferably 100 to 150 ° C. The reaction is preferably carried out at the boiling point of each solvent used. The reaction is preferably continued until HCl-generation ends. After cooling the reaction mixture to room temperature, the condensing agent is added and the mixture is refluxed until the water is completely removed.

The compound of formula 5 is worked up by conventional methods of distilling off the solvent and suspending the residue in a suitable anti-settling agent such as sodium hydrogen carbonate solution for an extended period of time, usually from 6 to 24 hours or more. The residue is then collected by filtration, washed with water and dried under vacuum at elevated temperature.

2-aminophenol (compound of Formula 3) to N- (2-hydroxyphenyl) -4- (chloromethyl) benzamide (compound of Formula 4; unsubstituted or substituted with 4- (chloromethyl) benzoyl chloride; process The reaction of step 1) of (b) is preferably carried out in N, N-dimethylacetamide. The product is precipitated by adding water. Subsequently, the ring closure reaction for obtaining the compound of formula 5 (second step of step (b)) is carried out in one of the inert organic solvents and condensing agents described above, preferably in p-xylene and p-toluenesulfonic acid. By removing water.

The preparation of the stilbene final product of formula 1 is preferably carried out in an aprotic polar anhydrous solvent, preferably NMP, DMA, DMF or DMSO. Dimethylformamide (DMF) is particularly very preferred. Dimerization is carried out by addition of sodium hydroxide, potassium hydroxide or alcoholates under alkaline conditions, and is usually added in at least 2 to 4 times the chloromethyl compound. Alkali hydroxides are usually added in powder form to facilitate the reaction. Typically the reaction is carried out at room temperature until the total amount of organically bound chlorine has reacted. It may be advantageous to add the corresponding compound, for example Na ₂ O, MgO, CaO or NaH, to bind the reaction water in the neutralization step.

The reaction typically takes 6 to 12 hours. After the reaction is finished, the reaction mixture is acidified with an acid, for example anhydrous organic acid, for example glacial acetic acid, or preferably with an HCl / H ₂ O mixture. For workup, the reaction mixture is heated until boiling to dissolve the byproducts, followed by thermal suction filtration. The product is then washed with solvent and water until no more chlorine ions are found in the wash water. After drying, a stilbene compound is obtained that is analyzed to be pure.

By the process of the present invention, the 4,4'-bis (2-benzoxazolyl) stilbene compound can be produced at low cost and high yield.

Compounds of formula 1 are well suited for use as fluorescent brighteners for organic polymeric materials. Accordingly, the present invention also relates to a method for fluorescence brightening of an organic polymer, including mixing at least one compound of formula (1) into these materials.

Suitable polymers include in particular from dicarboxylic acids and dialcohols and / or from hydroxycarboxylic acids or the corresponding lactones, for example polyethylene terephthalate (PET), polybutylene terephthalate, poly-1,4-dimethylolcyclohexane tere Phthalates, polyesters derived from polyhydroxybenzoates and block-polyether-esters derived from polyethers containing hydroxy end groups, and polyesters modified with polycarbonates or MBS.

Very particular preference is given to using compounds of the formula (1) in polyethylene terephthalate.

The amount of fluorescent brightener of formula 1 added depends on the respective substrate to be used and the expected end use thereof. A sufficient amount is usually 0.01 to 5% by weight, preferably 0.01 to 3% by weight, based on the polymer to be whitened. In particular suitable polymers according to the invention comprise from 0.01 to 5% by weight, preferably from 0.01 to 3% by weight of at least one compound of the formula (1).

In some cases, it may be advantageous to use two or more compounds of formula (I). Also other additives such as antioxidants, UV absorbers and light stabilizers, metal deactivators, peroxide-extinguishing compounds, fillers and reinforcing agents and other additives such as plasticizers, lubricants, emulsifiers, colorants, flame retardants, electrostatics It is possible to use one or more inhibitors and blowing agents.

The compound of formula 1 and possibly further additives are added to the polymer in the spinning mass, ie before or during the molding of the polymer, for example in powder form or in the melt or solution of the polymer. do.

Polymers stabilized in this way can be used in a very wide range of forms, for example fibers, foils, filaments, profiles, hollow articles or sheets.

The following non-limiting examples illustrate the invention in more detail.

Post Treatment Examples

Example 1:

Scheme:

47.2 g (0.25 mol) of 4- (chloromethyl) benzoyl chloride is cooled to 0-5 ° C. and contains 41.3 g (0.25 mol) of 2-amino-4-t-butyl-phenol and 200 ml of N, N-dimethylacetamide To the solution was added dropwise over 1 hour. The resulting yellow solution is raised to 20-25 ° C. and stirred for 2.5 hours. 150 ml of water is then added dropwise at 20-25 ° C. to give a tan precipitate. After stirring for 1 hour and filtration, the precipitate is washed with 2 liters of water and dried at 80 ° C. under vacuum.

Yield: 77.8 g (= 97.9%)

Solids Content: 99.29%

^One H-NMR Spectrum (300MHz; CDCl ₃ )

The ratio is 9: 2: 1: 2: 2: 2: 1: 1

delta = 1.3 (s); 4.6 (s); 7.0 (d); 7.2 (m); 7.5 (d); 7.9 (d); 8.2 (s); 8.4 (s)

Example 2:

Scheme:

In a 350 ml sulfonated flask, 63.4 g (0.2 mol) of compound of formula 101 are suspended in 220 ml of xylene and then 3.0 g (0.016 mol) of toluene-4-sulfonic acid monohydrate are added. A beige suspension is obtained and refluxed until all the water produced is distilled off by azeotropy. After the reaction is complete, the reaction mixture is cooled to 25 ° C. and the precipitated solid is filtered off, followed by first washing with xylene and ethanol and then with water.

The product is dried at 80 ° C. under vacuum.

Yield: 26.5 g (44.2%)

^One H-NMR spectrum (300 MHz; [D ₆ ] DMSO)

The ratio is 9: 2: 2: 2: 1: 2

delta = 1.4 (s); 4.9 (s); 7.5 (d); 7.7 (m); 7.8 (s); 8.2 (d)

Example 3:

Scheme:

A 350 ml sulfonated flask was charged with 80 ml of DMF, followed by addition of 8.9 g (0.03 mol) of compound of formula 102 under nitrogen. At 15-20 ° C., 4.2 g (0.075 mol) of potassium hydroxide are added. If the reaction mixture turns slightly dark, it is stirred for 1 hour at 15 to 20 ° C and then heated to 35 to 40 ° C for 1 hour. The reaction mixture is adjusted to pH 3 with 20 ml of HCl / water (1: 1 mixture). The yellow precipitate obtained is filtered off, washed with methanol and water and dried under vacuum at 80 ° C.

Yield: 6.4 g (81.0%)

^One H-NMR Spectrum (300MHz; CDCl ₃ )

The ratio is 18: 2: 2: 2: 2: 2: 4

delta = 1.4 (s); 7.3 (s); 7.5 (d); 7.6 (d); 7.7 (d); 7.8 (d); 8.2 (d)

Example 4:

Scheme:

9.45 g (0.05 mol) of 4- (chloromethyl) benzoyl chloride was added dropwise over 1 hour into a 100 ml sulfonated flask, cooled to 0 ° C., 6.15 g (0.05 mol) of 2-amino-p-cresol and dimethylacet A solution containing 50 ml of amide is generated. The resulting dark solution is raised to 20-25 ° C. and then stirred at 25 ° C. for 1.5 hours. The solution is then diluted with 25 ml of water and left overnight. After filtration, the product is washed with water and dried at 60 ° C. under vacuum.

Yield: 12.1 g (= 87.87%)

^One H-NMR spectrum (300 MHz; [D ₆ ] DMSO)

The ratio is 3: 2: 2: 1: 2: 2: 1: 1

delta = 2.3 (s); 4.8 (s); 6.8 (m); 7.5 (s); 7.6 (d); 8.0 (d); 9.4 (s); 9.5 (s)

This structure corresponds to the NMR spectrum.

Example 5:

Scheme:

A 750 ml sulfonic acid flask was charged with 250 ml of xylene and 92.25 g (0.75 mol) of 2-amino-p-cresol. 144.58 g (0.765 mol) of 4- (chloromethyl) -benzoyl chloride is then added dropwise over 1 hour. The mixture is heated to 90 ° C. to generate some HCl. When the mixture is heated to 110 ° C., the evolution of HCl becomes even more active and stops after about 2 hours.

1 g (5.3 mmol) of toluene-4-sulfonic acid monohydrate is added to the reaction mixture and the mixture is boiled under reflux (138-142 ° C.). Water is distilled off azeotropically at the same temperature. The mixture is cooled and then further 1 g of toluene-4-sulfonic acid monohydrate is added and the reflux is continued. 10 ml of water are further distilled. The mixture is cooled to 25 ° C., the precipitate is filtered off and the filtered product is again dissolved in ethanol. The product is purified by heat filtration and cooled overnight. The product is then filtered, washed with ethanol and dried under vacuum at 60 ° C.

Yield: 38.0 g (19.67%)

^One H-NMR Spectrum (300MHz; CDCl ₃ )

2: 1: 1: 3: 2 ratio

delta = 4.7 (s); 7.1 (d); 7.5 (d); 7.7 (m); 8.2 (d)

This structure corresponds to NMR analysis.

Example 6:

Scheme:

A 350 ml sulfonated flask was charged with 10.3 g (0.04 mol) of compound of formula 105 and 80 ml of DMF under a nitrogen atmosphere. 11.2 g (0.1 mol) of potassium tertiary butyrate are added in increasing amounts over 15 hours at 15-20 ° C. The resulting dark brown suspension is stirred at 25 ° C. for 2 hours. 20 ml of HCl / water (1: 1 mixture) is added dropwise to the suspension to give a tan precipitate. After filtration, the product is washed with acetone and finally with water and then dried at 70 ° C. under vacuum.

Yield: 3.8 g (42.74%)

This structure corresponds to NMR analysis.

Example 7:

Scheme:

A 350 ml sulfonated flask was charged with 80 ml of DMF. 4.45 g (0.015 mol) of the compound of formula 102 and 3.86 g (0.015 mol) of the compound of formula 105 are charged into a sulfonated flask under nitrogen and dissolved at 40 ° C. The solution is cooled to 15-20 ° C. and 8.4 g (0.075 mol) of potassium tertiary butyrate are charged. If the solution turns dark, stir at 15-20 ° C. for 1 hour. Adjust the pH to 3 with 15 ml of water / HCl (1: 1 mixture). The yellow precipitate obtained is filtered off, washed with methanol and finally with water. The product is then dried under vacuum at 80 ° C.

Yield: 6.5 g

^One H-NMR Spectrum (300MHz; CDCl ₃ )

The ratio is 9: 3: 2: 2: 2: 4: 2: 4

delta = 1.4 (s); 2.5 (s); 7.2 (d); 7.3 (s); 7.5 (m); 7.8 (d); 7.9 (s); 8.2 (d)

Claims (16)

A two-step process comprising reacting a compound of formula 2 with an aminophenol compound of formula 3 to obtain a compound of formula 5 and a second step of reacting a compound of formula 5 with a strong base to obtain a compound of formula 1 (a) or Reacting a compound of formula 2 with an amino compound of formula 3 to obtain an intermediate compound of formula 4, a second step of closing the compound to yield a compound of formula 5 and a compound of formula 5 with a strong base Method of producing a compound of formula 1 comprising a three-step process (b) comprising a third step to obtain a compound of formula (1). Formula 1 Formula 2 Formula 3 Formula 4 Formula 5 In Formula 1, 3, 4 and 5 above, R ₁ is hydrogen, C ₁ -C ₈ alkyl, —CO ₂ R ₂ , —NHCOR ₂ or —OR ₂ , R ₂ is C ₁ -C ₄ alkyl. The process of claim 1, wherein R ₁ is hydrogen or C ₁ -C ₅ alkyl. The process according to claim 1 or 2, wherein the first step of process (a) and the second step of process (b) are carried out in an inert organic solvent. The process of claim 3 wherein the reaction is carried out in trimethylbenzene, toluene, xylene, xylene isomer mixture, polyphosphoric acid or N-methyl-2-pyrrolidone. The process of claim 1, wherein the first step of process (a) is carried out in the presence of a condensing agent. The process of claim 5 wherein the reaction is carried out in the presence of boric acid, polyphosphoric acid, sulfuric acid or toluenesulfonic acid. The process according to claim 1, wherein the first step of process (a) is carried out in a temperature range of 80 to 200 ° C. 8. The process of claim 7 comprising performing the reaction at the boiling point of the solvent used. The process of claim 1, wherein the first step of step (b) is carried out in the presence of N, N-dimethylacetamide. 10. The process according to any one of the preceding claims, comprising performing the second step of process (a) and the third step of process (b) in an aprotic polar anhydrous solvent. The method of claim 10, comprising performing the reaction in NMP, DMA, DMF or DMSO. A method of fluorescence brightening an organic polymer, comprising mixing at least one compound of Formula 1 into a polymeric material. Use of a 4,4'-bis (2-benzoxazolyl) stilbene compound prepared according to any one of claims 1 to 11 as a fluorescent brightener for organic polymers. 14. Use according to claim 13, comprising using 4,4'-bis (2-benzoxazolyl) stilbene compound in polyethylene terephthalate (PET). 15. Use according to claim 13 or 14, comprising using the 4,4'-bis (2-benzoxazolyl) stilbene compound in an amount of 0.01 to 5% by weight, based on the polymeric material used. . Use according to any of claims 13 to 15, comprising adding a 4,4'-bis (2-benzoxazolyl) stilbene compound before or during the molding of the polymer.