DE2940620A1 - Tri:aryl phosphite prodn. from phosphorus tri:halide - and aromatic hydroxy cpd. in presence of nitrogen heterocycle as catalyst - Google Patents

Abstract

Prodn. of triarylphosphites P(OR)3 (I) (R is aryl opt. substd. by one or more opt. branched alkyl or by cycloalkyl, aryl or aralkyl) comprises reacting a P trihalide with ROH in the presence of 0.005-10 mole % (on ROH) of an aromatic N-contg. heterocycle as catalyst. Reaction is at 30-250 deg.C, opt. in presence of a solvent. The catalyst can be used as a salt derived from an inorganic acid or an organic sulphonic, phosphonic or carboxylic acid. (I) are (co)stabilisers for protecting polymers, e.g. polyolefins, against light- and heat-induced deterioration.

Description

Process for the preparation of triaryl phosphites

It is known that the corresponding phenols and triaryl phosphites PCl3 to represent (Houben-Weyl vol. 12/2, p. 59 r). It is still known this Accelerate conversion through catalysts. As such, t. 8. in the DE-AS 2,135,238 inorganic bases, guanidines, and amines have been proposed. In the USSR patent specification 48 8821 are inter alia. Alkali and alkaline earth halides, Lewis acids, phosphonium compounds as well as N-containing aromatic heterocycles. The latter are given in ä q u i -m o 1 a r e r amount, based on the hydrogen chloride formed, used, as from further steps are to be derived [e.g. 8. from Houben-Weyl 12/2, p. 60 and the original literature T. Milobendzki and K. Szulgin, Chem. Polski, cited there 15, 66 (1917); Chem. Ber. 1918 I, p. 914; Kosolapoff "Drganophosphorous Compounds", John Wiley & Sons Inc. 1956, New York, p. 184; DE-OS 2 204 701].

In the European patent application 0 000 757 it is finally stated that that the catalytic activity of N-Heterocy: len in the implementation of phosphorus trichloride with sterically hindered phenols is only slight. Other substances, such as B. some amines and phosphonium compounds are comparatively ineffective, as can be seen from this literature passage, page 14, table 1.

There is thus the need to use large amounts of the N-heterocycles to have to use what is to be regarded as a serious disadvantage. So it is with this procedure requires the resulting hydrochloride of the nitrogen base to separate from the reaction mixture, and to regenerate the free base with alkali and then to clean, which inevitably produces alkali chloride, which can be recycled will, d. H. the environment is a burden.

In addition, it is time-consuming and expensive to consume.

The reaction of halophenols with PC13 is due to the presence catalyzed by N-Baaen such as quinoline [Z. Anorg. and general

Chem. 372 p. 252 (197û)], however, allow the strongly acidic Phenols pre-rounded ratios do not allow any conclusions to be drawn about the behavior of the far less resistant alkylphenols.

It has now surprisingly been found that it is not necessary is, the N-containing heteroaromatics in one of the released hydrogen halide use equivalent amount in order to obtain good yields, but rather that Even with traces of these substances, the reaction takes place under extremely mild conditions carried out in short reaction times and with very high yields can be.

The present invention thus relates to an improved method for the preparation of triaryl phosphites of the formula (RO) 3P, in which R is an aryl radical stands by one or more linear or branched alkyl radicals or through Cycloalkyl, aryl or aralkyl groups may be substituted by reacting Phosphorus trihalides with hydroxyaromatics of the formula ROH in the presence of an aromatic one Nitrogen heterocycle as a catalyst and optionally a solvent, which is characterized in that the catalyst in an amount of 0.005 up to 10 mol%, based on the hydroxysryl aromatic compounds, is present and the reaction is carried out carried out at temperatures between 30 and 250 s.

It was surprising and not to be expected that the sromatic nitrogen-containing Heterocycles, which hitherto in accordance with the prior art in a molar excess or must be used in equimolar amounts in order to achieve satisfactory sales to come, are effective even in these low concentrations and even increase Yields lead to even the best of those in the cited European patent used catalysts, because against the use of N-heterocyclic aromatics in low concentration there was a serious prejudice due to the statement made in the European patent specification on page 17 in table 3, after which with these compounds under the process conditions mentioned there (reaction temperature 22 to 26) "only a slight increase in the rate of reaction during the implementation of phosphorus trichloride can be achieved with sterically hindered phenols. "The Compared to other catalyst substances disproportionate improvement in Catalyst activity through Increase in temperature in the case of the invention The way of working could therefore not be foreseen.

Among aromatic N-heterocycles which according to the invention are used as catalysts are used are pyrrole, pyrazole, imidazole, the triazoles, tetrazole, pyridazine, Pyrimidine, pyrazine, the triazines, indole, quinoline, isoquinoline, carbazole, acridine, Phenanthridine, indazole, benzimidazole, cinnoline, quinazoline, quinoxaline, phenazine, Phenazone, phenanthroline, purine, benzoxazole, phenoxazine, carboxylic acids derived therefrom and esters as well as alkyl or aryl derivatives, preferably alkyl and aryl derivatives des pyridine and pyridine carboxylic acids and their esters and especially pyridine to call yourself. The catalysts are used in amounts from 0.005 to 10, preferably 0.05 to 3 and in particular 0.1 to 1 inch% are used. You either use the free bases, which are formed under the action of the hydrogen halides formed during the reaction convert into the hydrohalides, but it can also be the salts of the N-heterocyclic Bases with other acids such as B. sulfuric acid, phosphorus and phosphorus Acid, the aliphatic or aromatic sulfonic acids, such as. S. of toluenesulfonic acid and the aliphatic or aromatic carboxylic acids such as the acetates or benzostes insert.

Hydroxyaromatic compounds suitable for reaction with phosphorus trihalide of the formula ROH are naphthols and phenols, which are also in any position of the aryl can be substituted. Preferably no more than three substituents are present.

In the case of the substituted phenols, the substituents are preferably located in the 2-, 4- and / or 5-position. The 2- and 2,4-positions are particularly preferred. If there are substituents in position 2 and 6, only one may one of them with a strong space envelope, e.g. B. a tertiary alkyl group, be.

Possible substituents include: linear or branched ones Alkyl radicals with 1 to 18, preferably 1 to 12 carbon atoms, such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, pentyl, hexyl, heptyl, n-octyl, tert-ûctyl, n-nonyl, iso-nonyl, decyl, n-dodecyl, tetradecyl, hexadecyl, octadecyl and eicosyl. The alkyl radical can also be substituted or interrupted by cycloalkyl, ie. it is Z. B. a Cyclohexylmsthyl or Methylcyclohexylethylrest.

Further substituents are cycloalkyl, preferably with a 5- or 6-membered ring Carbon atoms, such as cyclopentyl, cyclohexyl, methylcyclohexyl, ethylcyclohexyl, Octylcyclohexyl, cyclooctyl, and also aryl radicals, preferably phenyl, and aralkyl, in particular benzyl or α- or ß-phenylethyl. The aryl group can through this Alkyl groups with preferably 1 to 8 carbon atoms can be substituted. examples are Methylphenyl, ethylphenyl, methylbenzyl.

Finally, the aryl can also be substituted by oxyalkyl or oxyaryl be. Examples are oxymethyl, oxyethyl or oxyphenyl.

Examples of suitable hydroxysromates are specifically phenol, α- or ß-naphthol, methylnaphthol, 2- or 4-methylphenol, 2- or 4-ethylphenol, 2- or 4-propyl and isopropylphenol, 2- or 4-n-butyl, i-butyl and t-butylphenol, Pentyl-, hexyl-, heptyl-, n-octyl-, tert-octyl-, nonyl-, decyl-, dodecyl-, octedecylphenol, Cyclohexyl-, phenyl- or benzylphenol, 2,4- or 2,6-dimethyl-, dipropyl-, di-isopropyl-, Di-n-butyl-, di-isobutylphenol, 2,4-di-tert-butylphenol, 2-methyl-4-sthylphenol, 2-methyl-4-tert-butylphenol, 2-tert-uutyl-4-ethylphenol, 2-methyl-4-n-octylphenol, 2,4,6-tri1ethylphsnol, 2,4,6-triisopropylphenol, 2,6-dimethyl-4-octylphenol, 2-methyl-4-benzylphenol, 3-tert-butyl-4-hydroxyenieol, 4-phenexyphenyl, phenol and 2-tert-9utyl-4-phenoxyphonyl-phonol. Phenols with tert-butyl in the 2-position are preferred, inebeesidere 2-tert-sutylphenol 2,4-di-tert-butylphenol, 2-tert-butyl-4-methylphenol and 2-tert-butyl-5-methylphenol.

Among the phosphorus III halides that are used as starting compounds phosphorus trichloride is used to carry out the process according to the invention particularly preferred. There are preferably stoichiometric amounts of the reactants used.

But sometimes it can also be an advantage if you have a low Excess, e.g. B. 10 wt .-%, of hydroxysryl compound or phosphorus trihalide used.

The process is carried out at temperatures from 30 to 250, preferably 40 carried out up to 180 and inabesordere 40 to 150 s.

The components can be used either without a solvent or in the presence of such are made to react with one another.

The use of a solvent is particularly recommended when if the hydroxyaromatic presented is a solid substance, or if the end product is a product that crystallizes well and has a high melting point. Suitable solvents are z. B.

Ethers such as dialkyl ether, tetrahydrofuran or dioxane, alipetic or aromatic hydrocarbons and heptane, octane, toluene, xylene, mesitylene, or Halogenated hydrocarbons such as carbon tetrachloride, dichloroethane, trichlorethylene usP.

In carrying out the process, the general procedure is as follows: that the hydroxyaryl compound and the catalyst, optionally in a solvent dissolved, is presented and one at 30 to about 50 T phosphorus trihalide with stirring drops in the loud for 20 to 30 minutes, with a stormy development of helogen gas begins. The mixture is then stirred for a further hour at the dropping temperature and then the temperature of the batch slowly, in the course of about an hour, to about 120 raised up to 150 times. You can avoid excessive foaming by stirring faster and slowed heating speed.

After the final temperature has been reached, the mixture is stirred until it subsides the Evolution of hydrogen halide about a further hour and finally supports the elimination of the last traces of hydrogen halide by 20 minutes to one hour Apply a slight vacuum of approx. 1 to approx. 500 mbar.

That in general already temperatures to complete the reaction of 130 s are sufficient, in particular when the reaction takes place at a slightly reduced rate Printing is carried out to the end, is to be regarded as a particular advantage, since among these Conditions both the obtained reaction products and those still present Starting materials are not exposed to excessive thermal stress. This will on the one hand the yield increases and, on the other hand, the formation of decomposition products is avoided, so that the reaction mother liquor is often used in the subsequent approach without costly cleaning operations can be submitted again. This, too, is an advantage that should not be underestimated of the procedure.

The triaryl phosphites prepared according to the invention are as already mentioned as stabilizers or as co-stabilizers together with known antioxidants and optionally light stabilizers to stabilize the degradation of heat and light underlying polymers such as. B. polyolefins are suitable.

The following examples serve to further illustrate the invention.

Example 1 In a 500 ml four-necked flask, 206 g (1 mol) of 2,4-di-tert-butylphenol, Submitted 33 g of xylene as solvent and 0.5 g of pyridine (0.0063 mol). During 45.6 g (29 ml = 1/3 mol) of phosphorus trichloride are added dropwise over a period of 50 seconds over a period of 20 minutes, then stirs for an hour at 50 s and heats over the course of a further hour slowly to 130 T. At this temperature, the mixture is stirred for a further hour, whereupon one more time to remove the hydrogen chloride still present in the reaction mixture one hour under reduced pressure (at 10 to 200 mbar) stirs. It is then cooled to about 90 times and mixed with 200 ml of isopropanol. That I The product which separates out is washed with isopropanol and dried. You get 194 g (90% of theory

Yield) of a colorless and odorless phoephite with a melting point from 186 t.

COMPARISON EXAMPLE The procedure given in Example 1 was followed, but as a catalyst in accordance with the information in European PS O 000 757, example 4, 0.8 g of dimethylformamide were used. The yield of phosphite was only 81% d. Th.

Example 2 As in Example 1, 2,4-di-tert-butylphenol was used in the presence implemented by 1 g of picoline. The desired phosphite was found in 92.1 yield % d. Th. Received.

Examples 3 and 4 Analogously to Example 1, 2-tert-butyl-4-methylphenol was used the tris (2-tart.-butyl-4-methylphenyl) phosphite with a melting point of 115 s with a yield of 82.7% and from 2-tert-butyl-5-methyl-phenylphenol, tris- (2-tert-butyl-5-methyl-phenyl) -phoephite obtained with a melting point of 100 s with a yield of 81.5%.

COMPARISON EXAMPLE Analogously to Example 1, 1 mol of 2-tert-butyl-4-methylphenol was used in the presence of 0.8 g of dimethylformamide tris (2-tert-butyl-4-methylphenyl) phosphite manufactured. The product had a melting point of 106 to 109 parts. The yield was 73.2% d. Th.

Claims (2)

Claims 1. Process for the preparation of triaryl phosphites of the formula (RO) 3P, in which R stands for an aryl nucleus which is replaced by one or more Linear or branched alkyl groups or by cycloalkyl, aryl or aralkyl groups can be substituted by reacting phosphorus trihalides with hydroxyaromatics of the formula ROH in the presence of an aromatic nitrogen heterocycle as a catalyst and optionally a solvent, characterized by a. that the catalyst present in an amount of 0.005 to 10 mol%, based on the hydroxyaromatic and the reaction is carried out at temperatures between 30 and 250 s. 2. The method according to claim 1, characterized. that the aromatic Nitrogen heterocycle in the form of a salt with a cinal acid or an organic one Sulfonic, phosphonic or carboxylic acid is used.