Process for obtaining bis(2,4-di-tert-butylphenyl) halophosphite

Details Process for obtaining bis(2,4-di-tert-butylphenyl) halophosphite Process for obtaining bis(2,4-di-tert-butylphenyl) halophosphite

1992-07-06

1993-05-11

Brust, Joseph Paul

Organic compounds -- part of the class 532-570 series

Organic compounds

Phosphorus esters

C07F 9146

Patent

active

052102602

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

Bis(2,4-di-tert-butylphenyl) halophosphites are useful starting compounds for the preparation of phosphites (U.S. Pat. No. 4,739,000) or phosphonites (German Patent Applications P 38 43 016.9 and P 39 16 502.7) of industrial interest, which are used as stabilizers for synthetic polymers.
It is known from U.S. Pat. No. 4,739,000 that bis(2,4-di-tert-butylphenyl) chlorophosphite can be prepared by the reaction of phosphorus trichloride with twice the molar amounts of 2,4-di-tert-butylphenol and triethylamine to neutralize the hydrochloric acid liberated. In this process, the use of considerable amounts of a suitable aprotic solvent such as toluene is naturally unavoidable. The final product, according to the information there, has a purity of 85%.
For intended industrial production, such a procedure is particularly unfavorable, because not only do considerable amounts of solvents have to be worked up again, but the triethylammonium chloride formed also has to be neutralized with an alkali metal hydroxide solution in order to recover the base used as auxiliary. A forced yield of 2 equivalents of salt cannot be avoided in this case.
The preparation of diaryl halophosphites by direct reaction of phenols or naphthols and phosphorus trihalides in the molar ratio 2:1 is unsatisfactory because of disproportionation reactions and secondary reactions which cannot be controlled (Houben-Weyl, "Methoden der Organischen Chemie", [Methods of Organic Chemistry], E1, p. 373, 1982, see also Zh. Obsch. Khim. 37, 464-468, 1967).
The object of the present invention was therefore to obtain bis(2,4-di-tert-butylphenyl) halophosphites in a simple manner.
To achieve this object, the invention proposes a process for obtaining bis(2,4-di-tert-butylphenyl) halophosphites of the formula ##STR1## in which X is a halogen having an atomic weight of at least 35, preferably chlorine or bromine, in particular chlorine, which is characterized in that a 2,4-di-tert-butylphenyl dihalophosphite of the formula (II) ##STR2## is heated to 130.degree. to 280.degree. C. in the presence of a catalytically active compound containing nitrogen and/or phosphorus and the phosphorus trihalide formed in this way by disproportionation is removed from the reaction mixture.
According to a particularly preferred embodiment, a procedure is used in which, by addition of a less than stoichiometric amount of 2,4-di-tert-butylphenol, additional bis(2,4-di-tert-butylphenyl) halophosphite is produced.
The process according to the invention is not affected by the disadvantages which are associated with the known process.
The reaction, which can be carried out per se in any conceivable manner, is preferably carried out without the use of a solvent, although it can also be carried out with a solvent which is used as an azeotropic entraining agent. Advantageously, the dihalophosphorous acid monoester (II) is reacted with up to 0.9, preferably 0.3 to 0.6, equivalents of 2,4-di-tert-butylphenol and the mixture is heated in the presence of the catalyst to 130.degree.-280.degree. C. In this process, it is particularly advantageous, after completion of the evolution of hydrogen halide, to additionally carry out a sufficiently long afterreaction in the abovementioned temperature range, the content of (II) being reduced in favor of the product (I) by disproportionation processes without undesired by-products being formed to a noticeable extent. To isolate the desired product (I), residual starting material (II) is then distilled off under reduced pressure. In this process, the catalyst is usually also carried off.
Preferably, the reaction is carried out at temperatures from 160.degree. to 230.degree. C. The reaction is in general complete, depending on the temperature used, after 2 to 10 hours. The reaction is usually carried out in the course of 2 to 5 hours.
Generally, the reaction is carried out under normal pressure; however, it may sometimes be advantageous to favor the removal of the hydrogen chloride by the use of reduced pressure.
As the reactants are sensiti

REFERENCES:
patent: 4032602 (1977-06-01), Mazour et al.
patent: 4079103 (1978-03-01), Mazour
patent: 4118435 (1978-10-01), Kleinstuck et al.
patent: 4739000 (1988-04-01), Burton

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