DD246544A1 - UNIVERSAL PROCEDURE FOR THE PRESENTATION OF TRIALKYL PHOSPHITES - Google Patents

Abstract

The invention relates to a one-step process for the preparation of trialkyl phosphites directly from elemental phosphorus. The yield of trialkyl phosphite can be increased in the reaction of elemental phosphorus with a polyhalogenated hydrocarbon, alcohol and alkoxide in an inert aprotic solvent by adding a catalytic amount of a radical scavenger to the reaction mixture.

Description

Field of application of the invention

The invention relates to a process for the preparation of trialkyl phosphites of all kinds. Formula (RO) ₃ P where R = alkyl groups. , '

Such compounds are valuable intermediates in the chemical industry. They are indispensable for the synthesis of highly refined products, such as flame retardants, lubricants, plasticizers, herbicides, insecticides, fungicides, acaricides, nematocides, plant growth regulators or drugs.

Characteristic of the known technical solutions

Compounds of the above formula have been shown so far:

1. by reaction of P (III) halides with alcohols

2. by reaction of elemental phosphorus with a polyhalogenated hydrocarbon, alcohol and alcoholate (H.-A. Lehmann et al., WP 127.188 DD)

3. by reaction of phosphane PH ₃ with a polyhalogenated hydrocarbon, alcohol and alcoholate (H.-A. Lehmann, et al., WP 128.718 DD)

4. by reaction of elemental phosphorus or PH ₃ with a polyhalogenated hydrocarbon and an aliphatic - alcohol or phenol or substituted phenol in the presence of an organic base in a polar aprotic solvent

(WP 231.074)

The disadvantages of the above methods are mainly in the following

Method 1: This is a multi-stage process, consuming expensive halogen and produces strong corrosive or polluting Halogenwassestoff.

Methods 2 and 3: Only when using protic solvents are high yields of (RO) ₃ P achieved. However, the isolation of the trialkyl phosphites from these solutions causes very great difficulties and is associated with high yield losses. The immediate further processing of the synthesized trialkyl phosphites into PN or PNP compounds, for example according to WP 147.244 DD or WP 234.366 / 7.DD, can not take place in protic solvents. If aprotic solvents are used for the synthesis of the trialkyl phosphites, losses in yield occur, in particular in favor of forming PC compounds, for example dialkyl dialkoxymethanephosphonates or tetraalkyl methanediphosphonic acid esters.

Method 4: The use of excess amounts of organic bases necessitates a separate work-up process for the recycling of the excess bases used and for the recycling of the same resulting ammonium salts.

Object of the invention

The aim of the invention is to modify the economically favorable di-rect synthesis of trialkyl phosphites from P _{4 in} such a way that high yields of (PO) ₃ P are achieved even when using aprotic solvents.

Explanation of the essence of the invention

It has been found that in the synthesis of trialkyl phosphites from Ρ, ι / MOR / ROH / polyhalohydrocarbon, where M = metal or NH ₄ ⁺ and R = alkyl, according to WP 127.188 DD in an inert apolar or dipolar aprotic solvent by addition of small amounts of a radical scavenging substance, such as aromatic hydroxy compounds, the yield of trialkyl phosphite is significantly increased. At the same time, in particular, the proportion of PC compounds formed, such as Dialkoxymethanphosphonsäuredialkylester and Methandiphosphonsäuretetraalkylester. The yield increase by the addition of a radical scavenger is on average 10-20% and is independent of the solvent used. Particularly suitable radical scavengers are aromatic poly- or monohydroxy compounds, such as, for example, 2,6-di-tert-butyl-p-cresol or hydroquinone. Should it be necessary to isolate the trialkyl phosphites synthesized according to the invention, this is possible in a simple manner by fractional distillation without major losses in yield. The separation from the solvent is already completely possible by means of a rotary evaporator.

embodiments

All operations are carried out with exclusion of moisture in an inert gas atmosphere. The molar ratio of the reactants P ₄ , polyhalohydrocarbon, MOR, ROH is 1: 6: 6: 6 to 1: 6: 7: 6.

Example 1:

Preparation of tributyl phosphite (BuOIaP

To 2.06 g (0.0167 mol P ₄ ) of colorless phosphorus, which is finely dispersed in 40 ml of dry toluene, 9.6 ml (0.1 mol) of CCI ₄ and simultaneously the NaOBu / BuOH suspension ( 2.42 g [0.105 mol] of Na: 18.8 ml [0.205 mol] of butanol in 40 ml of toluene) are slowly added dropwise. The dropping rate of the reactants is controlled so as to ensure a reaction temperature of 30-40 ° C. The mixture is then stirred for 2 hours at room temperature. From the ³¹ P NMR spectrum it follows that the target product has formed to 65%. If 0.3 g (1.5 × 10 ^-3 mol) of ionol (2,6-di-t-butyl-p-cresol) is added to the initially introduced phosphorus, the yield determined by ³¹ P-NMR is 79%.

Example 2

Preparation of triethyl phosphite (EtO) ₃ P

The synthesis is carried out analogously 1) using 0.0167 mol of P ₄ suspended in 40 ml of acetonitrile, 0.1 mol of CCI ₄ , 0.105 mol of sodium and 0.205 mol of ethanol. The yield of (EtO ^ P is without Jonolzusatz 70% and with Jonolzusatz85%.

Example 3:

Preparation of tris (2-ethylhexyl) phosphite

The synthesis is carried out analogously 1) using 0.0167 mol of P ₄ , 0.1 mol of CCI ₄ , 0.105 mol of sodium and 0, 205 mol of 2-ethylhexanol.

The yield of the target product is 53% without and 68% with Jonol addition ¹ .

Claims (2)

Invention claim: 1. A process for the preparation of trialkyl phosphites of the general formula (RO) ₃ P, wherein R = alkyl groups, by reacting elemental, colorless phosphorus P ₄ with a polyhalocarbon, ionic alcoholate MOR, where M = metal or NH ₄ and R = alkyl and alcohol ROH in an inert aprotic solvent, characterized in that to increase the yield of the reaction mixture, a catalytic amount of a radical scavenger is added. 2. The method according to item 1, characterized in that the radical scavenger is an aromatic poly or monohydroxy, z. As 2,6-di-tert-butyl-p-cresol or hydroquinone, in amounts of 0.01-0.1 mol per mole of phosphorus is used.