DE3108790A1 - Process for the preparation of bis(dialkoxymethyl)benzenes - Google Patents

Abstract

Bis(dialkoxymethyl)benzenes which optionally have further substituents on the aromatic ring are prepared from alpha , alpha , alpha ', alpha '-tetrahaloxylenes by reacting them with alkali metal alcoholates.

Description

Process for the preparation of bis (dialkoxymethyl) benzenes

Bis (dialkoxymethyl) bentols are available as etraacetals from Tere-Iso- and Phthalaldehyde from the aldehydes by acetalization with various reagents has been manufactured.

The dialdehydes are used as starting materials, but they are technical difficult, can only be produced with considerable material losses and also impure.

Conversely, if you want to produce the dialdehydes, these ways are via the acetals useless.

The task was therefore to find the partly

to produce inconsistent dialdehydes.

The solution to the problem consists in the present manufacturing process the acetals, which are thermally stable and chemically reactive, and at Allow easy production of the dialdehydes as required.

The invention relates to a process for the production of optionally bis (dialkoxymethyl) benzenes containing further substituents in the aromatic nucleus, which is characterized in that the structurally corresponding O (, C (, 0 (', 0 ( -'lletrahalogen-xgLole can be reacted with alkali alcoholates at elevated temperatures.

According to the equation: wherein where R 'straight-chain and branched alkyl or alkenyl radicals with 1 to 10 carbon atoms, R!' Hydrogen, R ', aryl, halogen l.

Hydroxyl, carboyl, nitro, cyano or others are inert in the reaction Substituents; M alkali metal and Hal denote chlorine or bromine, the bis (dialkoxymethyl) benzenes are obtained in high yield and purity.

It was found, surprisingly, that despite the possible formation of Intermediate stages and side reactions a uniform reaction product can be obtained can. The otherwise expected formation of chlorinated derivatives of o-xylene condensed aromatics due to Friede-Crafts reactions are not observed.

The radicals R 'are alkyl radicals of 1 to 4 carbon atoms, especially methyl and ethyl are preferred.

The alkali metal of the alcoholates is sodium, and secondly potassium, preferred.

On the one hand, hydrogen is preferred as the radicals R ″, but it does exist from case to case a second preferred range, depending on the inert substituents in the dialdehydes to be prepared and their secondary products are preferred, with then generally one or two substituents ducks R "is not hydrogen and are mentioned as preferred inert radicals, for example, Cl, methyl and ethyl can be.

The tetrahaloxylene and the alkali metal alcoholate is preferred in Brought to react with each other in the presence of a solvent. This can be done that the starting materials are put together from the start or a reaction partner is gradually added. The stoichiometric ratios are within the range the values recognizable from the empirical formula, with an excess of alcoholates from 0 to 50% by weight, preferably 5 to 20% by weight, is advantageous. The amount of Solvent can be changed within wide limits and is adjusted so that the reaction mixture is easily stirrable and the heat of reaction can be dissipated and there are no avoidable difficulties in the work-up.

It is generally 2 to 10 times, preferably 3 to 5 times the amount by weight of the reactants.

The alcohol on which the alcoholate is based is preferably used, However, solvents which are inert under the reaction conditions of the aliphatic can also be used or aromatic series such as n-heptane or toluene can be used. Without a solvent, side reactions can occur which can become significant.

The reaction temperature is 90 to 19,000, preferably 120 to 1600C, The pressure is generally the autogenous pressure of the solvent used. The reaction has ended after several, generally from 4 to 8, hours.

In order to achieve good sales, it is essential to mix the Reaction batch required, e.g. by stirring. When implementation is complete, the Mixture, preferably at a higher temperature, of the alkali halide formed freed by filtration and after removal of the solvent according to the usual Process of distillation or crystallization to the pure acetal worked up.

The process products can be undecomposed for an unlimited period of time store and can, if necessary, simply by acidic aqueous hydrolysis or preferably be converted directly into the dialdehydes under anhydrous conditions.

The process has further advantages over known methods. The α, α, α ', α'-tetrahaloxylenes are inexpensive and easily accessible. Immediately before using the dialdehydes for the production of i.a. Dyes or Pharmaceutica these can simply be made from the acetals so that the decomposition and formation of by-products during storage of the aldehydes not applicable.

Especially for the production of o-phthaldialdehyde, the We is about the Acetal is a great advantage, since it does not produce phthalide.

Then there are the disadvantages and low yields of direct production the dialdehydes avoided by hydrolysis from chlorination products, in the self under the mild conditions of US-PS 4,206,152 unfavorable yields with disproportionate large amounts of catalysts occur.

o-Phthaldialdehyde tetramethyl acetal was previously unknown.

Example 1 242 g of α, α 'α'-tetrachloro-o-xylene become with 238 g of sodium methylate (793 g of a 30% strength by weight solution in methanol) and Treated for 9 hours in an autoclave with stirring at 1500C. Emptied after cooling the reaction vessel and the sodium chloride formed is filtered off.

After removal of the methanol, finally under reduced pressure, is obtained a pale yellow viscous distillate is rectified by vacuum distillation at 1 mbar 176 g of pure o-phthaldialdehyde tetramethylacetals are obtained.

Yield: 78% of theory.

Example 2 242 g of α, α, α ', O (' - tetrachloro-m-xylene and 238 g of sodium methylate (793 g of a 30% by weight solution in methanol) are as Treated described in Example 1. After rectification result from the reaction mixture 182 g of pure isophthalaldehyde tetramethyl acetal.

Yield: 81% of theory.

Example 3 242 g of α, α, α ', α'-tetrachloro-p-xylene and 238 g of sodium methylate (793 g of a 30% by weight solution in methanol) are as Treated described in Example 1. 231 g result from the reaction mixture pure terephthalaldehyde tetramethyl acetal.

Yield: 83% of theory.

Example 4 420 g of α, α, α ', α'-tetrabromo-o-xylene and 238 g Na methylate (793 g of a 30% by weight solution in methanol ) are treated at 140 ° C, but otherwise as described in Example 1. The reaction mixture after distillation gives 180 g of pure o-phthaldialdehyde tetramethylacetals.

Yield: 80% of theory.

Example 5 242 g of α, α, α ', α'-tetrachloro-o-xylene and 300 g of Na ethylate (1500 g of a 20 wt .-% solution in ethanol) are at 1550C, but otherwise treated as described in Example 1. From the reaction mixture After working up by distillation, 246 g of pure o-phthalaldehyde tetraethyl acetal are obtained.

Yield: 79% of theory.

Example 6 According to Example 1, 1,3-bis (dichloromethyl) -5 chlorobenzene is used under the stated conditions with an appropriate yield to 5-chloro-isophthal-tetramethylacetal implemented.

Claims (5)

Claims 1. A method for the production of optionally im aromatic xernary bis (dialkoximethyl) benzenes containing further substituents, characterized in that the structurally corresponding α, α, α ', α'-Tetrahalo-xylenes reacted with alkali alcoholates at elevated temperature will. 2. The method according to claim 1, characterized in that the alkali alcoholates be used in a stoichiometric excess. 3. The method according to any one of claims 1 or 2, characterized in that that the reaction is carried out at 90 to 19,000, preferably at 120 to 16,000. 4. The method according to at least one of claims 1 to 3, thereby characterized in that the reaction is carried out in the presence of solvents. 5. o-Phthalaldehyde tetramethyl acetal.