CS265264B1 - Process for preparing alkoxyphenoles - Google Patents

Abstract

Process for preparing general alkoxyphenols of formula H0-Ar-OR, wherein R is alkyl Οχ to 84, optionally branched and Ar is arylene, by the action of symmetrical dialkyl ethers tungsten acid catazysis free, optionally supported on the support temperatures of 100 to 300 ° C, preferably 180 to 300 ° C 280 ° C.

Description

The invention relates to a process for the preparation of alkoxyphenols from bifunctional phenols with an alkylalkyl dialkyl ether in the presence of tungstic acid as the reaction catalyst.

According to present knowledge alkoxyphenols with the formula HO-Ar-OR, where R is alkyl to C ₄ straight or branched chain, usually methyl or ethyl and Ar is erylen, optionally substituted, usually 1,2-phenylene can be prepared in several ways but among them, the dominant position is the alkylation of the bifunctional phenols in question. The oako alkylating agent used is generally the corresponding alkyl halide, or dialkyl sulfate, to treat the monosodium salt of the substrate. A significant disadvantage of this process, however, is the formation of the corresponding sodium halide or sulfate, which is formed as a by-product according to the general scheme:

HO-Ar-ONa + RX —HO-Ar-OR + NaX wherein Ar and R are as defined above and X is a halide or sulfate equivalent.

Recently a method (DOS

903 020) according to which the alkylation is carried out by dialkyl ethers according to the scheme:

HO-Ar-OH

R-O-R

HO-Ar-OR + ROH

265 264 in which alcohol is formed as a by-product, which can be easily isolated from the reaction mixture and used for other purposes, however, a considerable disadvantage of the method is that the reaction proceeds to date , which in turn leads to very low conversions in many cases. This, together with the not very different physical properties of the starting substrate and product, completely excludes in some cases the applicability of the process for industrial purposes.

It has now been found that the same catalytic effect can be achieved by tungstic acid, preferably anchored on a porous inorganic support. This catalyst is thermally stable over a wide range of temperatures and thus allows the working temperature of the alkylation to be raised to such an extent that the alkylation proceeds sufficiently quickly as necessary for industrial purposes.

Alkoxylphenols are important intermediates for the synthesis of a variety of pharmaceutical preparations, fragrances and dyes.

Method of sending. The invention is further described by the following examples.

Example 1

To a 0.3 L autoclave equipped with an electromagnetic stirrer and fittings necessary for working under pressure was added 5 g of finely crushed tungstic acid and 20 g of pyrocatechin and the autoclave was closed. After evacuation, 120 g of dimethyl ether was then charged from the pressure tank and heated to 200 ° C with stirring.

At this temperature, the contents of the autoclave were stirred for 7 hours. It was then cooled to normal temperature, the excess dimethyl ether was drained and the nonvolatile residue was removed. The organic portion of the residue was dissolved with ethyl alcohol and its composition analyzed by gas chromatography. The internal standard method showed that the residue contained a total of 11 g of 2-methoxyphenol (guaiacol).

Example 2,265,264

A device consisting of a high-pressure tube having an inner diameter of 27 mm and a length of 300 mm was assembled and equipped at both ends with flanges with an inlet and outlet steel capillary. The tube that served as the reactof was placed in an electric furnace, which allowed heating of the tubes to a temperature of up to 200 C with a control accuracy of + 1 C.

Prior to the experiment, the reactor was packed with a 5 mm diameter Rashhig ring shaped catalyst containing 5% tungstic acid and pure solvent (diethyl ether). starting reaction mixture. The mixture was discharged by a capillary at the opposite (upper) end of the reactor, which first passed through a 20 ° C water vessel, then through a pressure control valve to the product reservoir.

In the experiment, the control valve was adjusted to a pressure of 5 bar, the reactor contents heated to 220 ° C, and then a reaction mixture containing 10% pyrocatechin at a rate of 17 ml per hour was pumped through the reactor. After stabilization (twelve hours of operation), the composition of the effluent stream was analyzed by gas chromatography and was found to contain 6.23% -ethoxyphenol (giaethol).

Example 3

The experiment in Example 2 was repeated except that instead of diethyl ether, diisopropyl ether was used as the solvent and reagent, the reactor was heated to 270 ° C and the flow rate was increased to 30 ml / h. After stabilization, the mixture leaving the reactor contained 5.83% 2-isopropoxyphenol.

Example 4

The experiment described in Example 2 was repeated except that n-butyl ether was used as the ether, the alkylation was carried out

265 264 at 280 [deg.] C., the reactor pressure was 2.0 MPa and the flow rate was further increased to 40 ml / h. After stabilization, the reaction mixture contained 4.96% 2-butoxyphenol at the reactor outlet.

Claims (1)

A process for the preparation of alkoxyphenols of the formula HO-Ar-OR, wherein R is alkyl to C1-4 optionally branched and Ar is arylene, by symmetrical dialkyl ether, characterized in that the reaction is catalyzed by tungstic acid, free or optionally supported at 100 to 300 ° C, β preferably 180 to 280 ° C.