JPS62135443A - Production of p-hydroxybenzaldehyde - Google Patents

Abstract

PURPOSE:To shorten oxidation reaction time and to obtain the titled compound in improved selectivity, by oxidizing p-cresol, more precisely, the alkyl group of p-cresol with molecular O2 in an alcohol solvent by the use of an inexpensive iron compound(III) as a catalyst in the presence of a base. CONSTITUTION:p-Cresol is reacted with molecular O2 in the presence of an iron compound(III) and a base such as caustic soda, etc., in an alcohol solvent such as especially preferably methanol, etc., preferably at 60-80 deg.C for about 4hr at 1atm. to give the aimed compound. Ferric chloride, ferric sulfate, ferric acetate, iron(III)-acetylacetonato, ferric oxide, ferric nitrate, etc., may by cited as the iron compound(III) and ferric chloride and ferric sulfate are especially preferably. The amount of the catalyst is >=0.001mol, preferably 0.01-0.1mol based on p-cresol. The amount of the base used is >=1.5mol, preferably 2-5mol based on p-cresol.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing parahydroxybenzaldehyde. More specifically, the present invention relates to an improvement in the method for producing sulparahydroxybenzaldehyde by oxidizing the alkyl group of paracresol with molecular oxygen.

[Prior art]

A method for selectively producing para-hydroxybenzaldehyde or para-hydroxybenzaldehyde derivatives by oxidizing para-cresol or a para-cresol derivative with molecular oxygen includes AngCw, Chem, 86,58.
6 (1975); 12th Oxidation Reaction Symposium Abstracts,
P74 (1978); There is a method introduced in Japanese Patent Application Laid-Open No. 55-81832. These methods are characterized by oxidation with molecular oxygen in an organic solvent containing a basic compound in the presence or absence of a cobalt catalyst.

[Problem that the invention seeks to solve]

Conventional techniques, especially the method of JP-A-55-81832, are at a high level of technology, but even with this method, in the production of para-cresols or labadihydroxybenzaldehydes having a substituent at the ortho position, the conversion rate per unit reaction time is low. However, when applied to the oxidation of para-cresol that does not have a substituent at the ortho position, it is difficult to obtain a result that can satisfy '/+N' in terms of the required reaction time. The present inventor has completed the present invention by making earnest efforts to solve the technical problems of such conventional methods.

The present invention is a method for producing para-hydroxybenzaldehyde, which is characterized by oxidizing para-cresol with molecular oxygen in an alcohol solvent in the presence of iron (an Ill compound and a base). (III
) Since the compound is used as a catalyst, the time required for oxygen oxidation is shortened, which greatly contributes to productivity. In other words, the oxidation reaction, which required tens of hours or at least 6 hours in the conventional method, can reach reaction equilibrium in about 4 hours, and the conversion rate and selectivity at that time are 40 to 50%, respectively. , a commercially viable level of 40 to 60% can be expected.

The method of the invention uses para-cresol as a starting material. Iron ([1] compounds used as catalysts include ferric chloride, ferric sulfate, ferric acetate, iron (1111-acetylacetonate, ferric oxide, ferric nitrate, etc.), especially ferric chloride. Diiron and ferric sulfate are preferred.

Further, the amount of the catalyst is desirably at least o, ooi times mole relative to para-cresol, preferably 001 to 0
The range is 1 times the mole.

Examples of the base used in the present invention include alkali metal hydroxides such as caustic soda, caustic potash, and lithium hydroxide, and metal alkoxides such as sodium alkoxide and potassium alkoxide. The amount used is 1.5 times or more, preferably 2 to 5 times the mole of para-cresol.

As the alcohol used as the reaction solvent, lower alcohols such as methanol, ethanol, and ingropanol can be used. Particularly preferred is methanol.

The process of the invention is preferably carried out in the temperature range from 60 to 80°C; below 50°C the reaction rate decreases, while above 80°C the oxidation of the solvent or by-products increases.

Molecular oxygen used as an oxidizing agent includes oxygen gas,
There is air, etc., and the pressure is usually 1 atmosphere or more.

The target product can be separated and purified from the reaction mixture by extraction with an organic solvent or recrystallization.

Example 1 Para-cresol (59.5 N, 0.55 mol) and ferric chloride (1,4
9,9,0, (l [155 mol) Caustic soda (70,
989.1.65 mol) and methanol (180 ml) were charged and stirred for 4 hours at a reaction temperature of 60'C under an oxygen atmosphere of 1 atm.

The reaction mixture was analyzed by high performance liquid chromatography, and the results were as follows.

The conversion rate of para-cresol was 50 and the selectivity of para-hydroxybenzaldehyde was 60. Example 2 The reaction was carried out in the same manner as in Example 1 except that the catalyst in Example 1 was changed to basic ferric acetate.

The results were as follows.

Conversion rate of para-cresol: 50 Selectivity of parahydroxybenzaldehyde 425

Claims (1)

[Claims] A method for producing para-hydroxybenzaldehyde, which comprises oxidizing para-cresol with molecular oxygen in the presence of an iron compound (III) and a base in an alcoholic solvent.