JPH0320238A - Production of m-hydroxybenzaldehyde - Google Patents

Abstract

PURPOSE:To obtain the subject compound at a low cost by adding an alcohol and a quaternary ammonium salt to the system for the oxidation of m- hydroxybenzyl alcohol with oxygen in an alkaline aqueous solution in the presence of a platinum and/or palladium catalyst. CONSTITUTION:The subject compound useful as an intermediate for perfumery, pharmaceuticals, etc., and having new applications such as surface-treating agent and analysis reagent is produced by oxidizing m-hydroxybenzyl alcohol with oxygen or an oxygen-containing gas in an alkaline aqueous solution in the presence of platinum and/or palladium catalyst. In the above process. the reaction system is incorporated with (A) 0.01-100wt.% (preferably 0.05-50wt.%) (based on the reaction solvent) of an alcohol expressed by formula CnH2n+1OH ((n) is integer of 5-15) and (B) 0.0001-10wt.% (preferably 0.01-1wt.%) of a quaternary ammonium salt to suppress the by-production of m-hydroxybenzoic acid and to obtain the objective compound in high yield and selectivity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a process for producing m-hydroxybenzaldehyde by oxidation of -hydroxybenzyl alcohol. Demand for monohydroxybenzaldehyde is increasing not only as an intermediate for fragrances and pharmaceuticals, but also as a surface treatment agent (brightening agent for plating, etc.) and for analysis (quantitative analysis of tJ!), etc. ．． [Prior art] Regarding the oxidation method from hydroxybenzyl alcohol to hydroxybenzaldehyde, chromic acid oxidation,
Oxidation with 2,3-dichloro-5,6-dicyanobenzoquinone (hereinafter abbreviated as DDQ), oxygen oxidation, etc. are known, but both have the following drawbacks and are not satisfactory in terms of yield. It wasn't possible.

(1) Method using chromic acid oxidation Journal of Organic Chemistry (J.O.
rg. Chess. 26. ('61). 4814
), but the oxidation of tohydroxybenzyl alcohol is industrially disadvantageous because it uses an excess of chromium compound as an oxidizing agent and pyridine as a solvent. The reaction yield is also low at 75%. (2) Oxidation method by DD (l) Journal of Organic Chemistry (J.O.
rg. Chem, 45. ('8G). 1596) and performs oxidation under mild reaction conditions, but it is complicated because it requires the use of a stoichiometric amount of expensive DDQ as a reactant. (3) Oxygen oxidation method Hydroxybenzyl alcohol is oxidized with oxygen in an alkaline aqueous solution in the presence of a platinum or palladium catalyst, with the addition of catalytic amounts of bismuth, lead, silver, tellurium compounds, etc. The method is known. (
German Patent DH 2612844, Special Publication 1986-293
71) These methods are effective in converting 0- or p-hydroxybenzyl alcohol to the corresponding benzaldehyde and give the desired product in high yield, but there are no experimental examples for the above compound. In addition, the present inventors previously discovered a method for suppressing the by-product of 1-1-hydroxybenzoic acid and increasing the selectivity and yield of 1-hydroxybenzaldehyde in the oxygen oxidation reaction of hydroxybenzyl alcohol. C1 to C by adding a catalytic amount of a C1 to C
We proposed a method using a lower alcohol solvent with 4 carbon chains or a lower alcohol-water homogeneous solvent. [JP-A-62-61941, JP-A-63-93745, Chemistry Letter 1115 (1988)] [Problems to be Solved by the Invention] First, the present inventors have found that relatively less Having discovered that trihydroxybenzyl alcohol can be produced at a low cost, we intensively investigated a method for producing monohydroxybenzaldehyde using this as a starting material. In the conventional method for producing hydroxybenzaldehyde by oxygen oxidation of hydroxybenzyl alcohol,
For example, in Special Publication No. 60-29371, 0-
Alternatively, p-hydroxybenzyl alcohol is used in an alkaline aqueous solution under a platinum catalyst with the addition of lead, silver, tellurium, etc., but when the same conditions were applied to p-hydroxybenzyl alcohol, the target m-hydroxybenzaldehyde was further oxidized. A large amount of hydroxybenzoic acid was produced as a by-product (see Comparative Example). Although various catalysts were used according to the above-mentioned Japanese Patent Publication No. 60-29371, it was not possible to suppress the by-product of monohydroxybenzoic acid. Therefore, the cited method, which produced a large amount of by-products, was not satisfactory as an industrial production method when hydroxybenzyl alcohol was used as a raw material. Furthermore, even in the method proposed in JP-A No. 62-61941, the rank 2 element or lanthanide element compound as the catalyst is relatively expensive, and the lower alcohol is used as an explosive mixture with oxygen as the oxidizing agent. In addition, its explosive limit range is wide, making it dangerous for industrial implementation. The object of the present invention is to improve the production of monohydroxybenzoic acid by-product in the oxygen oxidation of tohydroxybenzyl alcohol without using expensive lanthanide elements or rank di-element compounds and lower alcohol solvents with a high risk of explosion. The present invention provides a method for obtaining the target m-hydroxybenzaldehyde in high yield and high selectivity while suppressing the [
Means to Solve the Problem] In order to efficiently oxidize m-hydroxybenzyl alcohol with oxygen, a platinum or palladium catalyst and an alkaline substance are essential, but m-hydroxybenzaldehyde can be oxidized with good selectivity and high yield. In order to obtain this, it is necessary to further consider the solvent system. In order to solve this problem, m-hydroxy We have found that the selectivity of benzaldehyde can be dramatically improved, and have perfected the present invention. That is, the present invention provides a method for producing hydroxybenzaldehyde by oxidizing Rin-1 hydroxybenzyl alcohol with oxygen or an oxygen-containing gas in an alkaline aqueous solution in the presence of a platinum and/or palladium catalyst. This is a method for producing m-hydroxybenzaldehyde, which is characterized by adding a quaternary ammonium salt. Next, the present invention will be explained in detail. As the platinum or palladium catalyst used in the present invention, it is usually preferable to use one in which platinum or palladium is supported on activated carbon in an amount of 6% by weight or less. Its usage is
0.01-1 for monohydroxybenzyl alcohol
It is used in an amount of 0% by weight, preferably 0.1 to 5% by weight. Furthermore, a cocatalyst is used to speed up the reaction rate. As a cocatalyst, one or more metals selected from the group of known boric acid, lead, silver, bismuth, tellurium, or tin, or one or more compounds thereof, are added to hydroxybenzyl alcohol. It may be added in an amount of 0.01 to 50% by weight, preferably 0.1 to 5% by weight. The oxygen-containing gas used in the present invention is pure oxygen or air, or oxygen diluted with an inert gas such as nitrogen. In the present invention, the concentration of m-hydroxybenzyl alcohol in the alkaline aqueous solution is usually 1 to 30% by weight. Further, in the method of the present invention, as the alkaline aqueous solution, a solution prepared by dissolving hydroxides, carbonates, bicarbonates, etc. of alkali metals and alkaline earth metals in water is used. Its usage is 0.1 to 1 to hydroxybenzyl alcohol.
0 gram equivalent, preferably in the range of 1.0 to 3.0 gram equivalent. The alcohol added in the method of the present invention is C
Those represented by ntltn+1011 (n is an integer from 5 to 15) are used, such as 1-bentyl alcohol, 1-hexyl alcohol, 1-hebutyl alcohol,
Examples include l-octyl alcohol, 2-ethyl-1-hexyl alcohol, l-nonyl alcohol, l-decyl alcohol, and l-undecyl alcohol. Even a small amount of it is effective, and it is 0% for the water solvent used.
．． 01-100% by weight, preferably 0.05-50% by weight
% range, and even if the amount used exceeds 100% by weight, no particular improvement in the reaction is observed, and as the amount of solvent is increased,
The volumetric efficiency of the reaction decreases.

Furthermore, if it is less than 0.01% by weight, it is ineffective, and a quaternary ammonium salt is added as a catalyst. Examples of quaternary ammonium salts include tetramethylammonium chloride, tetraethylammonium chloride, tetrabrobylammonium chloride, tetrabutylammonium chloride, penzyltrimethylammonium chloride, lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, and distearyldimethyl chloride. Examples include ammonium, bromide, sulfide, p-toluenesulfonate, etc. of the above-mentioned ammonium. Further, the following formula [wherein R is an alkyl group having 12 to 18 carbon atoms, and xSy both represent integers of 1 to 15]. ] Quaternary ammonium salt [trade name, I! TllOQtlA
D (Lion Akzo)] etc. The amount added is 0.0001 to 10% by weight based on the water solvent used.
, preferably in the range of 0.01 to 1% by weight, and 0.0
If it is less than 10% by weight, there is no effect, and if it exceeds 10% by weight, no improvement is seen. If alcohol and quaternary ammonium salt are not added to the aqueous solvent, a large amount of tohydroxybenzoic acid will be produced as a by-product. This reaction is carried out at a temperature range of 0 to 100°C, preferably 30 to 90°C. The reaction is slow below 0°C. Further, although the present invention can be carried out either under normal pressure or under elevated pressure, it is usually appropriate to carry out the reaction under normal pressure. A bubble column or a stirred tank is suitable as the type of reactor, and it can be carried out either batchwise or continuously. The catalyst may be used in suspension or in a fixed bed. The m-hydroxybenzaldehyde thus obtained can be isolated by conventional methods such as filtering and separating the catalyst, extraction with a solvent, and distilling off the solvent, or recrystallization. [Operation] In the known method for producing hydroxybenzaldehyde by oxygen oxidation of 0- and p-hydroxybenzyl alcohol, the target product is further oxidized and a large amount of hydroxybenzoic acid is produced as a by-product. Furthermore, in the method of carrying out an oxidation reaction in a lower alcohol solvent such as methanol or ethanol in order to increase the selectivity of monohydroxybenzaldehyde, there is a high risk of a mixed explosion of the lower alcohol and oxygen.

However, in the method of the present invention, an alcohol having a carbon chain of C5 to Cl5, which has a lower risk of mixed explosion with oxygen than a small amount of lower alcohol, and a trace amount of a quaternary ammonium salt are added to the water reaction solvent. By adding it as a catalyst, it is possible to improve the selectivity of m-hydroxybenzaldehyde by oxidizing monohydroxybenzyl alcohol and prevent the by-product of tohydroxybenzoic acid, which is an extremely valuable invention industrially. [Example] The present invention will be specifically explained below using Examples. The percentages in the examples are percentages by weight. Example-1 50% of hydroxybenzyl alcohol was added to the flask. 0
g (0.40 mol), 97% Na011 26.8
g (0.65 mol) After charging 500 1d of water, 3% platinum carbon Ig, 20g of 2-ethyl 1-hexanol, and 0.5g of penzyltrimethylammonium chloride, oxygen gas was removed through a ball-shaped glass filter (2G). It was written into Aiuchi. The oxidation reaction was carried out by stirring vigorously at 70° C. for 10 hours while blowing oxygen gas.

After the reaction was completed, the reaction mixture was filtered to remove platinum carbon as a catalyst, and then subjected to IIPLc analysis.

The conversion rate of monohydroxybenzyl alcohol was 95%, and the selectivity and yield of monohydroxybenzaldehyde were 91% and 86%, respectively. Furthermore, the by-product yield of tohydroxybenzoic acid was 6%. Afterwards, the reaction mixture is 20
% sulfuric acid water was added to make it slightly acidic, and ether extraction was performed. The ether layer was washed with saturated brine, dried over Glauber's salt, and the ether was distilled off to obtain crude m-hydroxybenzaldehyde. The obtained rflm-hydroxybenzaldehyde was recrystallized in toluene to obtain purified m-hydroxybenzaldehyde (melting point 100-103°C, purity 98%, yield 140.0
g, isolated yield 80%) was obtained. Example-2 In a reactor similar to Example-1, 50.0 g (0.40 mol) of hydroxybenzyl alcohol and 85% K01 were added.
152. 8 (0.80 mol) water 300 d, 3% platinum carbon 0.5 g, lead nitrate 0.5 g, l-hebutyl alcohol log, ETIIOQIIAD C/1
2 (Lio77kV', average molecule 9353) 0
．． After charging 3 g, oxygen gas was blown into the liquid phase. After blowing in oxygen gas, the mixture was vigorously stirred at 80°C for 3 hours.

After the reaction was completed, post-treatment and IIPLc fraction f were performed in the same manner as in Example-1. - Conversion rate of hydroxybenzyl alcohol was 93%, - Selectivity and yield of hydroxybenzaldehyde were 89% and 83%, respectively. Furthermore, the by-product yield of monohydroxybenzoic acid was 8%. Examples 3 to 5 and Comparative Examples 1 to 3 The reaction was carried out in exactly the same manner as in Example 1, except that the alcohol and quaternary ammonium salt were changed in Example 2, and the resulting reaction mixture was similarly subjected to IILPC. The results of the analysis are shown in Table-1.

(Left below) [Effects of the Invention] As is clear from the results of Examples and Comparative Examples, 1-hydroxybenzyl alcohol was oxidized with oxygen or oxygen-containing gas in an alkaline aqueous solution in the presence of a platinum and/or palladium catalyst. In the method for producing Rin-1 hydroxybenzaldehyde by
By adding a class ammonium salt, the production of the by-product monohydroxybenzoic acid is suppressed, and m-hydroxybenzaldehyde can be obtained with high selectivity. As described above, the present invention is extremely valuable when implemented industrially.

Claims (1)

[Claims] 1. A method for producing m-hydroxybenzaldehyde by oxidizing m-hydroxybenzyl alcohol with oxygen or an oxygen-containing gas in an alkaline aqueous solution in the presence of a platinum and/or palladium catalyst, and a method for producing m-hydroxybenzaldehyde, which comprises adding a quaternary ammonium salt. 2. The method according to claim 1, wherein the alcohol is C_nH_2_n_+_1OH (n is an integer from 5 to 15).