JPS6059234B2 - Method for producing 5-methylfurfural - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides 5-
This article relates to a new method for producing methylfurfural.

More specifically, the present invention selectively targets the chloromethyl group at the 5-position of 5-chloromethylfurfural by using a palladium-based catalyst in the presence of a reaction-inert organic solvent containing a basic additive. The present invention relates to a method for producing 5-methylfurfural by reducing it to a methyl group by the action of molecular hydrogen. As a conventional method for producing 5-methylfurfural, for example, the following method is known.

1 A method in which Flagdose is heat treated in the presence of hydrochloric acid and then reduced with stannous chloride (Org, Syn.

Collvol, 2, 393, (1943)).

This method is not practical as an industrial production method because it involves gelation and solidification of humic substances during the reaction and requires the use of more than an equivalent amount of stannous chloride, and the yield is 20 to 22.
% is low. A method of decomposing deoxy sugars represented by 2L-rhamnose or their glycosides with an acid.

This method is not necessarily suitable as an industrial production method, considering that it is difficult to obtain the raw material deoxysugar in large quantities at low cost, and the yield is generally low. A method of reacting 35-methylfuran with N,N-dimethylformamide and phosphorus oxychloride or phosgene (J, OrgChem, 22, 1269 (195
7) etc.).

However, even in this method, in addition to the difficulty in obtaining 5-methylfuran, it is necessary to use equivalent amounts or more of expensive and highly toxic chemicals such as phosphorus oxychloride, phosgene, and N,N-dimethylformamide, making it difficult to obtain industrially. It cannot necessarily be said that it is an excellent manufacturing method. As a result of intensive studies on the industrial production method of 5-methylfurfural, the present inventors found that using a palladium-based catalyst in the presence of an inert organic solvent for a reaction involving 5-chloromethylfurfural and a basic additive, When a reduction reaction using molecular hydrogen is performed, selective hydrogenation of the chloromethyl group at the 5-position occurs without saturation of the carbon-carbon double bond of the furan ring, cleavage of the furan ring, reduction of the aldehyde group, etc. The decomposition progresses and the objective 5-
The inventors discovered that methylfurfural can be produced in high yield and high selectivity, leading to the completion of the present invention. That is, the present invention consists of reacting molecular hydrogen on 5-chloromethylfurfural using a palladium-based catalyst in the presence of an organic solvent containing a basic additive and inert to the reaction.
- A method for producing methylfural.

Originally, benzyl, vinyl, and allyl halides are more easily hydrogenolyzed than alkyl halides, but even when a palladium catalyst is used for allyl halides, saturation of carbon-carbon double bonds progresses. However, unless there is further interference, this is usually carried out in parallel with the hydrogenolysis of the allyl halide.

Considering such conventional technical knowledge, palladium-based compounds such as 5-chloromethylfurfural (furan ring, aldehyde group) in the presence of an inert organic solvent for reactions containing basic additives It is a new finding that only the chloromethyl group at the 5-position can be selectively hydrogenated by a reduction reaction using a catalyst and the action of molecular hydrogen without any side reactions. 5-Chloromethylfurfural, which is the starting material for the method of the present invention, can be obtained from carbohydrate compounds such as monosaccharides and disaccharides in high yield and high selectivity as disclosed in JP-A No. 53-50155. 5-Methylfurfural, which is a compound that can be easily produced and is therefore important as a raw material for medicines, agricultural chemicals, fragrances, etc., can be produced easily and in high yield using the method of the present invention. , it plays an extremely important role.

Organic solvents used in the reaction include organic solvents that are inert to the reaction, such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene, and their halides, and fatty acids such as methylene chloride, chloroform, and carbon tetrachloride. Group halogenated hydrocarbons and the like are used.

It is also possible to use these together with alcohols such as methanol, ethanol, and isopropanol, acetic acid, and the like. Although the amount of these organic solvents is not particularly limited, it is usually preferable to use 1 part to w parts of the organic solvent based on the raw material 5-chloromethylfurfural. As the palladium-based catalyst used in this reduction reaction, both unsupported and supported types can be used.

Further, they may be used as powders, or may be molded into appropriate shapes and sizes. Examples of unsupported catalysts used include palladium black, palladium oxide, palladium chloride, and the like. As supported catalysts, for example, palladium-carbon, palladium-silica, palladium-alumina, palladium-barium sulfate, palladium-calcium carbonate, etc. with various loading rates are used. The amount of palladium catalyst used is not particularly limited, but in the case of a batch reaction, it is 0.001 to 1 mol, preferably 0.005 to 0.1 mol, per 1 mol of 5-chloromethylfurfural as a raw material. It is a mole. Basic additives include organic tertiary amines (triethylamine, pyridine, etc.), inorganic weak acid salts of alkali metals or alkaline earth metals (sodium carbonate, potassium carbonate, calcium carbonate, etc.), and organic acids of alkali metals or alkaline earth metals. Salts (sodium acetate, potassium acetate, etc.), alkaline earth metal oxides (magnesium oxide, calcium oxide, etc.)
, alkali metal hydroxides (potassium hydroxide, sodium hydroxide, etc.).

Among these, organic tertiary amines, alkali metal inorganic weak acid salts, and alkali metal organic acid salts are preferably used. The amount used as the basic additive is 0.1 to 5 mol, preferably 0.1 to 5 mol, preferably 0.
．． 3 to 1.5 mol is suitable. The hydrogen used in the reduction reaction in the present invention may be any commercially available hydrogen, and the amount used is not particularly limited as long as it is at least stoichiometric for the purpose of completing the reaction, and the pressure is also not particularly limited. There is no restriction, and the reaction easily proceeds even at normal pressure.

Pressure can also be applied to accelerate the reaction. The reduction reaction temperature is preferably heated in order to promote the reaction, but in order to suppress side reactions, a temperature of 100°C or lower, preferably in the range of about -10°C to 80°C, is appropriate.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
Of course, the present invention is not limited to these examples.

Example 1 5-chloromethylfurfural 1f (6.92 mmol) was placed in a four-loaf flask equipped with a hydrogen inlet tube, a cooling tube, a thermometer, and a stirrer, and dissolved in 10 ml of toluene.

Then 10% Pd-carbon 0.37y (5 mol% relative to 5-chloromethylfurfural) and sodium acetate 0.5
67V (100 mol % based on 5-chloromethylfurfural) was added.

After replacing the reaction container with hydrogen, it was heated in a water bath for 40 minutes.
heated to ℃. Subsequently, the mixture was stirred at 40°C and the reaction was continued for 7 hours. During this time, hydrogen was continuously introduced at almost atmospheric pressure through an inlet tube through a hydrogen-filled buret sealed with water (amount of hydrogen required for reaction: 212
m1). After the reaction was completed, the catalyst was removed and the reaction solution was quantitatively analyzed by gas chromatography. The results are shown in Table 1.

Examples 2-12 The reaction was carried out in the same manner as in Example 1.

Claims (1)

[Claims] 1 5-Chloromethylfurfural is reacted with molecular hydrogen using a palladium-based catalyst in the presence of an organic solvent containing a basic additive and inert to the reaction. -Method for producing methylfurfural. 2. Claims that use at least one of tertiary amines, inorganic weak acid salts and organic acid salts of alkali metals or alkaline earth metals, alkaline earth metal oxides, and alkali metal hydroxides as basic additives The method for producing 5-methylfurfural according to item 1.