JPS6045877B2 - Method for producing 5-methylfurfural - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for producing 5-methylfurfural, which is useful as an intermediate for pharmaceuticals or agricultural chemicals.

More specifically, the present invention is capable of converting 5-chloromethylfurfural into a methyl group through the action of molecular hydrogen on the chloromethyl group at the 5-position of 5-chloromethylfurfural using a palladium-based catalyst. The present invention relates to a method for producing 5-methylfurfural. Conventionally, the following method is known as a method for producing 5-methylfurfural.

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

Coll., Vol., 1, 393 (1943)). This method is not only impractical 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, but also has a yield of 20 to 22%. % is low. A method of decomposing deoxy sugars represented by 2L-rhamnose or their glycosides with an acid.

This method is also not necessarily suitable as an industrial production method, considering that it is difficult to obtain deoxy sugar in large quantities and at low cost, and the yield is generally low.
3. Method for reacting methylfuran, N9N-dimethylformamide, and oxysalt phosphorus (J, Org.

Chem, 22, 1269 (1957), etc.). However, even in this method, methylfuran is difficult to obtain, and more than equivalent amounts of phosphorus oxychloride and N,N-dimethylformamide must be used, so it is not necessarily an excellent industrial production method. I can't say that. Under these circumstances, the present inventors conducted intensive studies on an industrial method for producing 5-methylfurfural, and found that by reacting hydrogen to 5-chloromethylfurfural in the presence of a palladium catalyst, the compound can be converted into an aldehyde group. The inventors discovered that 5-methylfurfural can be produced in high yield and high selectivity despite having a furan skeleton, and after further various studies, the present invention was completed.

That is, the present invention is a method for producing 5-methylfurfural by causing molecular hydrogen to act on 5-chloromethylfurfural in the presence of an organic solvent using a palladium-based catalyst. 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. It is a compound that can be easily produced, and therefore, it is an important compound as a raw material for pharmaceuticals and agricultural chemicals using the method of the present invention.
Methylfurfural can now be produced easily and in high yield on an industrial scale, and it plays an extremely important role.

In the present invention, an organic solvent that dissolves the raw material 5-chloromethylfurfural is used as the solvent, and in particular, from the viewpoint of yield and operation, one or more of amide compounds, ether compounds, ester compounds, etc. Alternatively, it is preferable to use a mixed solvent containing these. As amide compounds, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N
- Methylpyrrolidone, hexamethylphosphortriamide, etc., ether compounds include diethyl ether, dimethoxyethane, tetrahydrofuran, dioxane, etc., and ester compounds include methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate. etc. are used. Various combinations of mixed solvents are possible, such as tetrahydrofuran and N,N-dimethylformamide, dioxane and N,N-dimethylformamide, acetone and N,N-dimethyl. Formamide, toluene and N,N-dimethylformamide are used. Although the amount of these organic solvents is not particularly limited, it is usually preferable to use 0.5 to 10 parts by weight of the organic solvent based on the raw material 5-chloromethylfurfural! Ru. As the palladium-based catalyst used in the present invention, 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/supported catalysts include palladium black, palladium oxide, palladium chloride, and the like. As supported catalysts, for example, palladium-carbon catalysts, palladium-silica catalysts, palladium-alumina catalysts, palladium-barium sulfate catalysts, etc. with various loading ratios 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 per 1 mol of 5-chloromethylfurfural as a raw material. The hydrogen used in carrying out the method of the present invention may be any ordinary 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 There are no particular restrictions, and the reaction proceeds easily even under normal pressure.

Although pressurization can be applied to promote the reaction, the pressure is preferably about 5 atmospheres or less in order to suppress side reactions. The reaction temperature is
There is no particular restriction, and it is preferable to heat the reaction to promote the reaction, but in order to suppress side reactions, the temperature is preferably 100°C or less, preferably in the range of about 10°C to 80°C.

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 6y (41.5 mmol) was placed in a four-bottle flask equipped with a hydrogen introduction tube, a cooling tube, a thermometer, and a stirrer, and 20 ml of N,N-dimethylformamide was added.
It was dissolved in

Then 0.148y (0.83 mmol) of palladium chloride was added. After replacing the reaction vessel with hydrogen, the temperature was 40°C in a water bath. It was heated to C. Subsequently, the mixture was stirred at 40°C and the reaction was continued for 3 hours. During this time, hydrogen was continuously introduced through an inlet tube under approximately atmospheric pressure from a hydrogen-filled buret sealed with water (amount of hydrogen required for the reaction: 998 ml). After the reaction was completed, the catalyst was removed and the reaction solution was quantitatively analyzed by gas chromatography (determined by G.C-1.S method using diphenyl ether as an internal standard). As a result, the yield of 5-methylfurfural was 98%.
and the conversion rate of 5-chloromethylfurfural is 9
It was 9.6%.

Gas chromatography analysis conditions Packing material: DEGS (diethyl glycol)
Succinate polyester, 1
0%) Support: Chromosorp W Column length: 7:111]1 Example 2 5-chloromethylfurfural 2.06y (14.26y)
mmol) was placed in a flask similar to that used in Example 1, and dissolved in 22.5 mL of tetrahydrofuran.

Thereafter, 0.1086 f (0.612 mmol) of palladium chloride was added and the reaction vessel was purged with hydrogen, and then heated to 40°C in a water bath. Subsequently, stirring was performed at 400C and reaction was continued for 5 hours. Hydrogen was supplied using the same equipment as in Example 1 (hydrogen consumption: 383 ml). After the reaction was completed, the catalyst was removed and quantitative determination was performed using gas chromatography. 5-methylfurfural yield; 95.2
% 5-Chloromethylfurfural conversion rate; 100% Example 35-chloromethylfurfural 2y1 Ethyl acetate 2
An experiment was conducted under the same reaction conditions as in Example 1 using 0ml 115% palladium-barium sulfate 1.179y.

5-Methylfurfural yield: 85.7% 5-chloromethylfurfural conversion rate 100% Example 4 5-chloromethylfurfural 2V 11,4-dioxane 20 mL 1
Example 1 using 5% palladium carbon 1.179f
The experiment was conducted under similar reaction conditions.

5-Methylfurfural yield: 83.5% 5-chloromethylfurfural conversion: 99.1% Example 5 5-chloromethylfurfural 2f1 Palladium chloride 0.110
4y and acetone 18 mL. ．． An experiment was conducted under the same reaction conditions as in Example 1, except that a mixed solvent consisting of N,N-dimethylformamide 2Tn1 was used and the reaction time was 5 hours.

5-Methylfurfural yield: 90.2% 5-chloromethylfurfural conversion rate: 99.0% Example 6 2 g of 5-chloromethylfurfural, palladium black 0.0
An experiment was conducted under the same reaction conditions as in Example 1, except that a mixed solvent consisting of 6y and 18 m of toluene and 2 ml of N,N-dimethylformamide was used and the reaction time was 8 hours.

5-methylfurfural yield: 86.1% 5-chloromethylfurfural conversion rate: 97.3%) Example 7 5-chloromethylfurfural 2y1 Palladium black 0.
An experiment was conducted under the same reaction conditions as in Example 1 using 20 ml of 06yNN,N-dimethylformamide.

Claims (1)

[Scope of Claims] 1. A method for producing 5-methylfurfural, which comprises reacting molecular hydrogen to 5-chloromethylfurfural using a palladium-based catalyst in the presence of an organic solvent. 2. The manufacturing method according to claim 1, which uses one or more of amide compounds, ether compounds, and ester compounds as the organic solvent. 3. The method for producing 5-methylfurfural according to claim 1 or 2, which uses a mixed solvent containing at least one of an amide compound, an ether compound, and an ester compound as an organic solvent.