Method for synthesizing isoxazole

Abstract

The invention aims to disclose a new method for synthesizing isoxazole, which has simple operation and low cost. The reaction formula is as the above. The method of the invention comprises the steps: alpha, beta- unsaturated oximes are dissolved in the organic solvent with the weight 1 to 20 times that of the oximes, 0.25 to 4 times of water by volume is added to form a system of homogeneous phase or non-homogeneous phase, then 0.3 to 2 times of inorganic base by mol ratio and 1 to 10 percent of catalyst by weight are added in sequence, whererin, under non-homogeneous phase conduction, 1 to 10 percent of phase transfer catalyst by weight is added, the temperature is gradually increased to 10 to 100 DEG C, oxidant is added, continuously reacting for 8 to 20 hours, after complete reaction, excess oxide is removed by using inorganic reducing agent, through extracting layering an organic layer is layered out, decompression fractionating is carried out after precipitation, the product can be gained after collecting main distillate fraction with 60 to 90 percent of yield rate and purity higher than 95 percent.

Description

technical field [0001] The invention relates to a method for synthesizing isoxazole, which belongs to the technical field of fine chemical preparation. Background technique [0002] Isoxazole is an important organic intermediate. The usual preparation methods are as follows: [0003] 1), 1,3-biscarbonyl compound and hydroxylamine form carbonyl oxime, and then dehydrate to obtain. This method uses 1,3-dicarbonyl compound as a raw material, and selectivity is involved in the synthesis, and it is difficult to obtain a pure single product, so the separation and purification are complicated. [0004] 2), α-alkyne ketone (aldehyde) and hydroxylamine form α-alkyne oxime, and then intramolecular ring closure is obtained. This method uses α-alkyne ketone (aldehyde), and raw material stability is poor, and is not easy to obtain, therefore is not suitable for industrial production. [0005] 3) Halogenated α, β-unsaturated carbonyl compound forms oxime with hydroxylamine, and then o...

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Problems solved by technology

Although this method is convenient, it will use a large excess of iodine-potassium iodide (3 to 4 times), and use a large amount of organic solvent (generally tetrahydrofuran), so the cost is very expensive

[0008] In the general method, only the epoxy intermediate can be obtained directly by oxidizing with an oxidant, and the product must be separated and then acid-catalyzed to close the ring to obtain the product. The yield of this method is generally relatively low, about 50-70%.

In addition, the method of the prior art directly uses iodine-potassium iodide, although a higher yield can be obtained, but its cost is very high, and it is not suitable for industrial production

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