5-Methyl-4-isoxazolecarboxylic acid Chemical Properties

Melting point:

144-148 °C(lit.)

Boiling point:

308.3±22.0 °C(Predicted)

Density 

1.348±0.06 g/cm3(Predicted)

storage temp. 

Sealed in dry,Room Temperature

solubility 

DMSO (Slightly), Methanol (Slightly)

form 

Solid

pka

2.85±0.25(Predicted)

color 

White to Pale Brown

BRN 

116000

CAS DataBase Reference

42831-50-5(CAS DataBase Reference)

Safety Information

Hazard Codes 

Xi,F

Risk Statements 

36/37/38-37/38-36-10

Safety Statements 

22-26-36/37/39-36-16

WGK Germany 

3

HazardClass 

IRRITANT

HS Code 

29349990

MSDS

• Language:English Provider:SigmaAldrich
• Language:English Provider:ALFA

5-Methyl-4-isoxazolecarboxylic acid Usage And Synthesis

Chemical Properties

Cream to brown Solid

Uses

5-Methylisoxazole-4-carboxylic Acid (Leflunomide EP Impurity D) is an intermediate for synthesis of Leflunomide (L322750). Herbicidal activities towards Digitaria ciliaris.

Flammability and Explosibility

Non flammable

Synthesis

Example 4 Preparation of 5-methylisoxazole-4-carboxylic acid To a two-necked flask equipped with a mechanical stirrer and a horizontal condenser for distillation were added 40.0 g of crude ethyl 5-methyl-4-isoxazolecarboxylate and 44 g of 60% sulfuric acid solution. The mixture was heated to 85°C while the ethanol generated from the reaction was continuously distilled. After 4 hours of reaction, thin layer chromatography (TLC) analysis showed complete disappearance of spots of ester compounds. After cooling the reaction mixture to room temperature, the solid product (16.5 g) was collected by filtration. The filtrate was retained for a second product collection at room temperature. The resulting crude acid was dissolved in 60 mL of 2% acetic acid-toluene mixed solvent and crystallized to give 5-methylisoxazole-4-carboxylic acid (9.5 g) of about 99.9% purity. The crystallized mother liquor was retained for subsequent batch processing. The crystallization process was performed as follows: the crude acid was added to 2% acetic acid-toluene solvent mixture and heated for 30 minutes until dissolved. Separate and remove the brown oil from the bottom of the flask. The upper clear organic phase was carefully transferred to another container and left to crystallize.

References

[1] Patent: US2003/139606, 2003, A1
[2] Letters in Drug Design and Discovery, 2016, vol. 13, # 9, p. 912 - 920
[3] Journal of Heterocyclic Chemistry, 1991, vol. 28, # 2, p. 453 - 457
[4] Yakugaku Zasshi, 1959, vol. 79, p. 836
[5] Chem.Abstr., 1960, p. 1493

5-Methyl-4-isoxazolecarboxylic acid(42831-50-5)Related Product Information

• Methyl acrylate
• Methyl acetate
• Bensulfuron methyl
• 2-(Trifluoromethyl)benzoic acid
• 4-(Aminomethyl)benzoic acid
• m-Toluic acid
• o-Toluic acid
• 4-(Chloromethyl)benzoic acid
• Kresoxim-methyl
• 4-Bromomethylbenzoic acid
• p-Toluic acid
• Sulfamethoxazole
• Methylparaben
• 5-Methylisoxazole
• Thiophanate-methyl
• Methyl
• A77 1726
• Leflunomide 3-Isomer