5-Methylisoxazole-4-carboxylic acid chloride

Methylisoxazole-3-carboxylic acid chloride 4-(p-Aminoethyl)benzene sulfonamide hydrochloride Chloroformic acid methyl ester N-Amino-hexamethyleneimine... 

Methylisoxazole-5-carboxylic acid was converted into the corresponding 5-carboxamides and 5-(l/7-pyrazol-l-ylcarbonyl) derivatives in satisfactory yields by treatment with thionyl chloride and amines or pyrazoles <2002SC425>. A three-component assembly of isoxazole-5-carboxylic acid chloride, 1,1-dimethylallene, and bis-pinacolatodiboron, catalyzed by a phosphine-free palladium complex, gave 2-acylallylboronate derivatives regiose-lectively (Equation 47) <2003JA12576>. On the other hand, a mild procedure allowed the preparation of /3,7-unsaturated ketones by simple reaction of 3-aryl-5-methylisoxazole-4-carboxylic acid chlorides with allyl bromide and indium in DMF (Equation 48) <1997TL8745>. 

Properly substituted isoxazolecarboxylic acids can be converted into esters, acid halides, amides and hydrazides, and reduced by lithium aluminum hydride to alcohols. For example, 3-methoxyisoxazole-5-carboxylic acid (212) reacted with thionyl chloride in DMF to give the acid chloride (213) (74ACS(B)636). Ethyl 3-ethyl-5-methylisoxazole-4-carboxylate (214) was reduced with LAH to give 3-ethyl-4-hydroxymethyl-5-methylisoxazole (215) (7308(53)70). 

The 3-o-chlorophenyl-5-methylisoxazole-4-carboxylic acid, from which the acid chloride was prepared, was obtained by hydrolysis of the ester product of the reaction between o-chlorobenzohydroxamic chloride and ethyl acetoacetate in methanolic sodium methoxide. Reaction with thionyl chloride gave the starting material. 

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