3- isoxazole-5-carboxylates

The reaction of methyl acetylpyruvate (312) with hydroxylamine hydrochloride gave the 3-carboxylate (313) in 76% yield together with traces of the isomeric 5-carboxylate (314) (78MIP41600). However, the sodium salt (315) of acetylpyruvic acid resulted in 3-methyl-isoxazole-5-carboxylic acid (316) as the major product. 

Aminoisoxazoles 22 have been synthesized by nucleophilic addition of lithiated alkyl nitriles to a-chloroximes <06OL3679>. The cyclization of oxime dianions with diethyl oxalate afforded isoxazole-5-carboxylates 23 by acid-mediated dehydration of intermediate hydroxyisoxazolines <06S2515>. 

C3H9N03 ammonium lactate 52003-58-4 20,00 1.2006 1 2497 C4H3N03 isoxazole-5-carboxylic acid 21169-71-1 25.00 1.4025 2... 

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>. 

AI mixed with the amides of isoxazole-5-carboxylic acids, the mixture being difficult to separate (75ACS(B)65). Such problems are typical in the preparation of many other amino-substituted heterocycles by these nitrene rearrangements (Scheme 73). 

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