An Efficient Synthesis of 4-Acyl-5-hydroxy-3-methylisoxazoles through an Acyl-Transfer Reaction

Abstract

Acylation of 3-methyl-3-isoxazolin-5-one (2a) with acyl chlorides was investigated. 2-Acyl-3-methyl-3-isoxazolin-5-ones 5 and 5-acyloxy-3-methylisoxazoles 6, which were prepared from 2a and acyl halides, underwent acyl-transfer reaction in the presence of 4-(N, N-dimethylamino)-pyridine or potassium carbonate to give 4-acyl-5-hydroxy-3-methylisoxazoles 4. By using this reaction, 4-(2, 4-dichlorobenzoyl)-5-hydroxy-3-methylisoxazole (4h), which can be viewed as a bioisostere of the herbicidal compound, 4-(2, 4-dichlorobenzoyl)-1, 3-dimethyl-5-hydroxypyrazole (1a), was synthesized.