New Synthesis of 3-Chloroisoxazoles.

Abstract
A synthesis of 3-chloroisoxazoles, based on treatment of 2-methyl-4-isoxazolin-3-ones with POCl3, is described. The use of mixtures of PCl5 and POCl3 instead of the latter reagent alone gave lower yields and more contaminated products. The 2-methyl-4-isoxazolin-3-ones were obtained together with the isomeric 3-methoxyisoxazoles by treatment of 3-isoxazolols with diazomethane or methyl iodide and base. The ratio between N- and O-methylated products proved strongly dependent on the type of methylating reagent and the structure of the 3-isoxazolols.