- Process for the preparation of 3,5-disubstituted isoxazoles
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A novel process for the preparation of 3-bromo- and 3-chloro-5-substituted isoxazoles is provided. Dibromo- or dichloro-formaldoxime is reacted with an excess of an 1-alkyne derivative of the formula where R is hydrogen, phenyl or 1-6 C alkyl optionally substituted by halogen, OH, OR', CHO, COR', COOR', CONH2, CONR'R" or NHCOR' where, in turn, R' and R", which may be the same or different, are a 1-6 C alkyl or haloalkyl, in the presence of (i) at least an equimolecular amount, with respect to the dibromo- or dichloro-formaldoxime, of an alkaline base selected from the class consisting of sodium and potassium carbonate and bicarbonate and (ii) an inert solvent in which the 1-alkyne is soluble at room temperature.
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