| 摘要 |
<p>3-Isoxazolole having the formula (I), wherein R1 designates lower alkyl or substituted lower alkyl, aryl or substituted aryl, and R2 designates hydrogen, lower alkyl or substituted lower alkyl, or R1 forms together with R2 and the carbon atoms, to which they are attached, a ring having 5 to 7 carbon atoms, and tautomers thereof, are prepared in that to an aqueous alkaline solution of hydroxylamine having a pH-value in the range 8 to 12 one adds either a) a beta-keto ester having the formula R1 .CO.CH(R2)COOR3, where R1 and R2 have the stated meaning, and R3 is an ester-forming group, which may be part of R2, or b) diketene, taking care of quick intermixing with the alkaline solution and of maintenance of the pH-value of the mixture within the stated range during the reaction, as well as of keeping the temperature of the mixture below about 30oC, and that after completion of the reaction of hydroxylamine with beta-keto ester or dikatene one mixes the reaction mixture quickly with an excess of aqueous acid to obtain a strongly acid mixture so that 3-isoxazolole isformed as a predominant reaction product, whereupon this product is isolated. </p> |
