Synthesis of 3-Ethoxyisoxazole Derivatives and 3-Ethoxy-1<b><i>H</i></b>-pyrazole Derivatives from<b><i>β</i></b>-Oxo Thionoesters
作者:Tetsuo Ohta、Hironori Fujisawa、Yasuto Nakai、Isao Furukawa
DOI:10.1246/bcsj.73.1861
日期:2000.8
3-Ethoxyisoxazoles and 3-ethoxy-1H-pyrazoles were obtained in high yields from β-oxo thionoesters. The reaction of the ethyl β-oxo thionoesters with hydroxylamine hydrochloride in the presence of triethylamine at room temperature for 2 h gave the ethyl 3-oxopropiohydroximates and their hemiacetals, which were easily converted to the 3-ethoxyisoxazoles by refluxing for 3 h at pH 3—5. On the other hand, the reaction of the ethyl β-oxo thionoesters with hydrazine derivatives in the presence of triethylamine for 3—8 h at room temperature directly yielded the 3-ethoxy-1H-pyrazoles.
从β-噻吩酯中以高产率得到了3-乙氧基异噁唑和3-乙氧基-1H-吡唑。在室温下,将乙基β-噻吩酯与盐酸羟胺在三乙胺存在下反应2小时,得到乙基3-氧代丙基羟胺和它们的半缩醛,这些产物可以通过在pH 3—5下回流3小时轻松转化为3-乙氧基异噁唑。另一方面,将乙基β-噻吩酯与肼衍生物在三乙胺存在下在室温下反应3—8小时,可以直接得到3-乙氧基-1H-吡唑。