- 作者: Mei-Hsiu Shiha,b, Kuei-Hua Hera and Mou-Yung Yeha
- 中文摘要: Cycloadditions of 3-arylsydnone nitrile oxides (1) with various cyclic alkenes led to 4-isoxazolyl or 4-isoxazolinyl sydnones. The reactions were controlled either by the HOMO (dipole)-LUMO (dipolarophile) interaction or by the LUMO (dipole)-HOMO (dipolarophile) interaction. The former were accelerated by electron withdrawing substituted dipolarophiles, such as 2-cycloalken-1-ones (3a~3c), etc., while the latter were improved by the dipolarophiles with electron-donating substituents, such as 1-morpholino-1-cyclohexene (3d), 1,3-cyclohexadiene (3e). Besides that, methylenecycloalkanes 3f~3g are more active than cyclohexene toward cycloaddition with nitrile oxides 1. The cycloaddition adducts may serve as useful building blocks in synthesis through chemical modification and ring cleavage, and also be employed in the syntheses of many natural products with significant and special activities.
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