1, 3-Dipolar cycloadditions of the C-aryl-N-alkylnitrones 2a-c and the C, N-dialkylnitrones 2e-g with the (E)-1-alkyl-2-nitroethenes 1a, b afforded predominantly or exclusively the cis-3-substituted 4-nitroisoxazolidines 3a-d and 3f-h. Exceptions are the reactions of C-phenyl-N-isopropylnitrone (2d) and C, N-diisopropylnitrone (2h) with 1a which gave the 3, 4-trans isomers 4e and 4i as the major products. These results can be rationalized in terms of secondary orbital interactions and steric effect.
C-芳基-N-烷基
肟 2a-c 和 C, N-二烷基
肟 2e-g 与 (E)-1-烷基-2-
硝基乙烯 1a, b 的 1, 3-偶极环加成反应主要或完全生成了 cis-3-取代的 4-硝基
异噁唑啉 3a-d 和 3f-h。例外的是 C-
苯基-N-
异丙基肟 (2d) 和 C, N-
二异丙基肟 (2h) 与 1a 的反应,生成了主要产物 3, 4-反型异构体 4e 和 4i。这些结果可以用次级轨道相互作用和立体效应进行解释。