1,3-Dipolar cycloadditions of (1Z,4R*,5R*)-1-(arylmethylidene)-4-benzamido-5-(4-methoxyphenyl)-3-oxopyrazolidin-1-ium-2-ides 6a–6f and their 5-(1H-indol-3-yl) analogues 6g–6j to olefinic dipolarophiles 7–9 were studied. Stereochemistry was controlled by the structure of dipoles 6 and dipolarophiles 7–9. Reactions of ortho-unsubstituted dipoles 6a–6c, 6g gave the major isomers 10 and 14 with syn-oriented protons H-3 and H-5, whilst ortho-disubstituted dipoles 6d, 6e, 6j gave cycloadducts 11 and 12 with anti-oriented protons H-3 and H-5. In comparison with their 5-phenyl-substituted analogues, dipoles 6a–6e, 6g, 6j were less reactive in cycloadditions to olefinic dipolarophiles 7–9. This was reflected in longer reaction times, lower yields, and sometimes in lower selectivity as well. The relative configurations of cycloadducts were determined by NMR.
(1
Z,4
R*,5
R*)-1-(芳基甲基亚甲基)-4-苯甲酰
氨基-5-(4-
甲氧基苯基)-3-氧代
吡咯啉-1-ium-2-ides
6a–
6f 及其5-(1
H-
吲哚-3-基)类似物
6g–
6j 与烯烃双极亲受体
7–
9 的1,3-偶极环加成反应进行了研究。立体
化学由偶极子
6 和双极亲受体
7–
9 的结构控制。未取代的邻位偶极子
6a–
6c,
6g 反应主要得到异构体
10 和
14,其氢原子H-3和H-5朝向相同,而取代的邻位偶极子
6d,
6e,
6j 反应得到具有反向朝向氢原子H-3和H-5的环加成产物
11 和
12。与它们的5-苯基取代类似物相比,偶极子
6a–
6e,
6g,
6j 在与烯烃双极亲受体
7–
9 的环加成反应中反应性较低。这反映在反应时间较长、产率较低,有时也反映在选择性较低。环加成产物的相对构型通过NMR确定。