Reactivity, regiochemistry, and stereochemistry of a cyclic nitrone and its α-keto derivative in 1, 3-dipolar cycloaddition reactions
作者:Sk.Asrof Ali、Mohammed I.M. Wazeer
DOI:10.1016/s0040-4020(01)85105-x
日期:1988.1
Rate constants for the cycloadditions of 3,4,5,6-tetrahydropyridine 1-oxide (1) , and 3-oxo-3,4,5,6-tetrahydropyridine 1-oxide (2) to several mono- and disubstituted alkenes have been determined at 36°C by 1H NMR Spectroscopy. Small solvent effect on the rate constant indicate the concerted nature of the reaction. It is found that nitrone 2 reacts slower than 1 because of the presence of bond opposition
3,4,5,6-四氢吡啶-1-氧化物(1)和3-氧代-3,4,5,6-四氢吡啶1-氧化物(2)与几种单或双取代烯烃的环加成反应的速率常数为在36°C下由1确定1 H NMR光谱。溶剂对速率常数的影响很小,表明反应是协调一致的。已经发现,由于在前一种硝酮的过渡态中存在键对立应变,因此硝酮2的反应比1慢。加成率受硝酮的偶极矩影响。这些加成反应的反应性通常遵循边界轨道近似的预测。两种硝酮均表现出非常相似的区域化学和立体化学性质。与几种缺电子的烯烃观察到显着的次级轨道相互作用。然而,发现马来酸酐主要通过exo攻击模式进行加成。