Intramolecular (4+3) Cycloadditions of Oxidopyridinium Ions: Towards Daphnicyclidin A
Intramolecular (4+3) Cycloadditions of Oxidopyridinium Ions: Towards Daphnicyclidin A
复制标题
氧化吡啶鎓离子的分子内 (4 3) 环加成：朝向 Daphnicyclidin A
DOI：
10.1002/chem.202200370
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Harmata, Michael
中科院分区：
文献类型：
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作者：
Tu, Jianzhuo;Ripa, Rawshan A.;Kelley, Steven P.;Harmata, Michael
5-羟基烟酸酯与含有二烯官能团的亲电试剂的N-烷基化产生盐，其在碱存在下加热时经历分子内（4+3）环加成反应。初步研究使用三碳系链连接吡啶离子和二烯，揭示了与此类底物反应的固有选择性的某些方面。更具挑战性的是合成仅具有两个碳系链的相关物种。然而，这些化合物的环加成是成功的，直接导致生物碱daphnicyclidin A的ABC环系统。
N‐alkylation of 5‐hydroxynicotinic acid esters with electrophiles containing diene functionality produces salts that undergo intramolecular (4+3) cycloaddition reactions upon heating in the presence of base. Initial studies used a three‐carbon tether to join the pyridinium ion and diene, revealing some aspects of the inherent selectivity of the reaction with such substrates. Much more challenging was the synthesis of related species possessing only a two‐carbon tether. Nevertheless, the cycloaddition of such compounds was successful, leading directly to the ABC ring system of the alkaloid daphnicyclidin A.