Department of Chemistry, University of Missouri-Columbia, 601 S. College Avenue, Columbia, Missouri, 65211, USA.
Chemistry. 2022 Jul 20;28(41):e202200370. doi: 10.1002/chem.202200370. Epub 2022 Jun 13.
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.
用含有二烯官能团的亲电试剂对 5-羟基烟酸酯进行 N-烷基化，生成的盐在碱性条件下加热会发生分子内（4+3）环加成反应。初步研究使用三碳键将吡啶鎓离子和二烯连接起来，揭示了此类底物反应固有选择性的一些方面。更具挑战性的是合成仅具有两个碳键的相关化合物。尽管如此，这些化合物的环加成反应还是成功的，直接得到了生物碱 daphnicyclidin A 的 ABC 环系统。
