Povarov Reactions Involving 3-Aminocoumarins: Synthesis of 1,2,3,4-Tetrahydropyrido[2,3-<i>c</i>]coumarins and Pyrido[2,3-<i>c</i>]coumarins
作者:Amit A. Kudale、Jamie Kendall、David O. Miller、Julie L. Collins、Graham J. Bodwell
DOI:10.1021/jo801411p
日期:2008.11.7
Yb(OTf)3 to afford 1,2,3,4-tetrahydropyrido[2,3-c]coumarins. Yields were generally good, but the diastereomeric ratios were highly variable. The products arose through a formal [4 + 2] cycloaddition (inverse electron demand Diels-Alder reaction) followed by tautomerization. As such, these are examples of the Povarov reaction. A range of 1,2,3,4-tetrahydropyrido[2,3-c]coumarins was then synthesized using a
3-氨基香豆素(5)与4-硝基苯甲醛(8)的缩合反应得到2-氮杂二烯(9),在Yb(OTf)3存在的情况下,它与各种富含电子的烯烃反应(10个实例),得到1,2 ,3,4-四氢吡啶并[2,3-c]香豆素。收率通常不错,但是非对映异构体的比例变化很大。通过正式的[4 + 2]环加成反应(逆电子需求Diels-Alder反应),然后进行互变异构化,产生了产物。因此,这些是Povarov反应的实例。然后使用该反应的三组分形式合成一系列1,2,3,4-四氢吡啶并[2,3-c]香豆素,该反应涉及原位形成2-氮二烯组分。这些产品中的一部分经各种氧化剂处理后转化为相应的吡啶并[2,3-c]香豆素,