Phosphine-catalyzed synthesis of 6-substituted 2-pyrones: Manifestation of E/Z-isomerism in the zwitterionic intermediate
Phosphine-catalyzed synthesis of 6-substituted 2-pyrones: Manifestation of E/Z-isomerism in the zwitterionic intermediate
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DOI：
10.1021/ol050946j
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发表时间：
2005-07-07
期刊：
影响因子：
5.2
通讯作者：
Kwon, O
中科院分区：
文献类型：
--
作者：
Zhu, XF;Schaffner, AP;Kwon, O
我们报道了一步膦催化醛和烯丙酸乙酯之间的环形成6-取代的2-吡酮。该反应的机理原理需要明确讨论通过在异丙酸盐上加成磷化氢而形成的两性离子中间体的ez -异构。立体要求高的三烷基膦促进平衡向e -异构体两性离子转移，并导致6-取代的2-吡酮的形成。各种芳香族和脂肪族醛在中等到优异的产量中进行转化。
We report a one-step phosphine-catalyzed annulation between aldehydes and ethyl allenoate to form 6-substituted 2-pyrones. The mechanistic rationale for this reaction requires explicit discussion of the EIZ-isomerism of the zwitterionic intermediate formed by the addition of a phosphine to the allenoate. Sterically demanding trialkylphosphines facilitate the shift of equilibrium toward the E-isomeric zwitterion and lead to the formation of 6-substituted 2-pyrones. Various aromatic as well as aliphatic aldehydes undergo the transformation in moderate to excellent yield.