Mechanistic Investigation of the Palladium-Catalyzed Decarboxylative Cyclization of γ-Methylidene-δ-valerolactones with Isocyanates: Kinetic Studies and Origin of the Site Selectivity in the Nucleophilic Attack at a (π-Allyl)palladium
作者:Ryo Shintani、Takaoki Tsuji、Soyoung Park、Tamio Hayashi
DOI:10.1021/ja1023223
日期:2010.6.2
of this selectivity is provided. The selectivity between 3 and 4 is also influenced by the nature of the nitrogen substituent on isocyanates 2, and more electron-rich substituents tend to give higher selectivity toward azaspiro[2.4]heptanones 4. These studies represent the first systematic investigation into the selectivity between terminal attack and central attack at (pi-allyl)palladium species by
描述了钯催化的 γ-亚甲基-δ-戊内酯 1 与异氰酸酯 2 的脱羧环化反应的机理研究。该反应可以被钯三芳基膦配合物有效催化,得到哌啶酮 3 和/或氮杂螺[2.4]庚酮 4。通过使用 NMR 光谱的动力学研究,已经确定内酯 1 氧化加成到钯 (0) 是转换-催化循环的限制步骤。通过改变三芳基膦配体的电子特性,可以轻松控制 3 和 4 之间的产物分布,并解释了这种选择性的起源。3 和 4 之间的选择性还受异氰酸酯 2 上氮取代基的性质影响,