Intramolecular Oxyallyl鈥揅arbonyl (3 + 2) Cycloadditions

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• 作者：Elizabeth H. Krenske ; Shuzhong He ; Jian Huang ; Yunfei Du ; K. N. Houk ; Richard P. Hsung
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：April 10, 2013
• 年：2013
• 卷：135
• 期：14
• 页码：5242-5245
• 全文大小：289K
• 年卷期：v.135,no.14(April 10, 2013)
• ISSN：1520-5126

文摘

Cycloadditions involving oxyallyl intermediates typically require an electron-rich diene or alkene, but we have discovered the first examples of the cycloaddition of heteroatom-stabilized oxyallyls onto carbonyl groups. An oxazolidinone-substituted oxyallyl undergoes chemoselective (3 + 2) cycloaddition onto the carbonyl group of a tethered dienone in preference to formation of the expected (4 + 3) cycloadduct. Density functional theory calculations indicated that the (3 + 2) cycloaddition takes place through a concerted, highly asynchronous mechanism. The transition state features simultaneous interactions of the oxyallyl LUMO with the carbonyl 蟺 and lone-pair orbitals, making this reaction 鈥渉emipseudopericyclic鈥?(halfway between purely pericyclic and purely pseudopericyclic). Further (3 + 2) cycloadditions involving tethered phenyl ketones and a tethered enone were predicted theoretically and verified experimentally.