Theoretical Study on the Mechanism of the [2 + 1] Thermal Cycloaddition between Alkenes and Stable Singlet (Phosphino)(silyl)carbenes

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• 作者：Bego&ntilde ; a Lecea ; Mirari Ayerbe ; Ana Arrieta ; Fernando P. Cossí ; o ; Vicenç ; Branchadell ; Rosa M. Ortu&ntilde ; o ; Antoine Baceiredo
• 刊名：Journal of Organic Chemistry
• 出版年：2007
• 出版时间：January 19, 2007
• 年：2007
• 卷：72
• 期：2
• 页码：357 - 366
• 全文大小：560K
• 年卷期：v.72,no.2(January 19, 2007)
• ISSN：1520-6904

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The mechanism and the origins of the stereocontrol observed in the reaction between differently substitutedalkenes and stable (phosphino)(silyl)carbenes giving cyclopropanes have been studied computationally.These cyclopropanation reactions proceed via asynchronous concerted mechanisms involving earlytransition structures with a significant charge transfer from the carbene to the alkene moiety. The geometricfeatures of these transition structures preclude a significant overlap between the orbitals required forsecondary orbital interactions between the reactants. The stereoselectivity observed experimentally stemsfrom favorable electrostatic and steric interactions between the reactants leading to the stereoisomers inwhich the phosphanyl and carbonyl or aryl groups are cis to each other.