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碘代芳烃和苯并环丁醇偶联的机理研究
首发时间：2023-04-10
摘要：本文运用密度泛函理论（dft）计算，研究了手性膦氧配体络合pd(0)催化碘代芳基烯丙基醚合成苯并二氢呋喃衍生物的反应机理。计算确定了最优反应路径包括氧化加成、烯烃迁移插入、β-c消除和还原消除。计算结果表明，烯烃迁移插入pd-c键是立体选择性决定步，β-c消除是区域选择性决定步和整个反应的决速步。计算预测反应的主产物是r构型--2,3-二氢苯并呋喃衍生物，与实验报道一致。独立体密度模型分析表明，空间效应影响了烯烃迁移插入过程中的立体选择性。生成r构型的五元环pd(ii)中间体时所经历的过渡态中，相应结构的空间位阻较小，容易形成r构型产物。生成s构型的五元环pd(ii)中间体时所经历的过渡态存在烯烃和叔丁基、苯环和环己基之间的较大排斥，该过程需要跨越的能垒较高，难形成s构型的产物。苯并环丁醇底物自身的几何扭曲是β-c消除的区域选择性发生的主要原因。
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coupling reaction of aryl iodides and benzocyclobutanol: a computational study
abstract：density functional theory (dft) calculations were employed to study palladium-catalyzed cross-coupling reaction of o-iodoaryl-derived allyl ethers and benzocyclobutanol.the mechanism of this reaction is consist of oxidative addition, alkene insertion, o-h activation, β-c elimination and reductive elimination. theoretical calculations indicate that, the regioselectivity is controlled by the alkene insertion step, the regioselectivity-limiting step and the rate-limiting step is the β-c elimination. our computational results demonstrated that, r-configurational 2,3-dihydrobenzofuran skeleton is confirmed to be the major product. independent gradient model analysis shows that spatial effects affect the stereoselectivity of olefin migration and insertion reactions. the r-configurational five-membered pd(ii) intermediate could afford through alkene insertion transition state, which reveals smaller steric interaction. in contrast, the s-configurational five-membered pd(ii) could be formed via palladacycle transition state with larger repulsion between alkene and tert-butyl, and between benzene and cyclohexyl. the geometric distortion of the benzocyclobutanol is the main reason for the regioselectivity of β-c elimination.
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碘代芳烃和苯并环丁醇偶联的机理研究
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