Mechanistic Investigation into the Regio-Controllable Hydroallylations of Alkynes with Allylborons under Pd-Based Synergetic Catalyses,The Journal of Organic Chemistry

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Mechanistic Investigation into the Regio-Controllable Hydroallylations of Alkynes with Allylborons under Pd-Based Synergetic Catalyses
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2023-03-17 , DOI: 10.1021/acs.joc.3c00004
Lingjun Liu ₁ , Yuxia Liu _{1,

2} , Qiao Wu ₁ , Xufang Zhao ₂ , Yulin Li ₃ , Guang Chen _{2,

3} , Siwei Bi ₁

Affiliation

Density functional theory calculations were employed to investigate the Pd-catalyzed regio-selective hydroallylations of alkynes with allylborons: cooperation of Cu(OAc)₂ and dppe resulting in 1,4-dienes while combination of AdCO₂H and PCy₃ leading to 1,5-dienes. A unified rationalization mechanism called “Lewis-acid–base-interaction promoted deprotonation/3,3-rearrangement” was proposed. Compared with the commonly reported metathesis pathway to only afford the metal-allyl intermediate, in the newly established mechanism, an additional Brønsted acid (as an initiator of the Pd⁰ oxidative addition) is generated by the interaction of the allylboron (Lewis acid) B atom with the ⁿBuOH (Lewis base) O atom, and subsequent 3,3-rearrangement ensures the thermodynamic feasibility of the reaction. In addition, it was found that excess Cu(OAc)₂ plays two potential roles in the oxidative addition/alkyne insertion: (i) the participation of one AcO^– of Cu(OAc)₂ ensures a large orbital overlap between the migrating H and Pd atoms, facilitating the formal AcO–H cleavage and (ii) the extra (OAc)₂Cu···O(carboxyl) σ-coordination indirectly contributes to the (Me)C≡C(Ph) insertion into the Pd–H bond. Further analysis showed that the origin of the regioselectivity is closely related to the employed phosphorus ligand. These revealed results, which have been overlooked in the previous documents, would aid the development of new related catalytic reactions.

中文翻译：

钯基协同催化下炔烃与烯丙基硼的区域可控氢烯丙基化机理研究

密度泛函理论计算用于研究 Pd 催化的炔烃与烯丙基硼的区域选择性氢烯丙基化反应：Cu(OAc) ₂和 dppe 的合作产生 1,4-二烯，而 AdCO ₂ H 和 PCy ₃的组合产生 1, 5-二烯。提出了一种称为“路易斯酸碱相互作用促进去质子化/3,3-重排”的统一合理化机制。与通常报道的仅提供金属-烯丙基中间体的复分解途径相比，在新建立的机制中，通过烯丙基硼（路易斯酸）B 的相互作用产生额外的布朗斯台德酸（作为 Pd 0 氧化加成的引发剂^）原子与ⁿBuOH（路易斯碱）O原子，以及随后的3,3-重排保证了反应的热力学可行性。此外，发现过量的 Cu(OAc) ₂在氧化加成/炔烃插入中起着两个潜在的作用：(i) Cu(OAc) _2的一个^AcO的参与确保了迁移的 H 和Pd 原子，促进正式的 AcO–H 裂解和 (ii) 额外的 (OAc) ₂Cu···O(羧基) σ-配位间接有助于 (Me)C≡C(Ph) 插入 Pd-H 键。进一步分析表明，区域选择性的来源与所使用的磷配体密切相关。这些揭示的结果在以前的文件中被忽视，将有助于开发新的相关催化反应。

更新日期：2023-03-17

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