Atropisomeric Phosphine Ligands Bearing C–N Axial Chirality: Applications in Enantioselective Suzuki–Miyaura Cross-Coupling Towards the Assembly of Tetra-<i>ortho</i>-Substituted Biaryls
of chiral phosphines featuring a C–N axial chirality and their applications in enantioselective Suzuki–Miyaura cross-coupling for accessing highly steric hindered tetra-ortho-substitutedbiaryls (26 examples up to 98:2 er). It is worth noting that the embodied carbazolyl framework is crucial to succeed the reaction, by the fruitful steric relief of bulky substrate coordination and transmetalation via
带有 C (Ar) -C (Ar)轴向手性的联芳基膦是众所周知的,并已成功应用于许多不对称催化剂中。然而,开发具有轴向手性 C (Ar)的手性配体-N 骨架由于其不受欢迎的较少限制的旋转屏障而仍然难以捉摸。事实上,克服配体开发中的这一挑战非常有吸引力,因为在手性轴上掺入 N 供体组分更有利于瞬态金属配位,因此,预计接近的底物会有更好的立体通信结果. 在此,我们提出了一种新的具有 C-N 轴向手性的手性膦的合理设计及其在对映选择性 Suzuki-Miyaura 交叉偶联中的应用,以获得高位阻四邻-取代的联芳基(26 个实例,最高 98:2 er)。值得注意的是,通过短暂的 Pd-N 跃迁到 Pd-π 方式,大量的底物配位和金属转移有效地释放空间位阻,体现的咔唑基框架对于反应的成功至关重要。DFT 计算揭示了一个有趣的 Pd-芳烃在咔唑平面上的行走特性,用于在催化循环中获得较低能量的首选路
Concise, efficient and practical assembly of bromo-5,6-dimethoxyindole building blocks
作者:Paul B. Huleatt、Jacelyn Lau、Sheena Chua、Yun Lei Tan、Hung Anh Duong、Christina L.L. Chai
DOI:10.1016/j.tetlet.2011.01.076
日期:2011.3
A concise, efficient and simple route to a series of bromoindole building blocks is described. The synthetic routes are highlighted by purification-free preparation of o-nitrocinnamate intermediates and clean, modified Cadogan indole syntheses. The scope of this indole synthesis has been explored and expanded through the use of a range of solvents and easily removable phosphine reagents.
Enantioselective Cross-Coupling for Axially Chiral Tetra-ortho-Substituted Biaryls and Asymmetric Synthesis of Gossypol
作者:He Yang、Jiawei Sun、Wei Gu、Wenjun Tang
DOI:10.1021/jacs.0c02686
日期:2020.4.29
Axiallychiral tetra-ortho-substituted biaryl skeleton exists in numerous biologically important natural products, pharmaceutical molecules, chiral catalysts and ligands. The efficient synthesis of chiral tetra-ortho-substituted biaryl structures remains a challenging but unsolved problem. Among various asymmetric synthetic protocols, enantioselective Suzuki-Miyaura cross-coupling represents one of