Phosphino Hydrazones as Suitable Ligands in the Asymmetric Suzuki–Miyaura Cross-Coupling
作者:Abel Ros、Beatriz Estepa、Antonio Bermejo、Eleuterio Álvarez、Rosario Fernández、José M. Lassaletta
DOI:10.1021/jo300548z
日期:2012.5.18
Phosphino hydrazones derived from C2-symmetric hydrazines exhibit excellent catalytic activity and provide good enantioselectivities in the asymmetric Suzuki–Miyaura cross-coupling to axially chiral biaryls, in particular for the most challenging reactions of monocyclic, functionalized aryl bromides and triflates. X-ray analysis of preformed [Pd(P/N)Cl2] precatalysts [(P/N) = phosphino hydrazone] revealed
衍生自C2对称肼的膦具有出色的催化活性,并且在不对称的Suzuki-Miyaura与轴向手性联芳基的偶合中具有良好的对映选择性,特别是对于单环,官能化的芳基溴化物和三氟甲磺酸酯最具挑战性的反应。预先形成的[Pd(P / N)Cl2]预催化剂[(P / N)=膦)的X射线分析表明,moiety部分具有很强的n-π共轭,通过吡咯烷N(sp3)的高平面度可以确定)原子,这使得围绕N–N键的旋转无关紧要。配合物的特征还在于具有包膜样的构象,其中Pd原子位于吡咯烷基的最接近立体异构中心的2-苯基的相反侧。