Planar chiral palladacycle precatalysts for asymmetric synthesis

Abstract

<p>The first demonstration of a chiral palladacycle precatalyst in Pd(0) mediated asymmetric synthesis is achieved by a novel ligand synthesis/palladium capture procedure.</p>

Application of a Ferrocene‐Based Palladacycle Precatalyst to Enantioselective Aryl‐Aryl Kumada Coupling

“…In our previous work sodium dimethyl malonate was used to deprotonate the coordinated phosphine 2 and promote CÀ P bond formation by reductive elimination. [10] Therefore, after the addition of aryl iodide 7 b, 10 mol% of this base was added followed (after five minutes) by the Grignard reagent 8 and the mixture heated at 80 °C for 72 hours. This resulted in a quantitative conversion to (S a )-9 formed in 71 % e.e.…”

“…Dimeric palladacycle ( S p )‐ 4 was dissolved in THF and the phosphine complex ( S p )‐ 19 formed in situ following the addition of two equivalents of diphenylphosphine. In our previous work sodium dimethyl malonate was used to deprotonate the coordinated phosphine 2 and promote C−P bond formation by reductive elimination [10] . Therefore, after the addition of aryl iodide 7 b , 10 mol% of this base was added followed (after five minutes) by the Grignard reagent 8 and the mixture heated at 80 °C for 72 hours.…”

“…[9] We reported recently the transformation of planar chiral palladacycle 1, via 2, into PÀ N ligated Pd(0) complex 3 by a novel ligand synthesis/palladium capture procedure (Scheme 1). [10] In the absence of maleic anhydride this resulted in an active and enantioselective PÀ N/Pd(0) catalyst for asymmetric allylic alkylation. In light of these outcomes there are two reasons why palladacycle 4 also has significant potential as a precatalyst for this ligand synthesis/palladium capture procedure.…”

Structures and Synthetic Strategies of Chiral Oxazolinyl Ferrocene Derivatives

“…随后, Pfaltz 等 [108] 利用噁唑啉二 茂铁为骨架, 有效扩充单取代 P,N-噁唑啉二茂铁配体结 构, 并在铱催化的非官能团化烯烃还原反应进行应用. Bryce 课题组 [109] 将胱氨酸及蛋氨酸等含硫氨基酸为 反应底物, 合成多种单取代 S,N-噁唑啉二茂铁化合物 (35); 其在不对称烯丙基烷基化反应产物得到中等的对 映选择性.…”

“…图 2 典型含噁唑啉片段手性配体举例 Figure 2 Examples of typical chiral ligands with oxazoline fragments 将噁唑啉片段引入二茂铁结构中, 形成噁唑啉二茂 铁衍生物在过渡金属催化反应中具有广泛应用 [23][24][25][26][27][28] . 通 过梳理文献发现, 在二茂铁结构的手性噁唑啉环的作用 有三个方面: 其一, 以二茂铁层状结构为基础, 利用手 性噁唑啉片段作为导向基团, 可获得具有高非对应选择 性平面手性二茂铁衍生物及过渡金属催化剂 [29][30][31][32][33][34][35] . 其 二, 噁唑啉环中的氮原子与其他配位原子形成双齿/多 齿配体共同与过渡金属络合, 成为具有高催化活性及立 体选择性的过渡金属络合物.…”