Mechanism and Enantioselectivity in Palladium-Catalyzed Conjugate Addition of Arylboronic Acids to β-Substituted Cyclic Enones: Insights from Computation and Experiment
作者:Jeffrey C. Holder、Lufeng Zou、Alexander N. Marziale、Peng Liu、Yu Lan、Michele Gatti、Kotaro Kikushima、K. N. Houk、Brian M. Stoltz
DOI:10.1021/ja401713g
日期:2013.10.9
Enantioselective conjugate additions of arylboronic acids to β-substituted cyclic enones have been previously reported from our laboratories. Air- and moisture-tolerant conditions were achieved with a catalyst derived in situ from palladium(II) trifluoroacetate and the chiral ligand (S)-t-BuPyOx. We now report a combined experimental and computational investigation on the mechanism, the nature of the
我们实验室以前曾报道过芳基硼酸与 β 取代的环烯酮的对映选择性共轭加成。使用由三氟乙酸钯 (II) 和手性配体 (S)-t-BuPyOx 原位衍生的催化剂实现了耐空气和耐湿条件。我们现在报告了对机制、活性催化剂的性质、对映选择性的起源以及配体和这种转化的底物的立体电子效应的联合实验和计算研究。对映选择性主要由手性配体的 t-Bu 基团与对映决定碳钯化步骤中烯酮底物的 α-亚甲基氢之间的空间排斥控制。计算表明,该反应通过形成阳离子芳基钯 (II) 物种而发生,随后烯酮烯烃的碳钯化形成关键的碳-碳键。对分离的 (PyOx)Pd(Ph)I 配合物的非线性效应以及化学计量和催化反应的研究表明,单体芳基钯-配体配合物是选择性决定步骤中的活性物质。水和六氟磷酸铵的加入协同增加了反应速率,证实了阳离子钯物质参与反应途径的假设。这些添加剂还允许反应在 40 °C 下进行,并有助于扩大底物范围。对分离的 (PyOx)Pd(Ph)I
Synthesis of diverse β-quaternary ketones via palladium-catalyzed asymmetric conjugate addition of arylboronic acids to cyclic enones
作者:Jeffrey C. Holder、Emmett D. Goodman、Kotaro Kikushima、Michele Gatti、Alexander N. Marziale、Brian M. Stoltz
DOI:10.1016/j.tet.2014.11.048
日期:2015.9
The development and optimization of a palladium-catalyzedasymmetricconjugateaddition of arylboronicacids to cyclic enone conjugateacceptors is described. These reactions employ air-stable and readily-available reagents in an operationally simple and robust transformation that yields β-quaternary ketones in high yields and enantioselectivities. Notably, the reaction itself is highly tolerant of
Sodium Tetraarylborates as Effective Nucleophiles in Rhodium/Diene-Catalyzed 1,4-Addition to β,β-Disubstituted α,β-Unsaturated Ketones: Catalytic Asymmetric Construction of Quaternary Carbon Stereocenters
A rhodium-catalyzed1,4-addition of sodium tetraarylborates to beta,beta-disubstituted alpha,beta-unsaturated ketones is described. Highly efficient asymmetric catalysis has also been achieved by employing a readily available chiral diene ligand, leading to the construction of quaternary carbon stereocenters with high enantioselectivity.
Chiral Tetrafluorobenzobarrelenes as Effective Ligands for Rhodium-Catalyzed Asymmetric 1,4-Addition of Arylboroxines to β,β-Disubstituted α,β-Unsaturated Ketones
and Two Smoking Barrelenes: The rhodium‐catalyzed 1,4‐addition of readily available arylboronic acid anhydrides to simple β,β‐disubstituted α,β‐unsaturated ketones creates quaternary carbon stereocenters with high enantiomeric excesses using a chiraltetrafluorobenzobarreleneligand.
Palladium-Catalyzed Asymmetric Conjugate Addition of Arylboronic Acids to Five-, Six-, and Seven-Membered β-Substituted Cyclic Enones: Enantioselective Construction of All-Carbon Quaternary Stereocenters
作者:Kotaro Kikushima、Jeffrey C. Holder、Michele Gatti、Brian M. Stoltz
DOI:10.1021/ja200664x
日期:2011.5.11
The first enantioselective Pd-catalyzed construction of all-carbon quaternary stereocenters via 1,4-addition of arylboronic acids to β-substituted cyclic enones is reported. Reaction of a wide range of arylboronic acids and cyclic enones using a catalyst prepared from Pd(OCOCF(3))(2) and a chiral pyridinooxazoline ligand yields enantioenriched products bearing benzylic stereocenters. Notably, this