Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States.
KAUST Catalysis Center and Division of Physical Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
J Am Chem Soc. 2021 Oct 13;143(40):16709-16717. doi: 10.1021/jacs.1c07857. Epub 2021 Oct 4.
Crystallographic characterization of RuX(CO)(η-CH)(JOSIPHOS), where X = Cl, Br, or I, reveals a halide-dependent diastereomeric preference that defines metal-centered stereogenicity and, therefrom, the enantioselectivity of C-C coupling in ruthenium-catalyzed -diastereo- and enantioselective C-C couplings of primary alcohols with 1-aryl-1-propynes to form products of carbonyl -(α-aryl)allylation. Computational studies reveal that a non-classical hydrogen bond between iodide and the aldehyde formyl CH bond stabilizes the favored transition state for carbonyl addition. An improved catalytic system enabling previously unattainable transformations was developed that employs an iodide-containing precatalyst, RuI(CO)(η-CH), in combination with trifluoroethanol, as illustrated by the first enantioselective ruthenium-catalyzed C-C couplings of ethanol to form higher alcohols.
RuX(CO)(η-CH)(JOSIPHOS)（其中 X = Cl、Br 或 I）的晶体学特性表明，卤化物依赖性的非对映选择性偏好决定了金属中心的手性，并由此定义了手性钌催化剂催化的伯醇与 1-芳基-1-丙炔的 C-C 交叉偶联反应的对映选择性和 C-C 交叉偶联反应产物的羰基-（α-芳基）烯丙基化反应。计算研究表明，碘化物和醛基甲酰 CH 键之间的非经典氢键稳定了有利于羰基加成的有利过渡态。开发了一种改进的催化体系，该体系使用含有碘化物的前催化剂 RuI(CO)(η-CH)，结合三氟乙醇，如图所示，首次实现了手性钌催化的乙醇 C-C 偶联反应，形成了更高的醇。
