Article
Chemistry, Multidisciplinary
Jun-Hao Zhang, Hui Xu, Xiaodong Tang, Yanfeng Dang, Fa-Guang Zhang, Jun-An Ma
Summary: In this study, the efficient and stereoselective hydrogenation of congested tetra-substituted cyclic beta-enamido phosphonates/phosphine oxides was achieved using a commercially available Rh-Josiphos system. This method enables the synthesis of chiral beta-amino phosphorus compounds with two vicinal stereocenters. The protocol is applicable to various ring systems and different phosphonate/phosphine oxide groups, and it has been successfully applied to the preparation of amino-phosphine ligands. The DFT mechanistic explorations suggest that the C=C migratory insertion into the Rh-III-H bond is the rate- and stereo-determining step, and the origins of stereoselectivity are regulated by dispersion interactions and steric repulsions.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Organic
Ze Wang, Xianghua Zhao, Shiliang Wang, An Huang, Yifan Wang, Jiaying He, Fei Ling, Weihui Zhong
Summary: The asymmetric hydrogenation catalyzed by iridium/f-diaphos L1, L5 or L12 was successfully demonstrated for the first time, affording chiral alcohols with high conversions and moderate to excellent enantioselectivities. The protocol could be easily scaled up to gram-scale with a Turnover Number (TON) of 9700.
ORGANIC & BIOMOLECULAR CHEMISTRY
(2021)
Article
Chemistry, Organic
Hong-Quan Du
Summary: Catalytic asymmetric hydrogenation of alpha- and beta-enamido phosphonates was achieved using a chiral hybrid phosphine-bicyclic bridgehead phosphoramidite ligand and rhodium metal precursor as the catalyst. The reaction showed high yields (96-99%) and high enantiomeric excess (<= 99%) with low catalyst loading (S/C up to 10,000) and mild reaction conditions. The hydrogenation reaction selectively occurred at the C = C bond of the enamido phosphate stage without tautomerization to the imine form. Tandem hydrolysis reactions of the hydrogenated products provided alpha- and beta-amino phosphonic acids in high yield, which can serve as versatile building blocks for bioorganic chemistry, medicinal chemistry, and organic synthesis.
ORGANIC & BIOMOLECULAR CHEMISTRY
(2022)
Article
Chemistry, Multidisciplinary
Wendy L. Williams, Neyci E. Gutierrez-Valencia, Abigail G. Doyle
Summary: This paper reports the first branched-selective cross-coupling of 2-alkyl aziridines with aryl iodides using a Ti/Ni dual-catalytic system. The study demonstrates the tolerance towards functional groups and the effect of the steric and electronic profile on reactivity, resulting in predictive reactivity models and insights into the mechanism.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2023)
Article
Chemistry, Physical
Prabin Nepal, Suneth Kalapugama, Michael Shevlin, John R. Naber, Louis-Charles Campeau, Cristofer Pezzetta, Armando Carlone, Christopher J. Cobley, Steven H. Bergens
Summary: Cationic Rh-JosiPhos complexes were tethered to ROMP-active norbornene groups to form linear, polycationic copolymers. These copolymers could be readily absorbed onto PTA on Al2O3 via electrostatic attractions, and exhibited excellent catalytic activity and stability in enantioselective hydrogenation reactions.
Article
Chemistry, Organic
Qian-Kun Zhao, Xiong Wu, Lin-Ping Li, Fan Yang, Jian-Hua Xie, Qi-Lin Zhou
Summary: A practical method for efficient asymmetric hydrogenation of beta-aryl alkylidene malonates was reported. By using a site-specifically tailored chiral spiro iridium catalyst, a series of chiral malonate esters were successfully synthesized with good to excellent enantioselectivities (up to 99% ee) and high turnover numbers (up to 19000). The results demonstrated that incorporating an ester group in alpha,beta-unsaturated carboxylic esters significantly enhanced the efficiency of their asymmetric hydrogenation reactions.
Article
Chemistry, Organic
Chao Dong, Dao-Sheng Liu, Lei Zhang, Xiang-Ping Hu
Summary: An enantioselective Rh-catalyzed hydrogenation of E/Z mixtures of trisubstituted vinyl esters has been achieved using a chiral ferrocenylphosphine-phosphoramidite ligand. The reaction showed high yields and good to high enantioselectivities, with the presence of a small amount of t-butanol benefiting the hydrogenation outcome.
TETRAHEDRON LETTERS
(2021)
Article
Chemistry, Organic
Xixia Tang, Lu Qian, Guixia Liu, Zheng Huang
Summary: Asymmetric transfer hydrogenation of 1-aryl-1-alkylethenes with ethanol using a chiral (PCN)Ir complex as the precatalyst has been developed, demonstrating high enantioselectivities, good functional group tolerance, and operational simplicity. This method is also applied to formal intramolecular asymmetric transfer hydrogenation of alkenols without an external H-donor, allowing for the production of a tertiary stereocenter and remote ketone group simultaneously. The utility of the catalytic system is highlighted by gram scale synthesis and the synthesis of the key precursor of (R)-xanthorrhizol.
Article
Chemistry, Organic
Xiu-Qin Dong, Xuanliang Yang, Gang Liu, Xun Xiang, Dezheng Xie, Jinyu Han, Zhengyu Han
Summary: Efficient Ni/(S,S)-Ph-BPE-catalyzed asymmetric hydrogenation of alpha-substituted alpha,beta-unsaturated phosphine oxides/phosphonates/phosphoric acids has been successfully developed, and a wide range of chiral alpha-substituted phosphine hydrogenation products were obtained in generally high yields with excellent enantioselective control (92%-99% yields, 84%->99% ee). This method features a cheap transition metal nickel catalytic system, high functional group tolerance, wide substrate scope generality, and excellent enantioselectivity. A plausible catalytic cycle was proposed for this asymmetric hydrogenation according to the results of deuterium-labeling experiments.
Article
Chemistry, Organic
Fang Xie, Shijie Dong, Yajun Sun, Wenxing Liu, Xiaodan Liu, Lu Liu, Qin Zhao, Jiangli Wang
Summary: A CuH-catalyzed coupling reaction between aryl alkenes and 3-aryl-2H-azirines has been developed to synthesize optically active beta,beta-disubstituted ketones. The reaction proceeds via the regioselective attack of a chiral alkylcopper complex on the N-C2 bonds of azirines, generating chiral beta-aryl imines that can be further hydrolyzed to give ketones. This method provides a novel and efficient approach for the synthesis of chiral beta,beta-disubstituted ketones under mild conditions.
Article
Chemistry, Organic
Xiaolei Ji, Chaoren Shen, Xinxin Tian, Kaiwu Dong
Summary: A palladium-catalyzed asymmetric hydroesterification reaction was developed for preparing chiral alpha-substituted succinates with moderate yields and high ee values. The kinetic profile of the reaction progress indicated that the alkene substrate underwent hydroesterification followed by esterification with alcohol. The enantioselectivity was elucidated by density functional theory computation.
Article
Chemistry, Inorganic & Nuclear
Nora Jannsen, Christian Fischer, Carmen Selle, Cornelia Pribbenow, Hans-Joachim Drexler, Fabian Reiss, Torsten Beweries, Detlef Heller
Summary: In this study, we systematically investigate and quantify the influence of solvent coordination on reactions of cationic rhodium(i) diphosphine complexes. We propose a method to analyze and quantify solvent binding using MeCN as a replacement for diolefins. By using UV-vis and P-31{H-1} NMR spectroscopy, we determine and compare stability constants of different complexes, and discuss the impact of different ligands and reaction temperature. DFT study reveals the relationship between stability and thermodynamics of the exchange reaction. Additionally, variable temperature NMR spectroscopy confirms the existence of a mixed solvate complex as an intermediate in the MeCN-MeOH exchange.
DALTON TRANSACTIONS
(2022)
Article
Chemistry, Organic
Zhen Luo, Xue Zhang, Zheng-Qiang Liu, Chuan-Ming Hong, Qing-Hua Li, Tang-Lin Liu
Summary: This study presents a ruthenium-catalyzed intra-molecular aryl migrative isomerization, providing a mild and environmentally friendly method for synthesizing ketones with high step-and atom-economy and broad substrate scope. Additionally, the researchers discovered a heuristic paradigm for transition-metal-catalyzed C-C activation.
Article
Chemistry, Organic
Yuan-Zheng Wang, Le'an Hu, Shao-Tao Bai, Xumu Zhang
Summary: A user-friendly and simple catalytic method for the synthesis of high value primary &α;-(trifluoromethyl)aryl-methylamines via ruthenium-catalyzed asymmetric reductive amination of aryl-trifluoromethylketones using cheap NH4OAc as the nitrogen source and H-2 as the reductant is reported. This method tolerates various aromatic functions with electron-withdrawing or -donating substituents, as well as challenging heteroaromatic functions, leading to the formation of primary &α;-(trifluoromethyl)aryl-methylamines with excellent chemoselectivities, enantioselectivities, and useful yields (80-97% ee, 51-92% isolated yields).
Article
Chemistry, Physical
Yuliang Xu, Yizhou Yang, Yizhen Liu, Zhen Hua Li, Huadong Wang
Summary: The hydrogenolysis of C-C bonds is a crucial process in the petroleum industry, but it often requires high temperatures and pressures with limited selectivity. However, a borenium complex has been discovered to catalyze the selective hydrogenolysis of unstrained C(aryl)-C(alkyl) bonds at ambient temperature without the need for directing groups. Mechanistic studies have revealed that the reaction involves the synergistic activation of dihydrogen by the borenium complex and alkylarenes, followed by retro-Friedel-Crafts reaction to cleave the C(aryl)-C(alkyl) bonds. The synthetic utility of this protocol has been demonstrated by converting post-consumer polystyrene into valuable benzene and phenylalkanes with a mass recovery rate of over 90%.
