Phosphine–Olefin Ligands Based on a Planar-Chiral (π-Arene)chromium Scaffold: Design, Synthesis, and Application in Asymmetric Catalysis
| Autor: | Ken Kamikawa, Masamichi Ogasawara, Takeshi Nakaya, Sachie Arae, Wei Yi Wu, Tamotsu Takahashi, Tomotaka Morita, Ya Yi Tseng |
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| Rok vydání: | 2014 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 136:9377-9384 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | The NMR and X-ray crystallographic studies clarified that planar-chiral alkenylene-bridged (phosphino-π-arene)(phosphine)chromium complexes 3 were capable of coordinating to a rhodium(I) cation in a bidentate fashion at the (π-arene)-bound phosphorus atom and at the olefin moiety. The P-olefin chelate coordination of 3 constructs the effective chiral environment at the metal center, and thus, these rhodium complexes display high performances in various rhodium-catalyzed asymmetric 1,4- and 1,2-addition reactions with arylboron nucleophiles. The control experiments demonstrated that the (η(2)-olefin)-Rh interaction as well as the bridging structure in 3 played the pivotal roles in the high enantioselectivity of the Rh-catalyzed asymmetric reactions. To enhance the synthetic utilities of these phosphine-olefin ligands, an enantiospecific and scalable synthetic method was developed. The novel synthetic method is flexible in terms of the substituent variation, and a library of the planar-chiral (arene)chromium-based phosphine-olefin ligands was established by the combinatorial approach. Among the newly prepared ligand library, compound 3g, which is with a bis(3,5-dimethylphenyl)phosphino group on the η(6)-arene ring, was found to be a far better chiral ligand in the rhodium-catalyzed asymmetric reactions showing excellent enantioselectivity and high yields. |
| Databáze: | OpenAIRE |
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