- Asymmetric Hydroarylation of Enones via Nickel-Catalyzed 5- Endo-Trig Cyclization
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A nickel-catalyzed reductive cyclization of enones affords a wide array of indanones in high enantiomeric induction. The reaction is featured with an unprecedented broad scope of substrates. The versatility of the new method is demonstrated in several short stereoselective syntheses of medically valuable (R)-tolterodine, parent and deuterated (+)-indatraline, and an antitumor natural product, (+)-multisianthol. In comparison, these compounds cannot be prepared satisfactorily via analogous processes catalyzed by palladium.
- Qin, Xurong,Yao Lee, Marcus Wen,Zhou, Jianrong Steve
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p. 5990 - 5994
(2019/08/20)
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- Lewis Base-Catalyzed Enantioselective Conjugate Reduction of β,β-Disubstituted α,β-Unsaturated Ketones with Trichlorosilane: E/ Z-Isomerization, Regioselectivity, and Synthetic Applications
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The chiral bisphosphine dioxide-catalyzed asymmetric conjugate reduction of acyclic β,β-disubstituted α,β-unsaturated ketones with trichlorosilane affords saturated ketones having a stereogenic carbon center at the carbonyl β-position with high enantioselectivities. Because the E/Z-isomerizations of enone substrates occur concomitantly, reduction products with the same absolute configurations are obtained from either (E)- or (Z)-enones. Conjugate reduction is accelerated in the presence of an electron-rich aryl group at the β-position of the enone owing to its carbocation-stabilizing ability. Computational studies were also conducted in order to elucidate the origin of the observed enantioselectivity. The regio- and enantioselective reductions of dienones were realized and applied to the syntheses of ar-turmerone, turmeronol A, mutisianthol, and jungianol, which are optically active sesquiterpenes.
- Sugiura, Masaharu,Ashikari, Yasuhiko,Takahashi, Yuka,Yamaguchi, Koki,Kotani, Shunsuke,Nakajima, Makoto
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p. 11458 - 11473
(2019/10/11)
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- (+)- And (-)-mutisianthol: First total synthesis, absolute configuration, and antitumor activity
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The first synthesis of the natural product (+)-mutisianthol was accomplished in 11 steps and in 21% overall yield from 2-methylanisole. The synthesis of its enantiomer was also performed in a similar overall yield. The absolute configuration of the sesquiterpene (+)-mutisianthol was assigned as (15,37?). Key steps in the route are the asymmetric hydrogenation of a nonfunctionalized olefin using chiral iridium catalysts and the ring contraction of 1,2-dihydronaphthalenes using thallium(III) or iodine(III). The target molecules show moderate activity against the human tumor cell lines SF-295, HCT-8, and MDA-MB-435.
- Bianco, Graziela G.,Ferraz, Helena M. C.,Costas, Arinice M.,Costa-Lotufo, Leticia V.,Pessoa, Claudia,De Moraes, Manoel O.,Schreins, Marcus G.,Pfaltz, Andreas,Silva Jr., Luiz F.
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experimental part
p. 2561 - 2566
(2009/09/25)
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