255850-51-2Relevant articles and documents
Iron-Catalyzed Vinylzincation of Terminal Alkynes
Huang, Qiang,Su, Yu-Xuan,Sun, Wei,Hu, Meng-Yang,Wang, Wei-Na,Zhu, Shou-Fei
supporting information, p. 515 - 526 (2022/01/08)
Organozinc reagents are among the most commonly used organometallic reagents in modern synthetic chemistry, and multifunctionalized organozinc reagents can be synthesized from structurally simple, readily available ones by means of alkyne carbozincation. However, this method suffers from poor tolerance for terminal alkynes, and transformation of the newly introduced organic groups is difficult, which limits its applications. Herein, we report a method for vinylzincation of terminal alkynes catalyzed by newly developed iron catalysts bearing 1,10-phenanthroline-imine ligands. This method provides efficient access to novel organozinc reagents with a diverse array of structures and functional groups from readily available vinylzinc reagents and terminal alkynes. The method features excellent functional group tolerance (tolerated functional groups include amino, amide, cyano, ester, hydroxyl, sulfonyl, acetal, phosphono, pyridyl), a good substrate scope (suitable terminal alkynes include aryl, alkenyl, and alkyl acetylenes bearing various functional groups), and high chemoselectivity, regioselectivity, and stereoselectivity. The method could significantly improve the synthetic efficiency of various important bioactive molecules, including vitamin A. Mechanistic studies indicate that the new iron-1,10-phenanthroline-imine catalysts developed in this study have an extremely crowded reaction pocket, which promotes efficient transfer of the vinyl group to the alkynes, disfavors substitution reactions between the zinc reagent and the terminal C–H bond of the alkynes, and prevents the further reactions of the products. Our findings show that iron catalysts can be superior to other metal catalysts in terms of activity, chemoselectivity, regioselectivity, and stereoselectivity when suitable ligands are used.
PYRROLE DERIVATIVES USEFUL FOR THE TREATMENT OF CYTOKINE-MEDIATED DISEASES
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Page/Page column 80, (2008/06/13)
A compound of Formula (I) or a pharmaceutically acceptable salt or prodrug ester thereof, wherein the groups R1-R6 and A are as defined in the specification.
Assembly and Binding Properties of Osmate Ester-Bridged Binuclear Macrocycles
Jeong, Kyu-Sung,Cho, Young Lag,Chang, Sung-Youn,Park, Tae-Yoon,Song, Jung Uk
, p. 9459 - 9466 (2007/10/03)
Osmium (VI)-bridged macrocycles 1a-c, 2, and 3 assemble spontaneously when osmium tetraoxide, olefins, and L-shaped bispyridyl ligands are mixed in CHCl3. The macrocycles possess well-defined square or rectangular cavities enclosed by aryl walls and act as host molecules. Hydrogen-bond donors on the inner surface of the hosts offer binding sites to acceptors of guests with complementary dimensions. The host 1a binds adipamide G2 (Ka = 3.6 × 104 M-1) and terephthalamide G6 (Ka = 2.0 × 104 M-1), while it binds negligibly (Ka -1) benzamide G5, isophthalamide G9, or 1,4-naphthalenedicarboxamide G10. The larger hosts 2 and 3 bind the longer guests biphenyldicarboxamide G12 and terphenyldicarboxamide G17, respectively, but shorter guests such as adipamide G2 and terephthalamide G6 are not well-bound (Ka -1). Hosts 1a-c with different remote substituents (H, OMe, NO2) but identical cavity size were prepared and their binding affinities were measured. The relative binding affinities of the hosts 1a-c to the keto amide G19, ester amide G20, and diester G21 are in the order of 1c (NO2) ? 1a (H) > 1b (OCH3). The substituent effects on the binding strength are interpreted in terms of the electron density at the pyridine nitrogen of the hosts and its effect on bifurcated hydrogen bonding.
