98085-85-9Relevant academic research and scientific papers
Diastereo- And Atroposelective Synthesis of Bridged Biaryls Bearing an Eight-Membered Lactone through an Organocatalytic Cascade
Lu, Shenci,Ong, Jun-Yang,Yang, Hui,Poh, Si Bei,Liew, Xi,Seow, Chwee San Deborah,Wong, Ming Wah,Zhao, Yu
supporting information, p. 17062 - 17067 (2019/11/03)
We present herein an unprecedented stereoselective synthesis of bridged biaryls with defined axial and central chirality from readily available starting materials. This N-heterocyclic carbene-catalyzed method proceeds through propargylic substitution of azolium enolates followed by two-directional cyclization, as supported by DFT calculation. A range of benzofuran/indole-derived bridged biaryls bearing an eight-membered lactone are accessed with uniformly high stereoselectivity (>98:2 dr, mostly >98% ee).
Complete chiral induction from enantiopure 1,2-diamines to benzophenone-based achiral bisphosphane ligands in noyori-type RuII catalysts
Jing, Qing,Sandoval, Christian A.,Wang, Zheng,Ding, Kuiling
, p. 3606 - 3616 (2012/12/23)
We report the design and synthesis of a novel class of RuII catalysts (3) composed of achiral benzophenone-based bisphosphane ligands and enantiopure 1,2-diamines for the asymmetric hydrogenation of aryl ketones. The developed catalysts show excellent enantioselectivities (up to 97 % ee) and activities (up to S/C = 10,000) in the hydrogenation of a variety of aromatic ketones. Complete chiral induction from the enantiopure 1,2-diamine to the achiral bisphosphane ligand was observed. The coordination of the C=O moiety in 3 to the cationic RuII center is considered to be of key importance in providing a higher thermodynamic and kinetic rotation barrier for the flexible bisphosphane ligand, resulting in the preferential formation of only one diastereomer, and thus explaining the high enantioselectivity of the catalyst. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
Tetrakis(2-hydroxyphenyl)ethene and derivatives. A structurally preorganized tetradentate ligand system for polymetallic coordination chemistry and catalysis
Verkerk, Udo,Fujita, Megumi,Dzwiniel, Trevor L.,McDonald, Robert,Stryker, Jeffrey M.
, p. 9988 - 9989 (2007/10/03)
A topologically unique, conformationally constrained tetradentate ligand system for polymetallic coordination chemistry has been developed: tetrakis(2-hydroxyphenyl)ethene (1a) and substituted derivatives. The design exploits the planarity of the tetraphenylethylene core to impart rigidity to the roughly square oxygen binding array, while maintaining a degree of conformational mobility associated with rotation about the aryl-ethylene carbon-carbon bonds. Tetrakis(2-hydroxyphenyl)ethene derivatives are designed to promote multiple metal bridging over chelating coordination modes. The ligand is synthesized from anisole or 4-tert-butylanisole in four steps via the 2,2-dimethoxybenzophenone hydrazones 4a,b. The sterically hindered ortho-substituted tetraphenylethylene core is produced in high yield by acid-catalyzed decomposition of the corresponding diaryl diazomethane prepared in situ by oxidation of the hydrazone using nickel peroxide. Deprotection of the methyl ethers using boron tribromide gives tetrakis(2-hydroxyphenyl)ethene (1a), characterized by X-ray crystallography, and tetrakis(5-tert-butyl-2-hydroxyphenyl)ethene (1b). Sterically isolating substituents in the 3-position can be installed via Claisen rearrangement/hydrogenation, providing tetrakis(3-n-propyl-2-hydroxyphenyl)ethene (6) efficiently. To illustrate potential applications of this unprecedented ligand class, two coordination complexes are reported, including tetrakis(2-diethylaluminoxyphenyl)ethene (8), a structurally robust eight-membered-ring aluminum/oxygen crown complex characterized both in solution and in the solid state. Copyright
