Chiral organosilicon compounds in asymmetric synthesis of chiral 1,3-diols
摘要:
Chiral 1,3-diols can be prepared in high enantiomeric purity (>99% ee) from the reactions of the chiral silylcarbanion 2 with epoxides followed by oxidative cleavage of the carbon-silicon bond with hydrogen peroxide. The absolute configurations of some of the chiral 1,3-diols were determined by circular dichroism (CD).
Homogeneous catalysis. transition metal based lewis acid catalysts.
作者:T. Keith Hollis、William Odenkirk、N.P. Robinson、John Whelan、B. Bosnich
DOI:10.1016/s0040-4020(01)87259-8
日期:1993.1
Transition metal basedLewisacids provide catalysts for the Diels-Alder and Mukaiyama reactions. These catalysts must possess an electron deficient axophilic metal center and a labile coordination position. Unlike traditional Lewisacids, those derived from transition metals can function in the presence of water and have welldefined structures. It is shown how a normally electron rich ruthenium atom
Highly Controlled Chemoselectivity of Tin Enolate by Its Hybridization State. Anionic Complex of Tin Enolate Coordinated by Tetrabutylammonium Bromide as Halo Selective Reagent
作者:Makoto Yasuda、Keiko Hayashi、Yasuhiro Katoh、Ikuya Shibata、Akio Baba
DOI:10.1021/ja972190s
日期:1998.2.1
bromide (Bu4NBr) to neutral four-coordinated tin(IV) enolates 1(e). The highly coordinated enolates which attained a marked change in chemoselectivity have higher nucleophilicity to organichalides. In addition, they showed low nucleophilicitytoward carbonyl moieties by the coordination of the bromide anion, whereas carbonyl addition readily proceeds using the usual four-coordinated tin enolate. NMR studies
Asymmetric transfer hydrogenation of unsaturated ketones; factors influencing 1,4- vs 1,2- regio- and enantioselectivity, and alkene vs alkyne directing effects
作者:Thomas H. Hall、Hannah Adams、Vijyesh K. Vyas、K.L. Michael Chu、Martin Wills
DOI:10.1016/j.tet.2020.131771
日期:2021.1
A detailed study has been completed on the asymmetric transferhydrogenation (ATH) of a series of enones using Ru(II) catalysts. Electron-rich rings adjacent to the CO group reduce the level of CO reduction compared to CC. The ATH reaction can readily discriminate between double and triple bonds adjacent to ketones, reducing the double bond but leaving a triple bond intact in the major product.
the reagent prepared from n-Bu3SnLi and Et2AlCl or from SnCl2 and Et2AlCl affords enolates which react with ketone or aldehyde to give β-hydroxy carbonyl compounds in good to excellent yields. The reactions proceed similarly with the reagents which are generated from R3PbLi (R=Ph, n-Bu) and Et2AlCl. Catalysis by the added Pd(PPh3)4 complex promotes the reduction effectively and improves the yields of
new approach has been demonstrated for the regiospecific aldol synthesis by the simultaneous addition of α-halo carbonyl derivatives and aldehydes or ketones to a suspension of diethylaluminum chloride and zinc in tetrahydrofuran at low temperature. This technique is also employable under mild conditions for the Reformatsky reaction to give β-hiydroxy esters in excellent yield. One of the unique synthetic