Ni-Catalyzed chemoselective alcoholysis of <i>N</i>-acyloxazolidinones
作者:Pei-Qiang Huang、Hui Geng
DOI:10.1039/c7gc03534a
日期:——
(catalytic) asymmetric synthetic methodologies occupy an important position in modern organic synthesis, the catalytic cleavage of a chiralauxiliary remains underdeveloped. We report the Ni(cod)2/bipyr.-catalyzed alcoholysis of N-acyloxazolidinones to deliver esters. The reaction is broad in scope for both N-acyloxazolidinone substrates and alcohol nucleophiles, and displays good functional group tolerance
Scandiumtrifluoromethanesulfonate (Sc(OTf)3) is found to be quite effective as a Lewis acid catalyst in the Diels-Alder reaction. The novel catalyst is available in both aqueous and organic media, is easily recovered from aqueous layer after the reaction is completed, and can be reused.
Scandium perfluoroalkanesulfonate-catalyzed Diels–Alder reactions proceeded smoothly in dry dichloromethane in the presence of molecular sieves (MS) 5 Å. It was found that water interfered with the reactions, contrary to most rare earth-catalyzed reactions that proceed smoothly in aqueous media. Among scandium perfluoroalkanesulfonates tested, scandium triflate (Sc(OTf)3), scandium pentafluoroethanesulfonate
在分子筛(MS)5Å存在下,全氟链烷磺酸alk催化的Diels-Alder反应在干燥的二氯甲烷中顺利进行。已发现水干扰了反应,这与大多数在水介质中平稳进行的稀土催化反应相反。在测试的全氟烷磺酸scan中,三氟甲磺酸((Sc(OTf)3),五氟乙烷磺酸scan (Sc(OSO 2 C 2 F 5)3)和九氟丁烷磺酸scan(Sc(OSO 2 C 4 F 9)3)的收率最高,选择性。
Scandium(III) Triflate/Isopropyl-Pybox Complex as an Efficient Catalyst for Asymmetric Diels-Alder Reaction
The chiral scandium(III) triflate/i-Pr-pybox complex efficiently catalyzes the asymmetric Diels-Alder reaction of 1,3-dienes with acyl-1,3-oxazolidin-2-ones (1 a - c) afford the corresponding adducts in good yields with up to 90% ee. The reaction can be carried out in less toxic benzotrifluoride and supercritical carbon dioxide while remaining good selectivity (65-75% ee).
手性钪(III)三late/i-Pr-pybox 复合物可高效催化 1,3-二烯与酰基-1,3-噁唑烷-2-酮(1 a - c)的不对称 Diels-Alder 反应,以高产率和高达 90% 的 ee 生成相应的加合物。该反应可在毒性较低的三氟甲苯和超临界二氧化碳中进行,同时保持良好的选择性(65-75% ee)。
SuperQuat 5,5-dimethyl-4-iso-propyloxazolidin-2-one as a mimic of Evans 4-tert-butyloxazolidin-2-one
作者:Steven D. Bull、Stephen G. Davies、A. Christopher Garner、Dennis Kruchinin、Min-Suk Key、Paul M. Roberts、Edward D. Savory、Andrew D. Smith、James E. Thomson
DOI:10.1039/b605244d
日期:——
The incorporation of a gem-dimethyl group at the 5-position of a chiral oxazolidinone biases the conformation of the adjacent C(4)-stereodirecting group such that the gem-dimethyl-4-iso-propyl combination mimics a C(4)-tert-butyl group, providing higher levels of stereocontrol than a simple 4-iso-propyloxazolidinone. The generality of this principle is demonstrated with applications in stereoselective enolate alkylations, kinetic resolutions, Diels–Alder cycloadditions and Pd-catalysed asymmetric acetalisation reactions.