C−O Hydrogenolysis Catalyzed by Pd-PMHS Nanoparticles in the Company of Chloroarenes
作者:Ronald J. Rahaim、Robert E. Maleczka
DOI:10.1021/ol102757v
日期:2011.2.18
Catalytic Pd(OAc)2 and polymethylhydrosiloxane (PMHS), in conjunction with aqueous KF, and a catalytic amount of an aromaticchloride, effects the chemo-, regio-, and stereoselective deoxygenation of benzylic oxygenated substrates at room temperature in THF. Preliminary mechanistic experiments suggest the process to involve palladium−nanoparticle-catalyzed hydrosilylation followed by C−O reduction
Prompt Determination of Absolute Configuration for Epoxy Alcohols via Exciton Chirality Protocol
作者:Xiaoyong Li、Babak Borhan
DOI:10.1021/ja805058t
日期:2008.12.3
A microscale protocol for determination of absoluteconfigurations of 2,3-epoxy alcohols is described. 2,3-Disubstituted (cis and trans), 2,2-disubstituted, 2,2,3-trisubstituted, and 2,3,3-trisubstituted epoxy alcohols rendered prominent ECCD signals upon complexing with a Lewis acidic porphyrin tweezer and consequently provide straightforward assignment of chirality for epoxy alcohols. This method
The present invention relates to the synthesis of chiral epoxides via a catalytic asymmetric oxidation of olefins. Additionally, the methodology provides a method of asymmetrically oxidizing sulfides and phosphines. This asymmetric oxidation employs a catalyst system composed of a metal and a chiral bishydroxamic acid ligand, which, in the presence of a stoichiometric oxidation reagent, serves to asymmetrically oxidize a variety of substrates.
New opticallyactive hydroxamic acids bearing a 1,1′-binaphthyl group were prepared as ligands in a vanadium-catalyzed asymmetricepoxidation. The feature of these hydroxamic acids is a sterically hindered ligand. The asymmetricepoxidation with good selectivity and reactivity can be established by using VO(O-i-Pr)3 (5 mol%) and a small excess amount of ligand (7.5 mol%) with triphenylmethyl hydroperoxide
在钒催化的不对称环氧化反应中,制备了带有 1,1'-联萘基团的新型旋光异羟肟酸作为配体。这些异羟肟酸的特征是空间位阻配体。在-20 °C 的甲苯中,使用 VO(Oi-Pr)3 (5 mol%) 和少量过量的配体 (7.5 mol%) 与三苯甲基氢过氧化物 (TrOOH) 可以建立具有良好选择性和反应性的不对称环氧化反应. 二取代的烯丙醇比单取代或三取代的烯丙醇环氧化得更快,并且以良好到高的对映选择性 (48-94%ee) 获得。讨论了基于 1e 的 X 射线晶体结构的过渡态。
Enantioselective Epoxidation of Allylic Alcohols by a Chiral Complex of Vanadium: An Effective Controller System and a Rational Mechanistic Model