Oxidation Catalysis of Nb(salan) Complexes: Asymmetric Epoxidation of Allylic Alcohols Using Aqueous Hydrogen Peroxide as an Oxidant
作者:Hiromichi Egami、Takuya Oguma、Tsutomu Katsuki
DOI:10.1021/ja100795k
日期:2010.4.28
Several opticallyactive Nb(salan) complexes were synthesized, and their oxidation catalysis was examined. A dimeric mu-oxo Nb(salan) complex that was prepared from Nb(OiPr)(5) and a salan ligand was found to catalyze the asymmetric epoxidation of allylicalcohols using a urea-hydrogen peroxide adduct as an oxidant with good enantioselectivity. However, subsequent studies of the time course of this
合成了几种光学活性 Nb(salan) 配合物,并研究了它们的氧化催化作用。发现由 Nb(OiPr)(5) 和 salan 配体制备的二聚体 mu-oxo Nb(salan) 复合物可催化烯丙醇的不对称环氧化,使用尿素-过氧化氢加合物作为氧化剂,具有良好的对映选择性。然而,随后对该环氧化的时间过程以及配体的 ee 与产物的 ee 之间关系的研究表明,mu-氧代二聚体在环氧化之前解离成单体物质。而且,发现由 Nb(OiPr)(5) 和 salan 配体原位制备的单体 Nb(salan) 配合物,然后进行水处理,发现使用过氧化氢水溶液在 CHCl(3)/盐水或甲苯/盐水溶液中更好地催化烯丙醇的环氧化具有高对映选择性,范围从 83% 到 95% ee,除了肉桂醇的反应显示 74% 的中等 ee。这是使用过氧化氢水溶液作为氧化剂对烯丙醇进行高度对映选择性环氧化的第一个例子。
Experimental Lineage and Functional Analysis of a Remotely Directed Peptide Epoxidation Catalyst
作者:Phillip A. Lichtor、Scott J. Miller
DOI:10.1021/ja410567a
日期:2014.4.9
describe mechanistic investigations of a catalyst (1) that leads to selective epoxidation of farnesol at the 6,7-position, remote from the hydroxyl directing group. The experimental lineage of peptide 1 and a number of resin-bound peptide analogues were examined to reveal the importance of four N-terminal residues. We examined the selectivity of truncated analogues to find that a trimer is sufficient to
Commercial zeolitespromotes the epoxidation of unsaturatedalcohols in chemo- and diastereoselective way.
商业沸石以化学和非对映选择性的方式促进不饱和醇的环氧化。
Function-oriented investigations of a peptide-based catalyst that mediates enantioselective allylic alcohol epoxidation.
作者:Nadia C. Abascal、Phillip A. Lichtor、Michael W. Giuliano、Scott J. Miller
DOI:10.1039/c4sc01440e
日期:——
an investigation of a peptide-based catalyst (6) that is effective for the site- (>100:1:1) and enantioselective epoxidation (86% ee) of farnesol. Studies of the substrate scope exhibited by the catalyst are included, along with an exploration of optimized reaction conditions. Mechanistic studies are reported, including relative rate determinations for the catalyst and propionic acid, a historical perspective
Tungsten-, Molybdenum-, and Cerium-Promoted Regioselective and Stereospecific Halogenation of 2,3-Epoxy Alcohols and 2,3-Epoxy Sulfonamides
作者:Chuan Wang、Hisashi Yamamoto
DOI:10.1021/ol503091n
日期:2014.11.21
The first catalytic regioselective and stereospecific halogenation of 2,3-epoxy alcohols and 2,3-epoxy sulfonamides has been developed. Under the catalysis of commercially available W- or Mo-salts, complemented by the method using cerium halides, the C-3 selective ring opening of structurally diverse epoxides with Cl-, Br-, and I-nucleophiles afforded various halohydrins in good yields and high regioselectivities.