Titanium<i>cis</i>-1,2-Diaminocyclohexane (<i>cis</i>-DACH) Salalen Catalysts for the Asymmetric Epoxidation of Terminal Non-Conjugated Olefins with Hydrogen Peroxide
Chiral Ti salalen complexes catalyze the asymmetric epoxidation of terminal non‐conjugated olefins with hydrogen peroxide. Modular ligands based on cis‐1,2‐diamino‐cyclohexane (cis‐DACH) were developed, giving high yields and enantiomeric excesses (ee, up to 96 %) at catalyst loadings as low as 0.1–0.5 mol %, and even under solvent‐free conditions.
Titanium Salalen Catalysts Based on<i>cis</i>-1,2-Diaminocyclohexane: Enantioselective Epoxidation of Terminal Non-Conjugated Olefins with H<sub>2</sub>O<sub>2</sub>
Help for the neglected: Terminal, non‐conjugated olefins, such as 1‐octene, are difficult to epoxidize asymmetrically. Ti salalen complexes based on cis‐1,2‐diaminocyclohexane catalyze this demanding reaction giving high yields and enantioselectivities (up to 95 % ee), with H2O2 as the oxidant. The X‐ray structures of the μ‐oxo and peroxocomplexes shed light on the coordination behavior of this novel
被忽视的帮助:末端非共轭烯烃(例如1-辛烯)难以不对称环氧化。基于顺式1,2-二氨基环己烷的Ti salalen络合物以H 2 O 2为氧化剂,可催化要求苛刻的反应,从而提供高收率和对映选择性(最高95% ee)。μ-oxo和peroxo配合物的X射线结构阐明了这类新型配体的配位行为。
Synthesis of Vicinal Dichlorides via Activation of Aliphatic Terminal Epoxides with Triphosgene and Pyridine
作者:Alexander H. Cleveland、Frank R. Fronczek、Rendy Kartika
DOI:10.1021/acs.joc.7b03197
日期:2018.3.16
Herein we report a novel synthetic reaction to convert unactivated terminal aliphatic epoxide to alkyl vicinal dichloride based on triphosgene–pyridine activation. Our methodology is operationally simple and readily tolerated by a broad of scope of substrates as well as protecting groups. Furthermore, these mild conditions generally yield clean reaction mixtures that are free of byproducts upon aqueous
The intramolecular cyclization of epoxy alcohols was catalyzed with excellent regio- and enantiocontrol by a [CoIII(salen)] complex. High endo selectivity was observed for the enantioselective cyclization of terminal epoxy alcohols [Eq. (a)], while the reaction of meso substrates produced novel cyclic and bicyclic ethers in good yields and high enantiopurity. TBME=tert-butyl methyl ether.