2-Ene-1,4-diols by Dimerization of Terminal Epoxides using Hindered Lithium Amides
摘要:
Reaction of hindered lithium amides with readily available (enantiopure) terminal epoxides gives 2-ene-1,4-diols via carbenoid dimerization of the corresponding ct-lithiated epoxides. D-Mannitol and D-iditol were synthesized using this method in three steps from (S)-tritylglycidyl ether.
Highly Selective Hydrolytic Kinetic Resolution of Terminal Epoxides Catalyzed by Chiral (salen)Co<sup>III</sup> Complexes. Practical Synthesis of Enantioenriched Terminal Epoxides and 1,2-Diols
作者:Scott E. Schaus、Bridget D. Brandes、Jay F. Larrow、Makoto Tokunaga、Karl B. Hansen、Alexandra E. Gould、Michael E. Furrow、Eric N. Jacobsen
DOI:10.1021/ja016737l
日期:2002.2.1
The hydrolytickineticresolution (HKR) of terminal epoxides catalyzed by chiral (salen)Co(III) complex 1 x OAc affords both recovered unreacted epoxide and 1,2-diol product in highly enantioenriched form. As such, the HKR provides general access to useful, highly enantioenriched chiral building blocks that are otherwise difficult to access, from inexpensive racemic materials. The reaction has several
Hydrolytic Kinetic Resolution of Epoxides Catalyzed by Chromium(III)-endo,endo-2,5-diaminonorbornane-salen [Cr(III)-DIANANE-salen] Complexes. Improved Activity, Low Catalyst Loading
作者:Albrecht Berkessel、Erkan Ertürk
DOI:10.1002/adsc.200606181
日期:2006.12
The hydrolytickineticresolution (HKR) of terminal epoxides, using chiral chromium(III)-salen catalysts based on DIANANE (endo,endo-2,5-diaminonorbornane), was studied. A broad substrate scope was found for the chromium(III)-DIANANE catalysts, and very low loadings (down to 0.05 mol %) were needed to achieve high enantiomeric purities of both the remaining epoxides and the product diols (up to >99 %
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 and catalytic reactivity of D4-symmetric dinorbornabenzene-derived metallotetraarylporphyrins
作者:Ronald L. Halterman、Shyi-Tai Jan、Heather L. Nimmons、David J. Standlee、Masood A. Khan
DOI:10.1016/s0040-4020(97)00729-1
日期:1997.8
D4-symmetry. The resolved benzaldehyde was synthesized in seven steps from p-benzoquinone and cyclopentadiene and included a resolution via diastereomeric ketals. A manganese chloride complex of porphyrin 1 was used as a catalyst for the asymmetric epoxidation of aromatic substituted alkenes in the presence of excess sodiumhypochlorite in up to 7,200 turnovers and up to 76% e.e and >90% yield.