Conformationally restricted perhydrobenzoxazines have been demonstrated to be good chiral ligands for one-pot asymmetric ethylation/epoxidation, and the unprecedented arylation/epoxidation of trisubstituted α,β-unsaturated aldehydes. The scope of the reaction has been studied and a wide set of substrates with allylic strain of different nature has been explored, obtaining good or total diastereoselectivities
The first asymmetric Cu-catalyzed conjugate addition of dialkylzinc zinc reagents to a large scope of enals in presence of phosphoramidite, SimplePhos, or (R)-BINAP ligands with enantiomeric excesses up to 90% is reported. Moreover, ACA of Grignard reagents afforded moderate to good 1,4-regioselectivities with enantioselectivities up to 90%.
Stereoselective Synthesis of Trisubstituted Olefins by a Directed Allylic Substitution Strategy
作者:Yvonne Schmidt、Bernhard Breit
DOI:10.1002/chem.201100843
日期:2011.10.10
α‐methylene aldehydes. Addition of an organometallic reagent and introduction of the o‐DPPB group by esterification was followed by the o‐DPPB‐directed copper‐mediated allylic substitution with a Grignard reagent to furnish stereodefined trisubstituted olefins. Additionally, incorporation of a stereocenter from the chiralpool allowed the preparation of an enantiomericallypureolefin that bore three alkyl
Kinetic resolution of racemic allylic alcohols <i>via</i> iridium-catalyzed asymmetric hydrogenation: scope, synthetic applications and insight into the origin of selectivity
作者:Haibo Wu、Cristiana Margarita、Jira Jongcharoenkamol、Mark D. Nolan、Thishana Singh、Pher G. Andersson
DOI:10.1039/d0sc05276k
日期:——
Asymmetric hydrogenation is one of the most commonly used tools in organic synthesis, whereas, kineticresolution via asymmetric hydrogenation is less developed. Herein, we describe the first iridium catalyzed kineticresolution of a wide range of trisubstituted secondary and tertiary allylic alcohols. Large selectivity factors were observed in most cases (s up to 211), providing the unreacted starting
不对称氢化是有机合成中最常用的工具之一,而通过不对称氢化进行动力学拆分的开发较少。在此,我们描述了各种三取代仲和叔烯丙醇的第一次铱催化动力学拆分。在大多数情况下观察到较大的选择性因子(高达211),从而以良好的收率和高水平的对映体纯度(ee 高达 >99%)提供未反应的起始材料。该方法的实用性在一些生物活性天然产物的对映选择性正式合成中得到了强调,包括 pumiliotoxin A、inthomycin A 和 B。提出了 DFT 研究和关于选择性起源的选择性模型。
Processes for Highly Enantio- and Diastereoselective Synthesis of Acyclic Epoxy Alcohols and Allylic Epoxy Alcohols
申请人:Walsh Patrick
公开号:US20090163728A1
公开(公告)日:2009-06-25
The inventive subject matter relates to novel processes for making an epoxy alcohol from an aldehyde, comprising the steps of: (a) adding (i) an organozinc compound or (ii) divinylzinc compound and an diorganozinc compound to said aldehyde in the presence of a first catalyst to form an allylic alkoxide compound; and (b) epoxidizing said allylic alkoxide compound in the presence of an oxidant and a second catalyst.