合成了基于α,α,α,α-四芳基-1,3-二氧戊环-4,5-二甲醇(TADDOL)的亚磷酰胺库,并将其用于Ni催化的不同二烯的环异构化。通过铅结构的三个结构基序(即胺部分,保护基和芳基取代基)的系统变化,可以优化配体特征,以使模型底物二烯丙基丙二酸二乙酯的不对称环异构化。新催化体系的底物范围已扩展到其他二烯丙基底物,包括不对称二烯。总体上具有高达13 500 h -1的极高活性,对五元外亚甲基亚环戊烷的选择性很高,对映选择性高达92% ee 已经实现。
Prochiral substrates (alkyl aryl ketones, cyclopropyl methyl ketone, 1-indanone, 1-tetralone, ethyl 2-oxo-4-phenylbutyrate, and N-(diphenylphosphinyl)acetophenoneimine) were subjected to asymmetric reduction with aluminum hydride reagents, which were prepared by modifications of NaAlH4 or AlH3 with chiral alpha,alpha,alpha',alpha'-tetraaryl-1,3-dioxolane-4,5-dimethanols (TADDOL). The effects of the nature of the substituents in TADDOL, the structure of the prochiral substrate, and the reaction conditions on the stereochemistry of reduction were investigated. The highest enantioselectivity (70-90% ee) was achieved upon reduction of alkyl aryl ketones and N-(diphenylphosphinyl)acetophenoneimine with NaAl(TADDOLate)H-2 in THF or diglyme at a temperature from -70 to -20 degreesC. The mechanism of asymmetric induction in the reduction reactions of ketones with aluminum hydride reagents is discussed. The stereochemical results of reduction were explained by comparing three-dimensional models of the most probable transition states.
Catalytic Asymmetric SiO Coupling of Simple Achiral Silanes and Chiral Donor-Functionalized Alcohols
作者:Andreas Weickgenannt、Marius Mewald、Thomas W. T. Muesmann、Martin Oestreich
DOI:10.1002/anie.200905561
日期:2010.3.15
Silicon alley: SiH and HOR are enantioselectively coupled in the presence of a chiral CuH complex. In this way, the kinetic resolution of racemic mixtures of alcohols is accomplished through asymmetric protection with standard silanes (see scheme; R=aryl or alkyl, Ar=3,5‐xylyl, Np=2‐naphthyl; s=selectivity factor).
硅胡同:硅 H和H 或者,对映选择性地耦合在手性铜的存在 H络合物。通过这种方式,醇的外消旋混合物的动力学拆分可通过使用标准硅烷进行不对称保护来实现(参见方案; R =芳基或烷基,Ar = 3,5-二甲苯基,Np = 2-萘基; s =选择性因子)。
Amide-Directed Catalytic Asymmetric Hydroboration of Trisubstituted Alkenes
作者:Sean M. Smith、James M. Takacs
DOI:10.1021/ja908257x
日期:2010.2.17
rhodium-catalyzed reaction is stereospecific. In addition, simple TADDOL-derived phenyl monophosphite ligands in combination with Rh(nbd)(2)BF(4) afford highly enantioselective catalysts (seven examples, 91-98% ee). These catalysts provide an alternative methodology to prepare Felkin or anti-Felkin acetate-aldol products and related derivatives that are obtainable from the intermediate chiral organoboranes
Highly Enantioselective Nickel-Catalyzed Hydrocyanation of Disubstituted Methylenecyclopropanes Enabled by TADDOL-based Diphosphite Ligands
作者:Rongrong Yu、Xianjie Fang
DOI:10.1021/acs.orglett.9b04374
日期:2020.1.17
A vast range of novel TADDOL-based diphosphite ligands were first synthesized and applied in the nickel-catalyzed asymmetric hydrocyanation of disubstituted methylenecyclopropanes. By employing these new catalysts, the conversion of diverse methylenecyclopropanes into their corresponding allylic nitriles was first enabled, in good yield with excellent enantioselectivities.
Enantioselective Nickel‐Catalyzed Migratory Hydrocyanation of Nonconjugated Dienes
作者:Rongrong Yu、Shanmugam Rajasekar、Xianjie Fang
DOI:10.1002/anie.202008854
日期:2020.11.23
Metal‐catalyzed chain‐walking reactions have recently emerged as a powerful strategy to functionalize remote positions in organic molecules. However, a chain‐walking protocol for nonconjugated dienes remains scarcely reported, and developments are currently ongoing. In this Communication, a nickel‐catalyzed asymmetric hydrocyanation of nonconjugated dienes involving a chain‐walking process is demonstrated
Enantioselective Palladium-Catalyzed Direct Arylations at Ambient Temperature: Access to Indanes with Quaternary Stereocenters
作者:Martin���R. Albicker、Nicolai Cramer
DOI:10.1002/anie.200905060
日期:2009.11.16
Ta daa: The title reaction proceeds under essentially neutral reaction conditions at ambienttemperature with a taddol‐based phosphoramidite ligand L* allowing the creation of indanes with quaternary stereogenic centers in high enantiomeric excess (see scheme; Tf=trifluoromethanesulfonyl, DMAc=dimethylacetamide).
Ta daa:标题反应在室温下基本基于中性反应条件下,使用基于taddol的亚磷酰胺配体L *进行,从而以对映体过量的形式生成具有季立体异构中心的茚满(见方案; Tf =三氟甲磺酰基,DMAc =二甲基乙酰胺)。