A Simple Batch Reactor for the Efficient Multiple Use of Polymer-Bound α,α,α‘,α‘-Tetraaryl-1,3-dioxolane-4,5-dimethanol Titanates in the Nucleophilic Addition of Dialkylzinc Reagents to Aldehydes
摘要:
A new apparatus for heterogeneous-catalyst-mediated transformations is described. Results for a variety of enantioselective dialkylzinc additions to aldehydes mediated by polymer-bound alpha, alpha, alpha', alpha'-tetraargl-1,3-dioxolane-4,5-dimethanol titanates (pb-Ti-TADDOLs) using this new apparatus are given, In particular the active catalyst:, once prepared, can be used many times with minimal loss of activity or enantioselectivity, The relative rate of reaction using the pb-Ti-TADDOLates as compared to a homogeneous Ti-TADDOLate has also been determined.
与普遍的想法相反,发现上清液的盐含量决定了 Rieke 锌的不同制备方法对有机卤化物的氧化加成的反应性差异。这一结论是通过结合单颗粒显微镜和系综光谱实验,并在 Rieke 锌制备过程中小心去除或保留上清液而得出的。具有单 Rieke 锌颗粒分辨率的荧光显微镜实验确定了在没有上清液的情况下 Rieke 锌的微观表面反应性,从而确定了其固有的反应性,与复杂的上清液成分无关。在平行实验中,扫描电子显微镜、能量色散谱、X射线光电子能谱和电感耦合等离子体质谱法在块体和单颗粒水平上表征了锌金属的化学成分。质子核磁共振波谱动力学表征了在存在和不存在不同上清液和外源盐添加剂的情况下小规模 Rieke 锌的反应性。总之,这些实验表明,钠还原的 Rieke 锌与锂还原的 Rieke 锌的反应性差异源于上清液中的残留盐,而不是固体的不同盐组成。该上清液盐还决定了最终有机锌产物的结构,生成二有机锌或单有机锌卤化物络合物。尽管
Catalytic Enantioselective Addition of Diorganozinc Reagents to Vinyl Sulfones
作者:Jean-Nicolas Desrosiers、William S. Bechara、André B. Charette
DOI:10.1021/ol800747v
日期:2008.6.5
An efficient method for the catalytic asymmetric conjugate addition of diorganozincreagents to vinyl sulfones is reported. Using a Binap*Cu complex, enantioselectivities up to 98% ee and high yields can be attained for a variety of substrates. Several dialkylzinc reagents are also compatible with this procedure.
Highly Diastereoselective Preparation of (<i>E</i>)-Alkenylsilanes Bearing an α-Chiral Center
作者:Sylvie Perrone、Paul Knochel
DOI:10.1021/ol063097o
日期:2007.3.1
The copper(I)-mediated anti-S(N)2' allylic substitution allows a highly stereoselective preparation of alkenylsilanes bearing a chiral center in the alpha-position with high transfer of chirality. These alkenylsilanes were converted into alpha,beta-unsaturated ketones or into the corresponding boronic esters without loss of the chiral information. [reaction: see text]
Chiral Allylic Cyanohydrins as Versatile Substrates for Diastereoselective Copper(I)-mediated S<sub>N</sub>2′ Allylic Substitutions
作者:Paul Knochel、Sylvie Perrone、Albrecht Metzger
DOI:10.1055/s-2007-973881
日期:2007.4
2,6-Difluorobenzoated derivatives bearing a protected cyanohydrin function undergo highly stereoselective copper(I)-mediated SN2′ allylicsubstitutionreactions with diorganozinc reagents leading to chiral unsaturated nitriles.
带有受保护的氰醇功能的 2,6-二氟苯甲酸衍生物与二有机锌试剂发生高度立体选择性的铜 (I) 介导的 SN 2' 烯丙基取代反应,产生手性不饱和腈。
Dynamic kinetic asymmetric transformation in copper catalyzed allylic alkylation
作者:Jean-Baptiste Langlois、Alexandre Alexakis
DOI:10.1039/b907722g
日期:——
The first dynamickineticasymmetrictransformation in copper catalyzed allylic alkylation is reported, with enantioselectivities up to 92%.
Catalytic Enantioselective Addition of Dialkylzinc Reagents to<i>N</i>-Acylpyridinium Salts
作者:M.â Ãngeles Fernández-Ibáñez、Beatriz Maciá、Mariaâ Gabriella Pizzuti、Adriaanâ J. Minnaard、Benâ L. Feringa
DOI:10.1002/anie.200904981
日期:2009.11.23
A pinch of salt: The first catalyticaddition of dialkylzincreagents to N‐acylpyridinium salts with good yields and excellent enantioselectivities uses a copper–(S)‐L complex as the catalyst. The versatility of the method is illustrated in the formal synthesis of the alkaloid (R)‐coniine. Bn=benzyl, Tf=trifluoromethanesulfonyl.