Asymmetric copper-catalyzed allylic alkylation between allyl bromides and alkyl Grignard reagents using a P-chiral monophosphorus ligand is described. A range of terminal olefins bearing tertiary or quaternary carbon centers were formed in good branched/linear selectivities and excellent enantioselectivities at copper loadings as low as 0.5 mol %.
Enantioselective Copper‐Catalysed Allylic Alkylation of Cinnamyl Chlorides by Grignard Reagents using Chiral Phosphine‐Phosphite Ligands
作者:Wibke Lölsberg、Shute Ye、Hans‐Günther Schmalz
DOI:10.1002/adsc.201000213
日期:2010.10.9
copper(I)-catalysed SN2′-type allylicsubstitution of E-3-aryl-allyl chlorides (cinnamyl chlorides) using Grignard reagents represents a powerful method for the synthesis of compounds carrying a benzylic stereocentre. By screening a small library of modular chiral phosphine-phosphite ligands a new copper(I)-based catalyst system was identified which allows the performance of such reactions with exceptional high
使用格氏试剂的铜(I)催化的E -3-芳基-烯丙基氯化物(肉桂酰氯)的S N 2'型烯丙基取代代表了一种合成具有苄基立体中心的化合物的有效方法。通过筛选小的模块化手性膦-亚磷酸酯配体文库,确定了一种新的基于铜(I)的催化剂体系,该体系可以以极高的区域和对映体选择性进行此类反应。使用TADDOL衍生的配体(3 mol%),溴化铜(I)·二甲基硫醚(CuBr·SMe 2)(2.5 mol%)和甲基叔丁基醚(MTBE)获得最佳结果。制备了具有高达99%ee的各种(1-烷基-烯丙基)苯衍生物(GC)的分离产率高达99%。在大多数情况下,产物包含少于3%的线性区域异构体(除了邻位取代的底物)。富电子和电子不足的肉桂酰氯均已成功使用。通过比较实验和计算出的CD光谱来确定产品的绝对构型。通过与亚硫酰氯反应,由相应的醇制备底物。通过在MTBE中在三苯基膦(PPh 3)(3mol%)的存在下在低温下用CuBr·SMe
Bidentate Hydroxyalkyl NHC Ligands for the Copper-Catalyzed Asymmetric Allylic Substitution of Allyl Phosphates with Grignard Reagents
作者:Magaly Magrez、Yann Le Guen、Olivier Baslé、Christophe Crévisy、Marc Mauduit
DOI:10.1002/chem.201203969
日期:2013.1.21
Demonstrating their potential: Bidentate alkoxy NHC ligands have been used in the copper‐catalyzed asymmetricallylic alkylation of allylphosphates with Grignard reagents (see scheme). The method provides access to tertiary and quaternary chiral centers with high regio‐ and enantioselectivity. The system is also applied to the synthesis of chiral E,E‐dienes, a key structural motif prevalent in natural
The application of chiral chelating hydroxy NHC in copper-catalyzedasymmetricallylicalkylation (Cu-AAA) involving various dialkylzincs and allylic phosphate substrates is reported here. From a library of 11 chiral chelating hydroxyalkyl NHC, a fine-tuning has been done to identify the best architectural features enabling to produce the expected γ-adducts in total regioselectivity, good isolated
A phosphite–phosphoroamidite and diphosphoroamidite ligand library was applied in the Cu-catalyzedallylicsubstitution of a range of cinnamyl-type substrates using several organometallic nucleophiles. Results indicated that selectivity depended strongly on the ligand parameters (position of the phosphoroamidite group at either C-5 or C-3 of the furanoside backbone, as well as the configuration of