所述的组合物[Cu(MeCN中)4 ] TFA·TFAH(TFA = O 2 CCF 3)与Feringa的的亚磷酰胺配位体(大号甲)提供了异常活性(0.75摩尔%)催化剂ZNR的不对称共轭加成2(R =的Et和Me在-40至-80°C的温度下生成烯酮。动能和加入ZnEt的其他研究2至环己-2-烯-1-酮指示的转变状态的化学计量组合物(ZnEt 2)3(烯酮)4的Cu 2(大号甲)3,其通过转移金属化从Et产生2锌(烯酮)2。催化剂的产生显着慢于周转速度(这已经限制了先前获得有用动力学数据的尝试);在初始阶段,存在着各种催化惰性,非循环物种。通过双剂量动力学分析方案可以克服这些问题。[ L A Cu(Et)(μ-TFA)(μ-{(enone)(ZnEt)2(enolate )})Cu L A 2 ] +的静止状态(通过烯醇化物的等价物=烯酮+ ZnEt 2)由DFT研究(ωB97X-D/ SRSC)支持。速率决定型ZnEt
15, which was derived from (S)-tert-leucinol, produced (S)-18 in preference to (R)-18. A series of azolium salts were synthesized from (S)-serine esters, and the reaction conditions for the ECA reaction were optimized to produce (R)-18 with 69% ee. The best results were obtained in the case of the reaction of 4,4-dimethyl-2-cyclohexen-1-one (34) with Et2Zn catalyzed by Cu(OTf)2 in combination with azolium
Chiral alkoxy-imidazolinium salts are easily available via a five-step procedure starting from β-aminoalcohols. This new family of alkoxy-N-heterocyclic carbene (NHC) precursors is shown to be highly active in the enantioselective copper-catalysed conjugateaddition to cyclic enones. Complete conversion with lowcatalystloading and good enantiomeric excesses up to 93% were obtained at room temperature
New phosphino‐oxazoline ligands have been developed, and the ligands have been used for Cu‐catalysed enantioselective conjugate additions to (E)‐nitroalkenes.
已开发出新的膦基-恶唑啉配体,该配体已被用于铜催化的(E)-硝基烯烃的铜对映体选择性共轭加成反应。
A new approach to switching of enantioselectivity in NHC–Cu-catalyzed conjugate addition of alkylzincs to cyclic enones
作者:Masaki Okamoto、Yuko Yamamoto、Satoshi Sakaguchi
DOI:10.1039/b916103a
日期:——
Conjugate addition of Et2Zn to 2-cyclohexen-1-one catalyzed by Cu(OTf)2 combined with an azolium salt derived from (S)-leucinol produced the corresponding (S)-adduct, while the use of Cu(acac)2 in combination with the same ligand afforded the (R)-adduct as a major product.
Reversal of Stereoselectivity in the Cu-Catalyzed Conjugate Addition Reaction of Dialkylzinc to Cyclic Enone in the Presence of a Chiral Azolium Compound
Reversal of enantioselectivity in a Cu-catalyzedasymmetricconjugateaddition reaction of dialkylzinc to cyclicenone with use of the same chiral ligand was successfully achieved. The reaction of 2-cyclohexen-1-one (30) with Et2Zn catalyzed by Cu(OTf)2 in the presence of an azolium salt derived from a chiral β-amino alcohol gave (S)-3-ethylcyclohexanone (31) in good enantioselectivity. Among a series