Cu(I)/Chiral Bisoxazoline-Catalyzed Enantioselective Sommelet–Hauser Rearrangement of Sulfonium Ylides
作者:Shu-Sen Li、Jianbo Wang
DOI:10.1021/acs.joc.0c01590
日期:2020.10.2
asymmetric thia-Sommelet–Hauser rearrangement of sulfonium ylides remains a great challenge due to its multistep reaction mechanism involving metal carbene formation, proton transfer, and [2,3]-sigmatropic rearrangement. In particular, the key problem of such reactions is the differentiation of the enantiotopic lone pair electrons of sulfur, which generates the sulfonium ylide intermediate bearing chirality
Catalytic Asymmetric Fluorination of Copper Carbene Complexes: Preparative Advances and a Mechanistic Rationale
作者:Michael Buchsteiner、Luis Martinez‐Rodriguez、Paul Jerabek、Iago Pozo、Michael Patzer、Nils Nöthling、Christian W. Lehmann、Alois Fürstner
DOI:10.1002/chem.202000081
日期:2020.2.21
Cu-catalyzed reaction of substituted α-diazoesters with fluoride gives α-fluoroesters with ee values of up to 95 %, provided that chiralindane-derivedbis(oxazoline) ligands are used that carry bulky benzyl substituents at the bridge and moderately bulky isopropyl groups on their core. The apparently homogeneous solution of CsF in C6 F6 /hexafluoroisopropanol (HFIP) is the best reaction medium, but
取代的 α-重氮酯与氟化物的铜催化反应可产生 ee 值高达 95% 的 α-氟酯,前提是使用手性茚满衍生的双(恶唑啉)配体,该配体在桥上带有大的苄基取代基和中等大的异丙基以团体为核心。CsF 在 C6 F6 /六氟异丙醇 (HFIP) 中的明显均匀溶液是最好的反应介质,但在两相混合物 CH2 Cl2 /HFIP 中的 CsF 也能提供良好的结果。DFT 研究表明,氟化物首先攻击瞬时供体/受体卡宾中间体的 Cu 原子,而不是 C 原子。这个不寻常的步骤之后是 1,2-氟化物位移;为了发生这种迁移插入,卡宾必须绕 Cu-C 键旋转以确保轨道重叠。C2 对称结合位点内的这种旋转运动的方向性决定了感应的感觉。该模型与使用通过毛细管结晶生长的这种先验蜡状材料的单晶通过 X 射线衍射测定的所得产物的绝对构型非常一致。
Efficient Synthesis of α-Aryl Esters by Room-Temperature Palladium-Catalyzed Coupling of Aryl Halides with Ester Enolates
作者:Morten Jørgensen、Sunwoo Lee、Xiaoxiang Liu、Joanna P. Wolkowski、John F. Hartwig
DOI:10.1021/ja027643u
日期:2002.10.1
arylation of alpha,alpha-disubstituted esters were developed with LiNCy(2) as base and P(t-Bu)(3) as ligand. In addition, tert-butyl esters, such as those of Naproxen and Flurbiprofen, were prepared from tert-butyl propionate and aryl bromides in high yields in the presence of Pd(dba)(2) and the hindered, saturatedheterocycliccarbene ligand precursor.
α-Arylation of Esters Catalyzed by the Pd(I) Dimer {[P(<i>t-</i>Bu)<sub>3</sub>]PdBr}<sub>2</sub>
作者:Takuo Hama、John F. Hartwig
DOI:10.1021/ol8002578
日期:2008.4.1
Conditions for the coupling of bromoarenes with esters using a single base and catalyst with improved turnovernumbers are described. These general conditions were made possible by using the Pd(I) catalyst [P(t-Bu)3]PdBr}2. Reactions of acetates, propionates, and isobutyrates are presented, and reactions of all three classes of esters on a 10 g scale are described.
Catalytic Asymmetric Syntheses of Alkylidenecyclopropanes from Allenoates with Donor‐Acceptor and Diacceptor Diazo Reagents
作者:Yoko Hasegawa、Thomas Cantin、Jonathan Decaens、Samuel Couve‐Bonnaire、André B. Charette、Thomas Poisson、Philippe Jubault
DOI:10.1002/chem.202201438
日期:2022.8.22
Chiral ACPs: The catalytic asymmetric synthesis of alkylidenecyclopropanes from electron-deficient allenes is described. The methodology, using donor-acceptor or diacceptor diazo reagents, catalyzed by a chiral rhodium complex furnished the corresponding ACPs in high yields with excellent diastereo- and enantioselectivities.