SmI2-Promoted Reformatsky-Type Reaction and Acylation of Alkyl 1-Chlorocyclopropanecarboxylates
摘要:
In the presence of HMPA in THF, highly stereoselective Sml(2)-promoted substitutions of alkyl 1-chlorocyclopropanecarboxylates 1 using various ketones, aldehydes (Reformatsky-type reaction), and acyl chlorides (acylation) proceeded to give trans-adducts (2 or 5) in good to high yield with excellent trans-stereoselectivity (trans-add/cis-add = > 99/1). The Reformatsky-type reaction of 1 with aldehydes and unsymmetrical ketones proceeded with moderate diastereoselectivity (re-face-adduct/si-face-adduct = 60/40-75/25).
Nickel‐Catalyzed Asymmetric Hydroaryloxy‐ and Hydroalkoxycarbonylation of Cyclopropenes
作者:Rongrong Yu、Song‐Zhou Cai、Can Li、Xianjie Fang
DOI:10.1002/anie.202200733
日期:2022.9.5
Highly enantioselective inter- and intramolecular Ni-catalyzed hydroalkoxycarbonylation yields various enantioenriched polysubstituted cyclopropanecarboxylic derivatives with quaternary carbon stereocenters.
高度对映选择性的分子间和分子内 Ni 催化的氢化烷氧基羰基化产生各种具有季碳立体中心的对映富集的多取代环丙烷羧酸衍生物。
Nucleophilic Carbenes Derived from Dichloromethane
作者:Mingxin Liu、Nguyen Le、Christopher Uyeda
DOI:10.1002/anie.202308913
日期:2023.10.16
Nickel catalysts promote cyclopropanation reactions of electron-deficient alkenesusing dichloromethane as a methylene source. An asymmetric variant using a chiral pyridine-bis(oxazoline) ligand provides access to pharmaceutically relevant 2-aryl cyclopropyl carboxylates in highly enantioenriched form. The proposed mechanism involves the formation of a nucleophilic nickel carbene that reacts by a
Bis(oxazoline)·copper(I)-catalyzed enantioselective cyclopropanation of cinnamate esters with diazomethane
作者:André B. Charette、Marc K. Janes、Hélène Lebel
DOI:10.1016/s0957-4166(03)00076-4
日期:2003.4
Chiral bis(oxazoline)-copper(l) complexes were found to be effective catalysts for the enantioselective cyclopropanation reaction of trans-cinnamate esters exploiting an argon flow mediated diazomethane addition method. After optimization of the catalyst structure, good yields and enantiomeric excesses were obtained with electron-poor methyl cinnamate derivatives. Sterically demanding esters gave lower yields and enantioselectivities. The correlation between the product enantiopurities and the sigma(+) values of the aromatic para-substituents was shown to be linear in a Hammet-type plot. (C) 2003 Elsevier Science Ltd. All rights reserved.