Asymmetric Catalytic Mannich Reactions Catalyzed by Urea Derivatives: Enantioselective Synthesis of <i>β</i>-Aryl-<i>β</i>-Amino Acids
作者:Anna G. Wenzel、Eric N. Jacobsen
DOI:10.1021/ja028353g
日期:2002.11.1
Highly enantioselective addition reactions between silyl ketene acetals and N-Boc aldimines are catalyzed by the thiourea-based catalyst 1c. Extraordinary scope is observed in this methodology with regard to the imine substrate, with aryl and heteroaromatic derivatives generally affording nearly quantitative yields of β-amino ester product in up to 98% enantioselectivity.
A Three-Component Reaction for the One-Pot Preparation of
β-Amino-α,α-Difluoroketones from Trimethyl(trifluoromethyl)silane (CF3TMS), Acylsilanes and Imines
the acylsilane compared to the imine allows the direct mixing of all the reagents in a three-component, one-pot process. A methodology allowing the direct preparation of β-amino-α,α-difluoroketones from the Ruppert–Prakash reagent (CF3TMS), acyltrimethylsilanes and N-Boc or N-(diphenylphosphinyl)imines is reported. The process, initiated by a catalytic amount of tetra-n-butylammonium difluorotriphenylsilicate
Chiral Ammonium Betaines: A Bifunctional Organic Base Catalyst for Asymmetric Mannich-Type Reaction of α-Nitrocarboxylates
作者:Daisuke Uraguchi、Kyohei Koshimoto、Takashi Ooi
DOI:10.1021/ja8041004
日期:2008.8.1
A chiralammoniumbetaine, an intramolecular ion-pairing quaternary ammonium aryloxide 3, has been designed and its vast potential as an enantioselective organic base catalyst has been successfully demonstrated in the highly enantioselective direct Mannich-type reaction of alpha-substituted alpha-nitrocarboxylates 2 with various N-Boc imines 1. The present study provides a conceptually new approach
Development of Chiral Ureates as Chiral Strong Brønsted Base Catalysts
作者:Azusa Kondoh、Sho Ishikawa、Masahiro Terada
DOI:10.1021/jacs.9b13922
日期:2020.2.26
Recently, chiralBrønsted bases having high basicity have emerged as a powerful tool in developing new catalytic enantioselective reactions. However, such chiral strong Brønsted base catalysts are still very scarce. Herein, we report the development of a chiral anionic Brønsted base having a N,N'-dialkyl ureate moiety as a basic site. Its prominent catalytic activity was demonstrated in the enantioselective
The first asymmetric Mannich-type reaction of stabilized phosphorus ylides and N-Boc aldimines was described promoted by a readily available and recyclable chiral bisthiourea organocatalyst. Subsequent reaction with formalin smoothly provides N-Boc-β-amino-α-methylene carboxylic esters in a highlyenantiomericallyenriched form (up to 96% ee).