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.
Structural optimization of thiourea-based bifunctional organocatalysts for the highly enantioselective dynamic kinetic resolution of azlactones
作者:Albrecht Berkessel、Santanu Mukherjee、Thomas N. Müller、Felix Cleemann、Katrin Roland、Marc Brandenburg、Jörg-M. Neudörfl、Johann Lex
DOI:10.1039/b607574f
日期:——
describes the synthesis of a library of structurally diverse bifunctionalorganocatalysts bearing both a quasi-Lewis acidic (thio)urea moiety and a Bronsted basic tertiary amine group. Sequential modification of the modular catalyst structure and subsequent screening of the compounds in the alcoholytic dynamickineticresolution (DKR) of azlactones revealed valuable structure-activity relationships. In particular
Chiral thiourea compounds and process for enantioselective reduction of ketones
申请人:Li Derun
公开号:US20090253919A1
公开(公告)日:2009-10-08
Chiral thioureas are effective catalysts for the borane reduction of prochiral ketones to optically active alcohols. A prochiral ketone may be reduced to an optically active alcohol in the presence of a substantially sub-stoichiometric amount of chiral thiourea. The asymmetric thiourea compound of the present invention may be produced according to a production method described herein.
such bifunctional chiral molecules, either neutral or protonated species, was investigated in the addition of acetylacetone to β-nitrostyrene as a model reaction. Using the best conditions, high yields and enantioselectivities of up to 85% were obtained. The same metalfreecatalysts were then employed in the addition of activated nucleophiles to imines: in the reaction of 1,3-diketones with N-CBz imines
A readily available, low cost bifunctional organic catalyst promoted the addition of nitroesters to imines; in the reaction between 2-nitropropionates and N-Boc protected aldehyde-imines the product bearing a new quaternarystereocenter was obtained in up to 81% ee. The positively charged catalyst was postulated to control the attack of the enolic form of nitroester to imine through a hydrogen bonding