Chiral Calcium Complexes as Brønsted Base Catalysts for Asymmetric Addition of α-Amino Acid Derivatives to α,β-Unsaturated Carbonyl Compounds
作者:Susumu Saito、Tetsu Tsubogo、Shū Kobayashi
DOI:10.1021/ja0709730
日期:2007.5.1
promote the catalyticasymmetric 1,4-addition reactions and [3+2] cycloaddition reactions of α-amino acidderivatives with α,β-unsaturated carbonyl compounds have been developed. The reactions proceeded smoothly in the presence of 5−10 mol % of the chiral calcium catalyst to afford the desired adducts in high yields with high diastereo- and enantioselectivities. A wide range of α,β-unsaturated esters and
Asymmetric Dihydroxylation of Esters and Amides of Methacrylic, Tiglic, and Angelic Acid: No Exception to the Sharpless Mnemonic!
作者:Fabian Weber、Reinhard Brückner
DOI:10.1002/ejoc.201403622
日期:2015.4
are contradictory and partly in conflict with the Sharpless mnemonic. We systematically screened the SAD of esters and amides of angelic, tiglic, and methacrylic acid. Enantiocontrol arose in 14 of the 15 reactions, culminating at 99 % ee for the Weinreb amide of tiglicacid. The absolute configurations of all the nonracemic products were established by (stereo)chemical correlations. Without exception
Enantioselective Enolate Protonation in Sulfa–Michael Addition to α-Substituted <i>N</i>-Acryloyloxazolidin-2-ones with Bifunctional Organocatalyst
作者:Nirmal K. Rana、Vinod K. Singh
DOI:10.1021/ol202808n
日期:2011.12.16
Organocatalytic conjugate addition of thiols to α-substituted N-acryloyloxazolidin-2-ones followed by asymmetric protonation has been studied in the presence of cinchona alkaloid derived thioureas. Both of the enantiomers are accessible with the same level of enantioselectivity using pseudoenantiomeric quinine/quinidine derived catalysts. The addition/protonation products have been converted to useful biologically
4-addition and [3 + 2] cycloaddition reactions using chiral calcium species prepared from calcium isopropoxide and chiral bisoxazoline ligands have been developed. Glycine Schiff bases reacted with acrylic esters to afford 1,4-addition products, glutamic acid derivatives, in high yields with high enantioselectivities. During the investigation of the 1,4-addition reactions, we unexpectedly found that a [3
A general strategy for the hydroalkylation of vinyl ketones using ethers catalyzed by an iron catalyst is described. This catalytic method permits direct transformation of easily accessible and abundant precursors into highly substituted, structurally diverse and functionally concentrated products.