External Chiral Ligand-Mediated Enantioselective Peterson Reaction of α-Trimethylsilanylacetate with Substituted Cyclohexanones
摘要:
graphicThe asymmetric Peterson reaction of an alpha-trimethylsilanylacetate with 4-substituted and 3,5-disubstituted cyclohexanones was mediated by an external chiral tridentate ligand to give the corresponding olefins with an axial chirality in high yields and enantioselectivities of up to 85%.
Asymmetric deprotonation of prochiral ketones using chiral lithium amide bases
作者:Christian M. Cain、Richard P.C. Cousins、Greg Coumbarides、Nigel S. Simpkins
DOI:10.1016/s0040-4020(01)85435-1
日期:1990.1
A number of chiral secondary amines have been prepared and used as precursors to the corresponding chirallithiumamidebases. Treatment of either cis-2,6-dimethylcyclohexanone or 4-tert-butylcyclohexanone with a chirallithiumamide, followed by electrophilic quench, gives chiral products in up to 88% enantiomeric excess. The results with 4-tert-butylcyclohexanone are in disagreement with an earlier
New Potentially Chelating Chiral Magnesium Amide Bases for Use in Enantioselective Deprotonation Reactions
作者:William Kerr、Michael Middleditch、Allan Watson
DOI:10.1055/s-0030-1259282
日期:2011.1
to prepare novel chiral magnesium bisamide reagents. These amide bases were subsequently applied within asymmetric deprotonation reactions to probe the potential for chelation-assisted selectivity enhancement. Good levels of selectivity could be achieved (up to 87:13 e.r. (R:S)) across a range of prochiral cyclohexanone substrates when employing a thiophene-derived magnesium bisamide complex.
合成了一系列手性仲胺,结合了 5 或 6 元杂环,并用于制备新型手性镁双酰胺试剂。随后将这些酰胺碱应用于不对称去质子化反应中,以探索螯合辅助选择性增强的潜力。当使用噻吩衍生的镁双酰胺复合物时,可以在一系列前手性环己酮底物上实现良好的选择性(高达 87:13 er (R:S))。
Solution structures of a monodentate chiral lithium amide in the presence of lithium halide
作者:Keizo Sugasawa、Mitsuru Shindo、Hiroshi Noguchi、Kenji Koga
DOI:10.1016/0040-4039(96)01681-4
日期:1996.10
Enantioselectivity of deprotonationreaction of 4-tert-butylcyclohexanone (2) by a monodentate chirallithiumamide ((R,R)-1) in THF is strongly influenced by the presence of lithium halides. Aggregationstates of this chirallithiumamide in THF-d8 in the absence and in the presence of lithium halides were studied by 6Li and 15N NMR. It is concluded that the mixed dimer (D) is the species to give
卤化锂的存在强烈影响4-叔丁基环己酮(2)在THF中被单齿手性锂酰胺((R,R)-1 )的去质子反应的对映选择性。通过6 Li和15 N NMR研究了该手性锂酰胺在不存在和存在卤化锂的情况下在THF- d 8中的聚集态。结论是混合二聚体(D)是赋予反应高对映选择性的物质。
A highly diastereoselective and enantioselectiveBrønstedacidcatalyzedreductive condensation of N−H imines was developed. This reaction is catalyzed by a chiral disulfonimide (DSI), uses Hantzsch esters as a hydrogen source, and delivers useful C2‐symmetric secondary amines.
Stereoselective reactions. 28. Effects of the alkyl group at the amide nitrogen of chiral bidentate lithium amides on enantioselective deprotonation reaction
作者:Kazumasa Aoki、Kiyoshi Tomioka、Hiroshi Noguchi、Kenji Koga
DOI:10.1016/s0040-4020(97)00901-0
日期:1997.10
chiral bidentate lithium amides () having an alkyl- or a fluoroalkyl substituent at the amide nitrogen was examined. having a 2,2,2-trifluoroethyl group at the amide nitrogen was found to be an excellent chiral base for the present deprotonation reaction. Structures of in solution and solid state are discussed.