Asymmetric alkylation using chiral cyclic diols to prepare a quaternary carbon
摘要:
Asymmetric alkylation of cyclic and acyclic beta-keto ester acetals (4, 5, 13, 14, and 18) with C-2-symmetric cycloalkane-1,2-dioxy moiety proceeded in a highly diastereoselective manner to afford enol ethers (9-12, 15-17, 19a-c) with a chiral quaternary carbon.
Enantioselective Palladium-Catalyzed Decarboxylative Allylation of β-Keto Esters Assisted by a Thiourea
作者:Lung Chung、Xumu Zhang、Hua Qian、Guoxian Gu、Qinghai Zhou、Jiaxiang Lu
DOI:10.1055/s-0036-1590869
日期:2018.1
decarboxylative allylation of β-keto esters catalyzed by a palladiumbis(phosphine)-thiourea complex is reported. This procedure is not only effective for β-keto esters, but also effective for β-keto amides. An intermolecular variant of the asymmetric decarboxylative allylation is also established. DFTcalculations indicate that an outer-sphere mechanism is viable for the decarboxylative allylation
Asymmetric alkylation of .alpha.-alkyl .beta.-keto esters
作者:Kiyoshi Tomioka、Kaori Ando、Yutaka Takemasa、Kenji Koga
DOI:10.1021/ja00321a050
日期:1984.5
Diastereoselective alkylation de lithio enamines obtenues a partir d'α-alkyl β-cetoesters et du (S)-valinate de t-butyle
非对映选择性烷基化脱硫烯胺减少部分 d'α-烷基 β-cetoesters et du (S)-valinate de t-butyle
Factors controlling the diastereoface selectivity in the complementary asymmetric alkylation of α-alkyl β-keto esters
作者:Kiyoshi Tomioka、Kaori Ando、Yutaka Takemasa、Kenji Koga
DOI:10.1016/s0040-4039(01)91410-8
日期:1984.1
Complementary asymmetricalkylation reaction of the lithioenamine derived from 2-methoxycarbonylcyclohexanone and (S)-valine tert-butyl ester was examined by employing the various electron pair donating additives in a toluene solvent, in order to clarify the factors controlling the diastereoface selectivity.
Enantioselective Synthesis of [
<i>b</i>
]‐Annulated Azepane Scaffolds
作者:Enno Aeissen、Aaron R. von Seggern、Marc Schmidtmann、Jens Christoffers
DOI:10.1002/ejoc.202300180
日期:——
Optically active α-allyl-β-oxoesters are submitted to olefin cross metathesis and subsequent exhaustive hydrogenation and reductive amination to furnish [b]-annulated azepane derivatives.
光学活性 α-烯丙基-β-氧代酯经过烯烃交叉复分解和随后的彻底氢化和还原胺化以提供 [ b ]-环氮杂环庚烷衍生物。
Stereoselective reactions. XXI. Asymmetric alkylation of α-alkyl β-keto esters to α,α-dialkyl β-keto esters having either (R)- or (S)-chiral quaternary center depending on the solvent system
作者:Kaori Ando、Yataka Takemasa、Kiyoshi Tomioka、Kenji Koga
DOI:10.1016/s0040-4020(01)80346-x
日期:——
Asymmetric alkylation reaction of chiral enamines prepared from alpha-alkyl beta-keto esters and (S)-valine tert-butyl ester leading to either enantiomer is described. Lithiated chiral enamines can be alkylated with alkyl halides in a toluene solvent in the presence of HMPA to give, after hydrolysis, alpha,alpha-dialkyl beta-keto esters in 70-99%ee. The reactions in the presence of THF, dioxolane, or trimethylamine. instead of HMPA, afford the corresponding antipodes with enantiomeric purities of 44-92%ee. The present method provides a procedure for the synthesis of both enantiomers of alpha,alpha-dialkyl beta-keto esters in high enantiomeric purities starting from the same chiral enamines.