Dispiroketals in synthesis (Part 16): Functionalised dispiroketals as new chiral auxiliaries; the synthesis of dihydroxylated dispiroketals in optically pure form and their application as bifunctional, C2-symmetrical, chiral auxiliaries for highly stereos
作者:Barend C. B. Bezuidenhoudt、Grant H. Castle、Jean E. Innes、Steven V. Ley
DOI:10.1002/recl.19951140410
日期:——
A range of rigid, architecturally complex diols derived from dispiroketals have been synthesised. A bifunctional, C2-symmetrical, chiralauxiliary derived from these dihydroxylateddispiroketals has been used to induce a high degree of asymmetry in Michael additions of cuprates to a variety of di-α, β-unsaturated ester systems.
A FACILE ASYMMETRIC SYNTHESIS OF β-SUBSTITUTED ALKANOIC ACID THE HIGHLY STEREOSELECTIVE MICHAEL ADDITION OF GRIGNARD REAGENTS TO α,β-UNSATURATED CARBOXYLIC AMIDES DERIVED FROM L-EPHEDRINE
作者:Teruaki Mukaiyama、Nobuharu Iwasawa
DOI:10.1246/cl.1981.913
日期:1981.7.5
The Michael addition of Grignard reagents to chiral α,β-unsaturated carboxylic amides derivedfrom 1-ephedrine affords highly optically active β-substituted alkanoic acids after acid hydrolysis. This high stereoselectivity is explained by considering the formation of rigid internal chelate complexes.
Asymmetric conjugate addition reaction by the use of ()-γ-trityloxymethyl-γ-butyrolactam as a chiral auxiliary
作者:Kiyoshi Tomioka、Toshiro Suenaga、Kenji Koga
DOI:10.1016/s0040-4039(00)84021-6
日期:1986.1
(S)-γ-Trityloxymethyl-γ-butyrolactam (2) serves as a chiralauxiliary in the conjugate addition reaction of the corresponding imide (3) of α,β-unsaturated carboxylic acids with Grignard reagents in the presence of CuBrSMe2 in THF to give, after hydrolysis, the β,β-disubstituted carboxylic acids (5) with predictable absolute configuration and high enantiomeric excess.
Asymmetric conjugate addition of Grignard reagents in the presence of tertiary amines to α,β-unsaturated amides derived from (S)-2-(1-hydroxy-1-methylethyl)pyrrolidine or (S)-prolinol
作者:Kenso Soai、Hideaki Machida、Atsuhiro Ookawa
DOI:10.1039/c39850000469
日期:——
In the presence of tertiaryamines, diastereoselective conjugateaddition of Grignardreagents to α,β-unsaturatedamides affords 3-substituted carboxylic acids of high enantiomeric excess (up to 89% e.e.).
Conjugateadditions of MeCu, PhCu and BuCu to the chiral enoylimides 2 a-c in the presence of iodotrimethylsilane and lithium iodide in THF give the adducts, 4a-c in yields above 90 % and diastereoselectivities from 80 to 93%. The dominating diastereomers are different from those formed with LiR2Cu/TMSCl or in copper(I)-mediated addition of Grignard reagents. Corresponding additions to enoylamides
在THF中存在碘三甲基硅烷和碘化锂的情况下,将MeCu,PhCu和BuCu共轭添加到手性烯丙酰亚胺2 ac中,得到加合物4a-c,收率超过90%,非对映选择性为80%至93%。占主导地位的非对映异构体不同于由LiR 2 Cu / TMSCl形成的非对映异构体,或在铜(I)介导的格氏试剂中添加的非对映异构体。邻三苯甲基脯氨醇向烯酰胺中的相应添加也可产生高产率的共轭加合物,但非对映选择性较低,酰基部分的主要构型与酰亚胺相反。