[3 + 2] Annulation of β-Heteroatom-Substituted α,β-Unsaturated Acylsilanes with Methyl Ketone Enolates: Scope and Investigation of the Reaction Course
作者:Kei Takeda、Kenji Yamawaki、Noriaki Hatakeyama
DOI:10.1021/jo0160219
日期:2002.3.1
A new route to (Z)-beta-silylacryloylsilanes 10 and the improved conditions for the [3 + 2] annulation using 10 and alkyl methyl ketone enolates are reported. Also, details of investigations defining a reactioncourse of the [3 + 2] annulation using beta-phenylthio- and beta-trimethylsilyl-acryloylsilanes 1 (X = SPh, SiMe(3)) and alkyl methyl ketone enolates are described.
Reaction of acylsilanes with potassium cyanide: Brook rearrangement under phase-transfer catalytic conditions
作者:Kei Takeda、Yuji Ohnishi
DOI:10.1016/s0040-4039(00)00560-8
日期:2000.5
The reactions of acylsilanes with KCN under liquid–liquid phase-transfer catalytic conditions proceeded smoothly via the Brook rearrangement to produce O-silylated cyanohydrin derivatives in excellent yields. We also found that α-cyano carbanions generated by the Brook rearrangement in the reaction of (β-(trimethylsilyl)acryloyl)silane 7 can undergo alkylation at the γ-position and that in the reaction
Low-temperature oxyanion-accelerated vinylcyclopropane-cyclopentene rearrangement. Reaction of 2-(2-(trimethylsilyl)-ethenyl)cyclopropyl acetates with methyl lithium
作者:Kei Takeda、Keiki Sakurama、Eiichi Yoshii
DOI:10.1016/s0040-4039(97)00579-0
日期:1997.5
yl acetates 7, derived from enol silyl ether 4 and Fischer carbene complex 6, with 2.2 equiv of MeLi at −80 ° to −30 °C afforded cyclopentenol 8 as a single diastereomer and acyclicenol silyl ethers 9 via the corresponding cyclopropanolates in ratios depending on the vinylsilane geometry. Predominant formation of 8 over 9 from (Z)-7 irrespective of the stereochemistry at C-1 was observed. This is
The α-carbanion-stabilizing ability of the phenylthio and trimethylsilyl groups was compared based on the relativerate of the base-catalyzed Brook rearrangement of the β-substituted α-silylallylalcohol.
Stereoselective Construction of Eight-Membered Carbocycles by Brook Rearrangement-Mediated [3 + 4] Annulation
作者:Kei Takeda、Yuji Sawada、Koichi Sumi
DOI:10.1021/ol0256318
日期:2002.3.1
[reaction: see text] A newly developed strategy for eight-memberedcarbocycles via [3 + 4] annulation that involves the combination of beta-substituted acryloylsilanes and enolates of cycloheptenone is described. A unique feature of this annulative approach is its capacity to generate, in two steps, eight-membered ring systems containing useful functionalities for further synthetic elaboration from