Vinyl anion equivalent V. Asymmetric synthesis of allylic alcohols using chiral 2-(trialkylsilyl)ethyl sulfoxides
作者:Shinya Kusuda、Yoshio Ueno、Takeshi Toru
DOI:10.1016/s0040-4020(01)80816-4
日期:1994.1
Both enantiomers of optically pure secondary allylic alcohols can be conveniently prepared by the diastereoselective reaction of the α-sulfinyl carbanion of p-tolyl 2-(trialkylsilyl)ethyl sulfoxides or tert-butyl 2-(trimethylsilyl)ethyl sulfoxide with aldehydes followed by either fluoride-induced desilylsulfinylation or thermal elimination of the sulfinyl group.
Substitution of secondary allylic phosphates with the anions derived from Ar2CH2 with BuLi or LDA proceeded regioselectively and stereoselectively without a metal catalyst, affording inversion products in good yield. Similarly,...
Natural 12-hydroxyheptadecatrienoic acid (12-HHT) with an S configuration was synthesised by a Suzuki–Miyaura coupling of C10–C17 iodo alcohol with C1–C9 vinylborane. The iodo alcohol was synthesised by utilising Sharpless asymmetric epoxidation of the corresponding trimethylsilyl alcohol. The method yielded more than 100 mg of 12-HHT. Similarly, syntheses of 5,6-dihydro- and 14,15-dehydro derivatives
A short formal synthesis of (−)-methylenolactocin via a nickel catalyzed intramolecular carbozincation
作者:Andrea Vaupel、Paul Knochel
DOI:10.1016/0040-4039(94)02243-5
日期:1995.1
The lactone 2 which can be converted in one step into (−)-methylenolactocin 1 was prepared in 4 steps, 30 % overall yield and > 92 % ee starting from (E)-3-trimethylsilylpropenal 4. The key step is a new nickel catalyzed cyclization of the polyfunctional bromo-alkenylsilane 3 mediated by Et2Zn. The intermediate organozinc species 7 has been directly oxidized to an aldehyde with oxygen.
Synthesis of optically active γ-trimethylsilyl-β,γ-epoxy tertiary alcohols by the diastereoselective addition reaction of β-trimethylsilyl-α,β-epoxyketones with Grignard reagents
作者:Sentaro Okamoto、Hiromi Tsujiyama、Toshiharu Yoshino、Fumie Sato
DOI:10.1016/s0040-4039(00)93556-1
日期:1991.10
β-epoxyketones, readily prepared in a chiral form by using the Sharpless kinetic resolution of γ-trimethylsilyl secondary allylic alcohols as a key reaction, with Grignardreagents proceeds highly diastereoselectivity to afford opticallyactive γ-trimethylsilyl-β,γ-epoxy tertiary alcohols.