Dipolar cyclization reactions in heterocyclic synthesis: a novel route to furanophanes
作者:Wolfgang Eberbach、Norbert Laber
DOI:10.1016/s0040-4039(00)77672-6
日期:1992.1
The multistep transformation of 2,3-bridged butenynyl oxiranes 8 into furanophanes 12 involving bridgehead olefins 11 as key intermediates is described. The two lower members of 12 undergo rapid air oxidation resulting in the formation of the dienediones 14a,b. 14b is converted by base into the bicyclo[6.3.0]undecadienone 15.
A convenient method for C-glycosidation (alkynylation) with various silylacetylenes to D-glucal by iodine molecule via iodo-oxonium intermediates provided exclusively the a-acetylene glycoside products. Eleven successful examples are shown under this condition. (C) 2003 Elsevier Ltd. All rights reserved.
Different C-Glycosidation Products of Glucal with Alkynyl or Propargyl Silanes under Acidic Conditions
[GRAPHICS]Propargylic and acetylenic silyl groups on propyne control the C-glycosidation products depending on the trimethylsilyl and triisopropylsilyl groups used. Some mechanistic discussions are included.
Vinyl Cation Stabilization by Silicon Enables a Formal Metal‐Free α‐Arylation of Alkyl Ketones
regioselectivity of alkyl-substituted alkynes are lifted. This allows the synthesis of a range of α-silyl-α'-arylketones under mild conditions in good to excellent yields and with high functionalgroup tolerance, whereby the silicon moiety in the final products can either be removed for a formal acetone monoarylation transform, or capitalized upon for subsequent electrophilic substitutions at either side of the