A highly stereoselective transformation of carboxylic esters to trisubstituted olefins via cationic cyclopropyl–allyl rearrangement of sulfonates of cis-1,2-disubstituted cyclopropanols
作者:Dzmitry G. Kananovich、Alaksiej L. Hurski、Oleg G. Kulinkovich
DOI:10.1016/j.tetlet.2007.09.172
日期:2007.11
Methanesulfonates of readily available cis-1,2-disubstituted cyclopropanols on reaction with magnesium bromide in diethyl ether undergo cyclopropyl–allyl rearrangement to afford allyl bromides, with an (E)-trisubstituted double bond, as main products. The amount of the corresponding (Z)-isomers did not exceed 5% when the reaction was performed at 0 °C, and the major concomitant products were the regioisomeric
Regio- and Stereospecific Formation of Protected Allylic Alcohols via Zirconium-Mediated S<sub>N</sub>2‘ Substitution of Allylic Chlorides
作者:Richard J. Fox、Gojko Lalic、Robert G. Bergman
DOI:10.1021/ja075967i
日期:2007.11.1
regio- and stereospecific SN2‘ substitution reaction between a zirconium oxo complex and allylicchloride has been achieved. The resulting allylic alcohol or TBS-protected allylic ether products were isolated in good to excellent yields with a wide range of E-allylic chlorides. A mechanism for the SN2‘ allylic substitution consistent with kinetic, stereochemical, and secondary isotope effect studies