α-Chloro-β,γ-ethylenic Esters: Enantiocontrolled Synthesis and Substitutions
作者:Douglas T. Genna、Christopher P. Hencken、Maxime A. Siegler、Gary H. Posner
DOI:10.1021/ol102142a
日期:2010.10.15
γ-seleno-α,β-ethylenic esters, when treated with sulfuryl chloride and ethyl vinyl ether in hexanes, produced α-chloro-β,γ-ethylenic esters in 65−75% yields, with ee values of 95−97%, and with 1,3-syn transfer of chirality. Reaction of these allylic chloride electrophiles with methylcuprate and with sodium azide nucleophiles afforded exclusively γ-substituted-α,β-ethylenic esters with faithful anti-transfer
Asymmetric, Organocatalytic, Three-Step Synthesis of α-Hydroxy-(<i>E</i>)-β,γ-unsaturated Esters
作者:Lindsey C. Hess、Gary H. Posner
DOI:10.1021/ol100615j
日期:2010.5.7
efficient and enantiocontrolled three-step synthesis of α-hydroxy-(E)-β,γ-unsaturated esters is reported. Enantioenriched α-selenyl aldehydes, prepared in one step by asymmetric, organocatalytic α-selenylation of aldehydes, were directly subjected to a Wittig reaction followed by allylic selenide to selenoxide oxidation and final spontaneous [2,3]-sigmatropicrearrangement to yield the target compounds in 43−65%