Diastereocontrol via lewis acid-promoted ene reaction with glyoxylates and its application to stereocontrolled synthesis of a 22-hydroxy-23-carboxylate steroid side chain
作者:Kōichi Mikami、Teck-Peng Loh、Takeshi Nakai
DOI:10.1016/s0040-4039(00)82332-1
日期:1988.1
ene reactions are shown to proceed with a high level of either erythro or threo diastereoselection. The utility of the ene methodology is demonstrated through the stereocontrolledsynthesis of a 22-hydroxy-23-carboxylate steroidsidechain.
A novel silyl triflate-mediated [2,3]sigmatropicrearrangement of (allyloxy)acetates and their ketene silyl acetals is described, which is proposed to proceed via rarely precedented oxygen ylides. The formal [2,3]Wittlg shift is characterized by the unique stereoselectivity, , the rarely precedented -selectivity and the high erythro-selectivity.
[3,3]Claisen vs. [2,3]Wittig Shift in Thermal and Fluolide Ion-Promoted Rearrangements of the<i>O</i>- and<i>C</i>-Silylated Forms of α-Allyloxy Esters
Thermolysis of the O-silylated forms of α-allyloxy esters is shown to afford exclusively the [3,3]Claisen products with high stereocontrol. In direct contrast, the fluoride ion-promoted rearrangement of the α-silylated esters gives exclusively the [2,3]Wittig products with moderate stereocontrol.