A simple and general chiral silicon Lewis acid for asymmetric synthesis: highly enantioselective [3+2] acylhydrazone-enol ether cycloadditions.
A highly diastereo- and enantioselective [3 + 2] acylhydrazone-enol ether cycloaddition mediated by a simple chiral silane Lewis acid is described. The reactions are highly practical, as demonstrated by a larger scale (5 g of the hydrazone) reaction in which the product was obtained after recrystallization in 93% yield and 99% ee. Evidence for a stepwise mechanism and a model for the asymmetric induction are presented, as well.
Shirakawa
Seiji
S
Department of Chemistry, Columbia University, New York, New York 10027, USA.
Lombardi
Pamela J
PJ
Leighton
James L
JL