Lewis acid mediator that successfully promotes highlyenantioselective cross‐aldolreactions between two aldehydes. The high yielding transformation is realized with the assistance of triisobutylamine, which does not decompose trichlorosilane but rather converts the aldol donor into the silyl enol ether that undergoes the enantioselective cross‐aldolreaction with a second aldehyde in combination with
A highly stereoselective direct aldol condensation of ketones to aromatic aldehydes was realized; the trichlorosilyl enolether generated in situ in the presence of tetrachlorosilane is activated by catalytic amounts of an enantiomerically pure biheteroaromatic phosphine oxide to react with aldehydes, coordinated as well as activated by the chiral cationic hypervalent silicon species. This Lewis acid-mediated Lewis base-catalyzed transformation allowed, starting from two carbonyl compounds, to directly synthesize beta-hydroxy ketones generally with high anti stereoselectivity and up to 93% ee for the anti isomer. (C) 2010 Elsevier Ltd. All rights reserved.
Enantioselective syntheses of aldols and homoallylic alcohols from 1,3-dioxolan-4-ones using mandelic acid as chiral auxiliary