Abstract
This work describes zinc(II)-catalyzed hydrative aldol reactions of 2-en-1-ynamides with aldehydes and water to afford branched aldol products regio- and stereoselectively. The anti and syn selectivity can be modulated by the sizes of sulfonamides to yield E- and Z-configured zinc(II) dienolates selectively. This new reaction leads to enantiopure aldol products by using a cheap chiral sulfonamide. The mechanistic analysis reveals that the sulfonamide amides of the substrates can trap a released proton to generate dual acidic sites to activate a carbonyl allylation reaction. EZ switch: The anti and syn stereoselectivity of the title reaction can be modulated by the size of the sulfonamides to yield E- and Z-configured zinc(II) dienolates selectively. This new reaction leads to enantiopure aldol products by using an inexpensive chiral sulfonamide. EWG=electron-withdrawing group.