Abstract
In the Oppolzer aldol reaction, aldehyde reacts exclusively on the Si face (C(α)-Si attack) of the double bond of the boryl enolate 2 derived from (1S, 2R)-N-propionylbornane-10, 2-sultam (1), providing only 3a stereoselectively. Hexafluoroacetone (4) caused complete reversal of the diastereo-face selectivity, reacting exclusively on the Re face (C(α)-Re attack) of 2 to give only 5. Trifluoroacetaldehyde (8) and 2, 2-difluoro-5-phenylpentanal (9) caused partial reversal of the diastereo-face selectivity, giving significant amounts of unexpected and unusual syn- (12c, 13c) and anti- (12d, 13d) aldols along with the normal syn-aldol (12a, 13a). This finding was applied to the reactions of the boryl enolate with phenylglyoxal (10) and ethyl glyoxylate (11).
