High enantio- and diastereoselective induction of BINOL- and TADDOL-modified vinyloxy ethoxides in C-C coupling reactions with aldehydes

The basic reagent vinyloxyethoxy titanium trisisopropyloxide, easily modified by replacing two of the isopropyloxides with the optically active diol (R)- or (S)-BINOL, reacts with simple, prochiral aldehydes to give chiral β-hydroxy-1,3-dioxolanes with enantiomeric ratios up to 99:1. The same reagents, (R)- or (S)-configured, react with the chiral 2,3-O-isopropylidene-d-glyceraldehyde to give the corresponding open chain pentose derivatives. The main components have opposite descriptors at the newly created stereogenic center, indicating strong reagent control. A comparable system, modified by (R,R)- or (S,S)-TADDOL shows a weaker induction with the chiral aldehyde, but now with the same product configuration for both reagents, indicating predominant substrate control.