Asymmetric addition of chiral methylmagnesium alkoxides to benzaldehyde.

The ability of chiral methylmagnesium alkoxides derived from enantiopure alcohols to effect asymmetric addition to benzaldehyde has been investigated. The addition to benzaldehyde of chiral methylmagnesium alkoxides prepared from (-)-borneol, (+)-menthol or (+)-N-methylpseudoephedrine afforded virtually racemic 1-phenylethanol. Equilibration of a more complex species, generated upon addition of one molar equiv of MeMgBr to various molar quantities of the dilithio salt of (+)-pseudoephedrine before addition of benzaldehyde had a dramatic effect on both the reactivity of the reagent and the enantioselectivity of the addition. [ABSTRACT FROM AUTHOR]