Ethyl-(R)-(4-methylphenylsulfinyl)-n-methoxy acetimidate a useful chiral acetate equivalent in aldol type condensations

Ethyl N-methoxyacetimidate was metallated by lithium amides and reacted with (-)-(S)-menthyl p-toluenesulfinate to afford, in excellent yield, (R) - (4-methylphenylsulfinyl)-ethyl-N-methoxy acetimidate (2). Compound (2) was tested in aldol-type condensations with various aldehydes, and the adducts, after desulfurization, were converted into optically active β-hydroxyesters with good ⩾80%) e.e. The stereochemical outcome of the reaction of benzaldehyde was found to be dramatically affected by changing either the counterion of the enolate from lithium to zirconium or by going from kinetic to thermodynamic control.