organocatalytic, stereoselective and directaldolreaction of activated thioesters with aldehydes has been accomplished. The trichlorosilyl ketene thioacetal generated in situ by adding a tertiary amine to a trifluoroethyl thioester in the presence of tetrachlorosilane is activated by catalytic amounts of an enantiomericallypure biheteroaromatic phosphine oxide to react with different aldehydes, coordinated