Two-carbon homologation of aldehydes via silyl ketene acetals. 2. Study ofthe stereochemical control in the formation of (E)-alkenoic acids

The condensation of C,O,O-tris(trimethylsilyl)ketene acetal 1 with aldehyde s 2 in the presence of catalytic amounts of mercuric iodide at room tempera ture affords syn and anti beta -trimethylsiloxy alpha -trimethylsilyl alkan oic acid silyl esters 3 in good yields. These new compounds gave, under aci dic or basic conditions, E and (or) Z enoic acids 4. The paths for the form ation of these alkenoic acids are discussed.