TRIPLY CONVERGENT, STEREOSPECIFIC ALKENE FORMATION VIA PETERSON OLEFINATION

alpha-Iodo silanes 8 were prepared from alpha-hydroxy silanes and after halogen/metal exchange and treatment with copper(I) bromide-dimethyl sulfide were coupled with acid chlorides to yield alpha-silyl ketones 2. Cram controlled addition with a variety of nucleophiles followed by treatment with acid or base led to either the (E)- or (Z)-alkene in good overall yields from the iodide (47-67%) and with excellent stereoselectivities ( > 95/ < 5 for disubstituted cases and 67/33 to 95/5 for trisubstituted). The procedure was used iteratively in the total synthesis of 4(E),8(Z)-tetradecadien-1-yl acetate (15) in > 95/ < 5 isomeric purity.