AN EFFICIENT STEREO-CONTROLLED STRATEGY IN THE CYCLOPROPANATION REACTIONS OF ALPHA,BETA-UNSATURATED KETONES WITH SEMISTABILIZED YLIDES - HIGHLY SELECTIVE SYNTHESIS OF 2 GEOMETRICAL-ISOMERS OF VINYL-SUBSTITUTEDCYCLOPROPANE DERIVATIVES

The semistabilized telluronium ylides 2a-e, generated in situ from the corresponding telluronium salts 1a-e, reacted with alpha,beta-unsatur ated ketones 6a-d to afford cis-2-vinyl-trans-3-substituted cyclopropy l ketones with high stereoselectivity and in high to excellent yields. Conversely, these enones gave trans-2-vinyl-trans-3-substituted cyclo propyl ketones, when the corresponding arsonium ylides 10a-e were empl oyed. Other factors such as solvent and amount of base also influenced the stereochemistry of this reaction. A mechanistic rationale is disc ussed briefly.