Stereochemical studies on the addition of allylsilanes to aldehydes. The S_E' component

Model compounds ul-1 and lk-1 have been studied to determine both the position of the silicon electrofuge and the relative orientation of the double bonds in the transition structure of the allylmetalaldehyde condensation. The use of the deuterium label allows an unbiased assessment of the syn versus anti S_E' pathways. The synthesis of configurational proof of model systems ul-1 and lk-1 are discussed as well as the cyclization of the model system. Cyclization of model 1 was found to proceed with high selectivity via an anti SE' pathway regardless of the proximal/distal ratio for all Lewis acids studied. Reactions promoted by fluoride ion favored the proximal product, but both syn and anti pathways were observed.