INTRAMOLECULAR ALLYLSTANNANE ALDEHYDE CYCLIZATIONS - STEREOCHEMICAL RESULTS WITH FLEXIBLE TETHERS FOR REACTIONS FORMING VINYLCYCLOHEXANOLS

Intramolecular Lewis acid-promoted cyclization reactions of both (Z)- and (E)-3-phenyl-8-(tri-n-butylstannyl)oct-6-enal and (Z)- and (E)-3-(benzyloxy)-8-(tri-n-butylstannyl)oct-6-enal have been examined using a variety of Lewis acids, specifically BF3 . Et(2)O, CF3CO2H, SnCl4, TiCl4, and MgBr2. Thermally promoted cyclizations were also examined. The results show that product stereochemistry is a sensitive function of both olefin stereochemistry and Lewis acid. The data acquired in these studies also suggest that such reactions are mechanistically more complex than previous studies with more constrained systems have revealed.