RING FORMATION THROUGH INTRAMOLECULAR SN' DISPLACEMENT OF AN ALLYLIC METHOXY SUBSTITUENT

Intramolecular S(N)' displacement of an allylic methoxy substituent by an organomagnesium nucleophile selectively generated vinylcyclopentan e and vinylcyclohexane products. This cyclization reaction was promote d by the addition of 5 mol % of CuI, CuBr, or CuBr-SMe2. The Z isomer resulted in more efficient five-membered ring formation than did the E isomer, while the E isomer cyclized to a greater extent than the Z is omer for six-membered ring formation. Formation of five- and six-membe red rings from organolithium intermediates were more efficient process es and did not show a significant dependence on olefin geometry. The s electivity obtained for cyclization of acyclic secondary allylic ether s was dependent on olefin geometry, and selective product formation wa s much greater for the organolithium cyclizations than for the Cu(I)-p romoted reactions. Bicyclic ring products formed from a secondary ally lic ether substrate were generated stereoselectively with cis ring fus ion.