Nucleophilic Addition to C, C Double Bonds. Proximity and homoconjugative effects. Preliminary communication

Proximity effects alone as well as in combination with electronic effects are responsible for the observed phenomenon of base‐catalyzed ether formation initiated by nucleophilic attack on a C, C double bond of the tricyclic olefin alcohols 1–10 (Scheme 1, Table 1) . With compounds 1–4 , bearing a keto group, formation of the ethers 11–14 proceeds through a corresponding homoenolate b (Scheme 2) as an intermediate. In one case such a species could be trapped as the methyl ether 21 (Scheme 3) . Special attention is given to the stereochemical course of the homoketonization. Ring opening in 21 under acidic conditions occurs regioselectively, however non‐stereoselectively (Scheme 3) . Full regio‐ and stereoselectivity (retention) is observed under basic conditions starting from the unsaturated keto alcohols 1 and 2 (Scheme 4) as well as from the keto ethers 11 and 12 (Scheme 5, Table 2) .