Doubly diastereoselective nucleophilic additions to a bicyclic β,γ-unsaturated ketone possessing a conformationally mobile double bond

Abstract

(7 R *)-7-Methyl-7-vinylbicyclo [3.2.0] hept-2-en-6-one was condensed with several chiral cyclopentenyllithium reagents for the purpose of assaying the diastereoselectivity of this coupling. Due to ring strain, the alkoxides that are formed spontaneously undergo anionic oxy-Cope rearrangement. The initial diastereoselectivity is thereby incorporated into additional stereogenic centers. The mechanistic details of the two steps are discussed. Although the resultant diastereoselectivity is low, it is shown that polycyclic networks with as many as nine asymmetric carbons can be cleanly elaborated in very few steps.