Diels-Alder cycloaddition and ring-closing metathesis: a versatile, stereoselective, and general route to embellished bridged bicyclic systems, carbocyclic framework of secoatisanes, and homologues.

A general and stereoselective methodology for the synthesis of bridged bicyclic octenones having various types of alkenyl chains and a tricyclic framework of secoatisanes and higher analogues is reported. In situ generation and cycloaddition of 2-allyl-6,6-spiroepoxycyclohexadienones with ethyl acrylate gave bicyclo[2.2.2]octanes having an allyl group at the bridgehead and other chemically distinguishable functionality in a regio- and stereoselective fashion. Selective manipulation of adducts led to the introduction of other olefinic chain of variable lengths at the carbon adjacent to the bridge head. Ring-closing metathesis in bicyclooctanes having olefin tethers provided an efficient route to tricyclic systems having bicyclo[2.2.2]octane framework having spiro-fused six-, seven-, and eight-membered rings.