Application of a metathesis reaction in the synthesis of sterically congested medium-sized rings. A direct ring closing versus a double bond migration-ring closing process.

An efficient double bond migration-ring closing metathesis reaction leading to cycloheptene derivatives is observed when specific sterically congested 1,9-dienes are treated with the Grubbs' imidazolidene ruthenium catalyst. The simultaneous use of the Grubbs' catalyst and RuClH(CO)(PPh(3))(3) facilitates the tandem bond migration-metathesis process. RuClH(CO)(PPh(3))(3) alone is capable of triggering an unactivated double bond migration that may have preparative applications.