New Surprises with Fischer Carbene Complexes: Formal [3+2] Cycloadditions with and without Preeceding Carben–Ligand Matathesis

The metal-induced dimerization of dienes with explusion of “CH2” is a formal description of the reaction of Fischer carbene complexes with certain solixydienes [Eq. (a)]. The key steps in the reaction are carbene ligand metathesis (the original carbene ligand is not incorporated in the product) and a highly diastereoselective [3 + 2]cycloaddition. TBS = tBuMe2Si; R = Ph, Me; R′ = Co2Me, Ph.