Abstract: A Rhodium(I)-species catalyzed cycloisomerization reaction of a wide spectrum of 1,6-enynes with an unusual intramolecular halogen shift was investigated. This Rh-catalyzed enyne cyclization reaction represents a new process for the synthesis of stereodefined α-halomethylene-γ-butyrolactones, lactams, tetrahydrofurans, pyrrolidines and cyclopentanes. Coordinatively unsaturated rhodium species ([Rh(COD)Cl]2 + dppb + AgSbF6) only catalyzes the reaction with enyne substrates bearing a Z-form double bond. While neutral rhodium species (RhCl(PPh3)3) could catalyze enyne substrates bearing a Z- or E-form double bond to form the desired products and has a wider substrate scopes. The mechanism of the reaction was studied by the employment of control experiments with different enyne isomers and a π-allyl rhodium intermediate was suggested to explain the formation of the cyclic products with intramolecular halogen shift. Further transformation of the halo-alkenyl species can be readily achieved through transition metal-catalyzed Suzuki cross-coupling reactions.

Key words: Rhodium-catalyzed, Cycloisomerization of 1, 6-enynes, Intramolecular Halogen Shift