Enantioselective Rhodium-Catalyzed Cycloisomerization of 1,5-Bis(allenes) to Access 1,2-cis-Ethynyl- and...

In this study, an enantioselective Rh-catalyzed cycloisomerization of 1,5-bis(allenes) to furnish 1,2-cis-ethynyl- and vinyl-substituted five-membered (hetero)cycles in high yields and with excellent diastereo- and enantioselectivity is presented. The possibility of further functionalization to access different chiral cyclic and bicyclic skeletons is provided by the two orthogonal functional groups (alkyne and alkene). We also demonstrate the scalability of the reaction through a gram-scale synthesis and illustrate the synthetic utility of the resulting 1,2-cis-ethynyl- and vinyl-substituted cyclic product via several transformations. The proposed reaction mechanism is supported by both density functional theory (DFT) calculations and control experiments.