Rhenium-Catalyzed Construction of Polycyclic Hydrocarbon Frameworks by a Unique Cyclization of 1,n-Diynes Initiated by 1,1-Difunctionalization with Carbon Nucleophiles

A regioselective cyclization of 1,n-diynes under rhenium catalysis was developed on the basis of a rare type of 1,1-difunctionalization of terminal alkynes with carbon nucleophiles, followed by sequential addition reactions of the resulting alkenylrhenium species. The reaction provides an efficient approach to the synthesis of complex cyclopentane-fused bi- and tricycles and spirocycles, which are useful building blocks for the construction of essential frameworks of biologically active compounds as well as functional materials, from simple starting materials by the formation of up to six new carbon–carbon bonds in a single step. The reaction proceeds under neutral conditions and does not require external ligands or additives. The key to this reactivity is the unique activation mode of the rhenium carbonyl complex, which prefers to interact with heteroatoms in polar carbon–heteroatom bonds as well as nonpolar carbon–carbon unsaturated π bonds.