AbstractBicyclo[7.3.1]diynes19aand19bwere prepared by using dibromo olefin11and ketone12as building blocks. The key step of the synthetic sequence is an intramolecular Nicholas reaction of17to give the bicyclo[7.3.1]diyn‐10‐one dicobalthexacarbonyl adducts18aand18b(66% total yield). Oxidative decomplexation of18aand18bwith cer(IV) ammonium nitrate gave the diynes19aand19b, respectively. Both diynes19aand19bcould be oxidatively converted into the enediyne20by using DDQ. In contrast to the unsubstituted enediyne4, compound20can be isolated at room temperature Quantitative kinetic measurements of the rate of the Bergman cyclization of20gave ΔG#(37°C) = 111 kJ mol−1. This value is 12.3 kJ mol−1higher than that of4. The difference in the free activation energy between20and4is attributed to electroni