Ruthenium-Catalyzed Cycloisomerization of 1,6-Diynes with Styryl Terminals Leading to Indenylidene Cycloalkanes

In the presence of a neutral ruthenium catalyst, Cp*RuCl­(cod), 1,5,10-enediynes bearing a styryl terminal underwent cycloisomerization to afford exocyclic 1,3-dienes with an indenylidene moiety. The reaction mechanism is proposed on the basis of the results of control experiments and density functional calculations. The transformations of the obtained cyclization products were also investigated to demonstrate the synthetic potential of this method.