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.