Ruthenium-catalysed cyclisation reactions of 1,11-dien-6-ynes leading to biindenes

1,2-Bis(2-allylphenyl)ethynes undergo cycloisomerisation reactions in the presence of Cp*Ru(ii) catalysts to produce 2,2 '-dimethyl-3H,3 ' H-1,1 '-biindenes. On the other hand, tandem ring-closing metathesis of 1,2-bis(2-allylphenyl)ethynes using the Hoveyda-Grubbs 2nd generation catalyst led to the formation of 2,2 '-unsubstituted biindenes. Various symmetrical and unsymmetrical bicyclic dienes were prepared by these ruthenium-based cyclisation methods.