Cycloaddition of Cyclopropenes with Alkynes via Carbon-Carbon Double Bond Cleavage Enabled by a Ruthenium Catalyst: Synthesis of Cyclopentadienes and Cycloheptatrienes

Transition-metal-mediatedcarbon-carbon single-bondcleavageof cyclopropenes has been widely exploited in organic synthesis. However,the ring-opening of cyclopropenes via the cleavage of their carbon-carbondouble bond remains a formidable challenge. Herein, we report an intramolecularcycloaddition of cyclopropenes with alkynes via cleavage of the carbon-carbondouble bond of cyclopropenes enabled by a ruthenium catalyst to afford1,2-fused cyclopentadienes, which are difficult to access by conventionalsynthetic methods. Density functional theory calculations indicatethat the reaction proceeds via a cyclopropane-fused ruthenacycle thatundergoes ring expansion to generate a six-membered cyclic biscarbenoid.We also synthesized fused cycloheptatrienes via the cycloadditionof cyclopropene-diynes.

Automated summary

Transition-metal mediated carbon-carbon single-bond cleavage of cyclopropenes has been achieved via an intramolecular cycloaddition with alkynes, leading to the formation of 1,2-fused cyclopentadienes. Fused cycloheptatrienes were also synthesized through the cycloaddition of cyclopropene-diynes.