Synthesis of vinylidenecyclopropanes gold(I)-catalyzed cyclopropanation of vinyl arenes with -stannylated propargyl esters.

The reaction of -stannylated propargyl esters in the presence of a cationic gold(I) catalyst affords vinylidenecyclopropane derivatives as a mixture of diastereomers. The -geometry of the alkenes is almost entirely retained in the product. DFT calculations suggest the involvement of the gold(I)-stabilized propargyl cation as a resonance form of gold(I)-coordinated allenylidene species.