Mercury(II) Triflate-Catalyzed Cycloisomerization of Allenynes to Allenenes

Cycloisomerizations of allenynes to allenenes have been studied in the presence of catalytic amounts of [Hg(OTf)2] in acetonitrile. The catalytic system is quite effective for terminal 1,6-allenynes: allenenes were obtained in reasonable to high yields. However, treatment of allenynes with disubstituents at the allenic terminal carbon yielded a triene and/or allenene as a major product(s) depending upon the substituents.