Hg(OAc)2•0.1Sc(OTf)3-catalyzed cycloisomerization of 2-(4-pentynyl)furan

Although the Hg(OTf)(2)center dot 3TMU-catalyzed Friedel-Crafts-type reaction of 3-(4-pentynyl)furan afforded the exo cyclization product, the reaction of 2-(4-pentynyl)furan furnished a very low yield. We found a 10:1 mixed reagent of Hg(OAc)(2) and Sc(OTf)(3) showed remarkable catalytic activity for the latter transformation. The actual reacting species is presumed to be Hg(OAc)(OTf), which is efficiently generated in situ by mixing the two reagents.