Bi(OTf)3-Mediated Cycloisomerization of γ-Alkynyl Arylketones: Application to the Synthesis of Substituted Furans

A novel Bi(OTf)(3)-mediated cycloisomerization of gamma-alkynyl arylketones 4, 7, or 10 with molecular sieve (MS) in MeNO2 affords 3-substituted furans 3, 8, or 11 at rt for 3 h in moderate to good yields. The method provides mild, less-toxic, atom-economic and efficient conditions. The mechanism has been studied and proposed. Moreover, this route can be enlarged to gram scale.