Bi(OTf)3-[Bmim]PF6: A novel and Recyclable Catalytic System for the Diasteroselective Synthesis of Cis-fused Pyrano and Furanobenzopyrans

The Stereoselective one-pot synthesis of cis-fused pyrano and furanobenzopyrans has been developed from o-hydroxybenzaldehydes, aromatic amines, and cyclic enol ethers in the presence of Bi(OTf)3 in air- and moisture-stable ionic liquid, [bmim]PF6 under mild conditions. The recovered ionic liquid containing Bi(OTf)3 can be reused three to five subsequent runs with only a gradual decrease in activity. The recovery of catalyst is facilitated by its hydrophobic nature of [bmim]PF6.