Chemistry Letters, Vol.33, No.11, 1436-1437, 2004
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.