Molecular iodine-catalyzed diastereoselective synthesis of cis-fused pyranobenzopyrans and furanobenzopyrans

A highly efficient method for the diastereoselective synthesis of cis-fused pyranobenzopyrans and furanobenzopyrans via 2 mol % of molecular iodine-catalyzed reaction of o-hydroxybenzaldimines with 3,4-dihydro-2H-pyran and 2,3-dihydrofuran at ambient temperature is described. 2-Butoxy-4-N-arylaminobenzopyrans were also synthesized from o-hydroxybenzaldimine and n-butyl vinyl ether using this procedure.