Synthesis of Unsymmetrical Δ4,4'-Bi-4H-pyrans and -thiopyrans

Article abstract of DOI:10.1021/jo01300a039

Unsymmetrical Δ^4,4'-bi-4H-pyrans and -thiopyrans are prepared from the Wittig reagent which is derived from (4H-pyran-4-yl)triphenylphosphonium salts or the thio analogues by allowing the reagent to react with a pyrylium or thiopyrylium salt wi