Bipyrans for electrochemical studies. Preparation of polyene‐separated bipyrans and bithiopyrans

Abstract

627 4,4'~ButS-ene-l,4-dienylidene>bi-4H-pyran and thiopyran derivatives were prepared by allowing the anion prepared from diethyl 4-(2,6-diphenyI-4H-pyranyl)phosphonate to react with 4-pyranylidene butenaldehydes or the corresponding thiopyranylidene aldehydes. The oxidation potentials are compared of some bi-4Hpyrans and thiopyrans with zero, two, and four methenyl groups separating the heterocyclic nuclei.J. Heferocycfic Chem., 18, 627 (1981). W e have investigated new methods for synthesizing A4.4'-bi-4H-pyrans and thiopyrans (1, X = 0 or S) (1-4), ~~ . .compounds which can form conducting charge-transfer salts (5). For studying the effect of changes in the structure of 1 on their physical properties, we prepared derivatives of 1 with a n ethanediylidene group separating the heterocyclic nuclei (2) (6). ( x = O o r S)