Darstellung und Photochemie eines (Anthrylvinyl)thiophenfulgids

Preparation and Photochemistry of an Anthrylvinyl Thiophene Fulgide The base‐catalyzed reaction of isopropylidenesuccinate 2 with phenylthienylpropenone 1a does not give a Stobbe condensation to 3a but results in an 1,4‐addition to 7 which under the basic conditions reacts further to 8 by an intramolecular condensation. The (anthrylvinyl)thiophene fulgide 4c is obtained, however, from 3‐glyoxyloyl‐2,5‐dimethylthiophene hydrate ( 11 ) via the 2 H ‐pyran 14 : Wittig olefination of 14 with the phosphonium salt 16 leads to the diester 3c which easily is converted to Z,E ‐ 4c . – Irradiation of Z,E ‐ 4c gives a mixture of all four possible E,Z isomers of 4c and the ring‐closed valence tautomers Z ‐ and E ‐ 17 . All isomers could be separated and characterized. Compound 18 , formed irreversibly in a thermally‐induced reaction, is enriched during irradiation.