Synthesis and photochromic properties of E,E-Bis-alpha-(2,5-dimethyl-3-furyl)ethylide anhydride and its 2-dicyanomethylene derivative

The deep yellow fulgide 6 and its dicyanomethylene 9 underwent a conrotator y ring closure to the colored forms 7 and 10 respectively. The latter compo unds revert back to the original forms on exposure to white light. The repl acement of the carbonyl group by the dicyanomethylene group resulted in a l arge bathochromic shift of both the colored and uncolored forms 9 and 10 re spectively.