Furyl Fulgide Derivatives

Upon UV irradiation the furyl fulgide undergoes not only cyclization but also an E-Z photoisomerization reaction (Scheme 6). The ratio between the cyclization and the E-Z isomerization depends on the steric hindrance of substituent R. Furyl fulgide derivatives with various R substituents were prepared and the quantum yields were compared [31-34]. The results are summarized in Table 4. 

Table 4. Quantum yields of furyl fulgide derivatives in toluene.

Furyl fulgide 20 (Eq. (7)) is the first known example of thermally irreversible photochromic molecules. Although phenyl fulgides such as 21 have been known to show photochromic reactions, photogenerated dihydronaphthalene derivatives such as 21C (Eq. (8)) are thermally unstable and undergo irreversible side reactions, i.e., 1,5-hydrogen shifts to produce 1,2-dihydonaphthalene derivatives [23-26]. This... 

A. P. Glaze, H. G. Heller, and J. Whittall, Photochromic heterocyclic fulgides. Part 7. (E)-Adamantylidene-[1 -(2,5,-dimethyl-3-furyl)ethylidene] succinic anhydride and derivatives Model photochromic compounds for optical recording materials, J. Chem. Soc., Perkin. Trans. 2, 1992, 591-594. 

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