Aryl Aromatic Fulgides

Ferrocenyl fulgide 34 gave only E — Z isomerization without any photochro-mic cyclization reaction.36 Fluorenylidene fulgide 32a was prepared as black crystals, and 32b as deep red crystals. Neither of them were photochromic. However, compound 32c, which was a deep red crystal, was photochromic and gave a blue color when irradiated over a wide range of wavelengths. 

Unlike normal fulgides, the bis-(9-anthrylmethylene)succinic anhydride 33 underwent a facile intramolecular [4+4] cycloaddition reaction on exposure to 

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Aryl-substituted fulgides are the products of condensation of aromatic ketones with succinic anhydride, and form one of the oldest and most important groups of organic photochromic materials241. First discovered in the early part of the last century by Stobbe242, they are now well known to owe their photochromic behavior to reversible (conrotatory)... 

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