Nucleophiles were added regioaelectivcty on the carbonyl group in conjugation with the diphenyl methylene group of fulgide 1, however in the heterocyclic fulgides such as lad 10a the addition takes place on the carbonyl group not in conjugation with the heterocycle ring. The addition of dicyanomethyl anion to heterocyclic fulgides resulted in novel photochromic derivatives 12a having an absorption maxima for the coloured forms above 620 nm.
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