Reaction of fulgides: Regioselectivety in the ring opening reactions of unsymmetrical bis-substituted dimethylene-succinic anhydrides with nucleophiles

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