Overcrowded molecules. Part 14. Photochromic systems involving (Z)-1-methylpropylidene(diphenylmethylene)succinic and (E)-3,5-dimethoxybenzylidene(alkyl-substituted methylene)succinic anhydrides

Abstract

Photochromic (Z)-1-methylpropylidene(diphenylmethylene)succinic anhydride undergoes photochemical conrotatory ring closure and thermal disrotatory ring closure reactions to form red 1,8a-dihydronaphthalene intermediates (1,8a-DHNs) which undergo a facile thermal 1,5-H shift to yield colourless 1,2-DHNs. Yellow (E)-3,5-dimethoxybenzylidene(alkyl-substituted methylene)succinic anhydrides undergo reversible photochemical ring closure to form deep blue solvatochromic 6,8-dimethoxy-1,8a-DHNs which do not undergo 1,5-H shifts at ambient temperatures but photochemical 1,7-H shifts to yield 1,4-DHNs. The spectra of blue 1,8a-DHNs can be determined using the Fisher method.