Preferred definitions:    R1, R2 = phenyl group with 1-3 substituents from lower alkoxy, mono(lower alkyl) amino, di(lower alkyl)amino and lower alkylthio.    SPECIFIC COMPOUNDS - 9 compounds (I) and 8 compounds (II) are disclosed, e.g. 7,7-dimethyl-5,6-bis(2-benzofuran)-2,3-bis(trifluoromethyl)-2,5-norbornadiene, and 2-(4-dimethylaminophenyl)-3-(2-benzofuran)-5,5-dimethylcyclopenta-1,3-diene.    EXAMPLE - 1.59 M n-butyl Li was added dropwise at 0degreesC to a solution of 4.98 g 4-bromo-N,N-dimethylaniline in 80 ml ether, stirred for 1.5 h at 0degreesC, a solution of 1.18 g 4,4-dimethyl cyclopentanediene (synthesized from 3,3-dimethyl glutaric acid) in 40 ml ether was added dropwise at 0degreesC, stirred at room temperature for 15 h, ether extracted, dried, solvent removed, and the product purified by silica column chromatography, to give 1.02 g (44% yield) (V). Next, 1.59 M n-butyl Li was added dropwise at 0degreesC to a solution of 4.98 g 4-bromo-N,N-dimethylaniline in 80 ml ether, stirred for 1.5 h at 0degreesC, a solution of 822 mg (V) in 10 ml tetrahydrofuran was added at 0degreesC, stirred at room temperature for 15 h, ether extracted, dried, solvent removed, and the product purified by silica column chromatography, to give 283 mg (23% yield) (VI), with 309 mg (38% yield) starting material recovered. A solution of 282 mg (VI) and 260 mg p-toluene sulfonic acid in 10 ml toluene was refluxed for 30 min, then made alkaline by adding a 10% NaOH aq. solution, ether extracted, dried, solvent removed, and the product purified by silica column chromatography, to give 156 mg (86% yield) 2,3-bis(4-dimethylaminophenyl)-5,5-dimethylcyclopento-1,3-diene. A solution of 78.5 mg this and 0.5 ml hexafluoro-2-butene in 5 ml toluene was heated at 120degreesC for 14 h, cooled, the product extracted with ether, solvent removed, and purified by silica column chromatography, to give 7,7-dimethyl-5,6-bis(4-dimethylaminophenyl)-2,3-bis(trifluoromethyl)-2,5-norbornadiene. This had a maximum absorption peak at 390 nm (log epsilon = 3.93) in 0.1 mM acetonitrile solution. A film of the compound in polymethylmethacrylate was modified by irradiation with a xenon lamp then left at room temperature. The modified product had a half-life of 149 d, compared to 11 min for a comparative example, (VII).    Me = methyl;    An = p-methoxyphenyl.