NEW PHOTOCHROMIC CYCLOHEXADIENES

The effect of structural modification on the behavior of highly substituted cyclohexadienes has been studied. The new photochromic compounds, prepared by condensation of vic-alkylarovl heterocycles with tetracyano-ethylene and related olefins, include 2,2-dicyano-1,2-dihydro-9-xanthenones, 2-cyano-1,2-dihydro-9-xanthenone-2,3-dicarboximides, 1,2- and 3,4-dihydrotricyanodibenzofurans, and a 1,2-dihydro-2,2,3-tricyano-9-acridone. In addition the synthesis of some new 4-alkyl-3-benzoylcoumarins and 4-alkyl-3-benzoylcarbostyrils has provided further examples of photochromic vic-alkylaroyl heterocycles. The color forming efficiencies and thermal fading rates of several of the photochromic cyclohexadienes are reported and their photochemical behavior at -196° in rigid media is described. © 1969, American Chemical Society. All rights reserved.