Thermally stable fatigue resistant near infrared active photochromic compounds, exemplified by 6-amino-7-cyano-3-(dicyclopropylmethylene)-4- (2,5-dimethyl-3-furyl)-benzofuran-2(3H)-one

Abstract

The title pale yellow photochromic compound 11b in toluene, on irradiation at 366 nm, cyclises to the thermally stable infrared active blue–green photochrome, 8-amino-7-cyano-4,4-dicyclopropyl-3a,4-dihydro-6-hydroxy-2,3a-dimethylnaph tho[2,1-b]furan-5,6-carbolactone, 12b which has a λ_max value of 720 nm for its broad long wavelength absorption band.