Naphthopyrans. Structural Features and Photochromic Properties

Abstract
Structural modifications to photochromic 3H-naphtho[2,1 -b]pyrans and 2H-naphtho[1,2-b]pyrans have produced compounds that have found utility in plastic ophthalmic lens applications. The influence of substituents on color, optical density, and fade rate are reported. Synthetic routes to products and key intermediates are also outlined.