Synthetic accesses to formylated photochromic 3,3-diphenyl-[3H]-naphthopyrans (or 2H-benzochromenes) are developed through classical cyclization between appropriate hydroxynaphthaldehydes and 1,1-diphenylpropyne-1-ol and also via substituent transformations on the naphthopyran skeleton including bromine/lithium exchange and the oxidation of an hydroxymethyl group. Examples of formyl group reactivity (Wittig and Knoevenagel reactions, imine formation) from these compounds are given, showing their interest in the subsequent preparation of supramolecular systems involving a photoreactive entity. (C) 1999 Elsevier Science Ltd. All rights reserved.
A Simple and Versatile Strategy for Rapid Color Fading and Intense Coloration of Photochromic Naphthopyran Families
are well-known photochromic molecules that undergo photochemical ring-opening reactions to form two colored open-ring isomers, the transoid-cis and transoid-trans forms, upon light irradiation. Though the transoid-cis form returns thermally to the uncolored closed form, the fading rate of the transoid-trans form is extremely slow because of its higher thermal stability. This slow fading behavior of the