Synthesis and Photochromic Behaviour of Naphthopyrans, Pyranoquinolines, Pyranoquinazolines and Pyranoquinoxalines

Abstract

Abstract New chromenes annulated with different six‐membered azaheterocycles were prepared, i.e. , the 3 H ‐pyra‐no[3,2‐ f ]quinolines 9/10 and 14 , the 8 H ‐pyrano[2,3‐ h ]isoquinoline 11 , the 8 H ‐pyrano[3,2‐ f ]quinazolme 12 , the 8‐ H ‐pyrano[3,2‐ f ]quinoxaline 13 , and the 2 H ‐pyrano[2,3‐ f ]isoquinoline 15. The synthesis was achieved using conveniently substituted α,β‐unsaturated aldehydes and organotitanium intermediates arising from azaheterocyclic phenols. Their photochromic behaviour (photocolouration yield, UV/VIS spectrum of photomerocyanines, rate constant of thermal bleaching) were studied besides those of corresponding naphthopyrans. The heterocycle effect and the role of substituents in the pyran moiety were investigated quantitatively through the study of the photochromic properties and the solvent effects. Diaryl‐substituted azino‐fused chromenes, especially isoquinoline derivatives, exhibit increased colourabilities and bathochromically shifted spectra for photomerocyanines which open up new prospects for photochromic applications.