The influence of a 1,1-diarylvinyl moiety on the photochromism of naphthopyrans

1,1,3-Triarylpent-4-en-1-yn-3-ols, efficiently obtained in two steps from 1,1,3-triarylprop-2-yn-1-ols by a Meyer-Schuster rearrangement and subsequent addition of lithium trimethylsilylacetylide, react with either a 1- or 2- naphthol to afford photochromic 1,1-diarylvinyl substituted naphtho[1,2-b]- or naphtho[2,1-b]-pyrans respectively. Irradiation of solutions of these naphthopyrans results in reversible electrocyclic ring-opening to afford photomerocyanines which possess an extended conjugated system and show a bathochromically-shifted λ_max relative to the non-vinyl substituted analogues.