Vilsmeier-Haack reagent: An efficient reagent for the transformation of substituted 1,3-naphthoxazines into xanthene-type dyes

Derivatives of 1,3-naphthoxazines containing from five to seven-membered Spiro ring - under Vilsmeier -Haack reaction conditions are rearranged into novel xanthene-type compounds. All synthesized ami-nochromene derivatives fluoresce in organic solvents with extra large Stokes shifts (100-133 nm). It was found that compounds containing five-membered annulated aliphatic rings in methanol solution have the best spectral characteristics. These compounds have moderate quantum yields of 2836-28.94%, and extra large Stokes shifts 106 and 115 nm. (C) 2019 Elsevier Ltd. All rights reserved.