Isomerization of 3H- to 2H-[1]Benzothieno[3,2-b]pyrroles and Synthesis of the First Merocyanine Dyes Based on Them

New 2H-[1]benzothieno[3,2-b]pyrroles were synthesized by a [1,5]-sigmatropic shift of 3H-benzothienopyrroles. The dependence of the rearrangement on solvent and temperature was studied. The first merocyanine dyes based on both 3H- and 2H-benzothienopyrroles were synthesized and characterized by NMR- and UV/Vis spectroscopy, mass spectrometry, and X-ray crystallography.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)