Reinvestigation of dimerization of Z-N-alkylarylmethylideneindoxyls upon exposure to UV-vis radiation

Abstract

N-Alkyl-2-arylmethylideneindoxyls upon exposure to UV or visible light undergo dimerization not to cyclobutane adducts as it has been reported earlier, but to spiropyrano[3,2-b]-pseudoindoxyls with a spiropseudoindoxyl fragment characteristic of many natural alkaloids. The structure of spiropyranopseudoindoxyls was established by NMR spectroscopy and X-ray crystallography.