Synthesis and photochromic properties of indolinospirochromenes with electron-donor substituents in the indoline part of the molecule

1,3,3-Trimethylspiro(indoline-2,2'-[2H]chromenes) with CH₃ and CH₃O groups in the 4–7 positions and NO₂ and CH₃O groups in the 6 and 8 positions were obtained by the reaction of 4,6-, 4,7-, 5,6-, and 6,7-dimethoxy- and 4-methyl-7-methoxy-2-methyleneindolines and 1,3,3,4,5,6,7-heptamethyl-2-methyleneindoline with 3- and 5-nitrosalicylaldehydes and their derivatives. Most of the compounds have photochromic properties. The introduction of electron-donor groups into the indoline fragment of the spirochromene molecules changes the rate of the dark reaction within the limits of one order of magnitude and has a small effect on the position of the long-wave absorption band of the photomerocyanine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1220–1224, September, 1982.