DARSTELLUNG UND EINIGE SPEKTRALEIGENSCHAFTEN DES 5,6-DIHYDRO-4,7-DITHIAINDAN-1,3-DIONS

The preparation of 5.6-dihydro-4.7-dithiaindan-1.3-dione (I) and its 2-methyl and 2-ethyl derivatives* is described, starting from 5.6-dihydro-pyrazine-2.3-dicarboxylic anhydride. The reaction of this anhydride with acetic anhydride, according theGabriel modification of thePerkin synthesis, resulted in 7-oxo-2.3.5.7-tetrahydrofuro[3.4-b]pyrazin-5-ylideneacetic acid while reaction with propionic acid anhydride and butyric acid anhydride resulted in 2-methyl (2-ethyl)-5.6-dihydro-4.7-dithiaindan-1.3-dione. The1H-NMR and electronic spectra of I were measured in solvents with different dielectric constant and it was found that I is more stable in the diketo form than 1.3-indandione.