Synthesis and Spectral Characterization of Novel Spiroindan-1,3-Dione: A Diels Alder Adduct

DMSO/Ac2O reagent converts 1,3-indandione (1) to an unusual dimer 1H,1′H-2,2′-biindene-1,1′,3,3′(2H,2′H) tetrone and a dimeric condensation product along with an ylide (1a) at room temperature. This reagent also brings about oxidation of secondary alcohols to corresponding ketones, methyl thiomethylation, and N-hydroxymethylation in phthalimide and converts 4-hydroxycoumarins and dicoumarol to different oxidative and degradation products under varying conditions. However, when 1,3-indandione was refluxed with DMSO/Ac2O reagent at 150°C, it afforded a novel compound, 2-spiroindan 1,3-dione (2), a Diels Alder Adduct, analogous to (3) obtained upon treatment of 1,3-indandione with formaldehyde in presence of primary amines.