ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 26, Number 2
JKCSEZ 26(2)
April 20, 1982 

Addition of dimedone to thioxanthylium ion generated from the oxidation of thioxanthene by thianthrene cation radical perchlorate in acetonitrile gave 9-(4,4-dimethylcyclohexane-2,6-dionyl)thioxanthylium perchlorate (2), whereas from the reverse addition between two reactants was obtained initially 9-(4,4-dimethylcyclohexane-2,6-dionyl)thioxanthene (1), which then underwent further reaction to give 2. The compound 2 was readily deprotonated in aq acetone to give 9-(4,4-dimethylcyclohexane-2,6-dionylidene)thioxanthene (3). However, 3 turned out to be in equilibrium with 2 in which three isosbestic points at 219, 289, and 348 nm were recorded in aq acetonitrile. The intensity and the position of the maximum absorption of 3 near 380 nm vary depending on the solvents which has been explained in terms of the solvent-solute interactions.