Electrochemical Reduction of 1H‐Thioxanthene‐1,4,9‐trione and 3‐Methyl‐1H‐thioxanthene‐1,4,9‐trione – Representatives of a New Class of Heterocycles Related to Thioxanthenone

Abstract

AbstractA convenient synthetic route was proposed for the synthesis of 3‐methyl‐1H‐thioxanthene‐1,4,9‐trione. This compound and its 3‐H congener are representatives of a new class of thioxanthone‐like heterocycles, which can be used as building blocks for materials used in organic electronics. Electrochemical reduction (ECR) of 1H‐thioxanthene‐1,4,9‐trione and its 3‐methyl derivative in DMF and acetonitrile is a three‐stage process leading to the formation of the corresponding long‐lived radical anions and unstable dianions at the first and second stages, respectively. In a protolytic equilibrium, dianions are converted into 1‐oxy‐4‐hydroxy‐1H‐thioxanthene‐9‐one anions. Their one‐electron reversible ECR leads to the corresponding radical dianions, followed by the formation of (3‐methyl/H)‐1,4‐dihydroxy‐1H‐thioxantene‐9‐ones as the final products. The latter compounds can be converted into the initial (3‐methyl/H)‐1H‐thioxanthene‐1,4,9‐triones. The main intermediates were characterized using a combination of cyclic voltammetry, EPR spectroscopy, 3D spectroelectrochemistry, and DFT calculations at the (U)B3LYP/6‐31+G*/PCM level of theory. A general ECR scheme was proposed for both types of compounds.