33 g. of the ethyl ester of 2-(2-thianthrenyl)-2-hydroxypropionic acid (obtainable by reacting thianthrene with ethoxalyl chloride in 1,2-dichloroethane in the presence of AlCl3 at 10°-20° and reacting the thus-obtained ethyl ester of 2-thianthrenylglyoxylic acid (m.p. 68°-69°) with CH3MgI in ether) is dissolved in 500 ml. of xylene; 1 g. of p-toluenesulfonic acid is added thereto, and the mixture is refluxed for 31/2 hours with the use of a water trap. After cooling, the reaction mixture is washed with sodium bicarbonate solution and water, separated, dried over sodium sulfate, and evaporated. The thus-produced oily ethyl ester of 2-(2-thianthrenyl)-acrylic acid is dissolved in 270 ml. of ethanol and hydrogenated on 8 g. of 4% palladium charcoal at 50° and under 6 atmospheres until the hydrogen absorption is terminated (3 hours). The product is filtered, concentrated by evaporation, and the ethyl ester of 2-(2-thianthrenyl)-propionic acid is thus obtained, b.p. 225°-229°/0.2 mm.
