To a suspension of 106 g of anhydrous aluminum chloride in 450 ml of carbontetrachloride is added dropwise, with vigorous stirring, 70 g of ethyl 8- chloroformylvalerate (H. Bergs, C. Wittfeld and H. Frank, Ber., 67B, 1622 (1947)). The temperature is maintained at 25°C. The cooling bath is removed and ethylene is passed in for a period of 2 hours. The reaction mixture is poured onto cracked ice, the organic layer separated, and the aqueous layer extracted with 200 ml of chloroform. The combined organic extracts are dried over anhydrous sodium sulfate and the solvent removed in vacuo. The dark colored oil remaining, crude ethyl 8-chloro-6-oxooctanoate is distilled in vacuo through a 6 in. Vigreaux column. After small forerun, the main fraction, 48-54 g (72-80%), B.P. 112-114°C (2 mm.); n25 D1-4485, is collected.
Redistilled thiolacetic acid (14.7 g) is cooled in an ice-bath and neutralized to the phenolphthalein end-point with a 10% solution of potassium hydroxide in ethanol (approximately 135 ml required). To this solution is added 29 g of ethyl-6,8-dibromooctanoate and the mixture is stirred and heated under reflux in an atmosphere of nitrogen for 5 hours. The reaction mixture, which contains ethyl 6,8-diacetyl-mercaptooctanoate, is cooled and 35 g of potassium hydroxide (85%) is added. The reaction mixture is stirred at room temperature in an atmosphere of nitrogen for 17 hours, then acidified (pH less than 1) with 6 N hydrochloric acid. Ethanol is removed in vacuo, suffic