2-propan-2-ylthiane-3,5-dione

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 204 g (1 mol) of 3-methoxycarbonylmethylthio-4-methyl-2-pentanone are added dropwise within one hour, at 0° C. with vigorous stirring, to a suspension of 108 g (2 mol) of freshly prepared sodium methylate in 2 liters of absolute toluene. The reaction mixture is stirred at 0° C. for a further 30 minutes, then poured into a mixture of 200 ml of concentrated hydrochloric acid and 800 ml of ice-water, and the organic phase is separated off, and the aqueous phase is extracted three times with dichloromethane. The combined organic phases are concentrated to 500 ml in vacuo and extracted with 500 ml of ice-cold 4N sodium hydroxide solution. The aqueous extracts are immediately acidified with a total of 400 ml of ice-cold hydrochloric acid and extracted three times with 200 ml of dichloromethane each time. The combined dichloromethane phases are dried over sodium sulphate and the solvent is removed in vacuo. The remaining solid is recrystallized from ligroin/ethanol. 150 g (87% of theory) of 2-isopropyltetrahydrothiopyran-3,5-dione of melting point 71° C. are obtained. ##STR53## the organic phase is separated off the aqueous phase is extracted three times with dichloromethane The combined organic phases are concentrated to 500 ml in vacuo extracted with 500 ml of ice-cold 4N sodium hydroxide solution extracted three times with 200 ml of dichloromethane each time The combined dichloromethane phases are dried over sodium sulphate the solvent is removed in vacuo The remaining solid is recrystallized from ligroin/ethanol