Carbon Dioxide → 5,8-Dimethyl-4-oxo-6-thiochromanecarboxylic acid

Participants

Reaction Conditions

Reaction Steps

46.38 g (0.15 mol) of 6-bromo-5,8-dimethylspiro[thiochromane-4,2′-[1,3]dioxolane] were dissolved in 500 ml of tetrahydrofuran and cooled to −65° C. 80 ml (0.2 mol) of 2.5 M n-butyllithium in hexane were subsequently slowly added dropwise such that the temperature did not exceed −55° C. The mixture was stirred for another 1 h, and 90 g of dry ice were then added a little at a time. The solution was subsequently allowed to warm to room temperature, 500 ml of hexane were added and the precipitate was filtered off with suction. The precipitate was taken up in 500 ml of water and made strongly acidic using conc. hydrochloric acid. The mixture was boiled under reflux for 1 h and then allowed to cool, and the precipitated product was filtered off with suction.

Provenance & Evidence