Hydrochloric Acid → precocene II

Participants

Reaction Steps

In a mixture of 75 ml of tetrahydrofurane and 25 ml of ethanol 4.7 g (20 millimoles) of 6,7-dimethoxy-2,2-dimethyl-4-chromanone are dissolved, whereupon 1.5 g (40 millimoles) of sodium tetrahydro borate are added in small portions. The reaction mixture is heated to boiling for an hour, cooled to 15° C., whereupon 50 ml of 4N hydrochloric acid are added and the mixture is stirred at a temperature not exceeding 20° C. for 3 30 minutes. The two-phase layer is separated, the aqueous phase is extracted twice with 40 ml of petrol-ether (30°-40° C.) each, the organic phases are collected, washed twice with 25 ml of 5% sodium hydroxide solution and twice with 40 ml water each, dried over sodium sulfate and evaporated. The residue is crystallized from 80% methanol. Thus 4.0 g of the desired compound are obtained, yield 92%. Mp.: 46°-47° C.

Provenance & Evidence