1,1-Ethanediol → 6-Bromo-5,8-dimethylspiro[thiochromane-4,2'-[1,3]dioxolane]

Participants

Reaction Conditions

Reaction Steps

58.4 g (0.22 mol) of 6-bromo-5,8-dimethyl-4-thiochromanone were dissolved in 380 ml of trimethyl orthoformate, admixed with 555 g (8.9 mol) of ethanediol and 0.2 g of p-toluenesulfonic acid monohydrate and stirred at 80° C. overnight. The mixture was subsequently allowed to cool, diluted with 500 ml of diethyl ether and washed with a 1:1 mixture of 1 M aqueous sodium hydroxide solution and sat. NaCl solution (2×500 ml) and subsequently with sat. NaCl solution (300 ml). The organic phase was dried over MgSO4 and concentrated using a rotary evaporator. The residue was taken up in 50 ml of heptaneldiethyl ether (9:1) and stored in a cold place. The crystals which had precipitated overnight were filtered off with suction, washed with cold heptane and dried.

Provenance & Evidence