Hexamethylphosphoramide → 1,1-Ethylenedioxy-4-(1-pentynyl)cyclohexane

Participants

Reaction Steps

A solution of 6.5 g of 4-ethynyl-1,1-ethylenedioxycyclohexane in 40 ml of tetrahydrofuran was treated at -20° C. with 39.1 ml of a 1.4M solution of butyl lithium in hexane. Subsequently, the mixture was treated at 0° C. with 60 ml of hexamethylphosphoric acid triamide (brief temperature rise to 26° C.) and then dropwise with 6.5 ml of propyl iodide. The cooling bath was removed and the mixture was left to warm to room temperature. A white precipitate formed. After 30 minutes, the mixture was treated with 150 ml of water and extracted three times with hexane. The organic phases were washed three times with water and the wash-water was back-extracted with hexane. The organic phases were dried over magnesium sulphate, filtered and freed from solvent on a rotary evaporator. Low-pressure chromatography of the resulting, yellow liquid (9 g) on silica gel with ethyl acetate/petroleum ether (vol. 10:90) and treatment with active carbon gave 6.23 g (76.5%) of 1,1-ethylenedioxy- 4-(1-pentynyl)cyclohexane as a light pale yellow liquid.

Provenance & Evidence