Imidazole → 5-(t-Butyldimethylsilyloxy)pent-1-yne

Participants

Reaction Conditions

Reaction Steps

A mixture of 186 ml of dimethylformamide, 93.5 g of 5-hydroxy-1-pentyne and 185.5 g of imidazole at room temperature (20-30° C.) is added with 185.5 g of t-butyldimethylsilyl chloride, in portions and under stirring, keeping this temperature with cooling bath. The resulting pale-yellow, dense suspension is cooled to 2° C., kept under stirring and monitored by TLC (eluent 7/3 diethyl ether/petroleum ether, developer: hot perchloric acid; Rf of the starting product=0.33, Rf of the final product=0.95); the reaction is complete after two hours. The reaction mixture is slowly added with 375 ml of water and 150 ml of toluene, and stirring is continued for 10 minutes, controlling the temperature with cooling bath. The organic phase is separated, the aqueous one is extracted with 100 ml of toluene, then combined organic phases are filtered under reduced pressure through Celite, washing the cake with 50 ml of toluene. The solution is concentrated under reduced pressure to obtain a pale-yellow oily residue which is distilled at a temperature-ranging from 23 to 34° C. at about 13 mbars and subsequently at 7.5 mbars at a temperature ranging from 35 to 60° C. The two resulting fractions are discarded. Continuing the distillation at 7.5 mbars, the fractions which distil above 60° C. are collected. The first fraction, which distils between 60 and 75° C. (89 g) is in turn discarded whereas the second one, which distils at 75° C., consists of 101 g of 5-(t-butyldimethylsilyloxy)pent-1-yne identical to the product of preparation I.

Provenance & Evidence