1,1-Dichloroethane → Fentanyl

Participants

Reaction Steps

A solution of 5.5 parts (w/w) of 4-anilino-N-phenethyl-piperidine preferably 1 to 3 parts in 5 to 15 parts (w/w) of dichloroethane preferably 8 to 12 parts was taken in a two neck round bottom flask fitted with a reflux condenser, pressure equalizing funnel and calcium chloride guard tube. To this stirred solution, 2 to 20 parts 9 w/w) of propionyl chloride preferably 5 to 15 parts was added drop wise through pressure equalizing funnel. After 2 to 6 hrs, preferably 4 to 5 hrs stirring at room temperature, the reaction mixture was washed with 20% sodium hydroxide solution. The washings were extracted with 2×50 parts, preferably 65 to 70 parts dichloroethane. The combined organic phase was dried over sodium sulphate and concentrated to give fentanyl. The crude compound was recrystallised from petroleum ether (60 to 80° C.) to give colourless crystals of pure fentanyl having mp 82 to 83° C.

Provenance & Evidence