Phosphoric Acid → Ristianol

Participants

Reaction Steps

In an alternative procedure, 2-mercaptoethanol (11.9 g., 0.152 mole) was dissolved in 138.5 ml. of absolute ethanol and cooled to 18° C. Sodium methoxide (15.7 g., 0.291 mole) was added; the temperature rose to 38° C. and a clear solution resulted. The reaction mixture was cooled somewhat and, while maintaining the temperature below 30° C., 4-picolyl bromide hydrobromide (35 g., 0.138 moles) was added portionwise over 10 minutes. The reaction mixture was then heated to reflux and refluxed for 80 minutes. The reaction was concentrated to a thick mass, which was dissolved in 140 ml. of water and extracted twice with 140 ml. of ethyl acetate. Salt was dissolved in the aqueous phase during the second extraction. The combined ethyl acetate extracts were back washed twice with 150 ml. of 1 N NaOH, dried over anhydrous magnesium sulfate, filtered, and concentrated to about half-volume. While maintaining the temperature between 30° and 35° C., phosphoric acid (12.0 g., 0.122 moles) was added very slowly to directly precipitate crude product as the dihydrogen phosphate salt, recovered by filtration after stirring for 1 hour. The crude was recrystallized from absolute ethanol, yielding purified 4-(2-hydroxyethylthiomethyl)pyridinium dihydrogen phosphate (14.0 g.).

Provenance & Evidence