Bromine → 1-(1-Bromo-2-keto-5-pentyl)-3,7-dimethylxanthine

Participants

Reaction Steps

4.93 Grams (0.031 moles) of bromine were added to a solution of 7.3 g (0.0276 moles) of compound (a) in 100 ml of methanol, at 10° C. After stirring for 15 hours at room temperature, the reaction mixture volume was concentrated to 30 ml under reduced pressure, then 60 ml of water, and 3 drops of conc. sulphuric acid were added. The mixture was stirred at room temperature for 4 hours, in order to hydrolyze any dimethylketals formed by reaction with methanol. After dilution with 50 ml of water, the pH of the mixture was adjusted to 8-9, by addition of a 10% sodium bicarbonate aqueous solution, the mixture was extracted with 3×50 ml of methylene chloride, washed with water, dried on anhydrous sodium sulfate, filtered and evaporated under vacuum. 8.3 Grams of compound were obtained, which, by TLC and NMR analysis, showed to be impure by the presence of the 1-(3-bromo-2-keto-5-pentyl)-3,7-dimethylxanthine regioisomer. The crude compound was directly used for the next step.

Provenance & Evidence