A solution of phenobarbital (69.6 g, 0.3 mole) in ethanol (150 ml) containing triethylamine (2.02 g, 0.02 mole) was stirred with butyl glycidyl ether (26.0 g, 0.2 mole) (available from Merck & Co.) for 6 hours at 70° C. The reaction mixture was then poured into water (500 ml) and the precipitated product was extracted with toluene (200 ml) at 70° C. The toluene layer was separated, washed with 3% aqueous sulphuric acid (200 ml) and left overnight at 4° C. The precipitated phenobarbital was filtered off and the filtrate extracted with 5% aqueous sodium carbonate (5×100 ml). The organic layer was then extracted with 1M aqueous sodium hydroxide (2×200 ml), the aqueous layers collected, washed with toluene (100 ml) and the pH was adjusted to 3 with sulphuric acid. The precipitated product was extracted with toluene (150 ml), the organic layer was separated, dried and evaporated under reduced pressure to give the title compound (40.1 g, 55%); purity by HPLC 99% m.p. 92° C.
