Sodium hydride → (S)-methyl 3,4-dihydro-2,8-diisopropyl-3-oxo-2H-1,4-benzoxazine-4-acetate

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Reaction Steps

To a solution of (S)-2,8-diisopropyl-2H-1,4-benzoxazin-3(4H)-one (4.66 g) in dimethylformamide (60 ml), was added portionwise 60% sodium hydride in oil (0.84 g). The mixture was stirred at room temperature for 10 minutes, and a solution of methyl bromoacetate (2.0 ml) in dimethylformamide (6.0 ml) was added thereto. The whole was stirred at room temperature for 30 minutes, diluted with water, and extracted with ethyl acetate. The ethyl acetate layer was washed with water, dried (MgSO4) and concentrated. The residue was crystallized from hexane to yield (S)-methyl 3,4-dihydro-2,8-diisopropyl-3-oxo-2H-1,4-benzoxazine-4-acetate as crystals (4.95 g, 81.1%). Recrystallization from hexane gave colorless needles, mp 67°-68° C. [α]D23 +3.7° (c=0.95, MeOH).

Provenance & Evidence