Benzyl chloroformate → 8-Bromo-6-chloro-2,3-dihydro-benzo[1,4]oxazine-4-carboxylic acid benzyl ester

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Reaction Steps

Benzyl chloroformate (1.877 g, 0.011 mol) was added dropwise to a solution of 8-bromo-6-chloro-3,4-dihydro-2H-benzo[1,4]oxazine (2.85 g, 0.01 mol) in a 1:1 mixture of ethyl acetate (30 mL) and 10% aqueous sodium hydroxide (30 mL). After 3 hours at ambient temperature, the layers were separated and the organic phase was washed with water (2×50 mL), saturated aqueous sodium bicarbonate (50 mL), dried (K2CO3) and concentrated in vacuo and the residue was purified by column chromatography on silica gel (eluting with hexane-ethyl acetate; 7:3, V/V) to give 8-bromo-6-chloro-2,3-dihydro-benzo[1,4]oxazine-4-carboxylic acid benzyl ester as an oil (3.47 g, 98%). A sample was recrystallized from ethanol-water. MS: MH+ 383. M.P. 95.0-97.7° C.

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