Hydrochloric Acid → 8-Bromo-6-methyl-2,3-dihydro-benzo[1,4]oxazine-4-carboxylic acid benzyl ester

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Reaction Steps

A solution of benzyl chloroformate (1.32 g, 0.008 mol) in dichloromethane (20 mL) was added dropwise under nitrogen to an ice-cold solution of 8-bromo-6-methyl-3,4-dihydro-2H-benzo[1,4]oxazine (1.78 g, 0.007 mol) and pyridine (1.06 g, 0.013 mol) in dichlormethane (40 mL). After 1 hour at ambient temperature, a 10% aqueous HCl solution was added. The layers were separated and the organic phase was washed with water (50 mL×2), dried (Na2SO4) and concentrated to give 8-bromo-6-methyl-2,3-dihydro-benzo[1,4]oxazine-4-carboxylic acid benzyl ester as a colorless oil (2.34 g, 96%) which was used in the step 2 without purification. Synthesis of 8-(4-tert-butoxycarbonyl-piperazin-1-yl)-6-chloro-2,3-dihydro-benzo[1,4]oxazine-4-carboxylic acid

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