2-Amino-4-chlorophenol → ethyl 6-chloro-3,4-dihydro-2H-1,4-benzoxazine-2-carboxylate

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Reaction Steps

43.0 g of 2-amino-4-chlorophenol was dissolved in 500 ml of anhydrous acetone containing 42.0 g of anhydrous potassium carbonate. That mixture was heated to reflux temperature and 23.0 g of ethyl 2,3-dibromopropionate was added slowly. In three additional portions each, additional ester and carbonate were added to the refluxing mixture until a total of 124 g of carbonate and 85.8 g of ester had been added. The mixture was refluxed for 21 hours. Solids were filtered from the mixture and the filtrate was stripped of solvent. The residue was taken up in water and the solution was extracted with ether. The ether extract was dried (MgSO4) and the solvent was stripped. The residue was recrystallized from ethanol, eluted through a silica gel column using a 4:30:66 by volume mixture of tetrahydrofuran, ethyl acetate and hexane as eluent, and the product was recrystallized from ethanol, and then from ether, to give 2 as white crystals, m.p.: 85.5°-86.5°.

Provenance & Evidence