5-Chloro-7-nitro-2,3-dihydro-1,3-benzoxazol-2-one → 7-Amino-2(3H)-benzoxazolone

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Reaction Conditions

Reaction Steps

107.5 g (1 mole) of 5-chloro-7-nitro-2(3H)-benzoxazolone prepared according to Example 1d was suspended in 1000 ml of ethanol. 9.25 g of Pd/C 5% and 50 ml of ethanol were added and the mixture was hydrogenated at 4 bar hydrogen pressure for four to six hours at 60-65° C. while vigorously stirring. When the hydrogenation was complete, the mixture was cooled to 45° C. and filtered over Hyflo®. The Hyflo® was washed twice with 175 ml of methanol. 500 ml of solvent was distilled off under reduced pressure at 50° C., followed by addition of 250 ml of water and removal of 300 ml of solvent was by distillation under reduced pressure at 50° C. The last procedure was repeated twice and finally 250 ml of water was added and 400 ml of solvent was distilled off. The resulting mixture was cooled to 0-5° C. in about one hour. The solid was filtered off, washed three times with 125 ml of cold water, and dried at 50° C. and 100 mbar under a gentle nitrogen stream till dry. Yield about 94%.

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