FC(F)(F)C(O)=O.[F:8][C:9]1[CH:18]=[CH:17][C:12]2[CH2:13][CH2:14][CH2:15][O:16][C:11]=2[C:10]=1[NH:19]C(=O)OC(C)(C)C.O.C(=O)(O)[O-].[Na+]>C(OCC)C>[NH2:19][C:10]1[C:11]2[O:16][CH2:15][CH2:14][CH2:13][C:12]=2[CH:17]=[CH:18][C:9]=1[F:8]
Trifluoroacetic acid, 50 mL, was stirred and cooled in an ice-water bath, and 6.1 grams (0.023 mole) of 1,1-dimethylethyl N-(3,4-dihydro-7-fluoro-2H-1-benzopyran-8-yl)carbamate was added portionwise. Upon completion of the addition, the reaction mixture was stirred for one hour, then stirred with water and diethyl ether and neutralized with solid sodium bicarbonate. The water layer was separated and extracted with diethyl ether. The extract was combined with the organic layer, and the combination was washed with water. The organic layer was dried with magnesium sulfate and filtered. The filtrate was concentrated under reduced pressure, yielding 3.7 grams of 8-amino-3,4-dihydro-7-fluoro-2H-1-benzopyran. The NMR spectrum was consistent with the proposed structure.
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