Hydrochloric Acid → Methyl 6-fluorochromane-4-carboxylate
Reaction equation
[F:1][C:2]1[CH:3]=[CH:4][C:5]2[O:10][CH2:9][CH2:8][CH:7]([C:11]([OH:13])=[O:12])[C:6]=2[CH:14]=1.Cl.[CH3:16]O>>[F:1][C:2]1[CH:3]=[CH:4][C:5]2[O:10][CH2:9][CH2:8][CH:7]([C:11]([O:13][CH3:16])=[O:12])[C:6]=2[CH:14]=1Participants
4
Procedure
A solution of 8.4 g of the 6-fluoro-2,3-dihydro-4H-benzopyran-4-carboxylic acid in 580 mL of methanol was perfused with HCl gas for 5 minutes. The resulting solution was stirred at room temperature overnight. The volatiles were evaporated and the residue dissolved in ether. The ether layer was washed with water then dried over Na2SO4, filtered and evaporated to give 8.7 g of crude product which was purified by chromatography on 300 g of silica gel eluting with CH2Cl2 to give 6.2 g of product as an oil. NMR (CDCl3) ppm (delta): 2.00-2.40 (m, 2H), 3.80 (s, 3H), 2.5 (t, 1H, J=4 Hz), 7.10-6.70 (m, 3H).