Trifluoroacetic acid → 4-[(4-Chlorophenyl)sulfonyl]-6-fluoro-3,4-dihydro-2H-1-benzopyran

Participants

Reaction Conditions

Reaction Steps

6-Fluorochroman-4-one (352 mg, 2.12 mmol) and 4-chlorothiophenol (320 mg, 2.2 mmol) were dissolved in 5 mL DCM. The reaction mixture was cooled to 0° C. and 2.4 mL of trifluoroacetic acid was added. After 5 min at 0° C., pyridine-borane complex (0.20 mL) was slowly added. The reaction mixture was stirred for 1 h at 0° C. Et2O (100 mL) and sat. NaHCO3 solution (100 mL) were added. The ether layer was dried over Na2SO4 and concentrated. The residue was dissolved in 10 mL DCM, mCPBA (77%, 1.01 g, 4.50 mmol) was added and the reaction mixture was stirred at room temperature overnight. 2 g of Na2SO3 in 20 mL of water was added and the reaction was stirred for 1 h then filtered. The layers were separated, then the organic layer was washed with 1N NaOH solution (100 mL), dried over Na2SO4 and concentrated. The product was purified by column chromatography using hex./EtOAc as the eluent (gradient from 100/0 to 30/70 in 60 min, 0.37 g, 53%). 1H NMR (CDCl3 400 MHz) δ 7.67 (d, J=8.8 Hz, 2H), 7.49 (d, J=8.8 Hz, 2H), 6.92 (m, 2H), 6.77 (m, 1H), 4.24 (m, 2H), 4.10 (m, 1H), 2.36 (m, 1H), 2.18 (m, 1H).

Provenance & Evidence