Hydroquinone → 4-[3-(trifluoromethyl)-1H-benz[g]indazol-1-yl]benzenesulfonamide

Participants

Reaction Steps

4,5-Dihydro-4-[3-(trifluoromethyl)-1H-benz[g]indazol-1-yl]benzenesulfonamide from Step 2 (393 mg, 1.0 mmol) was dissolved in 1,4-dioxane (50 ml), and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) (227 mg, 1.0 mmol) was added. The reaction was heated to reflux for 16 hours at which time a second equivalent of DDQ (227 mg, 1.0 mmol) was added and the reaction was heated to reflux for an additional 24 hours. At three successive 24 hour intervals, 1.0 mmol additional DDQ was added and heating continued until no starting material was left. The reaction was cooled to room temperature at which time most of the hydroquinone by-product precipitated. The reaction was filtered and concentrated. The residue was chromatographed on silica gel eluting with 50% ethyl acetate in hexane to yield 4-[3-(trifluoromethyl)-1H-benz[g]indazol-1-yl]benzenesulfonamide (352 mg, 90%): 1H NMR (acetone d6) δ=6.89 (broad s, 2H), 7.5 (m, 1H), 7.7 (m, 2H), 7.89 (s, 2H), 8.0 (d, 2H, j=8.7 Hz), 8.15 (d, 1H, j=8.3 Hz), 8.3 (d, 2H, j=8.7 Hz); 19F NMR (acetone d6) δ-61.7 ppm (s, 3F).

Provenance & Evidence