Trifluoroacetic acid → 1-(diphenylmethyl)-3-(6-hydroxy-3,4-dihydro-2H-chromen-7-yl)-1,3-dihydro-2H-indol-2-one

Participants

Reaction Steps

A 500 mL round-bottom flask was charged with chroman-6-ol (9.2 g, 61 mmol) and tetrahydrofuran (120 mL). A 2 M solution of isopropylmagnesium chloride in tetrahydrofuran (32.5 mL, 65.0 mmol) was added at 5° C. and the reaction mixture was stirred for 15 min and concentrated in vacuo. To the residue was added dichloromethane (180 mL), followed by a solution of 1-(diphenylmethyl)-1H-indole-2,3-dione (18.8 g, 60.0 mmol) in dichloromethane (180 mL) at 5° C. The reaction mixture was allowed to warm to ambient temperature and stirred for 24 h. Saturated aqueous ammonium chloride (7 mL) was added and the reaction mixture was concentrated in vacuo. Trituration of the residue in methanol/water (1/100, 200 mL) afforded 1-(diphenylmethyl)-3-hydroxy-3-(6-hydroxy-3,4-dihydro-2H-chromen-7-yl)-1,3-dihydro-2H-indol-2-one. A mixture of the 1-(diphenylmethyl)-3-hydroxy-3-(6-hydroxy-3,4-dihydro-2H-chromen-7-yl)-1,3-dihydro-2H-indol-2-one, triethylsilane (23.2 g, 200 mmol), trifluoroacetic acid (50.0 g, 438 mmol) and dichloromethane (200 mL) was stirred at ambient temperature for 20 h and concentrated in vacuo. Trituration of the residue in diethyl ether (150 mL) afforded 1-(diphenylmethyl)-3-(6-hydroxy-3,4-dihydro-2H-chromen-7-yl)-1,3-dihydro-2H-indol-2-one (24.3 g, 90%) as an off-white solid: MS (ES+) m/z 448.0 (M+1).

Provenance & Evidence