Triethylamine → racemic methyl 2-(3,4-dichlorophenyl)-2-methyl-2H-chromene-3-carboxylate

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Reaction Steps

A solution of crude methyl 2-(3,4-dichlorophenyl)-4-hydroxy-2-methylchroman-3-carboxylate (100 mg, 272 μmol) in dichloromethane (2.0 mL) was stirred on an ice bath and treated with triethylamine (76 μL, 545 μmol), then dropwise with methanesulfonyl chloride (23 μL, 300 μmol). After stirring for 1.5 h, the solution was warmed to rt. After stirring at rt for 6 h, the solution was diluted with dichloromethane, washed with 1.0 M aqueous HCl, dried over sodium sulfate and concentrated under vacuum. The resulting residue was dissolved in benzene (2.0 mL), treated with 1,8-diazabicyclo[5.4.0]undec-7-ene (55 μL, 408 μmol) and stirred at rt for 25 min. After this time, the resulting mixture was heated to 60° C. where it stirred for 5.25 h. After this time, the solution was cooled to rt, diluted with ethyl acetate, washed with water, 1.0 M aqueous HCl, saturated aqueous sodium bicarbonate and saturated aqueous sodium chloride, dried over sodium sulfate and then concentrated under vacuum to yield a residue. The residue was purified by rotary TLC (silica gel, 92:8 hexane-ethyl acetate) to provide racemic methyl 2-(3,4-dichlorophenyl)-2-methyl-2H-chromene-3-carboxylate as a colorless gum (44 mg, 46%). 1H NMR (400 MHz, CDCl3) δ ppm 2.02 (s, 3 H) 3.73 (s, 3 H) 6.82 (d, J=8.1 Hz, 1 H) 6.92 (dt, J=7.6, 1.0 Hz, 1 H) 7.15 (dd, J=7.6, 1.5 Hz, 1 H) 7.25 (dt, J=7.9, 1.5 Hz, 1 H) 7.37 (m, 2 H) 7.58 (s, 1 H) 7.61 (t, J=1.5 Hz, 1 H).

Provenance & Evidence