Trifluoromethanesulfonic acid → 5-Methanesulfonyl-3,3-dimethyl-2,3-dihydro-benzofuran

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Reaction Conditions

Reaction Steps

A mixture of 3,3-dimethyl-2,3-dihydro-benzofuran (example 14c) (870 mg, 5.87 mmol), trifluoromethanesulfonic acid (0.1 mL, 1.17 mmol) and methanesulfonic anhydride (2.04 g, 11.74 mmol) was heated to 135° C. After reaching this temperature, the heater was removed and the mixture was cooled down to room temperature. The mixture was poured into a solution of ice-water. The aqueous layer was extracted twice with ethyl acetate and the organic combined extract was washed with water, an aqueous solution of sodium bicarbonate, brine, dried (MgSO4), filtered, and evaporated. The residue was chromatographed on silica gel (30% to 50% ethyl acetate in hexane) to afford 317 mg of 5-Methanesulfonyl-3,3-dimethyl-2,3-dihydro-benzofuran. 24% yield. 1H-NMR (300 MHz, CDCl3): 1.39 (s, 6H), 3.04 (s, 3H), 4.36 (s, 2H), 6.90 (d, J=8.2 Hz, 1H), 7.67 (d, J=2.1 Hz, 1H), 7.74 (dd, J1=8.5 Hz, J2=2.1 Hz, 1H).

Provenance & Evidence