Acetyl chloride → 1-(3,4-dihydro-2H-1-benzopyran-6-yl)ethan-1-one

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Reaction Steps

AlCl3 (11.8 g, 88.2 mmol) was added in small portions to a stirred solution of AcCl (11.9 mL, 167.5 mmol) in dry DCM (250 mL) at −10° C. and the mixture stirred until homogeneous (15 min). The solution was added, via a cannula, to a stirred solution of chroman (229) (11.8 g, 88.2 mmol) in dry DCM (200 mL) at −10° C. and the solution stirred for 30 min at −10° C. and then poured into ice/cHCl (5:1 v/v, 1.5 L). The mixture was stirred for 2 h, extracted with DCM (3×100 mL), the combined organic fraction dried and the solvent evaporated. The residue was purified by chromatography, eluting with a gradient (10-20%) of EtOAc/pet. ether, to give 1-(3,4-dihydro-2H-chromen-6-yl)ethanone (230) (12.45 g, 80%) as a white solid: 1H NMR δ 7.68-7.22 (m, 2H, H-5, H-7), 6.82 (d, J=9.2 Hz, 1H, H-8), 4.24 (br dd, J=5.3, 5.2 Hz, 2H, H 2), 2.83 (br t, J=6.5 Hz, 2H, H-4), 2.53 (s, 3H, CH3), 2.00-2.06 (m, 2H, H-3).

Provenance & Evidence