3-Chloro-5-fluorobenzo[b]thiophene-2-carbonyl chloride → (3-Chloro-7-fluoro-benzo[b]thiophen-2-yl)methanol

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Reaction Steps

To an ice-cold suspension of a 6:1 mixture of 3-chloro-5-fluoro-benzo[b]thiophene-2-carbonyl chloride and 3-chloro-7-fluoro-benzo[b]thiophene-2-carbonyl chloride (5.46 g, 23.6 mmol) in THF (120 mL) was added lithium aluminum hydride (11.8 mL of a 1.0 M solution in THF, 11.8 mmol) dropwise. The mixture was stirred for 4 h then quenched with NaOH (0.35 N solution in H2O). The mixture was diluted with Et2O and the solution filtered. The filtrate was dried (Na2SO4) and concentrated. Purification by flash column chromatography (silica gel, hexanes/EtOAc, 9:1 to hexanes/EtOAc 8:2) gave the title compound (600 mg, 4% (2 steps), 7-fluoro isomer) as a light, yellow solid: 1H NMR (300 MHz, CDCl3) δ 7.59 (d, J=8.0 Hz, 1H), 7.41 (ddd, J=8.0, 8.0, 4.9 Hz, 1H), 7.10 (dd, J=9.1, 9.1 Hz, 1H), 5.00 (d, J=6.2 Hz, 2H), 2.04 (t, J=6.5 Hz, 1H).

Provenance & Evidence