Pyridine → Toluene-4-sulfonic acid 6-chloro-2-oxo-2H-1-benzopyran-4-yl ester

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Reaction Steps

6-Chloro-4-hydroxycoumarin (25.4 mmol, 5.0 g) is suspended in DCM (50 mL) and pyridine (63.3 mmol, 5.1 mL) is added. The mixture is cooled in an ice bath and p-toluenesulfonyl chloride (26.8 mmol, 5.1 g) is added. The ice bath is removed and the compound slowly dissolves and a solid is deposited (pyridine HCl). After 1 hr the mixture is transferred to a separatory funnel, HCl (2 M) is added, and a solid is formed. The organic layer is removed and the solid-containing aqueous layer is filtered to remove the precipitate. The filtrate is washed with DCM and the combined organic layers are washed with H2O, NaHCO3 (sat.), H2O, and brine. The extract is then dried over MgSO4 and is evaporated. The residue is triturated with Et2O to give the title compound (8.0 g, 90%) as a cream solid. 1H NMR (CDCl3, 400 MHz) δ 7.91 (2H, d, J=8 Hz), 7.54 (1H, d, J=2 Hz), 7.51 (1H, dd, J=2, 9 Hz), 7.42 (2H, d, J=8 Hz), 7.26 (1H, d, J=9 Hz), 6.38 (1H, s), 2.49 (3H, s); LCMS (MeCN—H2O, Luna 3μC18(2) 30×4.6 mm; MS (ESI, Pos.) calcd for C16H11ClO5S m/z [M+H]=351 found [no mass ion detected].

Provenance & Evidence