Benzophenone, 2,2',5-trimethoxy- → 2-Hydroxyxanthone

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Reaction Steps

A mixture of 2,2',5-trimethoxybenzophenone (6.52 g, 23,9 mmol, unpurified) prepared as described above, and pyridine hydrochloride (35.0 g, 0.3 mol) was refluxed (~210° C.) for 48 hours under N2. The mixture was then poured into ice (100 g), and the yellow-green precipitate which formed was collected by filtration and washed with water (2×60 mL). This residue was then suspended in water (~60 mL), and made alkaline (pH~12) with 45% (w/v) aqueous KOH. The resultant reddish-brown suspension was filtered, and added dropwise to a stirred mixture of ice (50 g) and 12N HCl (15 mL). The precipitated solid was filtered, washed with water (4×20 mL), and air dried. Yield: 4.25 g (84%). TLC: Rf 0.54 [benzene-EtOH (20:3)]. 1H-NMR (DMSO, 200 MHz) δ:8.17 (dd,J=1.5 and 7.9 Hz, 1H), 7.85 (t,J=7.7 Hz, 1H), 7.41-7.66 (m, 4H), 7.32 (dd,J=9.0 and 3.1 Hz, 1H). ##STR4##

Provenance & Evidence