反应详情

Trifluoromethanesulfonic anhydride (3.1 mL, 18.43 mmol) was slowly added to a solution of 1,3-dihydroxy-5-methoxy-xanthen-9-one (3.32 g, 12.85 mmol) and pyridine (32.0 mL) in CH2Cl2 (130 mL) at 0° C. See, D. K. Ho et al., J. Org. Chem., 52, pp. 342-347 (1987). The reaction mixture then was allowed to slowly warm to RT and stirred for 16 h. The resulting orange mixture was concentrated to a brown oil, then dissolved in EtOAc (750 mL) and washed with 5% citric acid (3×100 mL), water (1×100 mL), and brine (1×100 mL). The organics were dried (MgSO4) and concentrated to yield 3.0 g (60%) of trifluoromethanesulfonic acid, 1-hydroxy-5-methoxy-9-oxo-9H-xanthen-3-yl ester as a light brown solid. Rf=0.65 (50% EtOAc/hexanes). 1H NMR (DMSO-d6, 400 MHz) δ: 12.89 (s, 1H), 7.74 (d, 1H), 7.60 (m, 1H), 7.50 (m, 1H), 7.42 (s, 1H), 7.04 (s, 1H), 3.97 (s, 3H).

1. concentrationThe resulting orange mixture was concentrated to a brown oil
2. dissolutiondissolved in EtOAc (750 mL)
3. washwashed with 5% citric acid (3×100 mL), water (1×100 mL), and brine (1×100 mL)
4. dry with materialThe organics were dried (MgSO4)
5. concentrationconcentrated