2-Hydroxyxanthone → Pentanoic acid, 5-[(9-oxo-9H-xanthen-2-yl)oxy]-, ethyl ester

Participants

Reaction Conditions

Reaction Steps

2-hydroxyxanthone (7.7 g, 36 mmol) prepared as described in Example 1, was dissolved in DMF (50 mL), and potassium tert-butoxide (4.6 g, 41 mmol) was added in one portion. The mixture was stirred under N2 at 25° C. for 1.5 hours, and then ethyl 5-bromovalerate (8.74 g, 42 mmol) in DMF (20 mL) was added dropwise over 20 minutes. The reaction mixture was heated at 115° C. for 11 hours, then cooled, filtered, and washed with EtOAc (2×10 mL). The filtrate was concentrated to provide a light-brown oily residue, which slowly solidified at room temperature. Light-beige crystals were collected and washed with n-hexane (3×10 mL). TLC pure, Rf =0.79 benzene-EtOH 10:9. Yield: 9.70 g (79%). A small amount of the product was recrystallized from n-hexane-EtOH (10:1) for elemental analysis. White needles, 1H-NMR (CDCl3 δ: 8.34 (dd, J=1.6 and 8.0 Hz, 1H), 7.66-7.76 (m, 2H, 7.3-7.5 (m, 4H), 4.14 (q, J=7.1 Hz, 2H), 2.40 [t,J=6.9 Hz, 2H, CH2 (C=0)] 1.85 (m, 4H), 1.26 (t,J=7.1 Hz, 3H-CH3).

Provenance & Evidence