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A suspension of anhydrous phloroglucinol (20.0 g, 0.159 mol) in ethyl butrylacetate (26.3 g; 0.167 mol) was added over 30 min to 50 g of constantly stirred trifluoromethanesulfonic acid cooled in an ice bath. A drying tube was then fined to the reaction vessel and the mixture was stirred for 16h at 25° C., after which the resulting thick paste was combined with ice (200 g) and water (300 mL) with brisk stirring. After 30 min the solid material was collected by vacuum filtration and recrystallised from 95% ethanol to yield coumarin 15 (34.7 g; 99%) as lemon yellow crystals. mp 236°-238° C. 1H NMR (CDCl3 /CD3OD 3:1): δ6.13(1H, d; J =2.3 Hz), 6.04(1H, d; J=2.3 Hz), 5.68(1H, s), 2.76(2H, t; J=7.4 Hz), 1.47(2H, tq; J =7.7, 7.4 Hz), 0.82(3H, t; J =7.7 Hz). 13C NMR (CDCl3 /CD3OD 3:1): δ163.1, 160.7, 160.6, 157.3, 156.7, 107.8, 102.5, 99.2, 95.0, 37.7, 22.5, 13.4. Anal. calc. for C12H12O4.(H2O): C, 60.50; H, 5.92. Found: C, 60.47; H, 5.92.

1. temperaturecooled in an ice bath
2. customA drying tube was then fined to the reaction vessel
3. filtrationAfter 30 min the solid material was collected by vacuum filtration
4. customrecrystallised from 95% ethanol