1-(2,4-Dihydroxyphenyl)-2-(4-hydroxyphenyl)ethanone (119.000 g, 487.2 mmol, 1.0 equiv.) and ethyl acetate (400 mL) was added to a 2 L 3 neck round bottomed flask equipped with a stir bar a thermometer, a condenser and a nitrogen inlet. The flask was flushed with nitrogen for 2 minutes and 3,4-dihydro-2H-pyran (222.252 ml, 2436.1 mmol, 5.0 equiv.) was added from a graduated cylinder. The suspension was flushed with nitrogen for 2 minutes and p-toluenesulfonic acid (0.378 g, 2.2 mmol, 0.0 equiv.) was added to the reaction. An exothermic reaction took place and the temperature rose from 20 to 33° C. over 5 minutes. The yellow suspension became a red solution within 1 minute of PTSA addition. The reaction was stirred for 66 h at room temperature. The reaction was monitored by HPLC at 4, 5 and 6 hours. The chromatograms indicated the reaction was 74%, 90% and 100% complete at the time indicated respectively. TEA (5 mL) was added to the cream colored slurry to stop the reaction. The slurry was transferred to a round bottomed flask (2 L) and the three neck flask rinsed with ethyl acetate. The slurry was concentrated on a rotovap to give a cream colored powdery solid. The solid was transferred to a 2 L Erlenmeyer flask. Isopropyl alcohol (IPA) was used to rinse the flask. The solid was recrystallized from IPA (1.4 L). The suspension was cooled in an ice bath for 30 minutes and the solid collected by vacuum filtration. The solid was rinsed with ice cold IPA until the filtrate was colorless and dried in a vacuum oven to give a white powder (162.24 g). The mother liquor and washes were combined and concentrated to an orange oil (38.09 g).
