O[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1[C:8](=[O:10])[CH3:9].[C:11]1([C:17](C2C=CC=CC=2)=CC=O)[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1.[OH-].[Na+].Cl>O.CO>[C:11]1([CH:17]=[CH:9][C:8]([C:3]2[CH:4]=[CH:5][CH:6]=[CH:7][CH:2]=2)=[O:10])[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=1
A solution of 1.81 g (13.3 mmol) of 2'-hydroxyacetophenone, 2.75 g (13.2 mmol) of β-phenylcinnamaldehyde, 2.64 g NaOH (in 10 mL of water) and 100 mL MeOH was stirred for 24 hours before the solution was poured into 1000 mL water. The resulting mixture was neutralized with dilute HCl and the yellow precipitate was collected by filtration. Recrystallization from MeOH gave a pure intermediate chalcone product. Further oxidation of the above chalcone was carried out with excess H2O2 (30%) in basic (NaOH aq.) MeOH solution for 18 hours. This solution was poured into water, and neutralized with dilute HCl. The resulting light yellow precipitate was collected by filtration and the pure desired product was obtained by recrystallization from MeOH with 28% overall yield. MP: 215°-216° C. Quantum yield (relative to 3-hydroxyflavone in CH2Cl2) 0.004. Extinction coefficient εmax (M-1 cm-1) 23,000. λmax (abs)=378 nm and λmax (em)=470 nm.
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