[OH-:1].[K+].[OH:3][C:4]1[CH:5]=[C:6]([CH:23]=[CH:24][C:25]=1[O:26][CH3:27])[CH:7]1[CH2:16][C:15](=O)[C:14]2[C:9](=[CH:10][C:11]([O:19][CH2:20][CH2:21][Br:22])=[CH:12][C:13]=2[OH:18])[O:8]1.O.Cl>C(Cl)Cl.CO>[OH:18][C:13]1[CH:12]=[C:11]([O:19][CH2:20][CH2:21][Br:22])[CH:10]=[C:9]([OH:8])[C:14]=1[CH:15]=[CH:16][C:7]([C:6]1[CH:23]=[CH:24][C:25]([O:26][CH3:27])=[C:4]([OH:3])[CH:5]=1)=[O:1]Ten ml of 5% KOH is added to 400 mg (1.00 mmole) of 3',5-dihydroxy-4'-methoxy-7-bromoethoxy-flavanone giving a bright yellow solution which is stirred under argon at ambient temperature for 2 hours. The reaction mixture is then poured into 100 ml of water, acidified with 10% HCl, and extracted immediately with ethyl acetate (2 × 25 ml). The combined extracts are washed with dilute NaHCO3 (1 × 25ml), dried over MgSO4 and concentrated yielding 0.51 g of a partially crystalline orange oil. Tlc (silica gel F-254, CH2Cl2 --CH3OH 95:5), indicates the reaction to have proceeded nearly quantitatively showing only the product (Rf =0.28) and a barely observable spot for starting material (Rf =0.73). Preparative tlc on silica gel PF-254, eluting with CH2Cl2 --CH3OH 95:5, yielded 302 mg (75%) of the chalcone as a yellow solid. Recrystallization from hexaneethyl acetate gives orange clusters having mp 158°-162°C and spectra consistent with material 7b.
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