[OH:1][C:2]1[CH2:7][CH:6]([C:8]2[CH:9]=[C:10]3[C:14](=[CH:15][CH:16]=2)[CH2:13][CH2:12][CH2:11]3)[CH2:5][C:4](=[O:17])[CH:3]=1.O.[C:19](O)(=[O:22])[CH2:20][CH3:21]>C(OC(=O)CC)(=O)CC.FC(S(O)(=O)=O)(F)F>[OH:17][C:4]1[CH2:5][CH:6]([C:8]2[CH:9]=[C:10]3[C:14](=[CH:15][CH:16]=2)[CH2:13][CH2:12][CH2:11]3)[CH2:7][C:2](=[O:1])[C:3]=1[C:19](=[O:22])[CH2:20][CH3:21]3-Hydroxy-5-(5-indanyl)cyclohex-2-en-1-one (4.0 g; 18 mmole) was dissolved in a mixture of propionic acid (4 ml) and propionic anhydride (4 ml) at 130° C. under nitrogen. To the resulting clear solution was added 8 drops of trifluoromethyl sulphonic acid and the mixture was allowed to stir at 130° C. under nitrogen for a further 11/2 hours. The mixture was poured into water (500 ml) and stirred until all the anhydride had reacted (approx 30 min). The resulting solid was filtered off, pressed dry at the pump and then dissolved in dichloromethane and purified by column chromatography over silica gel (eluant dichloromethane) to give 3-hydroxy-5-(5-indanyl)-2-propionylcyclohex-2-en-1-one (1.88 g; 37%), mp 98° C.
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