S(=O)(=O)(O)O.[Br:6][C:7]1[CH:8]=[CH:9][C:10]([CH2:25][CH3:26])=[C:11]([CH:13]2[C:15]3([C:19](=[O:20])[C:18]([CH3:22])([CH3:21])[O:17][C:16]3([CH3:24])[CH3:23])[O:14]2)[CH:12]=1>ClCCCl>[Br:6][C:7]1[CH:8]=[CH:9][C:10]([CH2:25][CH3:26])=[C:11]([CH:13]2[C:19](=[O:20])[C:18]([CH3:21])([CH3:22])[O:17][C:16]([CH3:24])([CH3:23])[C:15]2=[O:14])[CH:12]=1To an ice-cold solution of concentrated sulphuric acid (2 ml) is added a second solution of 2-(5-bromo-2-ethylphenyl)-4,4,6,6-tetramethyl-1,5-dioxaspiro[2.4]heptan-7-one (0.995 g, 2.82 mmol) in 1,2-dichloroethane (2 ml) dropwise over 5 minutes. This biphasic mixture is stirred vigorously for 1 hour at 0° C., then poured into ice-cold water (15 ml). This aqueous mixture is then concentrated under vacuum to remove all organic volatiles, producing a free-flowing solid. The solid is filtered, dried under vacuum, then washed with hexanes to afford 4-(5-bromo-2-ethylphenyl)-2,2,6,6-tetramethylpyran-3,5-dione (0.81 g) as a cream-coloured solid.
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