C([O-])([O-])=O.[Cs+].[Cs+].[CH3:7][C:8]1([CH3:15])[CH2:13][O:12]S(=O)[O:10][CH2:9]1.[Br:16][C:17]1[C:22]([CH3:23])=[CH:21][C:20](O)=[CH:19][C:18]=1[CH3:25]>CN(C)C=O>[Br:16][C:17]1[C:22]([CH3:23])=[CH:21][C:20]([O:10][CH2:9][C:8]([CH3:15])([CH3:7])[CH2:13][OH:12])=[CH:19][C:18]=1[CH3:25]In a microwave vial Cs2CO3 (5.4 g) is added to a solution of 5,5-dimethyl-[1,3,2]dioxathiane 2-oxide (500 mg) and 4-bromo-3,5-dimethylphenol (670 mg) in N,N-dimethylformamide (5 mL). The vial is sealed and the mixture is heated to 120° C. for 12 hours. The mixture is partitioned between ethyl acetate and water. The organic phase is washed three times with 2 M aqueous NaOH and with brine. After drying (MgSO4) and concentration the residue is chromatographed on silica gel (cyclohexane/ethyl acetate 99:1→50:50) to give the title compound. Yield: 372 mg; LC (method 7): tR=1.17 min; Mass spectrum (ESI+): m/z=287 [M+H]+.
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