N[C:2]1[C:10]2[O:9][C:8]([CH3:12])([CH3:11])[CH2:7][C:6]=2[C:5]([Br:13])=[CH:4][C:3]=1[Cl:14].C1(C)C=CC=CC=1.S(=O)(=O)(O)O.N([O-])=O.[Na+]>C(O)C>[Br:13][C:5]1[C:6]2[CH2:7][C:8]([CH3:11])([CH3:12])[O:9][C:10]=2[CH:2]=[C:3]([Cl:14])[CH:4]=1
A stirred solution of 5.1 grams (0.018 mole) of 7-amino-4-bromo-6-chloro-2,3-dihydro-2,2-dimethylbenzofuran and 25 mL of toluene in 100 mL of ethanol was cooled in an ice bath, and 2 mL (0.036 mole) of concentrated sulfuric acid was added slowly. Upon completion of addition, 2.0 grams (0.029 mole) of sodium nitrite was then added. The ice bath was then removed, and the reaction mixture was warmed to 75° C., where it stirred for 30 minutes. After this time the reaction mixture was warmed to 95° C., where it stirred for one hour. The reaction mixture was then cooled and poured into 200 mL of water. The mixture was extracted with two 150 mL portions of diethyl ether. The combined extracts were dried with magnesium sulfate and filtered. The filtrate was concentrated under reduced pressure to a residue. The residue was subjected to column chromatography on silica gel. Elution was accomplished using petroleum ether. The product-containing fractions were combined and concentrated under reduced pressure, yielding 3.6 grams of 4-bromo-6-chloro-2,3-dihydro-2,2-dimethylbenzofuran. The NMR spectrum was consistent with the proposed structure.
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