Br[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][C:3]=1F.[O:9]1[CH2:13][CH2:12][O:11][CH:10]1[C:14]1[O:15][CH:16]=[CH:17][CH:18]=1.[Mg].[NH4+].[Cl-]>C1COCC1>[O:9]1[CH2:13][CH2:12][O:11][CH:10]1[C:14]12[O:15][CH:16]([C:2]3[C:7]1=[CH:6][CH:5]=[CH:4][CH:3]=3)[CH:17]=[CH:18]2
2-Bromofluorobenzene (36.0 g, 0.222M) in THF (200 ml) was added dropwise over one hour to a refluxing mixture of the above furan (28.0 g, 0.200M) and magnesium turnings (5.4 g, 0.206M) in dry THF (200 ml) under nitrogen. After the addition was complete, refluxing was continued for one hour. The cooled mixture was then poured onto saturated NH4Cl solution (250 ml), the organic layer separated and the aqueous layer re-extracted with ether. The combined organic extract was washed with saturated NH4Cl solution, dried over anhydrous K2CO3 -Na2SO4 and concentrated in vacuo. The residue was purified on the Waters Prep 500 HPLC using two columns and eluting with EtOAc/hexane (1:4). A total of 33.3 g of 1-(1,3-dioxolan-2-yl)-1,4-epoxy-1,4-dihydronaphthalene was obtained as a pale yellow oil. Crystallization of the oil from hexane gave 32.5 g (75% yield) as white crystals, mp 48°-49° C.
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