[Cl:1][C:2]1[CH:3]=[C:4]([OH:13])[C:5]([OH:12])=[C:6]([CH:11]=1)[C:7]([O:9][CH3:10])=[O:8].Br[CH2:15][CH2:16][CH2:17]Br.C([O-])([O-])=O.[K+].[K+]>CC(=O)C>[Cl:1][C:2]1[CH:11]=[C:6]([C:7]([O:9][CH3:10])=[O:8])[C:5]2[O:12][CH2:17][CH2:16][CH2:15][O:13][C:4]=2[CH:3]=1A mixture of intermediate (9) (0.3 mol), 1,3-dibromopropane (0.42 mol) and K2CO3 (0.66 mol) in 2-propanone (500 ml) was stirred and refluxed for 20 hours, then filtered hot and the filtrate was evaporated. The residue was purified by column chromatography over silica gel (eluent:DCM). The desired fractions were collected and the solvent was evaporated. Toluene was added and azeotroped on the rotary evaporator, yielding 69 g of methyl 8-chloro-3,4-dihydro-2H-1,5-benzodioxepin-6-carboxylate (intermediate 10).
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