[Cl:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][C:11]=1[Cl:12])[C:8](=O)[CH2:7][CH2:6][CH2:5]2.[ClH:14].[C:15]1(C)[CH:20]=[CH:19][C:18](S(O)(=O)=O)=[CH:17][CH:16]=1>C(OCC)C.C1(C)C=CC=CC=1>[Cl:1][C:2]1[CH:3]=[C:4]2[C:9](=[CH:10][C:11]=1[Cl:12])[C:8]([C:15]1[CH:20]=[CH:19][C:18]([Cl:14])=[CH:17][CH:16]=1)=[CH:7][CH2:6][CH2:5]2Magnesium turnings (1.5 g.) and diethyl ether (30 ml.) were stirred while a solution of p-bromochlorobenzene (12 g.) in diethyl ether (100 ml.) was added to form the Grignard reagent. The solution was heated under reflux for 10 minutes, then a solution of 6,7-dichloro-1,2,3,4-tetrahydro-1-oxonaphthalene (9 g.) in diethyl ether (100 ml.) was added over 20 minutes, and the mixture was then heated under reflux for 30 minutes. The reaction mixture was cooled and acidified with 2N hydrochloric acid (50 ml.), and the ether layer was separated, dried, and evaporated to dryness leaving an oil. This residual oil was dissolved in toluene (300 ml.), toluene-p-sulphonic acid (0.5 g.) was added, and the solution was heated under reflux in an Dean and Stark apparatus for 2 hours, while 0.5 ml. of water was collected. The toluene was evaporated under reduced pressure and the residual oil was chromatographed on silica (Merck's Grade 7734) using petroleum ether (b.p. 60°-80° C.) as the eluant, to give 6,7-dichloro-1-(4-chlorophenyl)-3,4-dihydronaphthalene as a white crystalline solid, m.p. 106°-108° C.
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