[CH3:1][C:2]1[CH:17]=[CH:16][C:5]2[C:6](=[O:15])[C:7]3[CH:14]=[CH:13][CH:12]=[CH:11][C:8]=3[CH2:9][CH2:10][C:4]=2[CH:3]=1.BrN1C(=O)CC[C:20]1=O>C(Cl)(Cl)(Cl)Cl>[CH2:1]([C:2]1[CH:17]=[CH:16][C:5]2[C:6](=[O:15])[C:7]3[CH:14]=[CH:13][CH:12]=[CH:11][C:8]=3[CH2:9][CH2:10][C:4]=2[CH:3]=1)[CH3:20]60.5 Gm. of 2-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-one is refluxed in 500 ml. of carbon tetrachloride with 58.2 gm. of N-bromosuccinimide for 8 hours. The solution is cooled and filtered and the solvent removed under vacuum. The residue is dissolved in 200 ml. of dimethylformamide and 44 gm. of 1,5-diazabicyclo[3.4.0]nonene-5 is added. The mixture is heated to 80° C. for 20 minutes, then cooled and added to water. The solution is extracted with ether and the extract washed, dried and evaporated. The residue is recrystallized from acetone/hexane to afford 39.7 gm., 69%, of 2-methyl-5H-dibenzo[a,d]cyclohepten-5-one,m.p. 78°-80° C. Use of 2-ethyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-one gives a similar yield of 2-ethyl-5H-dibenzo[a,d]cyclohepten-5-one,m.p. 62°-64° C.
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