[NH:1]1[C:8]2[CH:9]=[CH:10][CH:11]=[CH:12][C:7]=2[CH2:6][CH2:5][CH2:4][CH2:3][C:2]1=[O:13].P(Cl)(Cl)(Cl)(Cl)Cl.II.[Br:22]Br>C(Cl)(Cl)Cl>[Br:22][CH:3]1[CH2:4][CH2:5][CH2:6][C:7]2[CH:12]=[CH:11][CH:10]=[CH:9][C:8]=2[NH:1][C:2]1=[O:13]To a solution of 4.7 g of 3,4,5,6-tetrahydro-1-benzazocin-2(1H)-one, J. Chem. Soc. (C), 2176 (1969) in chloroform (75 ml), phosphorus pentachloride (5.9 g) is added in portions, while maintaining the temperature at 0°-5° C. When addition is complete, iodine (60 mg) is added, followed by bromine (4.5 g), which is added dropwise over five minutes. The mixture is then refluxed for 4 hours. The chloroform solution is evaporated and the residue partitioned between ice/water (60 ml) and dichloromethane (100 ml). The organic phase is dried over magnesium sulfate and evaporated under reduced pressure. The crude residue is purified by chromatography on silica gel, eluting with ether/hexane mixtures. Concentration of the appropriate fractions yields 3-bromo-3,4,5,6-tetrahydro-1-benzazocin-2(1H)-one.
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