C1(C(C2C=CC=CC=2)=[N:8][CH:9]([P:17]([CH:22]([N:30]=C(C2C=CC=CC=2)C2C=CC=CC=2)[CH2:23][C:24]2[CH:29]=[CH:28][CH:27]=[CH:26][CH:25]=2)(=[O:21])[O:18]CC)[CH2:10][C:11]2[CH:16]=[CH:15][CH:14]=[CH:13][CH:12]=2)C=CC=CC=1.[BrH:50]>C(O)(=O)C>[BrH:50].[NH2:8][CH:9]([P:17]([CH:22]([NH2:30])[CH2:23][C:24]1[CH:29]=[CH:28][CH:27]=[CH:26][CH:25]=1)(=[O:18])[OH:21])[CH2:10][C:11]1[CH:12]=[CH:13][CH:14]=[CH:15][CH:16]=1A solution of the bis-alkylated phosphinate 5 (205 mg; 0.31 mmol) in 30% strength hydrogen bromide in glacial acetic acid (11 ml) is heated to a temperature of 55°-65° C. for 25 minutes. The phosphinic acid hydrobromide 15 (136 mg, 94% of theory) is obtained after evaporating the reaction solution under reduced pressure and repeated coevaporation with methanol and toluene.
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