[Br:1][C:2]1[CH:7]=[CH:6][C:5]([CH2:8][C:9]2[N:10]=[N:11][NH:12][N:13]=2)=[CH:4][CH:3]=1.[C:14](O)([CH3:17])([CH3:16])[CH3:15].FC(F)(F)C(O)=O.S(=O)(=O)(O)O>>[Br:1][C:2]1[CH:7]=[CH:6][C:5]([CH2:8][C:9]2[N:10]=[N:11][N:12]([C:14]([CH3:17])([CH3:16])[CH3:15])[N:13]=2)=[CH:4][CH:3]=1A mixture of 5-[(4-bromophenyl)methyl]-2H-tetrazole (18.5 g. 77 mmol). t-butanol (11.4 g. 150 mmol), trifluoroacetic acid (76 mL. 1.0 mol) and concentrated sulfuric acid (3.8 g. 39 mmol) was stirred for 24 h and then partitioned between ethyl acetate (250 mL) and water (100 mL). The organic layer was washed with water (4×100 mL) and 1M NAOH (2×100 mL) and was dried over sodium sulfate. Filtration and removal of the solvent in vacuo produced a solid that was recrystallized from hexane to give 5-[(4-bromophenyl)methyl]-2-(1,1-dimethylethyl)-2H-tetrazole. (12.3 g, 47 mmol) in 54% yield, mp. 69°-70° C.
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