Hydrochloric Acid → 5-(2-Bromophenyl)-1H-tetrazole

Participants

Reaction Steps

A 64 g (350 mmol) sample of 2-bromobenzonitrile (Aldrich) was dissolved in 650 mL of xylene and treated with 22.75 g (350 mmol) of sodium azide and 95 mL (350 mmol) of tributyltin chloride at reflux for 48 h. The reaction was filtered; the filtrate was treated with 50 mL of anhydrous tetrahydrofuran (THF) and 20 g (550 mmol) of hydrogen chloride. The reaction was stirred for 2 h; filtration gave 59.6 g (76%) of 5-(2-bromophenyl)-1H-tetrazole: mp 178-180° C.; NMR (DMSO-d6) δ7.50-7.64 (m, 2H), 7.67-7.74 (m, 1H), 7.83-7.91 (m, 1H). A 41.8 g (187 mmol) sample of this material was dissolved in 650 mL of methylene chloride and treated with 55.5 g (193 mmol) of triphenylmethyl chloride and 30 mL (220 mmol) of anhydrous triethylamine. The reaction was stirred overnight at reflux, cooled to ambient tempeature, washed with water, dried (MgSO4), and concentrated in vacuo. Recrystallization from toluene/hexane gave 80.7 g (92% ) of N-triphenylmethyl-5-(2-bromophenyl)-1H-tetrazole: mp 60°-162° C.; NMR (CDCl3) δ7.14-7.21 (m, 6H), 7.26-7.45 (m, 11H), 7.70 (dd, J=8 and 1.5 Hz, 1H), 7.89 (dd, J=7.5 and 2 Hz, 1H). A 34.05 g (73.0 mmol) sample of this material was dissolved in 1700 mL of THF under a nitrogen atmosphere and treated with 73 mmol of n-butyllithium in hexane. The reaction was allowed to stir for 17 min and then was treated with 24.9 mL (220 mmol) of trimethyl borate. The reaction was allowed to come to ambient temperature overnight while stirring, quenched with 10 mL of methanol, and concentrated in vacuo. The residue was dissolved in 1M NaOH and extracted with toluene to remove any unreacted starting material. The pH was adjusted to 6 with 6M HCl and the product extracted with toluene and dried (MgSO4). Hexane was added and the solution kept in the freezer overnight. Filtration provided 31.3 g (99%) of 2-(N-triphenylmethyltetrazol-5-yl) phenylboronic acid: NMR (CDCl3) δ7.13-7.21 (m, 7H), 7.33-7.42 (m, 8H), 7.49-7.55 (m, 2H), 8.15-8.19 (m, 1H), 8.21-8.26 (m, 1H).

Provenance & Evidence