3-(2H-TETRAZOL-5-YL)-PHENYL-BORONIC ACID synthesis

Yield: 15%

Reaction Conditions:

with sodium azide;ammonium chloride in N,N-dimethyl-formamide at 120; for 2.5 h;

Steps:

1
The appropriate cyanophenylpinacolate boron ester or boronic acid (1 equiv) was dissolved in DMF (0.67 M). Sodium azide (6 equiv) and ammonium chloride (6 equiv) were added. The reaction mixture was heated to 120°C for 2.5 hours. After cooling down, the reaction mixture was poured into a mixture of ice water and EtOAc. Sodium nitrite was added and the aqueous phase was acidified by 6N HCl until pH 2. The mixture was allowed to stir at room temperature for 30 min and then was extracted with EtOAc and n-butanol. Organic fractions were collected, dried over sodium sulphate, filtered off and concentrated in vacuo, to yield a crude residue which was further purified accordingly:The crude residue was recrystallized from CH₂Cl₂ / hexane, obtaining the desired product as a white solid. [3-(lH-tetrazol-5-yl)phenyl]boronic acid: (15 % yield, 100 % purity) m/z (LC-MS, ESP): 191 [M+H]⁺ R/T = 2.49 min

References:

KUDOS PHARMACEUTICALS LIMITED WO2008/23161, 2008, A1 Location in patent:Page/Page column 108-109