Yield:-

Reaction Conditions:

with triphenylphosphine;diethylazodicarboxylate in tetrahydrofuran;toluene at 20 - 25; for 7 h;

Steps:

10

Reference Example 10 (6-Bromo-3-methyl-2-oxo-2,3-dihydro-1H-benzimidazol-1-yl)acetic acid To a solution of ethyl 6-bromo-2-oxo-2,3-dihydro-1H-benzimidazole-1-carboxylate (2.85 g, 10.0 mmol) obtained by the method disclosed in the literature ( ), methanol (962 mg, 30.0 mmol) and triphenylphosphine (3.93 g, 15.0 mmol) in tetrahydrofuran (60 mL) is added diethyl azodicarboxylate (40 % toluene solution, 6.53 g, 15.0 mmol), and the mixture is stirred at 20-25°C for 7 hours. The reaction solution is concentrated under reduced pressure, and the residue is purified by silica gel column chromatography (hexane/ethyl acetate = 5/ 1 to 2/1) to give a mixture of ethyl 6-bromo-3-methyl-2-oxo-2,3-dihydro-1H-benzimidazole-1-carboxylate and an impurity derived from diethyl azodicarboxylate. To this mixture is added toluene (25mL), and the mixture is stirred, and the precipitated crystals are collected by filtration to give crude ethyl 6-bromo-3-methyl-2-oxo-2,3-dihydro-1H-benzimidazole-1-carboxylate.

References:

EP1719761,2006,A1 Location in patent:Page/Page column 27-28