Ethyl Acetate → 2-Benzimidazolecarboxylic acid

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Reaction Steps

An acidic solution (e.g., HCl:water, 30:70) is added to compound (1a) dissolved in a solvent such as methanol. The mixture is refluxed until completion (˜12-36 hours), then concentrated under reduced pressure or in vacuo to afford compound (1b) as a solid. The recovered material may be used without further processing. Alternately, the solid may be dissolved in ethyl acetate, washed with saturated NaHCO3, dried over MgSO4 and concentrated. Acidic solutions used include sulfuric acid and a hydrogen chloride solution (30:70, HCl:H2O). Examples of compound (1a) include 7-methyl-2-propyl-3H-benzoimidazole-5-carboxylic acid (R2=methyl, R3=propyl), which is commercially available, and is particularly well-suited for use in preparing compounds of the invention. If desired, different R2 and R3 groups can be introduced in later steps. Examples of compound (1b) include 7-methyl-2-propyl-3H-benzoimidazole-5-carboxylic acid methyl ester.

Provenance & Evidence