2-Aminothiophenol → 5-(Benzothiazol-2-yl)-1-phenyl-2-(phenylmethoxy)methylbenzimidazole

Participants

Reaction Conditions

Reaction Steps

A 4-neck flask (500 mL) equipped with a reflux condenser was charged with 1-pheny-2-(phenylmethoxy)methylbenzimidazole-5-carboxylic acid (see Working Example 1-1) (4.00 g, 11.16 mmol) and anhydrous tetrahydrofuran (63 mL), and after the addition of oxalyl chloride (1.65 g, 13.0 mmol), this was warmed to 50° C. and stirred for 3 hours. After cooling to room temperature, the solvent was distilled off under reduced pressure. Anhydrous THF (30 mL) was again added to the greenish-milky white semisolid residue, and after gradual addition of 2-aminobenzenethiol (1.40 g, 11.22 mmol), this was warmed to 50° C. and stirred for 16 hours. After cooling to room temperature, the precipitated crystals were filtered off and washed with saturated aqueous sodium hydrogen carbonate solution (approx. 20 mL), and the precipitated solid was filtered off to yield a mixture of starting material and the title compound (2.43 g, an approx. 1:1 mixture of starting material/title compound, based on 1H-NMR). The filtrate was allowed to stand for a further 16 hours at room temperature and the precipitated crystals were filtered off, washed with saturated aqueous potassium carbonate solution, washed with distilled water, and then dried under reduced pressure with heating to yield the title compound (0.82 g, 16% yield) as a white powder.

Provenance & Evidence