Ammonia → 1-(Cyclopropylmethyl)-2-(2,2-dimethylpropyl)-5-(isopropylsulfonyl)-1H-benzimidazole

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Reaction Steps

To a solution of 2-amino-1-(N-cyclopropylmethylamino)-4-(isopropylsulfonyl)benzene (Step E, 113 mg, 0.38 mmol) in ethyl acetate (3 mL) was added tert-butylacetyl chloride (58 μL, 0.42 mmol) at room temperature. After stirring for 1 h, p-toluenesulfonic acid monohydrate (72 mg, 0.38 mmol) was added and the mixture was stirred under reflux for 3 h. Water (5 mL) and aqueous ammonia (0.5 mL) were added and the mixture was extracted with ethyl acetate (15 mL×3) and washed with brine (5 mL). The organic extracts were dried over sodium sulfate and concentrated. The residue was purified by pTLC (hexane:ethyl acetate=1:1 then dichloromethane:methanol=10:1 as eluent) to give colorless oil (74 mg), which was recrystalized from ethyl acetate and hexane to afford the title compound (28 mg, 21%) as a white solid.

Provenance & Evidence