Methyl 4-aminobenzoate → Methyl 4-{[cyclopentyl(3-methyl-1-benzothiophen-2-yl)methyl]amino}benzoate

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Reaction Steps

To a mixture of cyclopentyl(3-methyl-1-benzothiophen-2-yl)methanone (1.54 g) synthesized above, methyl 4-aminobenzoate (1.05 g), triethylamine (7.02 mL) and methylene chloride (30 mL) was added titanium (IV) chloride (829 μL), and the mixture was stirred under argon atmosphere at room temperature for 3 days. Saturated aqueous sodium hydrogen carbonate solution was added to quench the reaction, methylene chloride was evaporated in an evaporator, and the residue was extracted with ethyl acetate. The extract was washed with saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure to give a dark brown oil. To a solution (30 mL) of the obtained oil in tetrahydrofuran were added acetic acid (721 μL) and sodium cyanoborohydride (792 mg), and the mixture was stirred at room temperature for 1 hr. Saturated aqueous sodium hydrogen carbonate solution was added to quench the reaction, the organic solvent was evaporated in an evaporator, and the residue was extracted with ethyl acetate. The extract was washed with saturated brine, dried over magnesium sulfate, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (0-30% ethyl acetate/hexane) to give the title object compound (1.56 g, 65%) as an orange solid.

Provenance & Evidence