Dicyclohexylcarbodiimide → 3-Cyano-6-methoxy-2-[3-(3-methoxycarbonylphenyl)-[1,2,4]oxadiazol-5-yl]-indole-1-carboxylic acid tert-butyl ester

Participants

Reaction Steps

To a solution of 3-cyano-6-methoxyindole-1,2-dicarboxylic acid 1-tert-butyl ester (474 mg, 1.5 mmol) prepared above, and HOBt (200 mg, 1.5 mmol) in DCE/DMF (10 mL/1 mL), is added DCC (310 mg, 1.5 mmol), followed by 3-(N-hydroxycarbamimidoyl)benzoic acid methyl ester (291 mg, 1.5 mmol). The mixture is stirred at room temperature for 2 h and filtered. The filtrate is collected and the solvent is replaced with chlorobenzene, followed by the heating at 150° C. for 48 h. After cooling to room temperature, the solvent is removed in vacuo and the residue is chromatographed (silica gel, CH2Cl2/EtOAc, 8/2) to furnish the intermediate, 3-cyano-6-methoxy-2-[3-(3-methoxycarbonylphenyl)-[1,2,4]oxadiazol-5-yl]-indole-1-carboxylic acid tert-butyl ester, which is treated with 50% TFA in DCM (10.0 mL) at room temperature for 1 h. After removal of the volatiles in vacuo, the residue is suspended in water and neutralized with K2CO3 to provide the desired product, methyl 3-[5-(3-cyano-6-methoxy-1H-indol-2-yl-)[1,2,4]oxadiazol-3-yl]benzoate, compound 226 (350 mg, 62%).

Provenance & Evidence