Triethylamine → HCID 57835289, compound

Participants

Reaction Steps

1-((1,1-Dimethylethoxycarbonyl)amino)cyclobutanecarboxylic acid (1.40 g, 6.5 mmol) was dissolved in CH2Cl2 (45 mL) and reacted with TBTU in the presence of Et3N for a period of 30 min to pre-activate the acid. A solution of 4-amino-2-methyl-5-(methylamino)benzoic acid methyl ester 6-8 from Example 6 (1.33 g, 6.85 mmol) in CH2Cl2 (10 mL) was added slowly over a period of 30 min and stirring of the reaction mixture was continued for 20 h. The reaction mixture was concentrated to dryness, and the residue was re-dissolved in AcOH (10.0 mL) and stirred at 70° C. for 2 h to achieve cyclization of the benzimidazole ring. The reaction mixture was concentrated to dryness and the residue was dissolved in EtOAc (˜250 mL), extracted with aqueous saturated NaHCO3 (2×100 mL) and brine (100 mL). The organic layer was dried over anhydrous MgSO4 and evaporated to dryness. The residue was purified by flash column chromatography (using a solvent gradient from 40% to 50% EtOAc in hexane) to obtain the pure 2-(1-tert-butoxycarbonylaminocyclobutyl)-3,6-dimethyl-3H-benzoimidazole-5-carboxylic acid methyl ester 7-1 as a beige solid (1.41 g, 55% yield) and recover some of the unreacted diamino starting material.

Provenance & Evidence