p-Toluenesulfonic acid → 1-(2-bromo-pyridin-4-yl)-1H-benzoimidazole-5-carboxylic acid methyl ester

Participants

Reaction Conditions

Reaction Steps

3-Amino-4-(2-bromo-pyridin-4-ylamino)-benzoic acid methyl ester 4 (3 g; 9.3 mmol) was dissolved in 50 ml dry THF and added trimethyl orthoformate (1.4 ml; 13.9 mmol) and p-toluenesulphonic acid (1 g), the reaction mixture was heated to 60° C. for 6 h. LCMS showed almost complete conversion and the reaction was quenched with sodium bicarbonate and extracted with EtOAc (500 ml*3). The organic layer was washed with water and brine. Finally it was dried over sodium sulphate and concentrated in vacuo to give the expected product 5. The compound was pure enough for progress into the next step as seen by NMR and HPLC.

Provenance & Evidence