An efficient synthesis of the last step key intermediate for telmisartan via Pd-catalyzed carbonylative cyclization

Abstract

The Pd-catalyzed carbonylative cyclization method is adopted for the synthesis of the penultimate intermediate of telmisartan. This highly atom-efficient reaction proceeded smoothly to provide target intermediate 1 with 87% yield under CO pressure (1 MPa) in toluene at 100 °C. Furthermore, the utilization of HNO3/H2SO4 in making benzimidazole 5 and polyphosphoric acid (PPA) in making bis-benzimidazole 7 in the existing processes are avoided.