Efficient and improved synthesis of Telmisartan

Abstract

An efficient synthesis of the angiotensin II receptor antagonist Telmisartan (1) is presented involving a cross coupling of 4-formylphenylboronic acid 10 with 2-(2-bromophenyl)-4,4-dimethyl-2-oxazoline (11) as the key step (90% yield). The benzimidazole moiety 15 was constructed regioselectively via a reductive amination-condensation sequence, replacing the alkylation of the preformed benzimidazole step in the previously published route. This methodology overcomes many of drawbacks associated with previously reported syntheses.