Concise synthesis of telmisartan via decarboxylative cross-coupling
(Chemical Equation Presented) An efficient synthesis of the angiotensin II receptor antagonist telmisartan is presented involving a decarboxylative cross-coupling of isopropyl phthalate (1) with 2-(4-chlorophenyl)-1,3-dioxolane (2c) as the key step (85% yield). The benzimidazole moiety is constructed regioselectively via a reductive animation-condensation sequence, replacing the previously published route via alkylation of the preformed benzimidazole. The product is obtained in an overall yield of 35% in a convergent synthesis with the longest sequence consisting of eight steps.
Novel processes for preparing a telmisaitan nitrile intermediate (4'-[{2-n-propyl-4- methyI-6-f l-methyJbenzimidazol-2-yl)-benzimidazol- l -yl)-methyl]-biphenyl-2-nitrile) and further converting it to telmisaitan and/or salts thereof are disclosed.
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Page/Page column 8; 39
(2009/03/07)
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