The invention discloses a preparation method for
telmisartan, and belongs to the technical field of pharmaceutical synthesis. The key points of the technical scheme lie in that in the preparation method for the
telmisartan takes
ionic liquid as a reaction medium, and 3-methyl-4-
nitryl-
benzoic acid as a
raw material, 2-n-propyl-4-methyl-6- carboxyl
benzimidazole is obtained successively through an
esterification reaction, a reduction reaction, an
acylation reaction, a nitratlon reaction, a reduction reaction and a cyclization reaction, then under the action of a polyphosphoric acid, the 2-n-propyl-4-methyl-6-carboxyl
benzimidazole and N-methyl-o-phenlenediamine dihydrochloride are condensed to obtain 2-n-propyl-4-methyl-6-[1-methylbenzimidazole-2-yl]
benzimidazole, 2-n-propyl-4-methyl-6-[1-methylbenzimidazole-2-yl] benzimidazole is condensed with 4,-
bromine biphenyl-2-
carboxylic acid methyl ester, and
hydrolysis is carried out to obtain the
telmisartan. According to the method, the
ionic liquid is used for replacing
methanol with larger
toxicity in an original technology to be used as the reaction medium, raw materials are easy to obtain, the operation is simple and convenient, the yield is high, the purity of products is high, the residual quantity of an
organic solvent is small, and the method is environmentally-friendly and is suitable for industrialized production.