Patent ID: 7227024

Claim:
A process for the manufacture of 5-methoxy-2-[[(4-methoxy-3,5-dimethyl -2-pyridinyl)-methyl]-thio]-1H-benzimidazole of formula I, the process comprising the following reaction steps carried out in a consecutive order in a single solvent system without isolation of the intermediates formed during the process: a) reacting (4-methoxy-3,5-dimethyl-2-pyridinyl)methyl alcohol (pyrmethyl alcohol) of formula Ia, with a chloro-dehydroxylating agent to obtain (4-methoxy-3,5-dimethyl-2-pyridinyl)methyl chloride (pyrmethyl chloride) of formula Ib; and b) reacting the (4-methoxy-3,5-dimethyl-2-pyridinyl)methyl chloride of formula Ib with 2-mercapto-5-methoxybenzimidazole (metmercazole) of formula Ic, in the presence of a base to obtain 5-methoxy-2-[[(4-methoxy-3,5-dimethyl-2-pyridinyl)-methyl ]thio]-1H-benzimidazole (pyrmetazole) of formula I, wherein the solvent system is the same for the entire reaction sequence, and wherein the solvent system comprises a water-immiscible organic solvent and an amount of water in the range of between 0.3 and 5.5 mg water per ml of the water-immiscible organic solvent.