| abstract |
The present invention provides a process for the preparation of key intermediate for the synthesis 5,6-dimethoxy-2-[[1-(phenylmethyl)-4-piperidinyl]methyl]-1-indanone hydrochloride (donepezil hydrochloride). The present invention particularly provides a process for the preparation of 5,6-dimethoxy-2-(4-pyridylmethylene)-1-indanone comprising condensation of 5,6-dimethoxy-1-indanone with 4- pyridinecarboxaldehyde using an alkali metal hydroxide as a mild base in the presence of demineralized water as a solvent at a temperature in the range of 15°C to 45°C to yield 5,6-dimethoxy-2-(4-pyridylmethylene)-1-indanone, which is subsequently benzylated using benzyl bromide in the presence of solvent at a reflux temperature to yield 1-benzyl-4-[(5,6-dimethoxy-1-indanone-2-yl)methylene]pyridinium bromide. |