Disclosed is a process for preparing donepezil ((RS)-2-[(1-benzyl-4-piperidyl)methyl]- 5,6-dimethoxy-2,3-dihydroinden-1-one) or a salt thereof, the process comprising reducing a 1-benzyl-4-[( 5,6-dimethoxy-1-indanon-2-yl)methylene]pyridonium halide of formula II wherein X- is chloride or bromide, in the presence of an ionic compound, a solvent, a catalyst and a source of hydrogen, to form donepezil and optionally converting donepezil to the salt thereof. Also disclosed is donepezil prepared by the process, a pharmaceutical formulation comprising donepezil prepared by the process and the use of donepezil prepared by the process in the manufacture of a medicament for the treatment of a diseases treated by a cholinesterase inhibitor such as Alzheimer's disease.
