Patent ID: 8552195

Claim:
A method for making donepezil comprising: mixing (E)-2-((1-benzylpiperidine-4-yl)methylene)-5,6-dimethoxy-2,3-dihydro-1H-inden-1-one (hereinafter “E2M”), an organic solvent, a weak base, sodium dithionite, and a phase transfer catalyst to obtain an E2M mixture solution; heating the E2M mixture solution and adding water to obtain a heated E2M aqueous solution having an organic layer; and extracting the organic layer from the heated E2M aqueous solution, and condensing and drying the organic layer to obtain donepezil; wherein the weak base is sodium hydrogen carbonate, the phase transfer catalyst is tetrabutylammonium bromide; and the organic solvent is selected from the group consisting of: (a) methylbenzene, wherein the molar ratio of E2M:sodium hydrogen carbonate:sodium dithionite:tetrabutylammonium bromide is 1:18:9:0.5; (b) ethyl acetate, wherein the molar ratio of E2M:sodium hydrogen carbonate:sodium dithionite:tetrabutylammonium bromide is 1:6:2:0.5; and (c) isobutanol, wherein the molar ratio of E2M:sodium hydrogen carbonate:sodium dithionite:tetrabutylammonium bromide is 1:12:2:0.5.