2,3-Dihydro-5,6-dimethoxy-2-[(1-oxido-4-pyridinyl)methyl]-1H-inden-1-one is used in the preparation of 1-benzyl-4-[(5,6-dimethoxy-1-indanon-2-yl)methyl]piperidine. Impurity of Donepezil (D531750); an intermediate as an anti-Alzheimer's agent.