1,1-dibenzyl-4-((5,6-dimethoxy-1-oxo-2,3-dihydro-1H-inden-2-yl)methyl)piperidin-1-ium chloride,1,1-dibenzyl-4-((5,6-dimethoxy-1-oxo-2,3-dihydro-1H-inden-2-yl)methyl)piperidin-1-ium chloride,Impurity in commercial preparations of Donepezil.,Donepezil Impurity