Synonyms: 3-Ethyl-2-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-α]pyrimidin-4-one (Risperidone Impurity);3-Ethyl-6,7,8,9-tetrahydro-2-methyl-4H-pyrido[1,2-α]pyrimidin-4-one;Risperidone Impurity;3-Ethyl-2-methyl-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidin-4-one(Risperidone Impurity);3-Ethyl-6,7,8,9-tetrahydro-2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one