Compounds useful for the early diagnosis of malignant tumors, multiple sclerosis, and especially Alzheimer's Disease and related dementias； especially compounds of Formula (I) wherein R1 is selected from the group consisting of hydrogen, cyano, fluoro, iodo, alkyl, and aryl； R2 is selected from the group consisting of hydrogen, alkyl, and aryl； X is selected from the group consisting of CH2, CH2O, oxygen, OCH2, CH2S, SCH2, NH, N-alkyl, and N-aryl； Y is an optional spacer group, absent or selected from the group consisting of oxygen, sulfur, NH, N-alkyl, and N-aryl； and Z is selected from the group consisting of alkyl substituted with cyano, fluoro, or iodo and aryl substituted with cyano, fluoro, or iodo. In a preferred embodiment, R1 and R2 are hydrogen, X is CH2O, Y is absent, and Z is phenyl substituted with fluoro, cyano, or iodo. In some embodiments, Z is more specifically 18F-phenyl or 123I-phenyl or 131I-phenyl. Other compounds are also provided.
