The present invention relates to compounds of general formula wherein R1 is lower alkyl or lower alkyl substituted by halogen R2, R3 are hydrogen or tritium or to a pharmaceutically acceptable acid addition salt..The compounds may be used for binding and imaging tau aggregates and related beta-sheet aggregates including besides others beta-amyloid aggregates or alpha-synuclein aggregates.本發明係關於如下通式之化合物其中R1為低碳數烷基或經鹵素取代之低碳數烷基;R2、R3為氫或氚;或關於醫藥學上可接受之酸加成鹽。該等化合物可用於結合τ聚集體及包括尤其β-類澱粉聚集體之相關β-摺疊聚集體或α-突觸核蛋白聚集體且使其成像。
