The present invention relates to compounds of general formula wherein R1 is phenyl, optionally substituted by one or two substituents, selected from 3H, halogen, lower alkyl, di-methyl-amino, NHC(O)-lower alkyl, C(O)O-lower alkyl, lower alkoxy, OC(3H)3, O11CH3, OCH2CH218F, lower alkoxy substituted by halogen, hydroxy, lower alkyl substituted by hydroxy, S-lower alkyl, or by a heterocyclyl group or is benzo[d][1,3]dioxol-5-yl, 2,3-dihydrobenzo[b][1,4]dioxin-6-yl, indolin-2-one, or is heteroaryl, selected from the group consisting of thiophenyl, benzofuranyl, benzothiophenyl, pyrazinyl, or benzothiazolyl R2 is hydrogen, lower alkyl or lower alkyl substituted by halogen R3 is lower alkyl, C(3H)3, 11CH3, lower alkyl substituted by halogen, -(CH2)2-O-lower alkyl substituted by halogen or cycloalkyl or R2 and R3 form together with the N-atom to which they are attach a ring containing -CH2CH2CHRCH2CH2-, -CH2CH2CH2CH2-, -CH2CH2CH2-, -CH2CH2-NR-CH2CH2-, -CH2CH2-O-CH2CH2-, -CH2CH2CHRCH2-, -CH2CHRCH2- or R is hydrogcn, halogen, lower alkyl substituted by halogen or lower alkoxy or to a pharmaceutically acceptable acid addition salt, to a racemic mixture or to its corresponding enantiomer and/or optical isomers thereof.The compounds are suitable as imaging tool, which will improve diagnosis by identifying potential patients with excess of tau aggregates in the brain, which may be likely to develop Alzheimer’s disease.本發明係關於以下通式之化合物其中R1 係苯基,其視情況經一個或兩個選自以下之取代基取代:3H、鹵素、低碳數烷基、二甲基-胺基、NHC(O)-低碳數烷基、C(O)O-低碳數烷基、低碳數烷氧基、OC(3H)3、O11CH3、OCH2CH218F、經鹵素取代之低碳數烷氧基、羥基、經羥基取代之低碳數烷基、S-低碳數烷基,或經雜環基取代;或係苯并[d][1,3]二氧雜環戊烯-5-基、2,3-二氫苯并[b][1,4]二氧雜環己烯-6-基、吲哚啉-2-酮,或係雜芳基,其選自由以下組成之群:噻吩基、苯并呋喃基、苯并噻吩基、吡嗪基或苯并噻唑基;R2 係氫、低碳數烷基或經鹵素取代之低碳數烷基;R3 係低碳數烷基、C(3H)3、11CH3、經鹵素取代之低碳數烷基、經鹵素取代之-(CH2)2-O-低碳數烷基、或環烷基;或R2及R3與其所附接之N原子一起形成含有以下之環:-CH2CH2CHRCH2CH2-、-CH2CH2CH2CH2-、-CH2CH2CH2-、-CH2CH2-NR-CH2CH2-、-CH2CH2-O-CH2CH2-、-CH2CH2CHRCH2-、-CH2CHRCH2-或R 係氫、鹵素、經鹵素取代之低碳數烷基、或低碳數烷氧基;或係關於其醫藥上可接受之酸加成鹽、外消旋混合物、或其相應鏡像異構物及/或光學異構物。該等化合物適合作為成像工具,
