This invention relates to the enantiomers and / or acid addition salt optical isomers, racemic mixtures or its equivalent, or as a pharmaceutically acceptable compound of formula I. The compounds are suitable as an imaging tool, Alzheimers disease to improve the diagnosis by identifying potential patients with excess tau aggregates in the brain that can be developed: [Formula I] Wherein, R 1 is 3 H, halogen, lower alkyl, di-methyl-amino, NHC (O) - lower alkyl, C (O) O-lower alkyl, lower alkoxy , OC ( 3 H) 3 , O 11 CH 3 , OCH 2 CH 2 18 F, substituted by halogen, lower alkoxy, hydroxy, one or two selected from the group consisting of lower alkyl and lower alkyl substituted by hydroxy S- by a substituent, or an optionally substituted phenyl, or by a heterocyclyl, Benzo [d] [1,3] dioxol-5-yl, 2,3-dihydro-benzo [b] [1,4] dioxin-6-yl, or is indoline-2-one, Thiophenyl, benzofuran-yl, benzo thiophenyl, pyrazinyl and benzothiazolyl selected from the group consisting of heteroaryl, and R 2 is hydrogen, lower alkyl or lower alkyl substituted by halogen R 3 is lower alkyl, C ( 3 H) 3 , 11 CH 3 , lower alkyl substituted by halogen, halogen substituted - (CH 2 ) 2 -O- lower alkyl, or is cycloalkyl R 2 and R 3 -CH with the N- atom to which they are attached 2 CH 2 CHRCH 2 CH 2 -, -CH 2 CH 2 CH 2 CH 2 -, -CH 2 CH 2 CH 2 -, -CH 2 CH 2 -NR-CH 2 CH 2 -, -CH 2 CH 2 -O- CH 2 CH 2 -, -CH 2 CH 2 CHRCH 2 -, -CH 2 CHRCH 2 - or form a ring and containing R is hydrogen, halogen, lower alkyl substituted by halogen, or lower alkoxy.본 발명은 하기 화학식 I의 화합물 또는 이의 약학적으로 허용되는 산 부가 염, 라세믹 혼합물 또는 이의 상응하는 거울상이성질체 및/또는 광학이성질체에 관한 것이다. 상기 화합물은 알츠하이머병이 발달할 수 있는 뇌에서 과잉 타우 응집체를 갖는 잠재적인 환자를 확인함으로써 진단을 개선하는 이미징 도구로서 적합하다: [화학식 I]상기 식에서,R1은 3H, 할로겐, 저급 알킬, 다이-메틸-아미노, NHC(O)-저급 알킬, C(O)O-저급 알킬, 저급 알콕시, OC(3H)3, O11CH3, OCH2CH218F, 할로겐으로 치환된 저급 알콕시, 하이드
