The invention relates to imidazo[2,1-b]thiazol-3-one derivatives of formula wherein the variables are defined herein, or to a pharmaceutically acceptable acid addition salt, to a racemic mixture or to its corresponding enantiomer and/or optical isomers thereof. It has been shown that the present compounds may be used for binding and imaging tau aggregates and related b-sheet aggregates including besides others beta-amyloid aggregates or alpha-synuclein aggregates, especially for use in binding and imaging tau aggregates in Alzheimers patients.
