The present invention relates to ethynyl derivatives of formulawherein X is N or C-R1； Y is N or C-R2； Z is CH or N； R4 is a 6-membered aromatic substituent containing 0, 1 or 2 nitrogen atoms, optionally substituted by 1 to 3 groups, selected from halogen, lower alkyl, lower alkoxy or NRR’； R1 is hydrogen, lower alkyl, lower alkoxy, hydroxy, lower hydroxyalkyl, lower cycloalkyl or is heterocycloalkyl optionally substituted with hydroxy or alkoxy； R2 is hydrogen, CN, lower alkyl or heterocycloalkyl； R and R’ are independently from each other hydrogen or lower alkyl； or to a pharmaceutically acceptable salt or acid addition salt, to a racemic mixture, or to its corresponding enantiomer and/or optical isomer and/or stereoisomer thereof.It has now surprisingly been found that the compounds of general formula I are positive allosteric modulators (PAM) of the metabotropic glutamate receptor subtype 5 (mGluR5) and they are therefore useful for the treatment of diseases related to this receptor.本發明係關於下式之乙炔基衍生物：其中X 為N或C-R1；Y 為N或C-R2；Z 為CH或N；R4 為含0、1或2個氮原子之6-員芳族取代基，其視情況經1至3個選自鹵素、低碳數烷基、低碳數烷氧基或NRR'之基團取代；R1 為氫、低碳數烷基、低碳數烷氧基、羥基、低碳數羥烷基、低碳數環烷基，或為視情況經羥基或烷氧基取代之雜環烷基；R2 為氫、CN、低碳數烷基或雜環烷基；R與R'彼此獨立地為氫或低碳數烷基；或其醫藥可接受鹽或酸加成鹽，外消旋混合物，或其對應之對映異構體及/或光學異構體及/或其立體異構體。現已驚訝地發現，通式I之化合物為代謝型麩胺酸受體亞型5(mGluR5)之正向異位調節劑(PAM)，且彼等因此適於治療與此受體相關之疾病。
