The present invention relates to ethynyl derivatives of formula I wherein Y is N or C-R3； and R3 is hydrogen, methyl, halogen or nitrile； R1 is phenyl or pyridinyl, which are optionally substituted by halogen, lower alkyl or lower alkoxy； R2/R2’ are independently from each other hydrogen, lower alkyl or lower alkyl substituted by halogen, or R2 and R2’ may form together with the N-atom to which they are attached a morpholine ring, a piperidine ring or an azetidine ring, which are unsubstituted or substituted one or more substituents selected from lower alkoxy, halogen, hydroxy or methyl； R4/R4’ are independently from each other hydrogen or lower alkyl, or R4 and R4’ form together a C3-5 cycloalkyl-, tetrahydrofuran- or an oxetane-ring； or to a pharmaceutically acceptable 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).本發明係關於式I之乙炔基衍生物：其中Y N或C-R3；R3係氫、甲基、鹵素或腈；R1 苯基或吡啶基，其視需要經鹵素、低碳數烷基或低碳數烷氧基取代；R2/R2' 互獨立地為氫、低碳數烷基或經鹵素取代之低碳數烷基，或R2及R2'可與其等所鍵接之N原子一起形成嗎啉環、哌啶環或氮雜環丁烷環，其等係未經取代或經一或多個選自低碳數烷氧基、鹵素、羥基或甲基之取代基取代；R4/R4' 互獨立地為氫或低碳數烷基，或R4及R4'一起形成C3-5環烷基環、四氫呋喃環或環氧丙烷環；或關於其醫藥上可接受的酸加成鹽、外消旋混合物、或其相應的對映異構體及/或光學異構體及/或立體異構體。現已令人驚訝地發現該等通式I化合物係代謝型麩胺酸受體亞型5(mGluR5)之正向立體異位調節劑(PAM)。
