THE PRESENT INVENTION RELATES TO ETHYNYL DERIVATIVES OF FORMULA I WHEREIN X IS N OR C-R, WHEREIN R IS HYDROGEN OR HALOGEN； G IS N OR CH； WITH THE PROVISO THAT MAXIMUM ONE OF G OR X CAN BE NITROGEN； R1 IS PHENYL OR PYRIDINYL, WHICH ARE OPTIONALLY SUBSTITUTED BY HALOGEN； R2 IS HYDROGEN, LOWER ALKYL, HYDROXY, LOWER ALKOXY OR C(O)O-BENZYL； R3, R3’, R4, R4’, R6, R6’ ARE INDEPENDENTLY FROM EACH OTHER HYDROGEN OR LOWER ALKYL； OR R6 AND R4 MAY FORM TOGETHER WITH THE CARBON ATOM TO WHICH THEY ARE ATTACHED A C4-6-CYCLOALKYL RING, IF M IS 0 AND N IS 1 OR 2； R5 IS HYDROGEN OR LOWER ALKYL； N IS 0, 1 OR 2； M IS 0 OR 1； WITH THE PROVISO THAT N AND M ARE NOT SIMULTANEOUSLY 0； 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). THEY MAY BE USED FOR THE TREATMENT OF SCHIZOPHRENIA OR COGNITIVE DISORDERS. (NO SUITABLE FIGURE)
