The present invention relates to ethynyl derivatives of formula I wherein R1 is hydrogen or halogen； R2 is C1-3-alkyl or &mdash；(CH2)n&mdash；O&mdash；CH3； n is 2 or 3； m is 1 or 2； 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 been found that the compounds of general formula I are allosteric modulators of the metabotropic glutamate receptor subtype 5 (mGluR5) with improved properties for the treatment of schizophrenia, cognitive diseases, fragile X syndrome or autism.
