The present invention relates to ethynyl derivatives of formula Iwherein U is N or CH, R8is hydrogen, halogen, lower alkyl or lower alkoxy； Y is -N(R4)-, -O- or -C(R5R5’)-； wherein R4is hydrogen or lower alkyl and R5/R5’are independently hydrogen, hydroxy, lower alkyl or lower alkoxy； V is -N(R6)- or -C(R7R7’), wherein R6is hydrogen or lower alkyl and R7/R7’are independently from each other hydrogen, lower alkyl, CH2-lower alkoxy or may form together with the carbon atom to which they are attached a C3-C6-cycloalkyl； R1is phenyl or heteroaryl, which are optionally substituted by halogen, lower alkyl or lower alkoxy； m is 0 or 1； in case m is 1, R3/R3’are independently from each other hydrogen, lower alkyl, CH2-lower alkoxy or may form together with the carbon atom to which they are attached a C3-C6-cycloalkyl； n is 0 or 1； in case n is 1, R2/R2’are independently from each other hydrogen, lower alkyl, CH2-lower alkoxy or may form together with the carbon atom to which they are attached a C3-C6-cycloalkyl； or if m is 1 and n is 0, R3and R7may form together with the carbon atoms to which they are attached a C4-6-cycloalkyl； or if m is 1 and n is 1, R2and R3or R3and R7may form together with the carbon atoms to which they are attached a C4-6-cycloalkyl； 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).本發明係關於式I之乙炔基衍生物其中U 係N或CH，R8係氫、鹵素、低碳烷基或低碳烷氧基；Y 係-N(R4)-、-O-或-C(R5R5')-；其中R4係氫或低碳烷基且R5/R5'獨立地係氫、羥基、低碳烷基或低碳烷氧基；V 係-N(R6)-或-C(R7R7')，其中R6係氫或低碳烷基且R7/R7'彼此獨立地係氫、低碳烷基、CH2-低碳烷氧基或可與其所附接之碳原子一起形成C3-C6-環烷基；R1係苯基或雜芳基，其視情況由鹵素、低碳烷基或低碳烷氧基取代；m 係0或1；倘若m係1，則R3/R3'彼此獨立地係氫、低碳烷基、CH2-低碳烷氧基或可與其所附接之碳原子一起形成C3-C6-環烷基；n 係0或1；倘若n係1，則
