Substituted pyrazolopyrimidine derivatives of formula (I)wherein Y1, Y2, Y3, Y4represent N or C-, whereby at least two of the groups Y1to Y4denote a carbon atom, R1represents chloro or bromo, R2to R7 represent e.g. hydrogen, methyl or ethyl; and R10and R11independently represent e.g. hydrogen or C1-C6alkyl, are potent mGluR5 modulators and are useful for the prevention of acute and chronic neurological disorders.一種經取代之式(I)吡唑並嘧啶衍生物其中Y1、Y2、Y3及Y4代表N或C,其中Y1至Y4中至少兩個係碳原子;R1代表氯或溴;R2至R7代表例如氫、甲基或乙基;且R10和R11係各別代表例如氫或C1-C6烷基;係有效之mGluR5調節劑且係用於預防急性和慢性神經系統疾病。