the present invention relates to a series of substituted dihydro and tetrahydro oxazolopyrimidinones , specifically , to a series of 2 - substituted - 2 , 3 - dihydro - oxazolopyrimidin - 7 - ones and 2 - substituted - 2 , 3 , 5 , 6 - tetra - hydro - oxazolopyrimidin - 7 - ones of formula : wherein p , n , x , y , r 1 , r 2 , r 3 , r 4 , r 5 , r 6 , r 7 and r 8 are as defined herein . this invention also relates to methods of making these compounds including novel intermediates . the compounds of this invention are modulators of metabotropic glutamate receptors , particularly , mglur2 receptor . therefore , the compounds of this invention are useful as pharmaceutical agents , especially in the treatment and / or prevention of a variety of central nervous system disorders , including but not limited to acute and chronic neurodegenerative conditions , psychoses , convulsions , anxiety , depression , migraine , pain , sleep disorders and emesis .