The invention provides certain 3,4-dihydroisoquinolin-2(1H)-yl compounds, particularly compounds of formula I, and pharmaceutical compositions thereof. The invention further provides methods of using a compound of formula I to treat cognitive impairment associated with Parkinson’s disease or schizophrenia.本發明提供某些3,4-二氫異喹啉-2(1H)-基化合物、尤其式I化合物及其醫藥組合物。本發明另外提供使用式I化合物治療與帕金森氏病(Parkinson’s disease)或精神分裂症有關之認知缺損之方法。