The instant invention provides compounds of formula I which are JAK3 inhibitors. Specifically, the compounds of formula I are pyrrolo[2,3-d]pyrimidine derivative compounds. The instant invention also provides methods of treating JAK-mediated diseases such as rheumatoid arthritis, asthma, COPD and cancer, by administering the pyrrolo[2,3-d]pyrimidine-derivative compounds of formula I.