the present invention relates to phosphodiesterase type 4 , phosphodiesterase type 7 and dual pde type 4 / pde type 7 inhibitors . compounds disclosed hereinf having the structure of formula i : can be useful in the treatment , prevention , inhibition or suppression of cns diseases , for example , multiple sclerosis ; various pathological conditions such as diseases affecting the immune system , including aids , rejection of transplant , auto - immune disorders such as t - cell related diseases , for example , rheumatoid arthritis ; inflammatory diseases such as respiratory inflammation diseases including chronic obstructive pulmonary disease , asthma , bronchitis , allergic rhinitis , adult respiratory distress syndrome and other inflammatory diseases including but not limited to psoriasis , shock , atopic dermatitis , eosinophilic granuloma , allergic conjunctivitis , osteoarthritis ; gastrointestinal inflammation diseases such as crohn &# 39 ; s disease , colitis , pancreatitis as well as different types of cancers including leukaemia ; especially in humans . processes for the preparation of disclosed compounds , pharmaceutical compositions containing the disclosed compounds and their use as pde type 4 , pde type 7 and dual pde t e 4 / pde t e 7 inhibitors are rovided .