the present invention provides pyrazine derivatives of formula i and pharmaceutically acceptable salts thereof , wherein the designation of r 1 , r 2 , r 3 and r 4 is provided herein . the invention also provides syntheses for preparation of such compounds . the invention further provides methods of use of these compounds and pharmaceutical compositions containing them for treatment and / or prevention of diseases and for manufacture of medicaments . these compounds and pharmaceutical compositions have antioxidative and thrombolytic effects , and thus can be used for the treatment and / or prevention of cerebral stroke caused by ischemia , and used for manufacture of medicaments for the treatment and / or prevention of nervous system diseases caused by excessive amount of radicals and / or thrombosis , infectious diseases , metabolic system diseases , cardiovascular and cerebrovascular diseases , and age - related degenerative diseases .