The    first    parent    compound    N-(7-chloro-5-methyl-1,8-naphthyridine-2- yl)acetamide was reacted with both of ethyl thioglycolate forming ethyl [{7-(acetylamino)-4-methyl-1,8-naphthyridine-2yl} sulfanyl] acetate and ethyl[(-7-amino-4-methyl-1,8- naphthyridine-2yl) sulfanyl] acetate and with thioacetamide to afford N-[5-methyl-7- sulfanyl-1,8-naphthyridine-2-yl] acetamide. The last product was used as an intermediate for the synthesis of different novel mercapto derivatives. The second parent compound 7- amino-2-chloro-4-methyl-1,8-naphthyridine was reacted with several active organic compound (e.g. propanedinitrile, diethylpropanedioate, ethylcyanoacetate and acrylonitrile) forming polyfused naphthyridine derivatives. Additionally, its reaction with phenyl isothiocyanate   forms   1-(7-chloro-5-methyl-1,8-naphthyridine-2-yl)-3-phenylthiourea which in turn reacts with benzylidene- malononitrile to give 6-amino-1-(7-chloro-5-methyl-1,8- naphthyridine-2-yl)-3,4-di-phenyl-2-thioxo-1,2,3,4-tetra-hydropyrimidin-5-carbonitrile