synthesis of some pyrazolo[3,4-d]pyrimidine and pyrido[2,3-d]pyrimidine derivatives. These compounds were synthesized by the reaction of some substituted pyrazole or pyridine, thiourea and I2 in the presence of MWCNTs-COOH/CdO hybrid (5% mol) in warm water. The assigned structure was further established by CHN analyses, NMR and FT-IR spectra.