The importance of derivatives of pyrimidines such as pyrazolo, thiazolo and triazolo pyrimidines as biologically active compounds includes their use as antibacterial, antimicrobial , antibacterial, antihypertensive, antileishmanial, and anticonvulsants agents etc. Microwave assisted organic synthesis has proved to be excellent sophisticated tool for the synthesis of organic compounds. Alkylation reactions and condensation reactions are carried out with the said technique successfully in the present work.The synthesis of pyrazolo, thiazolo & triazolo pyrimidines has been successfully carried out with the said technique. The structures were confirmed on the basis of IR and PMR spectral data. The structures were confirmed on the basis of IR and PMR spectral data. The structural formulae when subjected to computer programme PASS, the prediction results are obtained for the synthesized compounds. This has been reported in the present book. The content in the books is highly significant for the researchers and students of synthetic organic chemistry, heterocyclic chemistry, pharmaceutical chemistry, medicinal chemistry as well as computational and combinatorial chemistry.