Background: ACE2 is a receptor for Corona virus. COVID-19 (coronavirus) is a deadly virus which can enter the human body through 'angiotensin-converting enzyme 2' human cells, hardly damages the respiratory system. On severe infection on these cells make the lungs weaker, results difficulty in breathing and lead to death. We took this major issue as a challenge and planned to synthesize chemical molecules (compounds), particularly pyrazole derivatives, and found good results. We prepared a convenient laboratory and planned according to our work. Aims and Objectives: Cinnamaldehydes prepared by Claisen condensation were made to react with hydrazine hydrate and phenylhydrazine derivatives to afford pyrazoles. Nano-TiO2 was influenced the reactions without using solvents. Green chemistry was employed by microwave irradiation. Comparitive studies with conventional method were done. The synthesised compounds were characterized by Fourier transform infrared (FT-IR), Proton NMR (1H NMR) and elemental analysis. Synthesised compounds were screened against COVID-19 as antiviral agents. Materials and Methods: We reported microwave method for the green synthesis of chemical molecules so that the reactions maintained under microwave irradiation. All the reactions were carried in microwave oven. In-vitro studies by MTT-assay method of synthesized chemical molecules exhibited good potency in inhibiting ACE2 infected human cells. Results: Microwave assisted reactions were completed in very short time compared to Conventional method. More compounds exhibited good inhibitory potency having cytotoxicity concentration (CC50) and effective concentration (EC50) values against COVID-19. Inhibition of ACE2 human cells infected from COVID-19 was determined by MTT method. Some compounds proved as good potent molecules by acting ACE2 human cells receptors against COVID-19. Conclusion: We afforded the Pyrazole molecules by green synthesis proved that these can act as effective drugs for ACE2 infected cells against Covid-19. Microwave method is proved to be an efficient and convenient one for the green synthesis.