The continuous production of ondansetron and carbazole derivative drugs in sustainable manner using flow-chemistry technique summary of the proposal: the heterocyclic compounds have pivotal importance owing to their biological activities in drug discovery. hence, these derivatives have received considerable attention from across the scientific comminuty. among all the heterocycle compounds, carbazole is an important privileged scaffold in drug discovery as well as it is found in many biologically active natural products. in particular, ondansetron have 1,2,3,9-tetrahydro-4h-carbazol-4-one as a core moiety and is used to prevent nausea and vomiting caused by cancer chemotherapy, radiation therapy, and surgery. to achieve the synthesis of ondansetron, the construction of carbazole ring and mannich reaction are the key steps. industrial production of ondensetron relies on continuous manufacturing process to fulfil the demand and maintain the low cost.in this context, continuous flow chemistry has emerged in the field of organic synthesis with a significant success. whereas, the batch process is behind the time because of several disadvantages including safety, sustainable and scalability. therefore, this technology has attracted immense attention of pharmaceutical industries. the chemical industries are trying to replace the traditional batch processes with continuous flow processes. to fulfil the demand of drugs in large quantity, continuous flow chemistry can be proven as an emerging technology over the batch. in this proposal, our aim is to develop a novel method for continuous production of ondansetron via fischer indole process and mannich reaction in a tandem manner using heterogeneous catalyst in continuous flow. in addition, other objective is to synthesize indole containing bioactive molecules and drug such as indomethacine. initially, we envision to scale up the fischer indole reaction in continuous flow for the synthesis of carbazole ring using commercially available 1,3-cyclohexadione and phenylhydrazine in the presence of inexpensive and readily available, reusable, nontoxic polymer-based catalyst such as amberlyst-15. the second step, we intend to validation of mannich reaction in continuous flow in solid phase mode using paraformaldehyde. the final step is a nucleophilic substitution of 2-methylimidazole to get ondansetron. finally, the integration of all the three steps in a single line for the continuous production of ondansetron for the on-demand supply. moreover, the above developed methodology for the fischer indole reaction will be investigated for other commercially available drugs and bioactive molecules. the manufacturing of ondansetron using emerging continuous flow technology exhibits great potential for the pharmaceutical industries. fig.1: the structure of the target drugs scheme 1: the proposed transformation for synthesis of ondanasetron under continuous flow