Continuous-Flow Approach for the Multi-Gram Scale Synthesis of C2-Alkyl- or β-Amino Functionalized 1,3-Dicarbonyl Derivatives and Ondansetron Drug Using 1,3-Dicarbonyls
Continuous-flow chemistry is a modern technology that encompasses the green chemistry principles for the multi-gram synthesis of various API and drugs. Herein, we have developed a highly efficient and environmentally benign metal-free alkylation of 1,3-dicarbonyl compounds using secondary alcohols in the presence of inexpensive Amberlyst®-15 under continuous-flow. This method is broad substrate scope with variety of secondary alcohols and water as a byproduct. The Amberlyst®-15 is recyclable and reusable for the alkylation reaction under batch/continuous-flow technology. Furthermore, a continuous-flow technology driven Mannich reaction is demonstrated under acid free condition. Besides, a continuous-flow Fischer indole strategy for the ondansetron with an improved yield is demonstrated. Additionally, all these reactions were demonstrated with multi-gram scale synthesis without lowering the yield under batch/continuous-flow technology.