Efficient Synthesis and Characterization of Novel Substituted 3-Benzoylindolizine Analogues via the Cyclization of Aromatic Cycloimmoniumylides with Electron-deficient Alkenes

Background: Indolizine pharmacophore is known to exhibit various promising pharmacological properties such as analgesic, anticancer, antihistaminic, antidiabetic, anti-inflammatory, antileishmanic, antimicrobial, antimutagenic, antioxidant, antitubercular, antiviral, larvicidal and herbicidal activities. Objective: In the present investigation, it was envisaged to synthesize a series of novel ethyl-7-substituted-3-(4- substituted benzoyl)-2-substituted indolizine-1-carboxylates by employing chromium(IV)oxide as dehydrogenating agent with triethylamine combination. Method: Synthesis of a series of proposed polysubstituted indolizines by employing chromium(IV)oxide as dehydrogenating agent with triethylamine combination. Final compounds were characterized by spectroscopic techniques viz fourier-transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, liquid chromatography- mass spectrometry, elemental analysis and selected title compound diethyl-3-(4- cyanobenzoyl)indolizine-1,2-dicarboxylate by single crystal X-ray method. Results: Aromatic cycloimmoniumylides undergo smooth cyclization with electron-deficient alkenes in the presence of triethylamine and DMF at room temperature to afford intermediates ethyl 7-substituted-2- substituted-3-(4-substituted benzoyl)-1,2,3,8a-tetrahydroindolizine-1-carboxylates, which on dehydrogenation with chromium(IV)oxide to obtain the title compounds ethyl-7-substituted-3-(4-substituted benzoyl)-2- substituted indolizine-1-carboxylates. Conclusion: The research was focused on developing an efficient protocol for the synthesis of a novel series of ethyl 3-substituted benzoyl-7-substituted-2-substituted indolizine-1-carboxylates with suitable pharmacological properties in good to excellent yields.