Synthesis of Poly-Functionalized Indolizines via [5+1] Annulative Access to Pyridines

Multi-functionalization of the pyridine motif of indolizine was achieved through [5+1] annulative construction of pyridine from 2-hydroxyacetophenone and pyrrole derivative in the presence of Cs2CO3. The reaction is proposed to take place via domino aldol-oxa Michael-Michael-elimination-oxidation procedure, leading to installation of three different functional groups at the C5, C6, and C7 positions of indolizines. Solvent (2-MeTHF) and the hydroxyl of 2-hydroxyacetophenones seemed to play crucial roles for this successful cyclization event. Further elaboration of the resulting scaffold and expansion of this protocol using other methyl ketones were demonstrated as well.

Automated summary

The study successfully achieved multi-functionalization of the pyridine motif in indolizine through [5+1] annulative construction, introducing three different functional groups at the C5, C6, and C7 positions. The solvent (2-MeTHF) and the hydroxyl of 2-hydroxyacetophenones were found to play crucial roles in the successful cyclization event. Furthermore, the elaboration of the resulting scaffold and the potential expansion using other methyl ketones were also demonstrated.