[(5 + 1) - 1] Cyclization of Nitroepoxides to Pyridinium 1,4-Zwitterionic Thiolates for the Synthesis of Indolizine Derivatives

The synthesis of indolizine derivatives was achieved through the reaction of pyridinium 1,4-zwitterionic thiolates with a diverse array of 2-methyl-2-nitro-3-aryloxiranes. Subsequent investigations unveiled a synthetic route to indolizines via a stepwise [(5 + 1) - 1] pathway, with unstable pyridothiazines serving as transient intermediates. DFT calculations elucidated that this transformation entails sequential annulation, deacylation, desulfurization, and oxidation steps.