Assembly of 3-Acylaminoindolizines through Domino Reaction of 4-Alkylidene Oxazolones with 2-(Pyridin-2-yl)acetates

A novel domino reaction for synthesizing 3-acylaminoindolizines from 4-alkylidene oxazolones and 2-(pyridine-2-yl)acetates has been developed. Promoted by <i>N</i>-iodosuccinimide and synergistically assisted by FeCl₃ and DABCO, this protocol provides direct access to a diverse array of functionalized indolizines in up to 92% yield. The method features a broad substrate scope (35 examples), high efficiency, operational simplicity, and excellent scalability. A plausible reaction mechanism involving a cascade of spiroannulation, hydrolytic ring-opening, decarboxylation, and oxidative aromatization is proposed.