Three-Component Approach to Pyridine-Stabilized Ketenimines for the Synthesis of Diverse Heterocycles

Ketenimines
are versatile synthetic intermediates capable of performing
novel transformations in organic synthesis. They are normally generated in situ due to their inherent
instability and high level of reactivity. Herein, we report pyridine-stabilized
ketenimine zwitterionic salts, which are prepared through click chemistry
from readily accessible alkynes and sulfonyl azides. To demonstrate
their synonymous reactivity to ketenimines, these salts have been
utilized in a cascade sequence to access highly functionalized quinolines
including the core structures of an antiprotozoal agent and the potent
topoisomerase inhibitor Tas-103.