Terminal Alkynes as One‐Carbon Donors in [5+1] Heteroannulation: Synthesis of Pyridines via Ynimine Intermediates and Application in the Total Synthesis of Anibamine B

Transition-metal-catalyzed [4+2] heteroannulation of α,β-unsaturated oximes and their derivatives with alkynes has been developed into a powerful strategy for the synthesis pyridines. It nevertheless lacks regioselectivity when unsymmetrically substituted are used. We report herein unprecedented polysubstituted pyridines by formal [5+1] two readily accessible building blocks. A copper-catalyzed aza-Sonogashira cross-coupling between β,γ-unsaturated oxime esters terminal affords ynimines, which, without isolation, undergo an acid-catalyzed domino reaction involving ketenimine formation, 6π-electrocyclization aromatization to afford Terminal served as one-carbon donor pyridine core in this transformation. Di- through pentasubstituted complete excellent functional-group compatibility. The first total anibamine B, indolizinium alkaloid potent antiplasmodial activity, was accomplished featuring key step.