An unexpected rearrangement that disassembles alkyne moiety through formal nitrogen atom insertion between two acetylenic carbons and related cascade transformations: new approach to Sampangine derivatives and polycyclic aromatic amides.

This work analyzes multiple new reaction pathways which originate from intramolecular reactions of activated alkynes with the appropriately positioned multifunctional hemiaminal moiety. Combination of experimental substituent effects with Natural Bond Orbital (NBO) analysis revealed that alkyne polarization controls partitioning between these cascades. A particularly remarkable transformation leads to the formation of six new bonds at the two alkyne carbons due to complete disassembly of the alkyne moiety and formal insertion of a nitrogen atom between the two acetylenic carbons of the reactant. This reaction offers a new synthetic approach for the preparation of polycyclic aromatic amides with a number of possible applications in molecular electronics. Another of the newly discovered cascades opens access to substituted analogues of Sampangine alkaloids which are known for their antifungal and antimycobacterial activity against AIDS-related opportunistic infection pathogens.