Journal of the American Chemical Society, Vol.140, No.11, 3858-3862, 2018
N-Alkynylpyridinium Salts: Highly Electrophilic Alkyne-Pyridine Conjugates as Precursors of Cationic Nitrogen-Embedded Polycyclic Aromatic Hydrocarbons
We achieved the first synthesis of N-alkynylpyridinium salts, by reacting pyridines with alkynyl-lambda(3)-iodanes. The N-alkynylpyridiniums exhibit highly electron-accepting character with extended, pi-conjugation. The electrophilic alkynyl groups were readily susceptible to Michael addition and 1,3-dipolar cyclo-addition to afford various N-alkenylpyridiniums. Ring fused pyridiniums were synthesized through intramolecular cyclization, demonstrating the utility of N-alkynylpyridiniums for the design of various electron-deficient cationic nitrogen-embedded polycyclic aromatic hydrocarbons with unique optical and electrochemical properties.