C3-Formylation of Pyridines via Streptocyanine Intermediates

Herein we develop a one-pot, multistep strategy for meta-selective C-H formylation of pyridines via streptocyanine intermediates. By combining aromatic nucleophilic addition, ring-opening, formylation, and ring-closing, nicotinaldehyde derivatives were efficiently synthesized. This method overcomes the limitations of traditional Vilsmeier-Haack reactions, offering a mild and versatile approach for functionalizing electron-deficient pyridines.