Organocatalyzed One-Step Synthesis of Functionalized N-Alkyl-Pyridinium Salts from Biomass Derived 5‑Hydroxymethylfurfural

An efficient and scalable method has been developed for the synthesis of N-alkylpyridinium salts from biomass derived 5-hydroxymethyl­furfural and alkyl amines using a catalytic amount of formic acid. This protocol is also extended to various diamines providing the exclusive formation of mono-N-alkylpyridinium salts. In addition, the mechanism for the formation of pyridinium salts was studied by DFT and using H218O isotope labeled experiments showing no incorporation of 18O in the product.