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

An efficient and scalable method has been developed for the synthesis of <i>N-</i>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-<i>N-</i>alkylpyridinium salts. In addition, the mechanism for the formation of pyridinium salts was studied by DFT and using H<sub>2</sub><sup>18</sup>O isotope labeled experiments showing no incorporation of <sup>18</sup>O in the product.