Valorization of Mn-Rich Invasive Alien Species as Janus Ecocatalysts for Sustainable N-Heterocyclic Carbene-Catalyzed Transformations

Abstract Water lettuce (Pistia stratiotes), a worldwide invasive alien species (IAS), is presented here for the first time as the source of innovative Janus ecocatalysts. These new ecocatalysts enabled the development of a novel one-pot strategy based on the N-heterocyclic carbene (NHC)-ecocatalyzed oxidative esterification of furfural toward methyl 2-furoate, an increasingly valuable yet challenging platform chemical. Guided by an all-natural approach, the catalytic system relies exclusively on the original combination of ecocatalysts and vitamin B1, as a natural carbene precursor. Careful optimization of the reaction parameters led to high conversion rates and excellent selectivity (yield of 75 ± 11%) in mild conditions with excellent green metrics (e.g., E-factor = 70). Mechanistic investigations and statistical analyses of the ecocatalyst composition associated with their structure highlighted the unique dual oxidative and basic behavior of the ecocatalysts. Remarkably, these catalytic properties remained consistent over seven years of P. stratiotes harvesting, ensuring the reproducibility of the synthetic performances. The scope of the new NHC-ecocatalytic methodology was extended to other aromatic aldehydes, notably enabling the first direct preparation of methyl 5-methyl-2-furoate. Beyond synthetic efficiency, this strategy demonstrates how whole plants of P. stratiotes can be transformed into value-added catalytic materials, offering a green and reproducible synthetic route that supports IAS management.