Ecofriendly Reductive Amination of a Levulinic Acid Platform Molecule for the Synthesis of 5-Methyl-<i>N</i>-Aryl-Pyrrolidones Exploiting Formic Acid as an LOHC

The unsustainable exploitation of fossil feedstocks for energy and chemical production has led, in the past few years, to the modern energy and environmental crisis, thus stimulating increased awareness in the definition of more sustainable alternatives. Among the transformations of biomass-derived levulinic acid, recognized as one of the top 10 platform molecules, the production of 5-methylpyrrolidinones is of great importance in diverse industrial fields. In this work, we defined a waste-minimized protocol for the production of N-aryl 5-methylpyrrolidinones, aiming both at the synergistic employment of a benign H-source and reaction media and at the optimization of the workup and purification step. The choice of formic acid as the hydrogen carrier and water as the solvent was beneficial for the replacement of gaseous hydrogen typically used in the synthesis of N-aryl 5-methylpyrrolidinones. Moreover, the safety and economic advantages of formic acid as a benign LOHC for this transformation were further confirmed by a comparison, with other H-sources, of the Ecoscale penalty points. The optimized extraction workup protocol allowed an E-factor reduction of 63% compared to a simple filtration for purification method. To further evidence the environmental improvement, Ecoscale was exploited, highlighting the benefits of our process in comparison to available literature protocols.