NH2OH-mediated lignin conversion to isoxazole and nitrile

Column: Research    Tag: Biomass conversion

Conversion of lignin to aromatic compounds via C–C/C–O bond cleavage has been an attractive but challenging subject in recent years. We herein report the first protocol that converts lignin models and preoxidized lignin to isoxazole and aromatic nitrile. The isoxazole motif is constructed by condensation of β-hydroxyl ketone with hydroxylamine. Magnesium oxide promotes an oximation reaction and an intramolecular condensation. Aromatic nitriles and esters are obtained via Beckmann rearrangement or an acidolysis reaction depending on the selected additive. The hydroxylamine-mediated strategy works well for the preoxidized lignin conversion to aromatic isoxazole, nitrile, and ester monomers with up to 7.6% yield.