Catalytic conversion of lignin into heteroatom functionalized chemicals is of great importance to bring the biorefinery concept into reality. In this talk, new strategies for the direct transformation of lignin β-O-4 model compounds and real lignin into benzylamines and pyrimidines in moderate to excellent yields in the presence of organic amines will be presented. The production of benzylamines from β-O-4 model compounds involves dehydrogenation of C<sub>α</sub>-OH, hydrogenolysis of the C<sub>β</sub>-O bond and reductive amination in the presence of Pd/C catalyst. Experimental data suggest that the dehydrogenation reaction proceeds over the other two reactions and secondary amines serve as both reducing agents and amine sources in the transformation. Moreover, the concept of "lignin to benzylamines" is demonstrated by a two-step process. In another example, pyrimidines synthesis from lignin β-O-4 model compounds mediated by NaOH through a one-pot multi-component cascade reaction will be discussed. Mechanism study suggests that the transformation starts by NaOH-induced C-O bond cleavage of β-O-4 model compounds, and involves highly coupled sequential cleavage of C-O bonds, alcohol dehydrogenation, aldol condensation, and dehydrogenative aromatization. With this protocol, an important marine alkaloid meridianin derivative can be synthesized, emphasizing the application feasibility in pharmaceutical synthesis. The above two cases provide us an unprecedented opportunity for N-containing aromatic compounds synthesis from biorenewable feedstock.

Sustainable production of benzylamines and pyrimidines from lignin

ACS Spring 2022

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