Open Access

ARTICLE

Acidic Magnetic Biocarbon-Enabled Upgrading of Biomass-Based Hexanedione into Pyrroles

Zhimei Li¹, Kuan Tian², Keping Wang², Zhengyi Li², Haoli Qin^1,*, Hu Li^2,*

1 School of Chemistry and Materials Science, Guizhou Normal University, Guiyang, 550001, China
2 National Key Laboratory of Green Pesticide, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry of Education, State-Local Joint Laboratory for Comprehensive Utilization of Biomass, Center for R&D of Fine Chemicals of Guizhou University, Guiyang, 550025, China

* Corresponding Authors: Haoli Qin. Email: ; Hu Li. Email:

(This article belongs to the Special Issue: Biochar Based Materials for a Green Future)

Journal of Renewable Materials 2023, 11(11), 3847-3865. https://doi.org/10.32604/jrm.2023.030122

Received 23 March 2023; Accepted 19 April 2023; Issue published 31 October 2023

Abstract

Sustainable acquisition of bioactive compounds from biomass-based platform molecules is a green alternative for existing CO₂-emitting fossil-fuel technologies. Herein, a core–shell magnetic biocarbon catalyst functionalized with sulfonic acid (Fe₃O₄@SiO₂@chitosan-SO₃H, MBC-SO₃H) was prepared to be efficient for the synthesis of various N-substituted pyrroles (up to 99% yield) from bio-based hexanedione and amines under mild conditions. The abundance of Brønsted acid sites in the MBC-SO₃H ensured smooth condensation of 2,5-hexanedione with a variety of amines to produce N-substituted pyrroles. The reaction was illustrated to follow the conventional PallKnorr coupling pathway, which includes three cascade reaction steps: amination, loop closure and dehydration. The prepared MBC-SO₃H catalyst could effectively activate 2,5-hexanedione, thus weakening the dependence of the overall conversion process on the amine nucleophilicity. The influence of different factors (e.g., reaction temperature, time, amount of catalyst, molar ratio of substrates, and solvent type) on the reaction activity and selectivity were investigated comprehensively. Moreover, the MBC-SO₃H possessed excellent thermochemical stability, reusability, and easy separation due to the presence of magnetic core-shell structures. Notably, there was no activity attenuation after 5 consecutive catalytic experiments. This work demonstrates a wide range of potential applications of developing functionalized core-shell magnetic materials to construct bioactive backbones from biomass-based platform molecules.

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