Selective Utilization of N-acetyl Groups in Chitin for Transamidation of Amines

Yu Xin,Buxing Han,Huizhen Liu,Xiaojun Shen

doi:10.3389/fceng.2020.634983

Abstract

The selective transformation of chitin into various renewable N-containing chemicals and medicines has attracted increasing attention. However, the N-acetyl groups in chitin construct strong hydrogen bond networks, which restricts its depolymerization and transformation. The selective conversion of robust chitin commonly requires considerable base catalysts to remove the N-acetyl group as a byproduct in advance, which is non-compliance with the principle of atomic economy. Herein, for the first time we demonstrate a novel approach to achieve the selective utilization of the N-acetyl group in chitin for transamidation of chitin with amines. A series of amine derivatives, mainly including aliphatic amine, cyclic amine and functionalized aromatic amine, could be selectively converted into the corresponding amide products frequently found in pharmaceuticals. Furthermore, the solid residue after removing the acetyl group (denoted as De-chitin) with the sufficient exposure of -NH2 groups as a solid base catalyst shows excellent performance in the aldol condensation reaction of furfural and acetone to produce fuel precursors. Our process provides a strategy that exploiting every functional group adequately in substrates to obtain value-added chemicals.

Highlights

Chitin, the second most abundant biopolymer on the earth after cellulose, consists of N-acetylglucosamine units with ß-1,4-glycosidic linkages. (Yabushita et al, 2015; Yan and Chen et al, 2015)
Aniline was employed as an amine source to investigate the transamidation reaction between chitin and aniline, and various catalysts were screened for the production of acetanilid at 140°C (Figure 1)
The degree of acetylation (DA) in chitin is 95.4% based on the elemental analysis and the theoretical moles of acetanilid were calculated to 58.5 mg when the amount of chitin substrate is 100 mg (Supplementary Table S1) (Chen et al, 2014)

Summary

INTRODUCTION

The second most abundant biopolymer on the earth after cellulose, consists of N-acetylglucosamine units with ß-1,4-glycosidic linkages. (Yabushita et al, 2015; Yan and Chen et al, 2015). Base catalysts gave remarkable catalytic performance owing to its strong ability to abstract a-protons and active substrate (Ngo et al, 2019) Homogeneous base catalysts, such as NaOH and KOH, were widely employed in the aldol reaction, but showed some disadvantages, mainly involving equipment corrosion, nonrecyclability and complex separation (West et al, 2008; Fakhfakh et al, 2008; Xing et al, 2010; Ramirez-Barria et al, 2016; Gu et al, 2017). The solid residue after transamidation reaction (De-chitin), as a solid base catalyst with exposure of lots of -NH2 groups, exhibited outstanding catalytic activity on aldol condensation of furfural with acetone to produce fuel precursor.

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT