Modification of Chitosan by Zincke Reaction: Synthesis of a Novel Polycationic Chitosan-Pyridinium Derivative

Fernanda Gonçalves,Rossimiriam Freitas

doi:10.21577/0103-5053.20190135

Abstract

Modification of Chitosan by Zincke Reaction: Synthesis of a Novel Polycationic Chitosan-Pyridinium Derivative

Highlights

Chitosan, a carbohydrate biopolymer composed of β (1 → 4) linked units of N-acetyl-D-glucosamine and D-glucosamine (Figure 1), is classically obtained by the controlled deacetylation of chitin, the second most abundant natural polysaccharide after cellulose.[1]
In special cases,[14] the best choice is the reaction between primary amines with highly electrophilic species, such as pyrylium[19] or Zincke salts (N-2,4-dinitrophenyl-pyridinium salt).[20]
The stage was the treatment of chitosan with 1 equivalent of the Zincke salt in refluxing 1-butanol for 15 h, an ideal condition established by Marazano and co-workers.[20]

Summary

Introduction

A carbohydrate biopolymer composed of β (1 → 4) linked units of N-acetyl-D-glucosamine and D-glucosamine (Figure 1), is classically obtained by the controlled deacetylation of chitin, the second most abundant natural polysaccharide after cellulose.[1]. The most common method to prepare pyridinium salts is the alkylation of the pyridine nitrogen atom with primary alkylating agents by an SN2 reaction.[18] in special cases (for example in the synthesis of N-arylpyridinium or pyridinium salts containing a chiral group which presents a significant risk of racemization during alkylation),[14] the best choice is the reaction between primary amines with highly electrophilic species, such as pyrylium[19] or Zincke salts (N-2,4-dinitrophenyl-pyridinium salt).[20] The latter salt, which may be prepared via SNAr from pyridine and 2,4-dichloronitrobenzene (Scheme 1),[21] is an important starting material for the Zincke reaction.

Modification of Chitosan by Zincke Reaction

Results and Discussion

Conclusions