Trans‐N‐alkylation Covalent Exchanges on 1,3,4‐Trisubstituted 1,2,3‐Triazolium Iodides

Abstract

Abstract1,3,4‐Trisubstituted 1,2,3‐triazolium salts having either aliphatic or benzylic substituents at the N‐1 and N‐3 positions were synthesized in two steps involving: i) copper(I) catalyzed azide‐alkyne 1,3‐dipolar cycloaddition (CuAAC), and ii) N‐alkylation of the 1,2,3‐triazole intermediates. Trans‐N‐alkylation reactions in bulk and in the presence of excess methyl iodide were monitored by 1H NMR spectroscopy for each 1,2,3‐triazolium molecular model. By assigning the different formed species and their respective evolution with time, it was possible to conclude that trans‐N‐alkylation exchange reactions are significantly faster for benzylic substituents than for aliphatic ones. Furthermore, the exchange reactions are noticeably faster at the N‐3 position than at the N‐1 position most likely due to the steric hindrance induced by the neighboring C‐4 substituent. The kinetics of trans‐N‐alkylation reactions are thus influenced by both the chemical nature of the N‐1 and N‐3 substituents and the regiochemistry of the 1,2,3‐triazolium group. This provides important structural design rules to improve the properties of thermosetting covalent adaptable networks involving trans‐N‐alkylation of 1,2,3‐triazolium salts.