Triazolinedione-based Click Reactions in Polymer Science

1,2,4-Triazoline-3,5-dione (TAD) derivatives are characteristically red (or pink) colored heterocyclic compounds, which are well known for their high reactivity towards π-electron rich systems, such as dienes, anthracene, indoles, naphthalenes, etc. via different Diels–Alder, Alder-ene, cycloaddition and electrophilic aromatic substitution (EAS) reactions. Among various other reactive molecules, TAD-based reactions surely deserve special attention due to their efficient orthogonal clicking and the variety of reactions that are possible using such molecules. Besides simple irreversible clicking and post-functionalization, the chemoselective reactivity of TAD with biologically important units like tyrosine and tryptophan present in the amino acids via EAS makes this TAD-click reaction an important tool for bioconjugation with small molecules, peptides, etc. The possibility of reversible TAD-click reactions with selective functionalities like substituted indoles, furans, anthracene and naphthalene makes this chemistry effective for designing various dynamic materials. In this chapter, we provide a brief overview of the different reactions possible with such molecules and their uses in polymer science for desired end applications.