A Multicomponent-Cascade Reaction for the Synthesis of Substituted 1,2,3-Triazoles

Triazoles are the most important heterocyclic compounds with a wide range of applications. Substituted 1,2,3-triazoles show high dipole moments, strong hydrogen bonds, and dipole-dipole interactions. These compounds have been extensively used in the fields of various materials, biology and medicine, like spacers to conjugate with biomacromolecules and linkers to multi-target drugs and pharmacophores. Substituted 1,2,3-triazoles include 1,4-disubstituted, 1,5-disubstituted, 4,5-disubstituted and 1,4,5-trisubstituted 1,2,3-triazoles. Well-known synthetic methods include copper-catalyzed cycloaddition of azides to alkynes that selectively forms 1,4-disubstituted 1,2,3-triazoles and a ruthenium-catalyzed process that gives rise to 1,5-disubstituted triazole rings through cycloaddition of azides to alkynes. Non-alkyne substrates have also been successfully employed in constructing functionalized triazoles. These non-alkyne substrates include carbonyl compounds like chalcones, arylacetones, deoxybenzoins, allyl ketones, and α- thioketones. Moreover, sustainable synthetic processes are demanded in modern organic synthesis and manufacturing industry. Multicomponent one-pot reactions are green synthetic methodologies due to reducing operative steps and wastes, decreasing purification procedures, and enhancing synthetic efficiency. In view of the compatibility of sequential reactions, it is not easy to efficiently, regioselectively, and chemoselectively construct cyclo-compounds with multicomponent one-pot reaction. This chapter describes the synthetic methodologies documented for substituted 1,2,3-triazoles with a multicomponent reaction, including one-pot four-component reaction, one-pot three-component reaction; classical and oxidative synthetic processes; terminal alkynes, internal alkynes, non-alkynes, organoazides, sodium azide, and sulfur and selenium powder substrates; regioselectively-substituted, fullysubstituted, cyclo, and thio-, seleno-, and amino-functionalized 1,2,3- triazole products.