Iridium-Catalyzed Synthesis of Chiral 1,2,3-Triazoles Units and Precise Construction of Stereocontrolled Oligomers

Abstract

Iridium-catalyzed azide-thioalkyne cycloaddition reaction (IrAAC) has proved to be a powerful tool for the synthesis of fully substituted 1,2,3-triazole compounds with exclusive regioselectivity. Here we report its successful use in the precise construction of stereocontrolled oligomers that have great potential in diverse applications. Starting with the azide derived from L-prolinol and different functionalized thioalkynes, chiral 1,2,3-triazole units were fabricated with high efficiency under the IrAAC condition, which were further assembled into stereocontrolled oligotriazoles through metal-free exponential growth strategies. The structure and uniformity of these oligomers were well identified by 1H NMR, size-exclusion chromatography, and mass spectrometry, the stereoregularity of which were studied through circular dichroism and circular polarized luminescence analysis.

Catalytic enrichment of oligothioalkynes: expanding horizons for functionalized oligotriazole synthesis through IrAAC-mediated post-modification

“…Recently, we have spearheaded the precise synthesis of macromolecules featuring 1,4,5-trisubstituted triazole units through growth strategies centered around the regiospecific iridium-catalyzed cycloaddition of organic azides with internal thioalkynes (IrAAC, Scheme 1b). 23–30 The success to achieve them, coupled with the robust capability of IrAAC showcased in these synthetic processes, inspired us to envisage the fabrication of discrete oligomers based on fully substituted triazoles in one facile and diverse fashion, which could be achieved by initially assembling thioalkyne monomers into oligothioalkynes, followed by the subsequent embellishment of diverse functionalized organic azides using IrAAC, thus leading to a multitude of oligotriazoles with substantial flexibility in their side chains for different materials properties (Scheme 1c). In addition, by strategically designing terminal groups, these uniform fragments can be extended or coupled to generate oligomers with more intricate structures and functionalities.…”