Synthesis of Stereoregular Uniform Oligomers Possessing a Dense 1,2,3-Triazole Backbone

Abstract

Recent remarkable progress of precision polymerization techniques has allowed researchers to synthesize polymers of controlled molecular weight, tacticity, and monomer sequence with narrow distributions. However, it is still a challenging subject to synthesize uniform polymers and oligomers, which possess specific molecular weight, tacticity, and monomer sequence. Utilizing the advantages of t-butyl 4-azido-5-hexynoate (tBuAH), which we designed recently, for the synthesis of uniform polymers and oligomers, uniform oligomers of different stereoregularities possessing a dense 1,2,3-triazole backbone were synthesized using optically active tBuAH precursors by iterative procedures containing azidation, deprotection of the protecting group, and copper­(I)-catalyzed azide–alkyne cycloaddition (CuAAC). The stereoregular uniform oligomers were characterized in the solid state by powder X-ray diffraction (PXRD) and in the solution state by pulse-field-gradient spin-echo (PGSE) NMR, ultraviolet (UV) absorption, and circular dichroism (CD) spectroscopic techniques. While the solubility of stereoregular uniform oligomers was investigated using common organic solvents, gelation was observed for solutions of two octamers of different stereoregularities in some solvents, e.g., toluene, tetrahydrofuran (THF), acetone, and methanol. It is noteworthy that the intermolecular attractive interaction depended on the stereoregularity in aprotic polar solvents, i.e., THF and acetone, presumably because of the different polarities of octamers.

Contrasting thermoresponsiveness of stereoisomers of a dense 1,2,3-triazole polymer carrying amide side chains

“…The starting materials in this study, i.e., the t-butyldimethylsilyl (TBDMS)-protected stereoregular dimers of t-butyl 4-azido-5hexynoate (tBuAH) (1RR and 1RS), were prepared according to our previous report. 75 The TBDMS-protected tBuAH dimer, 1RR (or 1RS), was hydrolyzed with trifluoroacetic acid (TFA) to remove the t-butyl groups. The obtained 2RR (or 2RS) was coupled with N-methylethylamine in the presence of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC), 1-hydroxybenzotriazole (HOBt), and diisopropylethylamine (DIPEA) to yield 3RR (or 3RS).…”

“…S1, ESI †). 74,75 Using the R-and S-isomers of ME precursor, it is possible to synthesize optically-pure stereoregular poly(ME) by CuAAC polymerization of the stereoregular dimers. In this study, we thus synthesized two types of poly(ME) (i.e., isotactic and syndiotactic) by CuAAC polymerization of ME dimers of the R-and R-isomers, and the R-and S-isomers (the RR and RS dimers), respectively, and investigated the LCST-type phase transition behavior of their aqueous solutions.…”

“…S1, ESI†). 74,75 Using the R - and S -isomers of ME precursor, it is possible to synthesize optically-pure stereoregular poly( ME ) by CuAAC polymerization of the stereoregular dimers. In this study, we thus synthesized two types of poly( ME ) ( i.e.…”

Unraveling Dynamic Helicity Inversion and Chirality Transfer through the Synthesis of Discrete Azobenzene Oligomers by an Iterative Exponential Growth Strategy

“…[21] Hashidzume et al synthesized discrete chiral oligomers with a 1,2,3triazole backbone and found that the chiral optical orientation of the precisely synthesized oligomers in the solution state depends on the terminal 1,2,3-triazole moieties rather than the internal structure, and the intensity of CD signals is linearly related to the chain length of the oligomer. [22] The precise self-assembly of chiral polymers using structurally well-defined macromolecular building blocks and the exploration of new chiral transfer mechanisms to expand their applications is an important topic in the research of mainchain azopolymers. This not only provides further theoretical basis for the application of chiral materials, but also provides the possibility to explore the role of chirality in living organisms.…”

Synthesis of an Alternating Polycation with the Dense 1,2,3-Triazole Backbone

“…However, there are fewer examples of sequence-controlled polycations compared to those of sequence-controlled polyanions presumably because of the low tolerance of controlled polymerization systems to cationic species. 2 We have been working on the synthesis of sequencecontrolled polymers by stepwise copper(I)-catalyzed azidealkyne cycloaddition (CuAAC) of 4-azido-5-hexynoic acid (AH) derivatives, 3,4 because CuAAC is a powerful tool for polymer synthesis. 5 Notably, polymers of AH derivatives possess the dense 1,2,3-triazole backbone consisting of many 1,2,3-triazole units linked through a carbon atom.…”