Aprotic Heterocyclic Anion Triazolide Ionic Liquids - A New Class of Ionic Liquid Anion Accessed by the Huisgen Cycloaddition Reaction

Abstract

The triazole core is a highly versatile heterocyclic ring which can be accessed easily with the Cu(I)-catalyzed Huisgen cycloaddition reaction. Herein we present the preparation of ionic liquids that incorporate a 1,2,3-triazolide anion. These ionic liquids were prepared by a facile procedure utilizing a base-labile pivaloylmethyl group at the 1-position, which can act as precursors to 1H-4-substituted 1,2,3-triazole. These triazoles were then subsequently converted into ionic liquids after deprotonation using an appropriate ionic liquid cation hydroxide. The densities and thermal decompositions of these ionic liquids were measured. These novel ionic liquids have potential applications in gas separations and in metal-free catalysis.

Synthesis of N-unsubstituted 1,2,3-triazoles via a cascade including propargyl azides, allenyl azides, and triazafulvenes

“…[1][2][3][4][5][49][50][51] This leads to a single set of (broad) NMR signals for NH-1,2,3-triazoles and excludes the possibility to separate and isolate the tautomers at ambient temperature. 52,53 We also obtained a single set of broad 13 C NMR signals for the carbon atoms C-4 and C-5 in each case of 5a-o and did not receive any hint that separation of the tautomers can be achieved at room temperature. Nevertheless, isolation of such tautomers by liquid column chromatography at ambient temperature was recently claimed for several NH-1,2,3-triazoles, including 5a and 5k, without any comment on the usually (very) rapid equilibration and any citation of the corresponding previous investigations.…”

“…In the case of very volatile nucleophiles like ammonia, methylamine, or dimethylamine, the second step has to be performed in an autoclave to avoid early loss of NuH. Alternatively, lower temperatures (50-60 °C) and longer reaction times can be used (entries [11][12][13]. When heated in the presence of organic azides, unsaturated compounds, such as allyl and propargyl alcohols, can undergo unwanted 1,3-dipolar cycloaddition to generate disubstituted 1H-1,2,3-triazoles.…”

“…1 H NMR spectra were recorded on Varian Gemini 2000 or Unity Inova 400 spectrometers operating at 300 and 400 MHz, respectively. Using the same spectrometers, 13 C NMR data were achieved at 75.4 and 100 MHz. NMR signals were referenced to TMS (δ = 0) or solvent signals and recalculated relative to TMS.…”

“…NMR signals were referenced to TMS (δ = 0) or solvent signals and recalculated relative to TMS. The multiplicities of 13 C NMR signals were determined with the aid of DEPT135 experiments. MS spectra were measured on a MS9 spectrometer from AEI/Manchester.…”

“…Thus, their synthesis requires special azides and a sequence involving cycloaddition and deprotection steps. [12][13][14][15][16] Alternatively, NH-1,2,3-triazoles are available by treating alkynes with electron-withdrawing substituents, such as propynals, with sodium azide. 17,18 Other routes include starting compounds, which are quite different to alkynes, for example, β-nitrostyrenes, 19-21 1-bromo-1-alkenes, 22 3-aryl-2,3-dibromopropanoic acids, 23,24 α-haloacrylates, 25 α-chloroacrylonitriles, 25 or 1-substituted 5-amino-1H-1,2,3-triazoles 26,27 (Dimroth rearrangement).…”