Multi‐Gram Scale Synthesis of 1,2,3‐Triazolium Ionic Liquids and Assay of Their Resistance towards Bases

Abstract

An easily upscalable synthesis method for 1,2,3‐triazolium ionic liquids is presented. Several ionic liquids were synthesized and characterized. The influence of the side chain structure on the base‐stability was investigated. One example, functionalized with linear alkyl side chains, was found to exhibit excellent stability against hot concentrated NaOH solutions and Grignard reagents.

Basic ionic liquids for catalysis: the road to greater stability

“…30,31 This is aided by attaching bulky or electron donating groups to the phosphonium centre. 27,29,30,31,32 Alternatives such as triazolium, 33 pyrazolium, 34 phosphonium, and cyclic ammonium (such as pyrrolidinium) 22 cations ( Figure 1) are often more stable to basic conditions, and are therefore more appropriate for the preparation of basic ionic liquids. Base stability is demonstrated by resistance to strong bases, 22,29,33, electrochemical stability, 34 and resistance of the cation to being reduced.…”

“…27,29,30,31,32 Alternatives such as triazolium, 33 pyrazolium, 34 phosphonium, and cyclic ammonium (such as pyrrolidinium) 22 cations ( Figure 1) are often more stable to basic conditions, and are therefore more appropriate for the preparation of basic ionic liquids. Base stability is demonstrated by resistance to strong bases, 22,29,33, electrochemical stability, 34 and resistance of the cation to being reduced. 20 Hofmann elimination of an acyclic ammonium cation (b), 22 ring opening decomposition of a pyridinium cation (c), 23,24 and formation of a phosphine oxide (d) 25,26 and phosphorus ylide (e) 27 from a phosphonium ionic liquid.…”

Triazolization of Enolizable Ketones with Primary Amines: A General Strategy toward Multifunctional 1,2,3‐Triazoles

“…Following these interesting results, a gram‐scale procedure for the synthesis of the tetrasubstituted 1,2,3‐triazolium ionic liquids 23 was developed (Scheme 7). [51] Aiming to avoid chromatographic purification, the triazolization reaction was carried out with 4‐azidobenzoic acid 21 instead of 4‐nitrophenyl azide 3 . This allowed for the purification of the desired 1,4,5‐trialkyl‐1,2,3‐triazoles 22 via simple washings with alkaline aqueous solutions.…”

“…In the years after the first report, the procedure has been adapted in order to broaden the scope with respect to the amines and ketones [46–49] . Moreover, triazolization products found applicability in the large‐scale preparation of triazolium‐based ionic liquids, [50,51] in several cyclization strategies [52–55] and as potential antiviral or anticancer agents [56–59] . In this highlight, the triazolization reaction along with its modifications will be discussed.…”

One-pot synthesis of symmetric imidazolium ionic liquids N,N-disubstituted with long alkyl chains

“…9,15,16 In spite of the importance of green scalable synthetic procedures for ionic liquids production, advanced synthetic procedures are only lately surfacing. [17][18][19][20][21][22][23][24] For example, imidazolium ionic liquids synthesis is generally carried out via a Menshutkin reaction between an N-alkyl imidazole and an alkyl halide (Scheme 1). Quarternisation is usually attained via a bimolecular nucleophilic substitution (S N 2) between an imidazole and an alkylation agent (oen an alkyl halide), which results in the formation of an imidazolium salt.…”