Synthesis of 1,2-Dialkyl-, 1,4(5)-Dialkyl-, and 1,2,4(5)-Trialkylimidazoles via a One-Pot Method

Abstract

Despite the utility of imidazoles for a wide variety of chemical and biological applications as well as the growing research in imidazolium-based ionic liquids (ILs), synthetic studies and characterization data for N-functionalized imidazole derivatives with substituents present at the C(2) and/or C(4) and/or C(5) positions are generally unreported. Here, we modify our prior method for synthesizing monofunctionalized imidazoles and apply it to the production of a library of 30 di- and trifunctionalized alkylimidazoles using only commodity chemicals and avoiding anhydrous solvents or air/water-sensitive reagents. For all products, purities of >98% could be readily achieved, although yields were lower than in our prior work with imidazole, which may be due to mass transfer limitations and/or increased nucleophilicity of substituted imidazole products. Interestingly, we also observe that, when 4-methylimidazole or 2-ethyl-4-methylimidazole is used as a starting material, two regioisomers are inevitably formed. We employed electronic structural calculations to aid in identifying the chemical shifts and quantifying the relative presence of the regioisomers. In both series of compounds where regioisomers could be formed, the 4-methyl regioisomer was favored. Although the formation of similar regioisomers has been previously noted in the literature, it has perhaps not been fully considered in works related to imidazolium-based ILs.

Recent Advances in the Design of Ionenes: Toward Convergence with High‐Performance Polymers

“…Imidazolium ionenes offer a much more tailorable platform than many other cationic moeities due to the many types of imidazole starting materials that are commercially available and bis(imidazole) compounds that can be readily synthesized . Imidazoles are also typically more convenient to work and more synthetically versatile than amines, pyridines, and especially phosphines . Furthermore, in addition to the Menshutkin reaction, modified Debus–Radziszewski reactions can also be employed to form imidazolium‐based ionenes .…”

Chemical and Physical Absorption of SO2 by N-Functionalized Imidazoles: Experimental Results and Molecular-level Insight

“…We have previously shown that a variety of imidazoles with electron donating groups can be readily synthesized at reasonably large scales with simple chemical reactions using inexpensive starting materials. 49,50 Here we focus on as series of 11 imidazole solvents with electron-donating groups attached to the imidazole ring at the C(2), C(4) and/or C(5) positions ( Figure 1) and the impact of substitutions on the binding strength of SO 2 −imidazole complexes.…”

Imidazole-Based Solvents and Membranes for CO2 Capture Applications

“…[21] Thus, imidazolium cations no longer have this lone pair of electrons available and are incapable of acting as proton acceptors or nucleophiles. [21] Thus, imidazolium cations no longer have this lone pair of electrons available and are incapable of acting as proton acceptors or nucleophiles.…”