An Expeditious and Greener Synthesis of 2-Aminoimidazoles in Deep Eutectic Solvents

Abstract

Abstract:A high-yield one-pot two-step synthesis of 2-aminoimidazoles (2-AI), exploiting an under-air heterocyclodehydration process between α-chloroketones and guanidine derivatives, and using deep eutectic solvents (DESs) as nonconventional, "green" and "innocent" reaction media, has been accomplished successfully. The combination of either glycerol or urea with choline chloride (ChCl) proved to be effective for decreasing the reaction time to about 4-6 h in contrast to the 10-12 h usually required for the same reaction run in toxic and volatile organic solvents and under an argon atmosphere. In addition, the use of the ChCl-urea as a DES also enables the direct isolation of triaryl-substituted 2-AI derivatives by means of a simple work-up procedure consisting in filtration and crystallization, and allows the recycle of the DES mixture. A plausible mechanism highlighting the potential role played by hydrogen bonding catalysis has also been illustrated.

Streamlined Routes to Phenacyl Azides and 2,5‐Diarylpyrazines Enabled by Deep Eutectic Solvents

“…The role of DESs as catalytic active species has been suggested in several other transformations. [9a], …”

Towards the development of continuous, organocatalytic, and stereoselective reactions in deep eutectic solvents

“…Among the plethora of possible DES mixtures [28–33], based on our previous experience [34–39] and preliminary studies on the physicochemical properties of DES combinations, we decided to focus our attention on the use of a few choline chloride (ChCl)-based eutectic mixtures as reaction media (Table 1) [40]. …”

Synthesis and Applications of 2‐Substituted Imidazole and Its Derivatives: A Review

“…Capua and colleagues have reported green, adept condensation‐mediated reaction run in choline chloride (ChCl)‐urea‐based deep eutectic solvents as an environmentally friendly and nonconventional reaction media for the preparation of 2‐aminoimidazole 27 . They have synthesized 2‐aminoimidazole compound 27 via appropriate chloroketone 25 , guanidine 26 , and triethylamine (TEA) (Scheme ) . Here, authors have noted that deep eutectic solvents components may speed up the reaction time via a hydrogen bonding by activating both the carbonyl group and the guanidine.…”