Synthesis of Imidazole-Based Molecules under Ultrasonic Irradiation Approaches

Imidazole-based compounds are a series of heterocyclic compounds that exhibit a wide range of biological and pharmaceutical activities. However, those extant syntheses using conventional protocols can be time-costly, require harsh conditions, and result in low yields. As a novel and green technique, sonochemistry has emerged as a promising method for organic synthesis with several advantages over conventional methods, including enhancing reaction rates, improving yields, and reducing the use of hazardous solvents. Contemporarily, a growing body of ultrasound-assisted reactions have been applied in the preparation of imidazole derivatives, which demonstrated greater benefits and provided a new strategy. Herein, we introduce the brief history of sonochemistry and focus on the discussion of the multifarious approaches for the synthesis of imidazole-based compounds under ultrasonic irradiation and its advantages in comparison with conventional protocols, including typical name-reactions and various sorts of catalysts in those reactions.

NiO nanocomposites/rGO as a heterogeneous catalyst for imidazole scaffolds with applications in inhibiting the DNA binding activity

Herein, we report a facile approach to synthesize a new highly versatile heterogeneous catalyst by spontaneous aerial oxidation based on nickel oxide nanocomposites immobilized on surface-functionalized reduced graphene oxide sheets. NiO nanocomposite/reduced graphene oxide (rGO-NiO-NC) is a highly efficient, cost-effective, reusable, selective, and eco-friendly nano-catalyst that does not lose any activity even after five reaction cycles. Nickel loading on the rGO-NiO nanocomposite was found to be 3.3 at%, which contributes to the effective and efficient use of rGO-NiO-NCs as a nano-catalyst for the synthesis of imidazole derivatives. Consequently, a series of imidazole derivatives were synthesized, catalyzed by rGO-NiO-NCs, in 60 min with high yields (86% to 96%) under green conditions. Furthermore, the present synthetic methodology was used for the synthesis of highly aromatic imidazole derivatives (B1-B3) whose calf thymus-DNA binding affinities suggest their superior inhibition ability to displace ethidium bromide (EB), which was further confirmed by molecular docking studies. Additionally, the green chemistry matrix of the synthesis reaction was found to be very close to ideal values, such as carbon efficiency (82.32%), E-factor (0.51), atom economy (77.86%), process mass intensity (1.51), and reaction mass efficiency (66.14%).

Cu(I)-Catalyzed Three-Component Cyclization for the Construction of Functionalized Thiazoles

A novel and straightforward strategy for the synthesis of functionalized thiazoles from thioamides, ynals, and alcohols via a copper(I)-catalyzed three-component reaction has been described. Through the formation of new C-S, C-N, and C-O bonds in one pot, it is easy to produce various valuable thiazoles fixed with aryl or heteroaryl groups. In addition, the reaction also exhibits other unique advantages, such as high step economics, good functional group tolerance, and good regioselectivity.