During recent years significant progress has been made towards the realization of a sustainable and carbon-neutral energy economy. One promising approach is photochemical splitting of H2O into O2 and solar fuels, such as H2. However, the bottleneck in such artificial photosynthetic schemes is the H2O oxidation half reaction where more efficient catalysts are required that lower the kinetic barrier for this process. In particular catalysts based on earth-abundant metals are highly attractive compared to catalysts comprised of noble metals. We have now synthesized a library of dinuclear Mn2(II,III) catalysts for H2O oxidation and studied how the incorporation of different substituents affected the electronics and catalytic efficiency. It was found that the incorporation of a distal carboxyl group into the ligand scaffold resulted in a catalyst with increased catalytic activity, most likely because of the fact that the distal group is able to promote proton-coupled electron transfer (PCET) from the high-valent Mn species, thus facilitating O-O bond formation.

of main observation and conclusion A highly efficient, simple, and clean single-step sonosynthetic procedure has been sophisticated for assembling new series of mono-and bis-pyridine dicarbonitriles from ketones, HCl, and tetracyanoethylene. The presented protocol is applicable for the preparation of a broad range of uniquely substituted pyridine dicarbonitriles and seems to be superior in comparison with other previously reported methods. The antiproliferative impact of the newly synthesized derivatives was screened towards three representative cancer cell lines (MCF-7, A549, and HCT116). Most of the evaluated derivatives showed a moderate to excellent anti-proliferative activity towards the selected cell lines. Of these, compounds 4h, 4k, 10, 12a, and 12b showed both potent anticancer activity (IC50<10 μM) and lower cytotoxic effect (IC50 > 58 μM) on non-tumorigenic cells (MCF-10A and NCM460), suggesting their promising potential to be lead molecules for future antitumor drug discovery. The structure-activity relationships have been also discussed. Moreover, quantum chemical studies based on Density Functional Theory (DFT) of the synthesized compounds were investigated and found to be consistent with the in vitro inhibitory activities. Results and DiscussionPreparation of 6-chloro-[2,2'-bipyridine]-4,5-dicarbonitrile (4a) by treatment of tetracyanoethylene (1, TCNE, 1.0 mmol), and 2-acetyl pyridine (2a, 1.0 mmol) with HCl (3.0 mL) was chosen as the template reaction (Scheme 1) under silent (70 o C) and ultra-502 www.cjc.wiley-vch.de

An eco-compatible pathway to the synthesis of mono and bis-multisubstituted imidazoles over novel reusable ionic liquids: an efficient and green sonochemical process † Wael Abdelgayed Ahmed Arafa * ab Novel and environmentally benign ionic liquids (ILs) comprised of DABCO were successfully synthesized.These ILs were used as robust catalysts for the sonochemical one pot multi-component synthetic route for the functionalized annulated imidazoles in water with excellent yields. The present protocol scored well in terms of yield economy as compared with the conventional procedures. The merits of the current green method include simplicity, applicability, broad functional groups tolerance, clean reaction profiles, and no tedious work-up and they give high-to-quantitative yields. From the environmental viewpoint, these eco-friendly green catalysts can be effortlessly retrieved and reused at least seven successive times without substantial loss in catalytic activity. IntroductionMulticomponent reactions (MCRs) have been demonstrated to be signicantly successful in producing the desired complex products from readily obtainable materials in a single synthetic reaction that comprises three or more substrates.1 The creating of novel MCRs and improving of published MCRs are presently under intensive focus due to their broad scope of applications in modern drug design.2 One of these applications is the assembly of multisubstituted imidazoles. The heterocyclic molecules comprised of an imidazole moiety whether synthetic or naturally occurring exhibit an array of pharmacological activities and play substantial roles in biochemical processes. They are well-known as anti-inammatory agents, P38 MAP kinase inhibitors, fungicides, herbicides, therapeutic and antithrombotic agents.3 As well, imidazole derivatives are employed in photography as photosensitive molecules.4 Moreover, several imidazole derivatives are utilized as IL-1 biosynthesis inhibitors and eclectic antagonists for the glucagon receptors.5 In addition, the skeleton of many drug molecules such as eprosartan and trifenagrel, as well numerous biological compounds such as histamine and histidine, comprise imidazole moieties.6 Applications such as N-heterocyclic carbenes in catalysts design 7 and ILs in green chemistry 8 are some other important merits of the imidazoles derivatives. Recently, the evolution of the synthetic protocols for imidazoles preparation has attracted continued interest among medicinal and organic chemists.9 Among these protocols, the multicomponent cyclocondensation reaction of diverse aldehydes, 1,2-dicarbonyl compounds (benzils or benzoins), and a nitrogen exporter that is widely utilized for the design of multisubstituted imidazole derivatives with alteration of catalysts and parameters. 10Nevertheless, some of these synthetic procedures associated with more than one serious drawback such as acidic media, low yield, long reaction time, formation of by-products and intricate work up and purication. Furthermore, the construction of such hetero...

A series of bis-thioureas was synthesized as viable precursors for the design of bis-2-iminothiazolidin-4-ones utilizing the ultrasonic irradiation as a sustainable energy source.