The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
John F Hartwig - One of the best experts on this subject based on the ideXlab platform.
-
regio and enantioselective n allylations of Imidazole benzImidazole and purine heterocycles catalyzed by single component metallacyclic iridium complexes
ChemInform, 2009Co-Authors: Levi M Stanley, John F HartwigAbstract:Highly regio- and enantioselective iridium-catalyzed N-allylations of benzImidazoles, Imidazoles, and purines have been developed. N-Allylated benzImidazoles and Imidazoles were isolated in high yields (up to 97%) with high branched-to-linear selectivity (up to 99:1) and enantioselectivity (up to 98% ee) from the reactions of benzImidazole and Imidazole nucleophiles with unsymmetrical allylic carbonates in the presence of single component, ethylene-bound, metallacyclic iridium catalysts. N-Allylated purines were also obtained in high yields (up to 91%) with high N9/N7 selectivity (up to 96:4), high branched-to-linear selectivity (98:2), and high enantioselectivity (up to 98% ee) under similar conditions. The reactions encompass a range of benzImidazole, Imidazole, and purine nucleophiles, as well as a variety of unsymmetrical aryl, heteroaryl, and aliphatic allylic carbonates. Competition experiments between common amine nucleophiles and the heterocyclic nitrogen nucleophiles studied in this work illustrate the effect of nucleophile pK(a) on the rate of iridium-catalyzed N-allylation reactions. Kinetic studies on the allylation of benzImidazole catalyzed by metallacyclic iridium-phosphoramidite complexes, in combination with studies on the deactivation of these catalysts in the presence of heterocyclic nucleophiles, provide insight into the effects of the structures of the phosphoramidite ligands on the stability of the metallacyclic catalysts. The data obtained from these studies have led to the development of N-allylations of benzImidazoles and Imidazoles in the absence of an exogenous base.
-
regio and enantioselective n allylations of Imidazole benzImidazole and purine heterocycles catalyzed by single component metallacyclic iridium complexes
Journal of the American Chemical Society, 2009Co-Authors: Levi M Stanley, John F HartwigAbstract:Highly regio- and enantioselective iridium-catalyzed N-allylations of benzImidazoles, Imidazoles, and purines have been developed. N-Allylated benzImidazoles and Imidazoles were isolated in high yields (up to 97%) with high branched-to-linear selectivity (up to 99:1) and enantioselectivity (up to 98% ee) from the reactions of benzImidazole and Imidazole nucleophiles with unsymmetrical allylic carbonates in the presence of single component, ethylene-bound, metallacyclic iridium catalysts. N-Allylated purines were also obtained in high yields (up to 91%) with high N9/N7 selectivity (up to 96:4), high branched-to-linear selectivity (98:2), and high enantioselectivity (up to 98% ee) under similar conditions. The reactions encompass a range of benzImidazole, Imidazole, and purine nucleophiles, as well as a variety of unsymmetrical aryl, heteroaryl, and aliphatic allylic carbonates. Competition experiments between common amine nucleophiles and the heterocyclic nitrogen nucleophiles studied in this work illustra...
Abiodun Omokehinde Eseola - One of the best experts on this subject based on the ideXlab platform.
-
Imidazole derivatives as antiparasitic agents and use of molecular modeling to investigate the structure-activity relationship.
Parasitology research, 2020Co-Authors: Oluyomi Stephen Adeyemi, Abiodun Omokehinde Eseola, Winfried Plass, Olubunmi Atolani, Tatsuki Sugi, Yongmei Han, Gaber El-saber Batiha, Kentaro Kato, Oluwakemi Josephine Awakan, Tomilola Debby OlaoluAbstract:Toxoplasmosis is a common parasitic disease caused by Toxoplasma gondii. Limitations of available treatments motivate the search for better therapies for toxoplasmosis. In this study, we synthesized a series of new Imidazole derivatives: bis-Imidazoles (compounds 1-8), phenyl-substituted 1H-Imidazoles (compounds 9-19), and thiopene-Imidazoles (compounds 20-26). All these compounds were assessed for in vitro potential to restrict the growth of T. gondii. To explore the structure-activity relationships, molecular analyses and bioactivity prediction studies were performed using a standard molecular model. The in vitro results, in combination with the predictive model, revealed that the Imidazole derivatives have excellent selectivity activity against T. gondii versus the host cells. Of the 26 compounds screened, five Imidazole derivatives (compounds 10, 11, 18, 20, and 21) shared a specific structural moiety and exhibited significantly high selectivity (> 1176 to > 27,666) towards the parasite versus the host cells. These Imidazole derivatives are potential candidates for further studies. We show evidence that supports the antiparasitic action of the Imidazole derivatives. The findings are promising in that they reinforce the prospects of Imidazole derivatives as alternative and effective antiparasitic therapy as well as providing evidence for a probable biological mechanism.
-
hemilability of 2 1h imidazol 2 yl pyridine and 2 oxazol 2 yl pyridine ligands Imidazole and oxazole ring lewis basicity ni ii pd ii complex structures and spectra
Polyhedron, 2010Co-Authors: Abiodun Omokehinde Eseola, Olalere G Adeyemi, N O Obiegbedi, Joseph Anthony Orighomisan WoodsAbstract:Abstract Fourteen new organic molecules A1–A4, B1–B5, C1–C4 and D and a series of transition metal(II) complexes (Ni1–Ni9 and Pd1–Pd2b) were synthesized and studied in order to characterize the hemilability of 2-(1H-imidazol-2-yl)pyridine and 2-(oxazol-2-yl)pyridine ligands (A1–A4 = 2-R2-6-(4,5-diphenyl-1R1-imidazol-2-yl)pyridines, R1 = H or CH3, R2 = H or CH3; B1–B5 = 1-R2-2-(pyridin-2-yl)-1R1-phenanthro[9,10-d]Imidazoles/oxazoles, R1 = H or CH3, R2 = H or CH3; C1–C4 = 2-(6-R2-pyridin-2-yl)-1H-imidazo/oxazo[4,5-f][1,10]phenanthrolines, R2 = H or CH3; D = 2-mesityl-1H-imidazo[4,5-f][1,10]phenanthroline). They were also used to study the substituent effects on the donor strengths as well as the coordination chemistries of the Imidazole/oxazole fragments of the hemilabile ligands. All the observed protonation–deprotonation processes found within pH 1–14 media pertain to the Imidazole or oxazole rings rather than the pyridyl Lewis bases. The donor characteristics of the Imidazole/oxazole ring can be estimated by spectroscopic methods regardless of the presence of other strong N donor fragments. The oxazoles possessed notably lower donor strengths than the Imidazoles. The electron-withdrawing influence and capacity to hinder the azole base donor strength of 4,5-azole substituents were found to be in the order phenanthrenyl (B series) > 4,5-diphenyl (A series) > phenanthrolinyl (C series). An X-ray structure of Ni5b gave evidence for solvent induced ligand reconstitution while the structure of Pd2b provided evidence for solvent induced metal–ligand bond disconnection. Interestingly, alkylation of 1H-Imidazoles did not necessarily produce the anticipated push of electron density to the donor nitrogen. Furthermore, substituents on the 4,5-carbons of the azole ring were more important for tuning donor strength of the azole base. DFT calculations were employed to investigate the observed trends. It is believed that the information provided on substituent effects and trends in this family of ligands will be useful in the rational design and synthesis of desired azole-containing chelate ligands, tuning of donor properties and application of this family of ligands in inorganic architectural designs, template-directed coordination polymer preparations, mixed-ligand inorganic self-assemblies, etc.
Koji Arimitsu - One of the best experts on this subject based on the ideXlab platform.
-
Imidazole type thermal latent curing agents with high miscibility for one component epoxy thermosetting resins
Journal of Polymer Science Part A, 2016Co-Authors: Kenji Kudo, Masahiro Furutani, Sawako Fuse, Koji ArimitsuAbstract:Epoxy resins are important thermosetting resins widely employed in industrial fields. Although the epoxy–Imidazole curing system has attracted attention because of its reactivity, solidification of a liquid epoxy resin containing Imidazoles proceeds gradually even at room temperature. This makes it difficult to use them for one-component epoxy resin materials. Though powder-type latent curing agents have been used for one-component epoxy resin materials, they are difficult to apply for fabrication of fine industrial products due to their poor miscibility. To overcome this situation and to improve the shelf life of epoxy–Imidazole compositions, we have developed a liquid-type thermal latent curing agent 1, generating an Imidazole with a thermal trigger via a retro-Michael addition reaction. The latent curing agent 1 has superior miscibility toward epoxy resins; in addition, it was confirmed that the epoxy resin composition has both high reactivity at 150 °C, and long-term storage stability at room temperature. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2680–2688
-
Imidazole derivatives with an intramolecular hydrogen bond as thermal latent curing agents for thermosetting resins
ACS Macro Letters, 2015Co-Authors: Kenji Kudo, Masahiro Furutani, Koji ArimitsuAbstract:Epoxy resins are important thermosetting resins widely used in industrial applications. Though Imidazoles as curing agents have attracted particular attention because of their high reactivity in chain polymerizations with epoxides, polymerization of a liquid epoxy resin containing Imidazoles proceeds gradually even at room temperature. This makes it difficult to use such mixtures as one-component materials for industrial applications. To improve the shelf life of the mixutures, we have developed a very simple and powerful thermal latent curing agent, a 2-(2-hydroxyphenyl)Imidazole derivative (1), having an intramolecular hydrogen bond between the phenolic hydroxyl group and the nitrogen atom of the Imidazole ring, leading to suppression of reactivity of 1 toward epoxy resins at room temperature. It was confirmed that high reactivity of 1 toward epoxy resins at 150 °C was based on breakage of the intramolecular hydrogen, whereas the epoxy resin composition showed long-term storage stability at room tempera...
-
Imidazole derivatives as latent curing agents for epoxy thermosetting resins
Materials Letters, 2015Co-Authors: Koji Arimitsu, Kenji Kudo, Sawako Fuse, Masahiro FurutaniAbstract:Abstract We have developed novel liquid-type thermal latent curing agents to generate Imidazoles in epoxy resins. The latent curing agents were synthesized using a Michael addition reaction of fumarate with Imidazoles in 14–53% yields. The latent curing agent, having a thermally labile bulky long-chain alkyl succinate group at the nitrogen atom of the Imidazole ring, underwent a thermal decomposition reaction in the temperature range from 200 to 280 °C, which generated the corresponding Imidazole by a retro-Michael addition reaction. The curing reaction of epoxy resins by thermally generated free Imidazoles proceeded at 150 °C. Furthermore, it was demonstrated that a mixture of the latent curing agent with epoxy resins has long storage stability at room temperature, which was not accomplished with the Imidazoles themselves.
Naoto Chatani - One of the best experts on this subject based on the ideXlab platform.
-
iridium catalyzed direct amidation of Imidazoles at the c 2 position with isocyanates in the presence of hydrosilanes leading to Imidazole 2 carboxamides
Synthesis, 2021Co-Authors: Yoshiya Fukumoto, Motohiro Shiratani, Hikaru Noguchi, Naoto ChataniAbstract:Regioselective coupling reaction of N-substituted Imidazoles with isocyanates in the presence of a stoichiometric amount of hydrosilanes catalyzed by Ir4(CO)12 to give Imidazole-2-carboxamides is reported. Imidazoles bearing an (O-silyl)carboximidate group at the 2-position appear to be initially formed in the reaction, which are then hydrolyzed to the final products in situ. The addition of the hydrosilane was essential for the catalytic reaction to proceed. Substituents on the Imidazole ring had no effect on the reaction, except for certain bulky substituents such as tBu and Ph groups at the 4-position. Triazoles such as 4-methyl-4H-1,2,4-triazole and 1-methyl-1H-1,2,4-triazole were also applicable to this C-H amidation, and the latter reaction proceeded regioselectively at the carbon atom between the sp 3 and sp 2 nitrogen atoms of the ring, and not between the two sp 2 nitrogen atoms.
-
direct and regioselective introduction of acetals into Imidazoles at the 2 position by an iridium catalyzed reaction with formates in the presence of hydrosilanes
European Journal of Organic Chemistry, 2017Co-Authors: Yoshiya Fukumoto, Yasuaki Iyori, Naoto ChataniAbstract:The iridium-catalyzed reaction of Imidazoles with formates in the presence of hydrosilanes as co-reactants, leading to the production of 2-[(alkoxy)(siloxy)methyl]Imidazoles, is described. Dimethyl acetylenedicarboxylate (DMAD) was the additive of choice for the reaction, in terms of reaction efficiency. No reaction was observed in the absence of the hydrosilanes. While substituents at the 1- and 5-positions on the Imidazole ring did not affect the reaction, substituents at the 4-position greatly retarded the reaction. The regioselective reaction of 1-methyl-1,2,4-triazole occurred at the carbon atom between the sp3 and sp2 nitrogen atoms of the ring, but not between two sp2 nitrogen atoms The products were converted into Imidazole 2-carbaldehydes by hydrolysis under acidic conditions.
Masahiro Furutani - One of the best experts on this subject based on the ideXlab platform.
-
Imidazole type thermal latent curing agents with high miscibility for one component epoxy thermosetting resins
Journal of Polymer Science Part A, 2016Co-Authors: Kenji Kudo, Masahiro Furutani, Sawako Fuse, Koji ArimitsuAbstract:Epoxy resins are important thermosetting resins widely employed in industrial fields. Although the epoxy–Imidazole curing system has attracted attention because of its reactivity, solidification of a liquid epoxy resin containing Imidazoles proceeds gradually even at room temperature. This makes it difficult to use them for one-component epoxy resin materials. Though powder-type latent curing agents have been used for one-component epoxy resin materials, they are difficult to apply for fabrication of fine industrial products due to their poor miscibility. To overcome this situation and to improve the shelf life of epoxy–Imidazole compositions, we have developed a liquid-type thermal latent curing agent 1, generating an Imidazole with a thermal trigger via a retro-Michael addition reaction. The latent curing agent 1 has superior miscibility toward epoxy resins; in addition, it was confirmed that the epoxy resin composition has both high reactivity at 150 °C, and long-term storage stability at room temperature. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2680–2688
-
Imidazole derivatives with an intramolecular hydrogen bond as thermal latent curing agents for thermosetting resins
ACS Macro Letters, 2015Co-Authors: Kenji Kudo, Masahiro Furutani, Koji ArimitsuAbstract:Epoxy resins are important thermosetting resins widely used in industrial applications. Though Imidazoles as curing agents have attracted particular attention because of their high reactivity in chain polymerizations with epoxides, polymerization of a liquid epoxy resin containing Imidazoles proceeds gradually even at room temperature. This makes it difficult to use such mixtures as one-component materials for industrial applications. To improve the shelf life of the mixutures, we have developed a very simple and powerful thermal latent curing agent, a 2-(2-hydroxyphenyl)Imidazole derivative (1), having an intramolecular hydrogen bond between the phenolic hydroxyl group and the nitrogen atom of the Imidazole ring, leading to suppression of reactivity of 1 toward epoxy resins at room temperature. It was confirmed that high reactivity of 1 toward epoxy resins at 150 °C was based on breakage of the intramolecular hydrogen, whereas the epoxy resin composition showed long-term storage stability at room tempera...
-
Imidazole derivatives as latent curing agents for epoxy thermosetting resins
Materials Letters, 2015Co-Authors: Koji Arimitsu, Kenji Kudo, Sawako Fuse, Masahiro FurutaniAbstract:Abstract We have developed novel liquid-type thermal latent curing agents to generate Imidazoles in epoxy resins. The latent curing agents were synthesized using a Michael addition reaction of fumarate with Imidazoles in 14–53% yields. The latent curing agent, having a thermally labile bulky long-chain alkyl succinate group at the nitrogen atom of the Imidazole ring, underwent a thermal decomposition reaction in the temperature range from 200 to 280 °C, which generated the corresponding Imidazole by a retro-Michael addition reaction. The curing reaction of epoxy resins by thermally generated free Imidazoles proceeded at 150 °C. Furthermore, it was demonstrated that a mixture of the latent curing agent with epoxy resins has long storage stability at room temperature, which was not accomplished with the Imidazoles themselves.
