Cu(acac)2 catalyzed oxidative C–H bond amination of azoles with amines under base-free conditions

Osmium(III) Acetylacetonate and Its Missing Polymorph: A Magnetic and Structural Investigation

Despite the potential for their application, the magnetic behavior of complexes containing 4d and 5d metal ions is underexplored, evidencing the need for benchmark multi-technique studies on simple molecules. We report here a structural and magnetic study on osmium(III) acetylacetonate [Os(acac)3]. X-ray single crystal diffraction did not allow us to determine the structure of the β-polymorph of [Os(acac)3]. The combined magnetic (dc magnetic measurements on powder and cantilever torque magnetometry on single crystal) and spectroscopic (electron paramagnetic resonance, EPR) characterization is here used to provide further evidence that its structure is indeed the one of the orthorhombic "missing polymorph", analogous to the ruthenium(III) derivative. Our study shows that all acetylacetonate complexes of the eighth group of the periodic table show dimorphism and are isomorphic. The EPR characterization allowed the experimental assessment of the easy axis nature of the ground doublet and the determination of the first hyperfine coupling in an osmium complex. Torque magnetometry, applied here for the first time on an osmium-based molecule, determined the orientation of the easy axis along the pseudo C3 axis of the complex. Ac magnetometric measurements revealed in-field slow relaxation of the magnetization further slowed by the suppression of dipolar fields via magnetic dilution in the isostructural gallium(III) analogue.

Metal-free visible light mediated direct C-H amination of benzoxazole with secondary amines

An efficient visible light mediated, eosin Y catalyzed direct C-H oxidative amination of benzoxazoles with secondary amines has been developed, which providing a straightforward, green, and environmentally benign access to a wide variety of substituted benzoxazole-2-amines under mild reaction conditions. The biological studies such as drug-likeness and molecular docking are also carried out on the molecule.

Direct Amination of Aromatic C-H Bonds with Free Amines

Aromatic amines belong to a highly important class of organic compounds which are found in various natural products, functional materials, and pharmaceutical agents. Their prevalence has sparked continuing interest in the development of highly efficient and environmentally benign synthetic strategies for the construction of these compounds. Cross-dehydrogenative coupling reactions between two unmodified C(X)-H bonds have recently emerged as a versatile and powerful strategy for the fabrication of new C(X)-C(X) bonds. In this context, several procedures have been reported for the synthesis of aromatic amines through the direct amination of aromatic C-H bonds with free amines. This review highlights recent advances and progress in this appealing research arena, with special emphasis on the mechanistic features of the reactions.

Methods to Access 2-aminobenzimidazoles of Medicinal Importance

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Benzimidazole (BI) and derivatives are interesting because several of these compounds have been found to have a diversity of biological activities with clinical applications. In view of their importance, the synthesis of BI and its derivatives is still considered as a challenge for synthetic chemists. Examples of compounds used in medicinal chemistry containing BI, as important nucleus, are Astemizole (antihistaminic), Omeprazole (antiulcerative) and Rabendazole (fungicide), some of these compounds have the 2- aminobenzimidazole (2ABI) as base nucleus. The structure of 2ABI derivatives contains a cyclic guanidine moiety, which is interesting because of its free lone pairs, labile hydrogen atoms and planar delocalized structure. The delocalized 10-π electron system and the extension of the electron conjugation with the exocyclic amino group, in 2ABI, making these heterocycles to have amphoteric character. The 2ABI has been used as building blocks for the synthesis of several BI derivatives as medicinally important molecules. On these bases, herein, we present a bibliographic review concerning the recent methodologies used in the synthesis of 2ABIs, including the substituted ones.

3d Transition Metals for C-H Activation

C-H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material sciences, crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these C-H functionalizations required precious 4d or 5d transition metal catalysts. Given the cost-effective and sustainable nature of earth-abundant first row transition metals, the development of less toxic, inexpensive 3d metal catalysts for C-H activation has gained considerable recent momentum as a significantly more environmentally-benign and economically-attractive alternative. Herein, we provide a comprehensive overview on first row transition metal catalysts for C-H activation until summer 2018.

Palladium-catalyzed intermolecular carbonylative cross-coupling of heteroaryl C(sp2)–H bonds with amines: an efficient strategy for oxidative aminocarbonylation of azoles

We report the first intermolecular carbonylative cross-coupling of heteroaryl C(sp²)–H bonds with amines using oxygen as the green oxidant.

Copper-catalyzed electrophilic amination of heteroarenes and arenes by C-H zincation

Direct amination of heteroarenes and arenes has been achieved in a one-pot CH zincation/copper-catalyzed electrophilic amination procedure. This amination method provides an efficient and rapid approach to access a diverse range of heteroaromatic and aromatic amines including those previously inaccessible using CH amination methods. The mild reaction conditions and good functional-group compatibility demonstrate its great potential for the synthesis of important and complex amines.