Manganese(III) acetate-mediated synthesis of biaryls under microwave irradiation

Stabilized Palladium Nanoparticles from Bis-(N-benzoylthiourea) Derived-PdII Complexes as Efficient Catalysts for Sustainable Cross-Coupling Reactions in Water

Stable palladium (II) complexes, incorporating a double (N-benzoylthiourea) arrangement bonded to a complex heterocyclic scaffold, are used as precursors of catalytic species able to promote Suzuki-Miyaura, Mizoroki-Heck, Hiyama, Buchwald-Hartwig, Hirao and Sonogashira-Hagihara cross-coupling transformations in water. These sustainable processes are chemoselective and very versatile. The nanoparticles responsible for these catalytic reactions were analyzed and studied. Their usefulness is demonstrated after several tests and analyses. The heterogeneous character of this species in water was also confirmed.

Generation of aryl radicals by redox processes. Recent progress in the arylation methodology

Arylation methods based on the generation and use of aryl radicals have been a rapidly growing field of research in recent years and currently represent a powerful strategy for carbon – carbon and carbon – heteroatom bond formation. The progress in this field is related to advances in the methods for generation of aryl radicals. The currently used aryl radical precursors include aryl halides, aryldiazonium and diaryliodonium salts, arylcarboxylic acids and their derivatives, arylboronic acids, arylhydrazines, organosulfur(II, VI) compounds and some other compounds. Aryl radicals are generated under mild conditions by single electron reduction or oxidation of precursors induced by conventional reagents, visible light or electric current. A crucial role in the development of the radical arylation methodology belongs to photoredox processes either catalyzed by transition metal complexes or organic dyes or proceeding without catalysts. Unlike the conventional transition metal-catalyzed arylation methods, radical arylation reactions proceed very often at room temperature and have high functional group tolerance. Without claiming to be exhaustive, this review covers the most important advances of the current decade in the generation and synthetic applications of (het)aryl radicals. Examples of reactions are given and mechanistic insights are highlighted.

The bibliography includes 341 references.

Metal-free arylation of pyrimidines through a photochemical process

Pyrimidinyl and pyrazinyl radicals were generated under moderate energetic irradiation conditions (UVA), and proved to be prompt to undergo C-C bond formation processes. Hetero-biaryl derivatives were obtained in good to high yields with highly interesting functional group selectivities. Bis hetero-biaryls were also easily accessible leading to original compounds, ready for further transformations. Experiments supporting radical processes have been reported.

KMnO4/AcOH-mediated C3-selective direct arylation of coumarins with arylboronic acids

An efficient protocol for KMnO₄/AcOH-mediated C3-direct radical arylation of coumarins with arylboronic acids to afford 3-arylcoumarin derivatives is described.

Synthetic applications of arylboronic acid via an aryl radical transfer pathway

The transition-metal-catalyzed functionalization of arylboronic acids is the most powerful tool for the formation of carbon-carbon and carbon-heteroatom bonds in modern organic synthesis. These transformations are generally considered to proceed via organometallic intermediates generated by transmetalation from the boronic acids. Interestingly, there is a novel recognition that arylboronic acids can serve as aryl radical precursors via oxidative carbon-boron bond cleavage in recent years. Manganese(III) acetate, Ag(I)/persulfate and iron(II or III)/persulfate catalytic systems have been shown to be effective for this transformation. In this review, recent advances in this new area are highlighted and their mechanisms are also discussed.

Palladium and copper-catalyzed ligand-free coupling of phenylhydrazines in water

An efficient methodology for the synthesis of biaryls via Pd/Cu catalyzed coupling of unprotected phenylhydrazines in water is reported.

Room temperature, open-flask C–H arylation of electron-deficient heteroarenes with triazenes: rapid synthesis of heterobiaryls

Aryl triazenes were coupled with heteroarenes via C–H functionalization to produce heterobiaryls in moderate to good yields at ambient temperature.

Elucidating the structure of poly(dopamine)

Herein we propose a new structure for poly(dopamine), a synthetic eumelanin that has found broad utility as an antifouling agent. Commercially available 3-hydroxytyramine hydrochloride (dopamine HCl) was polymerized under aerobic, aqueous conditions using tris(hydroxymethyl)aminomethane (TRIS) as a basic polymerization initiator, affording a darkly colored powder product upon isolation. The polymer was analyzed using a variety of solid state spectroscopic and crystallographic techniques. Collectively, the data showed that in contrast to previously proposed models, poly(dopamine) is not a covalent polymer but instead a supramolecular aggregate of monomers (consisting primarily of 5,6-dihydroxyindoline and its dione derivative) that are held together through a combination of charge transfer, π-stacking, and hydrogen bonding interactions.

Iron-catalyzed oxidative coupling of arylboronic acids with benzene derivatives through homolytic aromatic substitution

Fe(OTf)(3)-1,10-phenanthroline catalyzes oxidative coupling of arylboronic acids with benzene derivatives using t-BuOOt-Bu as an oxidant. The reaction proceeds through homolytic aromatic substitution with aryl radicals generated from arylboronic acids and t-BuO˙.