Transition-Metal-Catalyzed C−S, C−Se, and C−Te Bond Formation via Cross-Coupling and Atom-Economic Addition Reactions

CuO nanostructures: Synthesis, characterization, growth mechanisms, fundamental properties, and applications

Cu-catalysed arylation reactions devoted to the formation of C–C and C–heteroatom bonds (Ullmann-type couplings) have acquired great importance in the last decade. This review discusses the history and development of coupling reactions between aryl halides and various classes of nucleophiles, focusing mostly on the different mechanisms proposed through the years. Selected mechanistic investigations are treated more in depth than others. For example, evidence in favour or against radical mechanisms is discussed. Cu(I) and Cu(III) complexes involved in the Ullmann reaction and N/O selectivity in aminoalcohol arylation are discussed. A separate section has been dedicated to the synthesis of heterocyclic rings through intramolecular couplings. Finally, recent developments in green chemistry for these reactions, such as reactions in aqueous media and heterogeneous catalysis, have also been reviewed.

https://pubs.rsc.org/en/content/getauthorversionpdf/C3CS60289C

Copper catalysed Ullmann type chemistry: From mechanistic aspects to modern development

Iron-Catalyzed S-Arylation of Thiols with Aryl Iodides

Copper-catalyzed arylations of nucleophiles (Ullmann, Ullmann-Goldberg and UllmannHurtley condensations) have been well known for more than a century for being one the most useful and practical methods in the formation of C(aryl)-N, C(aryl)-C and C(aryl)-O bonds.[1] These reactions are thus involved in numerous industrial applications such as the synthesis of intermediates as well as synthetic targets throughout the life science and polymer industries. However until 2000, Ullmann condensations have not been employed to their full potential. They indeed suffered from reduced synthetic scope as a result of the harsh reaction conditions often required, a limited substrate scope and the moderate yields obtained. Condensations were traditionally conducted at temperatures as high as 210 °C, often in the presence of stoichiometric amounts of copper reagents and preferentially with activated aryl halides.[1]. Early studies revealed rate enhancement when arylation were conducted in the presence of copper additive.[2] The additive compounds were thought to increase catalyst solubility and stability, but their exact role was not well established. Finally in 2001, important breakthroughs [3] were achieved by two groups with the discoveries of versatile and very efficiency new copper/ligand systems (C-C, C-N or C-O coupling) allowing the use of catalytic amount of metal under very mild conditions (90-110°C). Since 2001, these works and the potentially attractiveness of copper has led to a spectacular resurgence of interest in catalyzed Ullmann-type reactions. Many groups have thus been developing so far new Cu/Ligand systems to improve the variety and efficiency of the coupling reactions. We present here recent major developments in Cu-catalyzed C-C, C-O and C-N bond formation. The two selected contributions are of highly impact for cross coupling reaction, and deal with enantioselective and chemoselectivitive copper catalytic systems.

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Catalytic C-C, C-N, and C-O Ullmann-type coupling reactions: copper makes a difference.

When molecules of a phenalenyl derivative, which has no net spin, are deposited on a ferromagnet, they develop into a magnetic supramolecular layer with spin-filtering properties; this could be the basis for a new approach to building molecular magnetic devices. Various types of molecular magnets carrying high localized spin have been studied as potential devices for information processing and storage, but it remains a considerable challenge to electronically couple to these spin centres. Moodera et al. have designed a phenalenyl derivative, essentially a graphene fragment, with the potential to act as an interface for the exchange of magnetic spin information in molecular spintronic devices. The graphene fragment has no net spin itself, but when deposited as a layer on a ferromagnet it transforms to produce a supramolecular magnetic film. The resulting nanoscale magnetic molecules, or memory 'bits', can be manipulated by external stimuli, and the resulting device exhibits an unexpectedly large magnetoresistance of 20% near room temperature. The use of molecular spin state as a quantum of information for storage, sensing and computing has generated considerable interest in the context of next-generation data storage and communication devices1,2, opening avenues for developing multifunctional molecular spintronics3. Such ideas have been researched extensively, using single-molecule magnets4,5 and molecules with a metal ion6 or nitrogen vacancy7 as localized spin-carrying centres for storage and for realizing logic operations8. However, the electronic coupling between the spin centres of these molecules is rather weak, which makes construction of quantum memory registers a challenging task9. In this regard, delocalized carbon-based radical species with unpaired spin, such as phenalenyl10, have shown promise. These phenalenyl moieties, which can be regarded as graphene fragments, are formed by the fusion of three benzene rings and belong to the class of open-shell systems. The spin structure of these molecules responds to external stimuli11,12 (such as light, and electric and magnetic fields), which provides novel schemes for performing spin memory and logic operations. Here we construct a molecular device using such molecules as templates to engineer interfacial spin transfer resulting from hybridization and magnetic exchange interaction with the surface of a ferromagnet; the device shows an unexpected interfacial magnetoresistance of more than 20 per cent near room temperature. Moreover, we successfully demonstrate the formation of a nanoscale magnetic molecule with a well-defined magnetic hysteresis on ferromagnetic surfaces. Owing to strong magnetic coupling with the ferromagnet, such independent switching of an adsorbed magnetic molecule has been unsuccessful with single-molecule magnets13. Our findings suggest the use of chemically amenable phenalenyl-based molecules as a viable and scalable platform for building molecular-scale quantum spin memory and processors for technological development.

/pdf/interface-engineered-templates-for-molecular-spin-memory-54prn8j0q7.pdf

Interface-engineered templates for molecular spin memory devices

Efficient CuO‐Nanoparticle‐Catalyzed CS Cross‐Coupling of Thiols with Iodobenzene

Synthesis, structure and electrochemical properties of 2,5-bis(alkyl/arylamino)1,4-benzoquinones and 2-arylamino-1,4-naphthoquinones

Detection of entangled states from experimental magnetic susceptibility is reported for an organic radical The present system exemplifies an ideal spin ½ chain with full isotropy Experimental susceptibility data are modelled by the formulation described by Bonner and Fisher An explicit correlation is established between the molecular structure and the spin chain interaction Using experimental magnetic susceptibility as entanglement witness, entanglement is observed to exist up to 28 K in the present system Evolution of entanglement with magnetic field is also studied and a surface plot is generated, which clearly exhibits the variation of entanglement with magnetic field and temperature

Experimental detection of thermal entanglement in a molecular chain

We report the synthesis and characterization of the first transition metal complex of a phenalenyl-based ligand. The reaction of Cu(OAc)2.H2O with 9-N-methylamino-1-N
 ′-methylimino-phenalene (LH) in 1:1 stoichiometric ratio results in the formation of a mononuclear copper complex [LCu(OAc)] (1). The molecular structure of 1 was established by X-ray crystallography. The electrochemistry of 1 indicates the formation of an anionic radical by one electron reduction into the non-bonding molecular orbital of the phenalenyl system. The complex 1 efficiently catalyses the C–C bond forming Henry reaction.

/pdf/phenalenyl-based-ligand-for-transition-metal-chemistry-3sdxfmqacg.pdf

Tamal K. Sen

Papers

Interface-engineered templates for molecular spin memory devices

Efficient CuO‐Nanoparticle‐Catalyzed CS Cross‐Coupling of Thiols with Iodobenzene

Synthesis, structure and electrochemical properties of 2,5-bis(alkyl/arylamino)1,4-benzoquinones and 2-arylamino-1,4-naphthoquinones

Experimental detection of thermal entanglement in a molecular chain

Phenalenyl-based ligand for transition metal chemistry: Application in Henry reaction