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A tandem C(sp(2))-H and C(sp(3))-H functionalization/C-O bond formation catalyzed by iodine(III) reagents generated in situ has been developed. The method shows wide scope under mild conditions and exhibits an unprecedented selectivity profile that can be switched depending on the catalyst employed., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Unlabelled: The low-grade inflammatory state present in obesity contributes to obesity-related metabolic dysregulation, including nonalcoholic steatohepatitis (NASH) and insulin resistance. Intercellular interactions between immune cells or between immune cells and hepatic parenchymal cells contribute to the exacerbation of liver inflammation and steatosis in obesity. The costimulatory molecules, B7.1 and B7.2, are important regulators of cell-cell interactions in several immune processes; however, the role of B7 costimulation in obesity-related liver inflammation is unknown. Here, diet-induced obesity (DIO) studies in mice with genetic inactivation of both B7.1 and B7.2 (double knockout; DKO) revealed aggravated obesity-related metabolic dysregulation, reduced insulin signalling in the liver and adipose tissue (AT), glucose intolerance, and enhanced progression to steatohepatitis resulting from B7.1/B7.2 double deficiency. The metabolic phenotype of B7.1/B7.2 double deficiency upon DIO was accompanied by increased hepatic and AT inflammation, associated with largely reduced numbers of regulatory T cells (Tregs) in these organs. In order to assess the role of B7 costimulation in DIO in a non-Treg-lacking environment, we performed antibody (Ab)-mediated inhibition of B7 molecules in wild-type mice in DIO. Antibody-blockade of both B7.1 and B7.2 improved the metabolic phenotype of DIO mice, which was linked to amelioration of hepatic steatosis and reduced inflammation in liver and AT., Conclusion: Our study demonstrates a dual role of B7 costimulation in the course of obesity-related sequelae, particularly NASH. The genetic inactivation of B7.1/B7.2 deteriorates obesity-related liver steatosis and metabolic dysregulation, likely a result of the intrinsic absence of Tregs in these mice, rendering DKO mice a novel murine model of NASH. In contrast, inhibition of B7 costimulation under conditions where Tregs are present may provide a novel therapeutic approach for obesity-related metabolic dysregulation and, especially, NASH., (© 2014 by the American Association for the Study of Liver Diseases.)

A Ni-catalyzed carboxylation of unactivated primary alkyl bromides and sulfonates with CO2 at atmospheric pressure is described. The method is characterized by its mild conditions and remarkably wide scope without the need for air- or moisture-sensitive reagents, which make it a user-friendly and operationally simple protocol en route to carboxylic acids.

A novel Ni-catalyzed reductive amidation of C(sp(2))-O and C(sp(3))-O electrophiles with isocyanates is described. This umpolung reaction allows for an unconventional preparation of benzamides using simple starting materials and easy-to-handle Ni catalysts.

A Ni/Cu-catalyzed silylation of unactivated C-O electrophiles derived from phenols or benzyl alcohols is described. This transformation is characterized by its wide scope and mild conditions, providing a direct access to synthetically versatile silylated compounds. The protocol allows for the coupling of C(sp(2))-O and even C(sp(3))-O bonds with similar efficiency.

In recent years a significant progress has been made for the carboxylation of aryl and benzyl halides with CO2, becoming convenient alternatives to the use of stoichiometric amounts of well-defined metal species. Still, however, most of these processes require the use of pyrophoric and air-sensitive reagents and the current methods are mostly restricted to organic halides. Therefore, the discovery of a mild, operationally simple alternate carboxylation that occurs with a wide substrate scope employing readily available coupling partners will be highly desirable. Herein, we report a new protocol that deals with the development of a synergistic activation of CO2 and a rather challenging activation of inert C(sp(2))-O and C(sp(3))-O bonds derived from simple and cheap alcohols, a previously unrecognized opportunity in this field. This unprecedented carboxylation event is characterized by its simplicity, mild reaction conditions, remarkable selectivity pattern and an excellent chemoselectivity profile using air-, moisture-insensitive and easy-to-handle nickel precatalysts. Our results render our method a powerful alternative, practicality and novelty aside, to commonly used organic halides as counterparts in carboxylation protocols. Furthermore, this study shows, for the first time, that traceless directing groups allow for the reductive coupling of substrates without extended π-systems, a typical requisite in many C-O bond-cleavage reactions. Taking into consideration the limited knowledge in catalytic carboxylative reductive events, and the prospective impact of providing a new tool for accessing valuable carboxylic acids, we believe this work opens up new vistas and allows new tactics in reductive coupling events.

A Ni-catalyzed arylation of inert C-O bonds that operates at temperatures as low as -40 °C is described. Unlike other methods for C-O bond cleavage utilizing organometallic species, this protocol operates at low temperatures, thus allowing the presence of sensitive functional groups with exquisite site-selectivity and stereoselectivity.

A practical synthesis of the previously unreported N-acetyl-D-allosamine glycomimetic DAJNAc is described. The reaction sequence involves Pd-catalyzed allylic substitution by phthalimide in an azaheterobicyclic scaffold as the key step. The new iminosugar resulted in being a stronger β-N-acetylglucosaminidase (human placenta) competitive inhibitor than the D-gluco (DNJNAc) and D-galacto (DGJNAc) stereoisomers.

A formal Cu-catalyzed C(sp(2))-H hydroxylation assisted by benzoic acids is described. The procedure is characterized by its mild reaction conditions and wide substrate scope utilizing simple and cheap Cu catalysts, thus becoming a user-friendly and operationally simple protocol for C(sp(2))-H hydroxylation.

A mechanistic and computational study on the reductive cleavage of C-OMe bonds catalyzed by Ni(COD)(2)/PCy(3) with silanes as reducing agents is reported herein. Specifically, we demonstrate that the mechanism for this transformation does not proceed via oxidative addition of the Ni(0) precatalyst into the C-OMe bond. In the absence of an external reducing agent, the in-situ-generated oxidative addition complexes rapidly undergo β-hydride elimination at room temperature, ultimately leading to either Ni(0)-carbonyl- or Ni(0)-aldehyde-bound complexes. Characterization of these complexes by X-ray crystallography unambiguously suggested a different mechanistic scenario when silanes are present in the reaction media. Isotopic-labeling experiments, kinetic isotope effects, and computational studies clearly reinforced this perception. Additionally, we also found that water has a deleterious effect by deactivating the Ni catalyst via formation of a new Ni-bridged hydroxo species that was characterized by X-ray crystallography. The order in each component was determined by plotting the initial rates of the C-OMe bond cleavage at varying concentrations. These data together with the in-situ-monitoring experiments by (1)H NMR, EPR, IR spectroscopy, and theoretical calculations provided a mechanistic picture that involves Ni(I) as the key reaction intermediates, which are generated via comproportionation of initially formed Ni(II) species. This study strongly supports that a classical Ni(0)/Ni(II) for C-OMe bond cleavage is not operating, thus opening up new perspectives to be implemented in other related C-O bond-cleavage reactions.

Emerging evidence points to a close crosstalk between metabolic organs and innate immunity in the course of metabolic disorders. In particular, cellular and humoral factors of innate immunity are thought to contribute to metabolic dysregulation of the adipose tissue or the liver, as well as to dysfunction of the pancreas; all these conditions are linked to the development of insulin resistance and diabetes mellitus. A central component of innate immunity is the complement system. Interestingly, the classical view of complement as a major system of host defense that copes with infections is changing to that of a multi-functional player in tissue homeostasis, degeneration, and regeneration. In the present review, we will discuss the link between complement and metabolic organs, focusing on the pancreas, adipose tissue, and liver and the diverse effects of complement system on metabolic disorders., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

A novel Ni-catalyzed carboxylation of benzyl halides with CO(2) has been developed. The described carboxylation reaction proceeds under mild conditions (atmospheric CO(2) pressure) at room temperature. Unlike other routes for similar means, our method does not require well-defined and sensitive organometallic reagents and thus is a user-friendly and operationally simple protocol for assembling phenylacetic acids.

An efficient Ni-catalyzed protocol for the reductive cleavage of inert C-O bonds has been developed. The method is characterized by its simplicity and wide scope, thereby allowing the use of aryl ethers as easily removable directing groups in organic synthesis.

The cores of many types of polymers, ligands, natural products, and pharmaceuticals contain biaryl or substituted aromatic structures, and efficient methods of synthesizing these structures are crucial to the work of a broad spectrum of organic chemists. Recently, Pd-catalyzed carbon-carbon bond-forming processes, particularly the Suzuki-Miyaura cross-coupling reaction (SMC), have risen in popularity for this purpose. The SMC has many advantages over other methods for constructing these moieties, including mild conditions, high tolerance toward functional groups, the commercial availability and stability of its reagents, and the ease of handling and separating byproducts from its reaction mixtures. Until 1998, most catalysts for the SMC employed triarylphosphine ligands. More recently, new bulky and electron-rich phosphine ligands, which can dramatically improve the efficiency and selectivity of such cross-coupling reactions, have been introduced. In the course of our studies on carbon-nitrogen bond-forming reactions, we found that the use of electron-rich and bulky phosphines enhanced the rate of both the oxidative addition and reductive elimination processes; this was the beginning of our development of a new family of ligands, the dialkylbiarylphosphines L1-L12. These ligands can be used for a wide variety of palladium-catalyzed carbon-carbon, carbon-nitrogen, and carbon-oxygen bond-forming processes as well as serving as supporting ligands for a number of other reactions. The enhanced reactivity of these catalysts has expanded the scope of cross-coupling partners that can be employed in the SMC. With use of such dialkylbiarylphosphine ligands, the coupling of unactivated aryl chlorides, aryl tosylates, heteroaryl systems, and very hindered substrate combinations have become routine. The utility of these ligands has been successfully demonstrated in a wide number of synthetic applications, including industrially relevant processes. In this Account, we provide an overview of the use and impact of dialkylbiarylphosphine ligands in the SMC. We discuss our studies on the mechanistic framework of the reaction, which have allowed us to rationally modify the ligand structures in order to tune their properties. We also describe selected applications in the synthesis of natural products and new materials to illustrate the utility of these dialkylbiarylphosphine ligands in various "real-world" synthetic applications.