Increasing Catalyst Efficiency in C−H Activation Catalysis

C−H activation reactions with high catalyst turnover numbers are still very rare in the literature and 10 mol % is a common catalyst loading in this field. We offer a representative overview of efficient C−H activation catalysis to highlight this neglected aspect of catalysis development and inspire future effort towards more efficient C−H activation. Examples ranging from palladium catalysis, Cp*Rh III - and Cp*Co III -catalysis, the C−H borylation and silylation to methane C−H activation are presented. In these reactions, up to tens of thousands of catalyst turnovers have been observed

Is the racial composition of your surroundings associated with your levels of social dominance orientation?

We investigate the extent to which minority group members are surrounded by outgroup members in their immediate environment as a predictor of social dominance orientation. Using a large representative sample of New Zealanders, we found that minority group members in outgroup dense environments reported lower levels of social dominance orientation (Study 1). In studies 2 and 3, Asian Australian and Black American participants who were surrounded by outgroup members reported lower social dominance orientation. For majority group (White) participants there was no association between social dominance orientation and outgroup density. Study 4 explained the overall pattern: Black Americans surrounded by outgroup members perceived their group to be of lower status in their immediate environment, and through this, reported lower social dominance orientation. This article adds to growing literature on contextual factors that predict social dominance orientation, especially among minority group members

Cp*Co-III Catalyzed Site-Selective C-H Activation of Unsymmetrical O-Acyl Oximes: Synthesis of Multisubstituted Isoquinolines from Terminal and Internal Alkynes

The synthesis of isoquinolines by site-selective CH activation of O-acyl oximes with a Cp*Co-III catalyst is described. In the presence of this catalyst, the CH activation of various unsymmetrically substituted O-acyl oximes selectively occurred at the sterically less hindered site, and reactions with terminal as well as internal alkynes afforded the corresponding products in up to 98% yield. Whereas the reactions catalyzed by the Cp*Co-III system proceeded with high site selectivity (15:1 to 20:1), use of the corresponding Cp*Rh-III catalysts led to low selectivities and/or yields when unsymmetrical O-acyl oximes and terminal alkynes were used. Deuterium labeling studies indicate a clear difference in the site selectivity of the CH activation step under Cp*Co-III and Cp*Rh-III catalysis

TGF-β signalling is required for CD4⁺ T cell homeostasis but dispensable for regulatory T cell function

TGF-β is widely held to be critical for the maintenance and function of regulatory T (T(reg)) cells and thus peripheral tolerance. This is highlighted by constitutive ablation of TGF-β receptor (TR) during thymic development in mice, which leads to a lethal autoimmune syndrome. Here we describe that TGF-β-driven peripheral tolerance is not regulated by TGF-β signalling on mature CD4⁺ T cells. Inducible TR2 ablation specifically on CD4⁺ T cells did not result in a lethal autoinflammation. Transfer of these TR2-deficient CD4⁺ T cells to lymphopenic recipients resulted in colitis, but not overt autoimmunity. In contrast, thymic ablation of TR2 in combination with lymphopenia led to lethal multi-organ inflammation. Interestingly, deletion of TR2 on mature CD4⁺ T cells does not result in the collapse of the T(reg) cell population as observed in constitutive models. Instead, a pronounced enlargement of both regulatory and effector memory T cell pools was observed. This expansion is cell-intrinsic and seems to be caused by increased T cell receptor sensitivity independently of common gamma chain-dependent cytokine signals. The expression of Foxp3 and other regulatory T cells markers was not dependent on TGF-β signalling and the TR2-deficient T(reg) cells retained their suppressive function both in vitro and in vivo. In summary, absence of TGF-β signalling on mature CD4⁺ T cells is not responsible for breakdown of peripheral tolerance, but rather controls homeostasis of mature T cells in adult mice