362 research outputs found
Ultra-rapid carbonylation using palladium(I) dimer precatalysts applied to 11CO-radiolabelling for PET
The use of functional near-infrared spectroscopy in tracking neurodevelopmental trajectories in infants and children with or without developmental disorders: a systematic review
Understanding the neurodevelopmental trajectories of infants and children is essential for the early identification of neurodevelopmental disorders, elucidating the neural mechanisms underlying the disorders, and predicting developmental outcomes. Functional Near-Infrared Spectroscopy (fNIRS) is an infant-friendly neuroimaging tool that enables the monitoring of cerebral hemodynamic responses from the neonatal period. Due to its advantages, fNIRS is a promising tool for studying neurodevelopmental trajectories. Although many researchers have used fNIRS to study neural development in infants/children and have reported important findings, there is a lack of synthesized evidence for using fNIRS to track neurodevelopmental trajectories in infants and children. The current systematic review summarized 84 original fNIRS studies and showed a general trend of age-related increase in network integration and segregation, interhemispheric connectivity, leftward asymmetry, and differences in phase oscillation during resting-state. Moreover, typically developing infants and children showed a developmental trend of more localized and differentiated activation when processing visual, auditory, and tactile information, suggesting more mature and specialized sensory networks. Later in life, children switched from recruiting bilateral auditory to a left-lateralized language circuit when processing social auditory and language information and showed increased prefrontal activation during executive functioning tasks. The developmental trajectories are different in children with developmental disorders, with infants at risk for autism spectrum disorder showing initial overconnectivity followed by underconnectivity during resting-state; and children with attention-deficit/hyperactivity disorders showing lower prefrontal cortex activation during executive functioning tasks compared to their typically developing peers throughout childhood. The current systematic review supports the use of fNIRS in tracking the neurodevelopmental trajectories in children. More longitudinal studies are needed to validate the neurodevelopmental trajectories and explore the use of these neurobiomarkers for the early identification of developmental disorders and in tracking the effects of interventions
Supported palladium nanoparticles as heterogeneous ligand-free catalysts for the Hiyama C C coupling of vinylsilanes and halobenzenes leading to styrenes
[EN] Palladium nanoparticles supported on magnesia is a highly efficient solid, reusable catalyst to promote in the absence of phosphine ligands the coupling of vinylsilanes with iodo- and bromobenzenes to form styrenes.Financial support by Spanish Ministry of Science and Innovation (Consolider MULTICAT and CTQ 2012-32316) is gratefully acknowledged. The Generalidad Valenciana is also thanked for partial financial support (Prometeo Grant).Grirrane, A.; García Gómez, H.; Corma Canós, A. (2013). Supported palladium nanoparticles as heterogeneous ligand-free catalysts for the Hiyama C C coupling of vinylsilanes and halobenzenes leading to styrenes. Journal of Catalysis. 302:49-57. doi:10.1016/j.jcat.2013.02.019S495730
One-electron oxidation of [M(PtBu3)2] (M=Pd, Pt) : isolation of monomeric [Pd(PtBu3)2]+and redox-promoted C−H bond cyclometalation
Oxidation of zero-valent phosphine complexes [M(PtBu3)2] (M=Pd, Pt) has been investigated in 1,2-difluorobenzene solution using cyclic voltammetry and subsequently using the ferrocenium cation as a chemical redox agent. In the case of palladium, a mononuclear paramagnetic PdI derivative was readily isolated from solution and fully characterized (EPR, X-ray crystallography). While in situ electrochemical measurements are consistent with initial one-electron oxidation, the heavier congener undergoes C−H bond cyclometalation and ultimately affords the 14 valence-electron PtII complex [Pt(κ2PC-PtBu2CMe2CH2)(PtBu3)]+ with concomitant formation of [Pt(PtBu3)2H]+
Mild, aqueous α-arylation of ketones : towards new diversification tools for halogenated metabolites and drug molecules
The authors thank the European Research Council (FP7/2007-2013/ERC grant agreement no 614779 to RJMG) and (FP7 2009-2014/ERC agreement no 227817 to SPN) for generous funding.The palladium-catalyzed aqueous α-arylation of ketones was developed and tested for a large variety of reaction partners. These mild conditions enabled the coupling of aryl/ alkyl-ketones with N-protected halotryptophans, heterocyclic haloarenes, and challenging base-sensitive compounds. The synthetic potential of this new methodology for the diversification of complex bioactive molecules was exemplified by derivatising prochlorperazine. The methodology is mild, aqueous and flexible, representing a means of functionalizing a wide range of halo-aromatics and therefore has the potential to be extended to complex molecule diversification.PostprintPeer reviewe
Chemical reactions at the graphitic step-edge: changes in product distribution of catalytic reactions as a tool to explore the environment within carbon nanoreactors
A series of explorative cross-coupling reactions have been developed to investigate the local nanoscale environment around catalytically active Pd(II)complexes encapsulated within hollow graphitised nanofiber (GNF). Two new fullerene-containing and fullerene-free Pd(II)Salen catalysts have been synthesised, and their activity and selectivity towards different substrates has been explored in nanoreactors. The catalysts not only show a significant increase in activity and stability upon heterogenisation at the graphitic step-edges inside the GNF channel, but also exhibit a change in selectivity affected by the confinement which alters the distribution of isomeric products of the reaction. Furthermore, the observed selectivity changes reveal unprecedented details regarding the location and orientation of the catalyst molecules inside the GNF nanoreactor, inaccessible by any spectroscopic or microscopic techniques, thus shedding light on the precise reaction environment inside the molecular catalyst-GNF nanoreactor.
Keywords: nanoreactor, catalysis, fullerene, salen, cross-couplin
Practical access to planar chiral 1,2-(α-Ketotetramethylene)- ferrocene by non-enzymatic kinetic resolution and conclusive confirmation of its absolute configuration
The asymmetric transfer hydrogenation (ATH) of racemic 1,2-(α-ketotetramethylene)ferrocene using the [N-(tosyl)-1,2-diphenylethylendiamine]ruthenium(II) complex [TsDPEN-Ru(II)] as catalyst takes place with a high level of kinetic resolution to deliver the ketone in up to 99% ee. The X-ray crystallographic structure of a derivative of the alcohol co-product serves to confirm conclusively both the absolute configuration of 1,2-(α-ketotetramethylene)ferrocene and the endo-reduction selectivity
Homocoupling of Phenylboronic Acid using Atomically Dispersed Gold on Carbon Catalysts: Catalyst Evolution Before Reaction
Coupling reactions to form new C-C bonds are extensively used in industrial synthetic processes. Gold has been shown to be an active catalyst for such reactions however, conflicting reports exist as to whether cationic Au or metallic Au is acting as the active species. We prepared a heterogeneous catalyst consisting of atomically dispersed Au-Clx supported on carbon and showed this to be active in the homocoupling of phenylboronic acid to biphenyl. However; characterisation of the catalyst materials, even after just a short exposure time to the reactants, revealed rapid reduction and sintering of the Au species into larger metallic nanoparticles which we propose to be the true active species in this instance. This study suggests that if cationic Au is an active catalyst, it must be stabilised against reduction and agglomeration by either forming complexes which are more stable than common chlorides or by strongly anchoring them firmly onto alternative support materials; as in this case the carbon supported Au-Cl species were easily reduced
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