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Insertion Reactions of Neutral Phosphidozirconocene Complexes as a Convenient Entry into Frustrated Lewis Pair Territory

2016

International audience; Neutral phosphidozirconocene complexes [Cp2Zr(PR2)Me] (Cp=cyclopentadienyl; 1a: R=cyclohexyl (Cy); 1b: R=mesityl (Mes); 1c: R=tBu) undergo insertion into the Zr-P bond by non-enolisable carbonyl building blocks (O=CRR), such as benzophenone, aldehydes, paraformaldehyde or CO2, to give [Cp2Zr(OCRRPR2)Me] (3-7). Depending on the steric bulk around P, complexes 3-7 react with B(C6F5)(3) to give O-bridged cationic zirconocene dimers that display typical frustrated Lewis pair (FLP)/ambiphilic ligand behaviour. Thus, the reaction of {[Cp2Zr(-OCHPhPCy2)][MeB(C6F5)(3)]}(2) (10a) with chalcone results in 1,4 addition of the Zr+/P FLP, whereas the reaction of {[Cp2Zr(-OCHFcPCy…

13C NMR of carbonyl compounds -4. Solution conformation of β-ionone and related dienones

1986

Abstract The steric factors relevant for the conformations of β-ionone and structurally related compounds were studied by dynamic n.m.r. and 1 H, 1 H-NOE measurements.

Crystal structure of 4-[(adamantan-1-yl)amino]­naphthalene-1,2-dione

2019

The title compound, an example of a stable 1,2-naphtho­quinone, illustrates steric buttressing of the adamantanyl group.

Innentitelbild: Strain-Promoted Cycloaddition of Cyclopropenes with o -Quinones: A Rapid Click Reaction (Angew. Chem. 32/2018)

2018

In vivoInvestigation of Plant-Cell Metabolism by means of natural-abundance13C-NMR spectroscopy

1994

Based on the natural abundance of 13C, in vivo13C-NMR was used for the first time to monitor the metabolism of sucrose and hydroquinone (1) in cell suspensions of the plant Rauwolfia serpentina (L.) BENTH. ex KURZ. Cells converted sucrose extracellularly into α-D- and β -D-glucose as well as into β -D-fructofuranose and β -D-fructopyranose, respectively. The sugar mixture was completely taken up by the cells after 4 days. Hydroquinone fed at that time resulted in optimum conversion into its β -D-glucoside arbutin (2) within 10 h. A further metabolite, the primeveroside (3) of hydroquinone, appeared as a trace compound after 10 h. The formation of this diglycoside can be increased by further…

An Easy Stereoselective Access to β,γ-Aziridino α-Amino Ester Derivatives via Mannich Reaction of Benzophenone Imines of Glycine Esters with N-Sulfon…

2007

Mannich-type addition of benzophenone imine glycinates across newly synthesized N-(p-toluenesulfonyl) alpha-chloroaldimines afforded gamma-chloro-alpha,beta-diamino ester derivatives with moderate diastereoselectivity as separable mixtures of anti and syn diastereomers. The gamma-chloro-alpha,beta-diamino esters were efficiently cyclized under basic conditions to the corresponding beta,gamma-aziridino alpha-amino ester derivatives, representing a new class of conformationally constrained heterocyclic alpha,beta-diamino acid derivatives. The relative configuration of the aziridines was determined via X-ray diffraction analysis. Mechanisms and intermediate transition states to explain the ste…

Non-volatile memory characteristics of a Ti/HfO2/Pt synaptic device with a crossbar array structure

2022

The resistive switching and synaptic behavior of a fabricated Ti/HfO2/Pt crossbar array device are investigated. The results demonstrated that TiOx layers are created by the movement of oxygen ions during the positive SET process, thereby improving the endurance and multilevel switching behavior of the device. The random properties of SET process were described with the help of stochastic model of memristor based on the length of conductive filament. The analysis of the mean first passage time allows estimating the parameters of the dielectric switching layer such as the activation energy of the diffusive defects, its variation under the influence of the driving voltage and the value of the…

Microcosmi. Il teatro di Seneca a Palermo tra marginalità e canone

2012

In the last thirty years the study of Seneca’s theatre has become central in Italy, and particularly in the microcosm of Palermo University. This paper analyses the processes that have originated this development and attempts to document the consequences of the shift of Seneca’s theatre from the margins to the centre of the research interests. Three aspects will be taken into account: the renewal of the Latin literary canon in academic education, the diffusion of the study of Seneca at school, and the contribution of Seneca’s studies to the construction of relevant academic identities in contemporary scientific debate.

Dinosaur bonebed amber from an original swamp forest soil

2021

AbstractDinosaur bonebeds with amber content, yet scarce, offer a superior wealth and quality of data on ancient terrestrial ecosystems. However, the preserved palaeodiversity and/or taphonomic characteristics of these exceptional localities had hitherto limited their palaeobiological potential. Here we describe the amber from the Lower Cretaceous dinosaur bonebed of Ariño (Teruel, Spain) using a multidisciplinary approach. Amber is found in both a root layer with amber strictly in situ and a litter layer namely composed of aerial pieces unusually rich in bioinclusions, encompassing 11 insect orders, arachnids, and a few plant and vertebrate remains, including a feather. Additional palaeont…

Caracterización molecular de la pérdida del poder patógeno en Agrobacterium tumefaciens

2003

Agrobacterium tumefaciens es una bacteria fitopatógena causante de tumores en el cuello y raíces de muchas especies vegetales de interés económico. En los viveros e invernaderos es donde más daños produce, al aparecer episodios epidémicos que pueden impedir la comercialización de producciones enteras, porque las plantas afectadas por esta enfermedad no pueden ser comercializadas. Los estudios epidemiológicos y de dinámica de poblaciones del patógeno son poco abundantes y han incidido en aspectos del desarrollo y mantenimiento de la enfermedad producida por la bacteria. Aunque se ha señalado el predominio de cepas no patógenas frente a patógenas en ambientes en los que las cepas productoras …