Hydrosilylation Reactions Catalyzed by Rhenium

Hydrosilylation is an important process, not only in the silicon industry to produce silicon polymers, but also in fine chemistry. In this review, the development of rhenium-based catalysts for the hydrosilylation of unsaturated bonds in carbonyl-, cyano-, nitro-, carboxylic acid derivatives and alkenes is summarized. Mechanisms of rhenium-catalyzed hydrosilylation are discussed.     

A convergent approach to 3-substituted-5-methoxyindoles. Application to the synthesis of melatonin [correction

A convergent, radical based synthesis of 5-methoxyindoles including melatonin is described.     

Cold collision frequency shifts in a 87Rb atomic fountain

We present measurements of cavity frequency pulling and collisional frequency shifts in a 87Rb fountain with a frequency resolution of 3x10(-16). Agreement with theory is found for the cavity pulling and the measured collisional shifts. The clock shift is found at least 50 times smaller than in 133Cs.     

Free-space lossless state detection of a single trapped atom

We demonstrate the lossless state-selective detection of a single rubidium 87 atom trapped in an optical tweezer. This detection is analogous to the one used on trapped ions. After preparation in either a dark or a bright state, we probe the atom internal state by sending laser light that couples an excited state to the bright state only. The laser-induced fluorescence is collected by a high numerical aperture lens. The single-shot fidelity of the detection is 98.6±0.2% and is presently limited by the dark count noise of the detector. The simplicity of this method opens new perspectives in view of applications to quantum manipulations of neutral atoms.     

Field emission tip as a nanometer source of free electron femtosecond pulses

We report a source of free electron pulses based on a field emission tip irradiated by a low-power femtosecond laser. The electron pulses are shorter than 70 fs and originate from a tip with an emission area diameter down to 2 nm. Depending on the operating regime we observe either photofield emission or optical field emission with up to 200 electrons per pulse at a repetition rate of 1 GHz. This pulsed electron emitter, triggered by a femtosecond oscillator, could serve as an efficient source for time-resolved electron interferometry, for time-resolved nanometric imaging and for synchrotrons.     

Synthesis of new iron–NHC complexes as catalysts for hydrosilylation reactions

A series of new piano‐stool iron(II) complexes comprising N‐heterocyclic carbene ligands [Fe(Cp)(CO)₂(NHC)]I (NHC = 1,3‐disubstituted imidazolidin‐2‐ylidene) have been synthesized and analyzed by ¹H NMR, ¹³C NMR, IR, elemental analysis and mass spectrometric techniques. These compounds were easily prepared from the reaction of disubstituted imidazolidin‐2‐ylidene with [FeI(Cp)(CO)₂] in toluene at room temperature. These complexes were tested in the catalytic hydrosilylation reaction of aldehydes and ketones with phenylsilane in solvent‐free conditions. After a basic hydrolysis step, the corresponding alcohols were obtained in good yields. Copyright © 2013 John Wiley & Sons, Ltd.     

Iron‐Catalyzed α‐Alkylation of Ketones with Alcohols

A general and benign iron‐catalyzed α‐alkylation reaction of ketones with primary alcohols has been developed. The key to success of the reaction is the use of a Knölker‐type complex as catalyst (2 mol %) in the presence of Cs₂CO₃ as base (10 mol %) under hydrogen‐borrowing conditions. Using 2‐aminobenzyl alcohol as alkylation reagent allows for the “green” synthesis of quinoline derivatives.     

Bridge between bound state and reaction effective nucleon-nucleon potentials

It has been a long standing problem to find the connection between the realistic nucleon-nucleon interaction and the interaction between two nucleons when they are embedded inside a nuclear medium, the so-called ‘effective interaction’. On the one hand various many-body approaches have been employed, while on the other hand, information is sought on the basis of static nuclear properties. Both provide partial information. An attempt is made to understand if there is an inherent link, a bridge, which connects all these informations, through the study of heavy ion fusion reactions.