Search results for "sel"

A green and efficient method for the synthesis of homodimeric (β-dicarbonyl) arylmethanes and dihydropyridine from dimedone in water

2018

A direct method has been developed for the synthesis of the dihydropyridine ring system by means of Michael reaction. The reaction of dimedone with 1 .0 equiv. of amines in water provides intermediate product, which allowed dihydropyridine derivatives by intramolecular cyclization in various yields. Of particular interest is the use of the water as solvent of reaction and in absence of catalyst. Also these operating conditions protect the environment and economic points of view.Keywords: aqueous synthesis; bioactivity; dihydropyridine; dimedone; green method; selective conditions

Exploring the Chemoselectivity towards Cysteine Arylation by Cyclometallated Au III Compounds: New Mechanistic Insights

2020

To gain more insight into the factors controlling the efficient cysteine arylation by cyclometalated Au(III) complexes, the reaction between selected gold compounds and different peptides was investigated by high‐resolution liquid chromatography electrospray ionization mass spectrometry (HR‐LC‐ESI‐MS). The deducted mechanisms of C–S cross‐coupling, also supported by density functional theory (DFT) and quantum mechanics/molecular mechanics (QM/MM) calculations, evidenced the key role of secondary peptidic gold binding sites in favouring the process of reductive elimination.

Synthesis of P-Chirogenic Diphosphinotriazoles and Their Use in Asymmetric Catalysis

2021

International audience; The stereoselective synthesis of P-chirogenic diphosphinotriazoles using ephedrine methodology was described. The coordination behavior of these compounds as P,P-ligands has been demonstrated by the preparation as well as the spectroscopic and X-ray crystallographic analyses of a palladium complex. The efficiency of these new P-chirogenic diphosphines in the palladiumcatalyzed asymmetric allylic substitution reaction was also evaluated.

A new hydrogen bonding motif involved in self-recognition in the solid state by functionalised macrocycles

2011

Self-recognition within the crystal lattices of three functionalised macrocycles results in the formation of arrays of remarkably similar hermaphroditic pairs of macrocycles. In the case of two of the macrocycles containing acylhydrazine substituents, a hitherto unknown recognition pattern is found in the interaction of the hydrazine moiety with crown-ether oxygen atoms.

Chiral footprint of the ligand layer in the all-alkynyl-protected gold nanocluster Au144(CCPhF)60

2019

The electronic structure and chiroptical properties of the recently isolated and structurally characterized all-alkynyl-protected gold nanocluster Au144(CCPhF)60 were analyzed via density functional theory (DFT) computations and compared to those of the structurally similar all-thiolate-protected Au144(SCH2Ph)60. While DFT predicts very strong CD signals of similar strength for both clusters, the origins of chiroptical activity are markedly different. The chiral response of Au144(CCPhF)60 originates only from the footprint of the outermost gold-ligand layer of 30 FPhCC-Au-CCPhF units covering an achiral Ih-symmetric Au114 core whereas the Au114 core of the Au144(SCH2Ph)60 cluster has a chir…

Access to α-Aminophosphonic Acid Derivatives and Phosphonopeptides by [Rh(P–OP)]-Catalyzed Stereoselective Hydrogenation

2020

The hydrogenation of N-substituted vinylphosphonates using rhodium complexes derived from P–OP ligands L1, ent-L1, or (R,R)-Me-DuPHOS as catalysts has been successfully accomplished, achieving very high levels of stereoselectivity (up to 99% ee or de). The described synthetic strategy allowed for the efficient preparation of α-aminophosphonic acid derivatives and phosphonopeptides, which are valuable building blocks for the preparation of biologically relevant molecules.

2015

Biphenols are important structure motifs for ligand systems in organic catalysis and are therefore included in the category of so-called "privileged ligands". We have developed a new synthetic pathway to construct these structures by the use of selenium dioxide, a stable, powerful, and commercially available oxidizer. Our new, and easy to perform protocol gives rise to biphenols and diaryl selenides depending on the solvent employed. Oxidative treatment of phenols in acetic acid yields the corresponding biphenols, whereas conversion in pyridine results in the preferred formation of diaryl selenides. As a consequence, we were able to isolate a broad scope of novel diaryl selenides, which cou…

A Molecular Electron Density Theory Study of the Role of the Copper Metalation of Azomethine Ylides in [3 + 2] Cycloaddition Reactions.

2018

The copper metalation of azomethine ylides (AYs) in [3 + 2] cycloaddition (32CA) reactions with electron-deficient ethylenes has been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G(d,p) level, in order to shed light on the electronic effect of the metalation in the course of the reaction. Analysis of the Conceptual Density Functional Theory reactivity indices indicates that the metalation of AYs markedly enhances the nucleophilicity of these species given the anionic character of the AY framework. These 32CA reactions take place through stepwise mechanisms characterized by the formation of a molecular complex. Both nonmetalated and metalated 32CA reactions …

Self-assembly of M4L4tetrahedral cages incorporating pendant PS and PSe functionalised ligands

2019

Herein, the synthesis of metal–organic tetrahedral cages featuring flexible thio- and selenophosphate-based ligands is described. The cages were prepared by sub-component self-assembly of AP(OC6H4NH2-4)3 (A = S, Se) or SP(SC6H4NH2-4)3, 2-pyridinecarboxaldehyde, and either Fe[BF4]2 or Co[BF4]2. Preliminary host–guest studies into the ability of the pendant PS and PSe groups to interact with suitable substrates will be discussed.

Understanding the Participation of Fluorinated Azomethine Ylides in Carbenoid-Type [3 + 2] Cycloaddition Reactions with Ynal Systems: A Molecular Ele…

2021

The carbenoid-type (cb-type) 32CA reaction of 1,1-difluoroated azomethine ylide (DFAY) with phenylpropynal has been studied using the molecular electron density theory (MEDT). Electron localization function (ELF) characterizes DFAY as a carbenoid species participating in cb-type 32CA reactions. The supernucleophilic character of DFAY and the strong electrophilic character of the ynal cause this polar 32CA reaction to have an unappreciable barrier; the reaction, which is highly exothermic, presents total chemo- and regioselectivity. ELF topological analysis of the bonding changes along the reaction establishes its non-concerted two-stage one-step mechanism, in which the nucleophilic attack o…