Search results for "MEDICINA"

A versatile rigid binucleating ligand for Rh2(μ-Cl)2 moieties: its application as a catalyst in hydrogenation and cyclopropanation

2003

A rigid non-deforming "MCl 2 M" binucleating ligand [7,8-μ-S(4'-C 6 H 3 (CH 3 ))S-C 2 B 9 H 1 0 ] - able to held the two rhodium atoms in a cooperative distance has been synthesized. The original two bridging chlorides are retained in [Rh 2 (C 5 Me 5 ) 2 Cl 2 {7,8-μ-S(4'-C 6 H 3 (CH 3 ))S-C 2 B 9 H 1 0 }] + . Hydrogenation of 1-hexene is 10 times faster with [Rh 2 (C 5 Me 5 ) 2 Cl 2 {7,8-μ-S(4'-C 6 H 3 (CH 3 ))S-C 2 B 9 H 1 0 }] + than with [Rh 2 (C 5 Me 5 ) 2 Cl 4 ]. A hydrogenation mechanism has been proposed which assumes that [Rh 2 (C 5 Me 5 ) 2 (Cl)(H){7,8-μ-S(4'-C 6 H 3 (CH 3 ))S-C 2 B 9 H 1 0 }] + is the first generated species in the process.

Cycloaddition reactions of 2H-1-benzothietes and 1,3,5,7-tetrathio-s-indacene-2,6-dithiones

2016

Abstract 2H-1-benzothiete (1) and 2H,5H-benzo[1,2-b:4,5-b′]bisthiete (3) react in form of their open valence isomers with the trithiocarbonic acid esters 2a–c. The one- or twofold cycloaddition reactions yield 1,3-dithiin rings, in which C-2 is a spiro-C atom, that bears four sulfur groups. The bifunctional reactant 3 gives additionally band-shaped, hardly soluble oligomers.

Deuterierter molekularer Rubin mit Rekord-Lumineszenzquantenausbeute

2018

Der kurzlich publizierte Chrom(III)-Komplex 13+([Cr(ddpd)2]3+) zeigt in wassriger Losung unter Umgebungsbedingungen eine bemerkenswert starke Emission im nahen Infrarot-Bereich mit einer Emissionswellenlange von 775 nm. Geschicktes Ligandendesign verhindert strahlungslose Desaktivierungsprozesse wie Photosubstitution, Ruck-Intersystem-Crossing und trigonale Verzerrungen und fuhrt damit zu einer Phosphoreszenzlebensdauer im Bereich von Mikrosekunden. In Abwesenheit von Energieakzeptoren wie molekularem Sauerstoff verbleibt nur Energietransfer zu hochenergetischen Oszillatoren der Liganden und Losungsmittelmolekule wie beispielsweise OH- und CH-Streckschwingungen als Desaktivierungspfad. Sele…

Thorough evaluation of OECD principles in modelling of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine derivatives using QSARINS.

2020

The human immunodeficiency virus is a lethal pathology considered as a worldwide problem. The search for new strategies for the treatment of this disease continues to be a great challenge in the scientific community. In this study, a series of 107 derivatives of 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine, previously evaluated experimentally against HIV-I reverse transcriptase, was used to model antiretroviral activity. A model of linear regression, implemented in the QSARINS software, was developed with a genetic algorithm for variable selection. The fit of its parameters was good and exhaustive validation, according to the OECD regulatory principles, was performed. Also, the applica…

Synthesis, reactivity and structural studies of carboranyl thioethers and disulfides.

2005

The equimolar reaction of 1-SH-2-R-1,2-closo-C2B10H10 (R = Me, H, Ph) with KOH in ethanol produces the thiolate species [1-S-2-R-1,2-closo-C2B10H10]−. These react with iodine to give the disulfide bridged dicluster (1-S-2-R-1,2-closo-C2B10H10)2 (R = H, Me, Ph) compounds as analytically pure, white and air-stable solids in high yield. Synthesis of monothioether bridged species is synthetically more difficult. In fact three procedures have been tested to obtain the thioether bridged dicluster compounds (2-R-1,2-closo-C2B10H10)2S (R = Me, H, Ph) but only (2-Me-1,2-closo-C2B10H10)2S was successfully synthesized and characterized. Attempts to produce mixed compounds (1-R-1,2-closo-C2B10H10)S(1-R…

Synthesis of Lamellarin G Trimethyl Ether by von Miller-Plöchl-Type Cyclocondensation

2018

Synthesis of copper(II) and gold(III) bis(NHC)-pincer complexes

2016

Abstract CuII and AuIII chlorido complexes bearing the bis(NHC) carbazolide pincer ligand (bimca) were synthesized by transmetallation from the respective lithium complex [Li(bimca)] (NHC=N-heterocyclic carbene). In the case of copper, two different molecular structures were obtained depending on the copper source. With Cu(II) chloride the paramagnetic mononuclear [Cu(bimca)Cl] complex is formed and has been characterized by EPR spectroscopy and X-ray structure analysis, while copper(I) chloride leads under oxidation to a dinuclear structure in which two cationic [CuII(bimca)] moieties are bridged by one chlorido ligand. The positive charge is compensated by the [CuCl2]− counter ion, as pro…

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.

An Entry to Mixed NHC-Fischer Carbene Complexes and Zwitterionic Group 6 Metal Alkenyls

2016

The addition of NHCs to α,β-unsaturated Cr(0) and W(0) (Fischer) carbene complexes is strongly dependent on the electrophilicity of the carbene carbon. Electrophilic alkoxy-carbene complexes quantitatively react with NHCs to yield stable zwitterionic (racemic) Cr(0) - and W(0) -alkenyls with total regio- and E-stereoselectivity. Less electrophilic aminocarbenes react with NHCs to promote the displacement of a CO ligand and yield "mixed" NHC/Fischer biscarbenes in a process that is unprecedented in group 6 metal-carbene chemistry. In fact, the compounds prepared, are some of the scarce examples of Fischer bisylidenes reported in the literature. The electrochemistry of the zwitterionic Cr(0) …

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 …