Quantum chemical study of the mechanism of ethylene elimination in silylative coupling of olefins

Highly selective synthesis of substituted (E)-alkenylsilatranes via catalytic trans-silylation and mechanistic implications

A new route for the synthesis of functionalized alkenylsilatranes has been developed based on ruthenium-catalyzed trans-silylation with olefins. This transformation allowed for the synthesis of new (E)-alkenylsilatranes in good yields and excellent selectivity. Experimental studies concerning the reaction mechanism were carried out and the intermediate ruthenium-silatranyl complex was isolated and characterized. Moreover, detailed DFT calculations regarding the mechanism of the silylative coupling catalytic cycle of silatranes catalyzed by [Ru]-H complexes were also performed.

Scope of the ring-opening metathesis polymerization (ROMP) reaction of 1-substituted cyclobutenes

The reactivities of a series of 1-substituted cyclobutene derivatives (carboxylate esters, carboxamides, and carbinol esters) were investigated as substrates for ring-opening metathesis polymerization (ROMP) with [(H(2)IMes)(3-Br-pyridine)(2)(Cl)(2)Ru=CHPh]. Both the secondary amides of 1-cyclobutenecarboxylic acid and the esters of 1-cyclobutene-1-methanol undergo polymerization. The secondary amides provide translationally invariant polymers (E-olefins). Although the carbinol esters yield stereo- and regiochemically heterogeneous polymers, the 1-cyclobutenecarboxylic acid esters and tertiary amides undergo ring-opening metathesis (ROM) but not ROMP. The regio- and stereochemical outcomes of these ROMP and ROM reactions were analyzed at the B3LYP/6-31G* and LANL2DZ levels of theory. Calculations suggest that the regiochemistry and stereochemistry of the addition to the propagating carbene to form the metallocyclobutane intermediate depend on both charge distribution and steric interactions.

Quantum chemical studies on substitution effects within silyl group in the silylative coupling of olefins

In this study quantum chemical calculations based on the density functional theory (DFT) have been carried out to examine the effects of methoxy substituent attached to a silicon atom on the reaction of silylative coupling of olefins. It has been shown, that substituted substrate undergoes the reaction according to the recently proposed insertion-rotation-elimination mechanism. During the rotation around C-C single bond additional stabilization by oxygen-ruthenium interaction was observed. Similarly to the (trimethylsilyl)ethene the rate determining step of the reaction is the insertion of the alkene into Ru-Si single bond. The substitution of SiMe(3) by Si(OMe)(3) decreases the energy span of the reaction by almost 3 kcal mol(-1) that is from 21 kcal mol(-1) to 18 kcal mol(-1). The decrease of the energy barrier of the reaction seems to be the result of the increase of point charge differences between the Ru and Si atoms which increases electrostatic attraction between these atoms. Moreover, for Si(OMe)(3) the rate-determining transition state is closer to the alkene interacting with the Ru centre side of the reaction.

The interactome: predicting the protein-protein interactions in cells

The term Interactome describes the set of all molecular interactions in cells, especially in the context of protein-protein interactions. These interactions are crucial for most cellular processes, so the full representation of the interaction repertoire is needed to understand the cell molecular machinery at the system biology level. In this short review, we compare various methods for predicting protein-protein interactions using sequence and structure information. The ultimate goal of those approaches is to present the complete methodology for the automatic selection of interaction partners using their amino acid sequences and/or three dimensional structures, if known. Apart from a description of each method, details of the software or web interface needed for high throughput prediction on the whole genome scale are also provided. The proposed validation of the theoretical methods using experimental data would be a better assessment of their accuracy.

Catalytic coupling of sp2- and sp-hybridized carbon-hydrogen bonds with vinylmetalloid compounds

In the Account given herein, it has been shown that silylative coupling of olefins, well-recognized as a new catalytic route for the activation of double bond C-H bond of olefins and double bond C-Si bond of vinylsilicon compounds with ethylene elimination, can be extended over both other vinylmetalloid derivatives (double bond C-E) (where E = Ge, B, and others) as well as the activation of triple bond C-H, double bond C aryl-H, and -O-H bond of alcohols and silanols. This general transformation is catalyzed by transition-metal complexes (mainly Ru and Rh) containing or initiating TM-H and/or TM-E bonds (inorganometallics). This new general catalytic route for the activation of double bond C-H and triple bond C-H as well as double bond C-E bonds called metallative coupling or trans-metalation (cross-coupling, ring-closing, and polycondensation) constitutes an efficient method (complementary to metathesis) for stereo- and regioselective synthesis of a variety of molecular and macromolecular compounds of vinyl-E (E = Si, B, and Ge) and ethynyl-E (E = Si and Ge) functionality, also potent organometallic reagents for efficient synthesis of highly pi-conjugated organic compounds. The mechanisms of the catalysis of this deethenative metalation have been supported by equimolar reactions of TM-H and/or TM-E with initial substances and reactions with deuterium-labeled reagents.