Rationale for the sluggish oxidative addition of aryl halides to Au(I)

The oxidative addition of Csp2–Br or Csp2–I bonds to gold(I) does not take place even under very favorable intramolecular conditions that could form five- or six-membered gold(III) metallacycles. DFT calculations reveal that although this process could be feasible thermodynamically, it is kinetically very sluggish

A computational study on the intriguing mechanisms of the gas-phase thermal activation of methane by bare [Ni(H)(OH)](+)

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.A detailed computational study on the reaction mechanisms of the thermal activation of methane by the bare complex [Ni(H)(OH)]+ has been conducted. The experimentally observed reaction features, i.e. the ligand exchange Ni(H) → Ni(CH3), the H/D scrambling between the incoming methane and the hydrido ligand of the nickel complex, the spectator-like behavior of the OH ligand, and the relatively moderate reaction efficiency of 6% relative to the collision rate of the ion/molecule reaction, can be explained by considering three competing mechanisms, and a satisfactory agreement between experiment and theory has been found.DFG, EXC 314, Unifying Concepts in Catalysi

Computationally Guided Design of a Readily Assembled Phosphite- Thioether Ligand for a Broad Range of Pd-Catalyzed Asymmetric Allylic Substitutions

A modular approach employing indene as common starting material, has enabled the straightforward preparation in three reaction steps of P-thioether ligands for the Pd-catalyzed asymmetric allylic substitution. The analysis of a starting library of P-thioether ligands based on rational design and theoretical calculations has led to the discovery of an optimized anthracenethiol derivative with excellent behavior in the reaction of choice. Improving most approaches reported to date, this ligand presents a broad substrate and nucleophile scope. Excellent enantioselectivities have been achieved for a range of linear and cyclic allylic substrates using a large number of C-, N-, and O-nucleophiles (40 compounds in total). The species responsible for the catalytic activity have been further investigated by NMR in order to clearly establish the origin of the enantioselectivity. The resulting products have been derivatized by means of ring-closing metathesis or Pauson–Khand reactions to further prove the synthetic versatility of the methodology for preparing enantiopure complex structures

Introducing the Catalytic Amination of Silanes via Nitrene Insertion

The direct functionalization of Si−H bonds by the nitrene insertion methodology is described. A copper(I) complex bearing a trispyrazolylborate ligand catalyzes the transfer of a nitrene group from PhINTs to the Si−H bond of silanes, disilanes, and siloxanes, leading to the exclusive formation of Si−NH moieties in the first example of this transformation. The process tolerates other functionalities in the substrate such as several C−H bonds and alkyne and alkene moieties directly bonded to the silicon center. Density functional theory (DFT) calculations provide a mechanistic interpretation consisting of a Si−H homolytic cleavage and subsequent rebound to the Si-centered radical.We thank the Ministerio de Ciencia e Innovación for Grants PID2020-113797RB-C21, PID2020-112825RB-I00, and CEX2019-000925-S as well as FEDER for “Una manera de hacer Europa” funding. We also thank Junta de Andalucía (P20-00348) and Universidad de Huelva (P.O.Feder UHU202016). A.M.R. and R.P.-S. thank Ministerio de Universidades for the FPU fellowships (FPU17/02738 and FPU18/ 01138, respectively), and J.P.-R. thanks Fondo de Garantía Juvenil for a research contract. CERCA Programme/Generalitat de Catalunya is also acknowledged. We thank Prof. T. R. Belderrain for helpful discussions on 29Si NMR spectroscopy. Funding for open access charge: Universidad de Huelva / CBU

Determining optimal flight paths for cellular network connectivity for the transmission of real-time physiological data in support of big data analytics during airborne critical care transport

This thesis presents a methodology for determining the optimal flight paths between two geographical points based on distance and cellular reception over the path. This methodology consists of two main concepts: coverage map generation, and path planning. Coverage map generation creates a grid map of the total planning space that contains coverage information for each grid point. Coverage is calculated based on geographical and technical information regarding each cell tower in the planning area. The planning step utilises the coverage map to plan a route based on minimum distance and maximum coverage, which is then smoothed into a feasible route for an aircraft to follow. This methodology is demonstrated in an airborne critical care transport within the Province of Ontario in Canada context. Leveraging available cellular information, this methodology is used to determine optimal paths between various care centres or their closest airport. Evaluation reveals that optimal routes can be found through this methodology

Cyclobutene vs 1,3-Diene Formation in the Gold-Catalyzed Reaction of Alkynes with Alkenes : The Complete Mechanistic Picture

The intermolecular gold(I)-catalyzed reaction between arylalkynes and alkenes leads to cyclobutenes by a [2 + 2] cycloaddition, which takes place stepwise, first by formation of cyclopropyl gold(I) carbenes, followed by a ring expansion. However, 1,3-butadienes are also formed in the case of ortho -substituted arylalkynes by a metathesis-type process. The corresponding reaction of alkenes with aryl-1,3-butadiynes, ethynylogous to arylalkynes, leads exclusively to cyclobutenes. A comprehensive mechanism for the gold(I)-catalyzed reaction of alkynes with alkenes is proposed on the basis of density functional theory calculations, which shows that the two pathways leading to cyclobutenes or dienes are very close in energy. The key intermediates are cyclopropyl gold(I) carbenes, which have been independently generated by retro-Buchner reaction from stereodefined 1a,7b-dihydro-1 H -cyclopropa[ a ]naphthalenes

Mechanistic and Computational Studies of the Atom Transfer Radical Addition of CCl4 to Styrene Catalyzed by Copper Homoscorpionate Complexes

Experimental as well as theoretical studies have been carried out with the aim of elucidating the mechanism of the Atom Transfer Radical Addition (ATRA) of styrene and carbon tetrachloride with a TpxCu(NCMe) complex as the catalyst precursor (Tpx = hydrotrispyrazolyl-borate ligand). The studies shown herein demonstrate the effect of different variables in the kinetic behavior. A mechanistic proposal consistent with theoretical and experimental data is presentedMICINN (Grants CTQ2008–00042BQU, CTQ2008-06866-CO2-02/BQU and Consolider Ingenio 2010 CSD2006-0003) and the Junta de Andalucía (Proyecto P07-FQM-02794)We thank the MICINN (Grants CTQ2008-00042BQU, CTQ2008-06866-CO2-02/BQU, and Consolider Ingenio 2010 CSD2006-0003) and the Junta de Andalucia (Proyecto P07-FQM-02794) for financial support