Traceless transition metal catalysis for synthetic applications

The report will present current trends in the development of catalytic chemistry and the importance of metal catalysis in organic synthesis.Research work was supported by RFBR № 19-33-50030

Substrate-Selective C-H Functionalization for the Preparation of Organosulfur Compounds from Crude Oil-Derived Components

The direct utilization of a natural feedstock in organic synthesis is an utmost challenge because the selective production of one product from a mixture of starting materials requires unprecedented substrate selectivity. In the present study, a simple and convenient procedure is evaluated for the substrate-selective alkenylation of a single component in a mixture of organosulfur compounds. Pd-catalyzed alkenylation of two-, three-, four-, and five-component mixtures of crude oil-derived sulfur species led to the exclusive C–H functionalization of only one compound. The observed remarkable substrate selectivity opens new opportunities for sustainable organic synthesis

Automated prediction of catalytic mechanism and rate law using graph-based reaction-path sampling

In a recent article [J. Chem. Phys., 143, 094106 (2015)], we have introduced a novel graph-based sampling scheme which can be used to generate chemical reaction paths in many-atom systems in an efficient and highly-automated manner. The main goal of this work is to demonstrate how this approach, when combined with direct kinetic modelling, can be used to determine the mechanism and phenomenological rate law of a complex catalytic cycle, namely cobalt-catalyzed hydroformylation of ethene. Our graph-based sampling scheme generates 31 unique chemical products and 32 unique chemical reaction pathways; these sampled structures and reaction paths en- able automated construction of a kinetic network model of the catalytic system when combined with density functional theory (DFT) calculations of free energies and resul- tant transition-state theory rate constants. Direct simulations of this kinetic network across a range of initial reactant concentrations enables determination of both the re- action mechanism and the associated rate law in an automated fashion, without the need for either pre-supposing a mechanism or making steady-state approximations in kinetic analysis. Most importantly, we find that the reaction mechanism which emerges from these simulations is exactly that originally proposed by Heck and Breslow; fur- thermore, the simulated rate law is also consistent with previous experimental and computational studies, exhibiting a complex dependence on carbon monoxide pres- sure. While the inherent errors of using DFT simulations to model chemical reactivity limit the quantitative accuracy of our calculated rates, this work confirms that our automated simulation strategy enables direct analysis of catalytic mechanisms from first principles

A hemilabile and cooperative N-donor functionalized 1,2,3-triazol- 5-ylidene ligand for selective and base-free rhodium(I) catalyzed alkyne hydrothiolation reactions

A series of novel cationic and neutral Rh-complexes with an N-donor functionalized 1,2,3-triazol-5-ylidene (TRZ) ligand (where pendant N-donor is NHBoc, NH2 or NMe2 respectively) is described. Their catalytic activity was evaluated towards the hydrothiolation of alkynes. Among the catalysts, a neutral dicarbonyl complex featuring the tethered-NBoc amido-TRZ ligand proved very selective for alkyne hydrothiolation with an aryl thiol. Remarkably, the reaction could be carried out in the absence of pyridine or base additive. In addition, during the reaction course, no evidence for oxidative addition of the thiol S-H was observed, strongly suggesting a reaction pathway whereby a bifunctional ligand is involved. Experimental and theoretical mechanistic investigations suggest a ligand-assisted deprotonation of substrate thiol, hemilabile dissociation of amine from metal and thiolate coordination, which is indicative of a different reaction mechanism to those previously reported for related alkyne hydrothiolation reaction.G. G.-B. thanks the MINECO for a postdoctoral grant (FPDI- 2013-16525) and Generalitat Valenciana (GV/2015/097) for financial support. E.P and I.F. gratefully acknowledge financial support from the Spanish MINECO-FEDER (CTQ2014-51999-P to E.P. and CTQ2013-44303-P and CTQ2014-51912-REDC to I.F.), UJI (P11B2014-02 to E.P.). D.I.B and I.S. gratefully acknowledge the National Research Foundation, South Africa (NRF 87890, 103698 and 92521), and Sasol Technology R&D Pty. Ltd., South Africa for financial support.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1521-37652018-01-31hb2017Chemistr

Promoting Difficult C–C Couplings: Which Ligand Does Best?

Producción CientíficaA Pd complex, cis-[Pd(C6 F5 )2 (THF)2 ] (1), is proposed as a useful touchstone for direct and simple experimental measurement of the relative ability of ancillary ligands to induce C-C coupling. Interestingly, 1 is also a good alternative to other precatalysts used to produce Pd0 L. Complex 1 ranks the coupling ability of some popular ligands in the order Pt Bu3 >o-TolPEWO-F≈tBuXPhos>P(C6 F5 )3 ≈PhPEWO-F>P(o-Tol)3 ≈THF≈tBuBrettPhos≫Xantphos≈PhPEWO-H≫PPh3 according to their initial coupling rates, whereas their efficiency, depending on competitive hydrolysis, is ranked tBuXPhos≈Pt Bu3 ≈o-TolPEWO-F>PhPEWO-F>P(C6 F5 )3 ≫tBuBrettPhos>THF≈P(o-Tol)3 >Xantphos>PhPEWO-H≫PPh3 . This "meter" also detects some other possible virtues or complications of ligands such as tBuXPhos or tBuBrettPhos.Ministerio de Economía, Industria y Competitividad (CTQ2013-48406-P)Ministerio de Economía, Industria y Competitividad (CTQ2014-52796-P)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA256U13

Evaluation of phytotoxicity and cytotoxicity of industrial catalyst components (Fe, Cu, Ni, Rh and Pd): A case of lethal toxicity of a rhodium salt in terrestrial plants

Until recently, chemical derivatives of platinum group metals have not been in a systematic direct contact with living organisms. The situation has changed dramatically due to anthropogenic activity, which has led to significant redistribution of these metals in the biosphere. Millions of modern cars are equipped with automotive catalytic converters, which contain rhodium, palladium and platinum as active elements. Everyday usage of catalytic technologies promotes the propagation of catalyst components in the environment. Nevertheless, we still have not accumulated profound information on possible ecotoxic effects of these metal pollutants. In this study, we report a case of an extraordinarily rapid development of lethal toxicity of a rhodium (III) salt in the terrestrial plants Pisum sativum, Lupinus angustifolius and Cucumis sativus. The growth stage, at which the exposure occurred, had a crucial impact on the toxicity manifestation: at earlier stages, RhCl3 killed the plants within 24 h. In contrast, the salt was relatively low-toxic in human fibroblasts. We also address phytotoxicity of other common metal pollutants, such as palladium, iron, nickel and copper, together with their cytotoxicity. None of the tested compounds exhibited phytotoxic effects comparable with that of RhCl3. These results evidence the crucial deficiency in our knowledge on environmental dangers of newly widespread metal pollutants

СALCIUM CARBIDE IN THE SYNTHESIS OF D-LABELED HETEROCYCLES

We gratefully acknowledge the financial support from the Russian Science Foundation (Project № 19-73-10032)

THE APPLICATION OF CALCIUM CARBIDE IN THE SYNTHESIS OF D-LABELED PYRAZOLES

We proposed a synthetic approaches to 4,5-dideuteropyrazoles and regioselectively labeled 5-deuteropyrazoles. The application of CaC2-D2O mixture as a source of D2-acetylene in the reaction with in situ generated nitrile imines led to a variety of 1,3-disubstituted D2-pyrazoles in up to quantitative yields (part A). The reaction was performed in two-vessel reactor, demonstrated in the part A.Acknowledgments: We gratefully acknowledge the financial support from the Russian Science Foundation (Project № 19-73-10032)

Transition metal catalyzed element–element′ additions to alkynes

The efficient and stereoselective synthesis of, or precursors to, multi-substituted alkenes has attracted substantial interest due to their existence in various industrially and biologically important compounds. One of the most atom economical routes to such alkenes is the transition metal catalyzed hetero element–element′ π-insertion into alkynes. This article provides a thorough up-to-date review on this area of chemistry, including discussions on the mechanism, range of Esingle bondE′ bonds accessible and the stoichiometric/catalytic transition metal mediators employed