21370-59-2Relevant academic research and scientific papers
Comparative investigation of the regioselectivity in styrene and α-methylstyrene hydroalkoxycarbonylation as a function of palladium catalyst structure
Benedek, Csilla,Toroes, Szilard,Heil, Balint
, p. 85 - 93 (1999)
Catalytic pathways of the styrene and α-methyl-styrene hydroalkoxycarbonylation in the presence of Pd(PPh3)2Cl2 and Pd(PPh3)2Cl2/SnCl2 catalyst precursors have been suggested. As a method, deuterium labelling with EtOD has been applied and it resulted in mixtures of mono- and polydeuterated reaction products, detected and determined by NMR methods. Comparative elucidation of the mechanisms governing these systems does support the assumption that the hydrido route is operative. The different behaviour of the metal-alkyl intermediates accounts for the observed strong influence of catalyst and substrate structure on regioselectivity.
Rhodium catalyzed deuteroformylation of styrene: (E)- and (Z)-β-deuterostyrene and Β, β-dideuterostyrene formation via selective β-hydride elimination from the branched alkylrhodium intermediate
Lazzaroni, Raffaello,Settambolo, Roberta,Raffaelli, Andrea,Pucci, Sergio,Vitulli, Giovanni
, p. 357 - 366 (1988)
Deuteroformylation of styrene in the presence of Rh4(CO)12 as a catalytic precursor was carried out at 160 atm of CO and D2 1/1 at two temperatures (20 and 90 deg C) and for times yielding partial or complete conversion.Compounds recovered from the mixture produced by reaction and partial conversion at 90 deg C include unlabeled styrene, (E)- and (Z)-β-deuterostyrene, C6H5CH=CHD, and β,β-dideuterostyrene, C6H5CH=CD2, whereas at room temperature the styrene does not take up deuterium.These results indicate that under hydroformylation conditions the branched alkylrhodium intermediate, which affords the branched aldehyde, in part dissociates into rhodium hydride and deuterated olefin.By contrast the linear alkyl intermediate does not disssociate under the same conditions, but instead yields almost completely the corresponding aldehyde.
Cyclopropanations via Heme Carbenes: Basic Mechanism and Effects of Carbene Substituent, Protein Axial Ligand, and Porphyrin Substitution
Wei, Yang,Tinoco, Antonio,Steck, Viktoria,Fasan, Rudi,Zhang, Yong
, p. 1649 - 1662 (2018)
Catalytic carbene transfer to olefins is a useful approach to synthesize cyclopropanes, which are key structural motifs in many drugs and biologically active natural products. While catalytic methods for olefin cyclopropanation have largely relied on rare transition-metal-based catalysts, recent studies have demonstrated the promise and synthetic value of iron-based heme-containing proteins for promoting these reactions with excellent catalytic activity and selectivity. Despite this progress, the mechanism of iron-porphyrin and hemoprotein-catalyzed olefin cyclopropanation has remained largely unknown. Using a combination of quantum chemical calculations and experimental mechanistic analyses, the present study shows for the first time that the increasingly useful C-C functionalizations mediated by heme carbenes feature an FeII-based, nonradical, concerted nonsynchronous mechanism, with early transition state character. This mechanism differs from the FeIV-based, radical, stepwise mechanism of heme-dependent monooxygenases. Furthermore, the effects of the carbene substituent, metal coordinating axial ligand, and porphyrin substituent on the reactivity of the heme carbenes was systematically investigated, providing a basis for explaining experimental reactivity results and defining strategies for future catalyst development. Our results especially suggest the potential value of electron-deficient porphyrin ligands for increasing the electrophilicity and thus the reactivity of the heme carbene. Metal-free reactions were also studied to reveal temperature and carbene substituent effects on catalytic vs noncatalytic reactions. This study sheds new light into the mechanism of iron-porphyrin and hemoprotein-catalyzed cyclopropanation reactions and it is expected to facilitate future efforts toward sustainable carbene transfer catalysis using these systems.
Synthesis and Reactivity of Organometallic Intermediates Relevant to Cobalt-Catalyzed Hydroformylation
Chirik, Paul J.,MacNeil, Connor S.,Mendelsohn, Lauren N.,Pabst, Tyler P.,Zhong, Hongyu
, (2020)
Intermediates relevant to cobalt-catalyzed alkene hydroformylation have been isolated and evaluated in fundamental organometallic transformations relevant to aldehyde formation. The 18-electron (R,R)-(iPrDuPhos)Co(CO)2H has been stru
Visible light-mediated metal-free double bond deuteration of substituted phenylalkenes
Iakovenko, Roman,Hlavá?, Jan
supporting information, p. 440 - 446 (2021/01/28)
Various bromophenylalkenes were reductively photodebrominated by using 1,3-dimethyl-2-phenyl-1H-benzo-[d]imidazoline (DMBI) and 9,10-dicyanoanthracene. With deuterated DMBI analogs (the most effective was DMBI-d11), satisfactory to excellent isotopic yields were obtained. DMBI-d11 could also be regenerated from the reaction mixtures with a recovery rate of up to 50%. The combination of the photodebromination reaction with conventional methods for bromoalkene synthesis enables sequential monodeuteration of a double bond without the necessity of a metal catalyst. This journal is
Iron(ii)-catalyzed intermolecular aziridination of alkenes employing hydroxylamine derivatives as clean nitrene sources
Berhal, Farouk,Grimaud, Laurence,Kirby, Georgina,Prestat, Guillaume,Vitale, Maxime R.
supporting information, p. 9428 - 9432 (2021/12/09)
The iron-catalyzed intermolecular aziridination of alkenes with hydroxylamine derivatives is described. Using simple iron(ii) sources and readily available ligands, the formal (2 + 1) cycloaddition process proved to be efficient on both styrenes and aliphatic alkenes, providing access to a wide range of aziridines. In these particularly sustainable reaction conditions, yields up to 89% could be obtained, with a catalyst loading which could be lowered to 5 mol% when the reaction was performed on large scale. Preliminary mechanistic studies suggest that both concerted and stepwise pathways are operating in this transformation. This journal is
The Catalytic Asymmetric Intermolecular Prins Reaction
Diáz-Oviedo, C. David,Maji, Rajat,List, Benjamin
supporting information, p. 20598 - 20604 (2021/12/14)
Despite their significant potential, catalytic asymmetric reactions of olefins with formaldehyde are rare and metal-free approaches have not been previously disclosed. Here we describe an enantioselective intermolecular Prins reaction of styrenes and paraformaldehyde to form 1,3-dioxanes, using confined imino-imidodiphosphate (iIDP) Br?nsted acid catalysts. Isotope labeling experiments and computations suggest a concerted, highly asynchronous addition of an acid-activated formaldehyde oligomer to the olefin. The enantioenriched 1,3-dioxanes can be transformed into the corresponding optically active 1,3-diols, which are valuable synthetic building blocks.
Geometric E→Z Isomerisation of Alkenyl Silanes by Selective Energy Transfer Catalysis: Stereodivergent Synthesis of Triarylethylenes via a Formal anti-Metallometallation
Fa?bender, Svenja I.,Molloy, John J.,Mück-Lichtenfeld, Christian,Gilmour, Ryan
, p. 18619 - 18626 (2019/11/16)
An efficient geometrical E→Z isomerisation of alkenyl silanes is disclosed via selective energy transfer using an inexpensive organic sensitiser. Characterised by operational simplicity, short reaction times (2 h), and broad substrate tolerance, the reaction displays high selectivity for trisubstituted systems (Z/E up to 95:5). In contrast to thermal activation, directionality results from deconjugation of the π-system in the Z-isomer due to A1,3-strain thereby inhibiting re-activation. The structural importance of the β-substituent logically prompted an investigation of mixed bis-nucleophiles (Si, Sn, B). These versatile linchpins also undergo facile isomerisation, thereby enabling a formal anti-metallometallation. Mechanistic interrogation, supported by a theoretical investigation, is disclosed together with application of the products to the stereospecific synthesis of biologically relevant target structures.
Hydrogen on Cobalt Phosphide
Delley, Murielle F.,Wu, Zishan,Mundy, M. Elizabeth,Ung, David,Cossairt, Brandi M.,Wang, Hailiang,Mayer, James M.
supporting information, p. 15390 - 15402 (2019/11/02)
Cobalt phosphide (CoP) is one of the most promising earth-abundant replacements for noble metal catalysts for the hydrogen evolution reaction (HER). Critical to HER is the binding of H atoms. While theoretical studies have computed preferred sites and energetics of hydrogen bound to transition metal phosphide surfaces, direct experimental studies are scarce. Herein, we describe measurements of stoichiometry and thermochemistry for hydrogen bound to CoP. We studied both mesoscale CoP particles, exhibiting phosphide surfaces after an acidic pretreatment, and colloidal CoP nanoparticles. Treatment with H2 introduced large amounts of reactive hydrogen to CoP, ca. 0.2 H per CoP unit, and on the order of one H per Co or P surface atom. This was quantified using alkyne hydrogenation and H-atom transfer reactions with phenoxy radicals. Reactive H atoms were even present on the as-prepared materials. On the basis of the reactivity of CoP with various molecular hydrogen donating and accepting reagents, the distribution of binding free energies for H atoms on CoP was estimated to be roughly 51-66 kcal mol-1 (δG°H 0 to -0.7 eV vs H2). Operando X-ray absorption spectroscopy gave preliminary indications about the structure of hydrogenated CoP, showing a slight lattice expansion and no significant change of the effective nuclear charge of Co under H2-flow. These results provide a new picture of catalytically active CoP, with a substantial amount of reactive H atoms. This is likely of fundamental relevance for its catalytic and electrocatalytic properties. Additionally, the approach developed here provides a roadmap to examine hydrogen on other materials.
Organoiron- And Fluoride-Catalyzed Phosphinidene Transfer to Styrenic Olefins in a Stereoselective Synthesis of Unprotected Phosphiranes
Geeson, Michael B.,Transue, Wesley J.,Cummins, Christopher C.
supporting information, p. 13336 - 13340 (2019/09/10)
Catalytic phosphiranation has been achieved, allowing preparation of trans-1-R-2-phenylphosphiranes (R = t-Bu: 1-t-Bu; i-Pr: 1-i-Pr) from the corresponding dibenzo-7-(R)-7-phospha-norbornadiene (RPA, A = C14H10, anthracene) and styre
